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Previous studies have mainly focused on changes in soil physical and chemical properties to evaluate the reclamation of sodic soils using flue gas desulfurization (FGD) gypsum. However, information on the effects of this reclamation method on microbial-based indicators of soil quality is limited, particularly after many years of FGD gypsum application. This study aimed to investigate the long-term effects of FGD gypsum on soil organic carbon (SOC), nutrients, microbial biomass and enzyme activity. Data were collected from soils of three exchangeable sodium percentage (ESP) classes (i.e., low-, middle- and high-ESP classes of 6.1–20, 20–30 and 30–78.4%, respectively) 17 years after FGD gypsum treatment in Inner Mongolia, China. Averaged across the three ESP classes, FGD gypsum application increased the SOC contents at the 0–20 and 20–40-cm soil depths by 18 and 35%, respectively, and increased available potassium at the 0–20-cm soil depth by 51% compared with the no-gypsum controls. The microbial biomass carbon and microbial biomass nitrogen contents at the 20–40-cm soil depth increased by 69 and 194%, respectively, under FGD gypsum. Except in the high-ESP class, urease activities in the 0–40 cm soil profile were significantly higher in the FGD gypsum treatments than in the controls. A significant increase in alkaline phosphatase activity was concentrated in the 20–40 cm soil layer; few classes showed significant increases in catalase and invertase activities in the 0–20 cm soil layer. Pearson correlation analysis showed that increases in soil fertility and biological activity could be attributed to reductions in electrical conductivity, pH and ESP caused by FGD gypsum application. These results confirm that FGD gypsum application is a viable strategy for reclaiming sodic soils due to its positive effects on soil fertility and biochemistry and that it may contribute to soil ecosystem sustainability.

The Andes Mountains stretch over about 8900 km and cross tropical, subtropical, temperate and arid latitudes. Very few, if any, of the diverse physiographic, climatic and biogeographic regions in the Andes have been preserved from human impact. Land use and management have significantly altered the magnitude and frequency of erosion events: deforestation and agricultural practices (such as soil tillage and cattle grazing) have modified erosion rates, river sediment loads and landslide occurrences.There is an urgent need to identify which soil conservation and management practices are most effective to combat soil erosion and to mitigate the on-site and off-site effects in the Andean region. Three large groups of water-related interventions can be identified: interventions based on land use and protective land cover including (1) restoration and protection of native ecosystems, such as montane forests or grasslands and (2) forestation with native or exotic species and (3) soil and water conservation measures including crop management, conservation tillage and slow-forming terraces and the implementation of linear elements such as vegetation strips and check dams. To expand the knowledge base on natural infrastructure for erosion mitigation in the Andes, it is necessary to move beyond case-by-case empirical studies to comprehensive assessments.This study reviews the state of evidence on the effectiveness of interventions to mitigate soil erosion by water and is based on Andean case studies. Based on a systematic review of peer-reviewed and grey literature involving more than 120 local case-studies from the Andes, this study addressed the following research questions: (1) Which erosion indicators allow us to assess the effectiveness of natural infrastructure? (2) What is the overall impact of working with natural infrastructure on on-site and off-site erosion mitigation? (3) Which locations and types of studies are needed to fill critical gaps in knowledge and research?From the suite of physical, chemical and biological indicators commonly used in soil erosion research, two indicators were particularly relevant: soil organic carbon of topsoil and soil loss rates at plot scale. The protection and conservation of natural vegetation has the strongest effect on soil quality, with 3.01 ± 0.893 times higher soil organic carbon content in the topsoil compared to control sites. Soil quality improvements are significant but lower for forestation and soil and water conservation measures. Soil and water conservation measures reduce soil erosion to 62.1 ± 9.2 %, even though erosion mitigation is highest when natural vegetation is maintained.The systematic review of the existing literature allowed us to identify critical gaps in knowledge and research. There is a need for future empirical work on soil quality, erosion and sediment yield before/after interventions in data-scarce regions, such as high elevations, regions with either low or high relief, and low to very low or very high precipitation. Besides, most erosion assessments are based on short-term measurements that tend to miss the impact of rare high-magnitude events. Further research is needed to evaluate whether the reported effectiveness holds during extreme events related to, for example, El Niño–Southern Oscillation.

The current study intended to understand the influence of Melia dubia based agroforestry system on soil properties. The research was carried out at Gillan Khera in district Fatehabad, situated in the semi-arid region of Haryana. Analysis of soil samples were done for pH, electrical conductivity (EC), organic carbon, soil moisture and available nitrogen, phosphorus and potassium. The soil pH and EC decreased more under trees than under control (sole wheat crop) i.e, 8.09 to 7.89 and 0.46 to 0.44 dSm-1 respectively. However, the amount of N, P, K, organic carbon (131.38, 16.00, 301.10 (kg/ha) and 0.46 % respectively) and soil moisture content was found higher in intercropped conditions at both soil depths. Extra moisture in shaded conditions resulting in the breakdown of litter, mineralization and nitrogen gain at a faster rate compared to full sunlight conditions justifies the increased amount of nutrients, organic carbon and other favorable changes in the soil under trees. The current study recommends Melia dubia based agroforestry system as an excellent opportunity in order to enhance soil fertility and for environmental sustainability.

Conservation tillage, residue management and optimizing nitrogen (N) fertilization are important strategies for soil and water conservation and sustainability of agricultural systems. In order to evaluate the effects of various residue management methods and N fertilizer rates on some soil quality indicators, accumulation of residual soil nitrate, and wheat yield under no till system, a split-plot experiment was arranged in a randomized complete block design with three replications. Main plots were three residue management methods, including retaining (R.M1), removing (R.M2) and shredding (R.M3) of corn residues. The subplots consisted of four N fertilizer rates, 100 (N1), 150 (N2), 200 (N3), and 250 (N4) kg N ha−1 from urea source. The results showed that soil organic carbon and total N in R.M1 and R.M3 treatments increased at the depth of 0–15 cm as compared to R.M2. The maximum accumulation of soil nitrate was observed in R.M1 × N4 and R.M3 × N4 interactions at the soil depth of 60-cm. The results of this study showed that R.M1 × N3 and R.M3 × N3 interactions had a greater impact on wheat yield than the sole effect of R.M1 or R.M3. According to our findings, application of 200 kg N ha−1 in combination with R.M1 which had once less tractor passing for mechanical shredding than R.M3, can contribute effectively to improve soil quality indicators, control soil residual nitrate and subsequently produce more wheat grain yield in the south-west of Iran.

Objectives Several studies have demonstrated an increased risk of adverse health effects, including reduced lung function and lung cancer among asphalt pavers, which has been related to occupational exposure to contaminants during asphalt paving. Consequently, occupational exposure among asphalt pavers must be reduced. The aim of this study was to compare the impact of hot mix asphalt (HMA) and warm mix asphalt (WMA) paving on occupational exposure levels during road paving in field experiments. Asphalt temperatures when paving with WMA are usually lower than when paving with HMA due to differences in the asphalt’s composition and method of application. Methods On 11 different road sections, one lane was paved with WMA and one with HMA during the same work shift under approximately identical weather conditions. The weather conditions and asphalt surface temperature were monitored during paving. Fifty-seven samples of fumes and vapor, organic and elemental carbon, amines, and respirable, thoracic, and inhalable particulate matter (PM) fractions were collected by stationary sampling. In addition, 30 samples of fumes and vapor were collected by personal sampling Results Compared to paving with HMA, paving with WMA significantly (P < 0.05; paired Student’s t-test) reduced the geometric mean (GM) air concentration of asphalt vapor (0.04 versus 0.08 p.p.m.), organic carbon (OC; 0.09 versus 0.18 mg m−3), and respirable PM (0.12 versus 0.22 mg m−3). Additionally, the air concentration of OC correlated strongly with the respirable fraction of PM (Pearson’s correlation coefficient 0.83). Conclusions Measured airborne concentrations of respirable PM, OC, and asphalt vapor were lower when paving with WMA than with HMA. Because exposure to airborne contaminants generated during asphalt paving is believed to be responsible for the adverse health effects observed among asphalt pavers, paving with WMA rather than HMA may have health benefits.

We analyzed the effect of different tillage systems on soils under different land-use histories, on biological properties of soil during one year. The experiment was carried out at a Petrocalcic Argiudoll of Tres Arroyos (Buenos Aires, Argentina). The specific aim was to describe and compare the soil organic carbon (SOC), the soil basal respiration (BR) and the activities of the enzyme dehydrogenase, urease and acid-phosphomonoesterase under zero and conventional tillage on soils under pasture and intensive agriculture. The SOC concentration was highest in summer (postharvest) independently of tillage system or land-use history. However, in autumn the plots under conventional tillage showed higher values of SOC than those with zero tillage, independently of land-use history. The BR had a significant benefit in favour of summer pasture soils. The effect of land-use history or the tillage system on the enzymes activity was dependent of sampling season. Therefore, the soil enzymes were more sensible than SOC and BR. In temporal studies the effect of sampling season is strongest that others factors as tillage systems or land-use history. EEA Barrow Fil: Moreno, María Virginia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomía. Area Microbiología; Argentina Fil: Biganzoli, Fernando. Universidad de Buenos Aires. Facultad de Agronomía. Departmento de Métodos Cuantitativos y Sistemas de Información; Argentina Fil: Casas, C. Universidad de Buenos Aires. Facultad de Agronomía. Departamento de Recursos Naturales. Cátedra de Edafología; Argentina Fil: Manso, Marina Lucrecia. Instituto Nacional de Tecnología Agropecuaria (INTA). Estación Experimental Agropecuaria Barrow; Argentina Fil: Moreira, E. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biología Funcional y Biotecnología; Argentina. Instituto Antártico Argentino; Argentina Fil: Silvestro, Luciana Belén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Cientifico Tecnolológico Mar del Plata. Instituto de Investigaciones en Biodiversidad y Biotecnología. Laboratorio de Biologia Funcional y Biotecnología; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Agronomía. Area Química; Argentina

The results of field, analytical, and experimental research at a number of production facilities reflect the properties of oil-contaminated soils in 3 landscapes: the permafrost treeless Arctic ecosystem, boreal forest, and temperate-climate grassland-woodland ecotone. Laboratory studies have revealed the concentrations of petroleum hydrocarbons in soils, ranging from medium levels of 2000–3000 mg/kg to critical figures over 5000 mg/kg, being 2–25 times higher than the permissible content of oil products in soils. The experimentally applied thermal effects for the oil products desorption from the soil allowed finding an optimal regime: the treatment temperature from 25 to 250 °C reduces the concentrations to an acceptable value. The conditions are environmentally sound, given that the complete combustion point of humates is ca. 450 °C. The outcomes suggest the eco-friendly solution for soil remediation, preserving the soil fertility in fragile cold environments and in more resilient temperate climates, where revitalized brownfields are essential for food production.

The aim of this study was to survey the behavior of water quality and surface sediment during the growth period of submerged macrophytes. Their dynamics were investigated by a microcosm experiment. In midsummer, the nitrogen and phosphorus concentration of the column with vegetation (Column A) was kept low and the inorganic nitrogen loading in the first 15 days was about 3 times lower than that of the column without vegetation (Column B). The vegetated column prevented algal blooms in midsummer and was checked to see zooplankton and zoobenthos during the biological active period. The rate of change of masses of carbon and nutrients in the sediment before and after the column experiment were calculated on the basis of the contents of each and sediment thickness (0 to 5 cm). Masses of organic carbon in Column A and Column B in the sediment after 100 days were estimated to decrease by 14 and 23%, respectively. Masses of nitrogen in Column A and Column B in the sediment after 100 days were estimated to decrease by 11 and 26%, respectively. Thus, the mass reduction rate of the vegetated column was 10 to 16% less than that of the column without vegetation.

The aim of this study was to quantify the current soil organic carbon stock under different types of savannah agrosystems in the Sudano-Sahelian zone of Cameroon in the context of greenhouse gas emissions and land degradation. It is so crucial for combating climate change and improving ecological restoration. Random field sampling was carried out on 0-10, 10-20 and 20-30 cm depth, then were collected in four types of savannah agrosystems. Soil bulk density, pH, moisture content, CEC, exchangeable bases, particle size distribution and soil organic carbon were determined using standard laboratory procedures and calculations. The results of the study did not reveal a significant difference in soil organic carbon stock between different types of savannah agrosystems (P>0.05). Soils of Tamarindus indica savannah agrosystems in recorded higher values SCOS (36.03 ± 3.31 tC/ha), Prosopis africana (33.40 ± 3.27 tC/ha), Haematostaphis barterii (31.83 ± 3.21 tC/ha) and Detarium microcarpum (31.19 ± 3.19 tC/ha) savannah agrosystems. Similarly, SCOS decreased with soil depth in all types of savannah agrosystems. Results showed a positive and significant (P0.05) with Density, K+, CEC, Sand %, Silt %, Clay %, Silt + Clay %. The results show the potential contribution of savannah agrosystems to improve soil organic carbon sequestration and environmental protection.

The variability of physico-chemical parameters and enzymatic activity in the surface horizons of brown soil (Cambisols) in the range of phytogenous fields (PF) of Korean pine plus trees of different size and age, growing on the territory of the Verkhneussuriysky forest Station, were investigated. The soil samples were taken inside PF within sectors in the direction: north-south; according to the scheme: I – near-trunk part (30 cm from the trunk); II – middle part (middle of the crown projection); III – the edge of the crown projection. The higher-level (Corg) parameters (28.4%) were under Korean pine with the bigger stem diameter (61 cm) and age (240 years). In the range of PF of Korean pine plus trees (200-210 years old, with stem diameters of 40 cm and size of crown 12.5 x 5.2 m) the middle Corg. factor was 22.5-23.8%. The higher pH average parameters determined under these trees too. The middle (Corg) parameters in the north sectors of PF trees were higher (26.3%) than in south (23.5%). The major trend of decreasing pH value in the edge parts of the PF investigated trees compared with the near-trunk parts.

International audience; Floodplains play a crucial role in water quality regulation via denitrification. This biogeochemical process reduces nitrate (NO3-), with aquifer saturation, organic carbon (OC) and N availability as the main drivers. To accurately describe the denitrification in the floodplain, it is necessary to better understand nitrate fluxes that reach these natural bioreactors and the transformation that occurs in these surface areas at the watershed scale. At this scale, several approaches tried to simulate denitrification contribution to nitrogen dynamics in study sites. However, these studies did not consider OC fluxes influences, hydrological dynamics and temperature variations at a daily time step. This paper focuses on a new model that allows insights on nitrate, OC, discharge and temperature influences on daily denitrification for each water body. We used a process-based deterministic model to estimate daily alluvial denitrification in different watersheds showing various pedo-climatic conditions. To better understand global alluvial denitrification variability, we applied the method to three contrasting catchments: The Amazon for tropical zones, the Garonne as representative of the temperate climate and the Yenisei for cold rivers. The Amazon with a high discharge, frequent 2 flooding and warm temperature, leads to aquifers saturation, and stable OC concentrations. Those conditions favour a significant loss of N by denitrification. In the Garonne River, the low OC delivery limits the denitrification process. While Arctic rivers have high OC exports, the low nitrate concentrations and cold temperature in the Yenisei River hinder denitrification. We found daily alluvial denitrification rates of 119.4 ± 47.5, 7.6 ± 5.4 and 0.1 ± 0.5 kgN.ha-1 .yr-1 during the 2000-2010 period for the Amazon, the Garonne and the Yenisei respectively. This study quantifies the floodplains influence in the water quality regulation service, their contribution to rivers geochemical processes facing global changes and their role on nitrate and OC fluxes to the oceans.

The aim of the study was to determine the effect of soil management systems of Brunic Arenosols on total content of organic carbon and its fraction susceptible to oxidation in comparison with soils under forests. Samples for study were taken from the humus horizon at sites located in forests and soils from little mid-forest cultivated fields (hunting plots). The agrotechnical treatments increased the content of plant-available forms of P, K and Mg in the soils of most hunting plots in comparison to forest soils. In the arable horizon of the hunting plots there was found a varied total content of organic carbon and its fraction susceptible to oxidation. Cultivation of soil in hunting plots caused a decrease in content of total organic carbon as well as its labile and non-labile fraction. To evaluate the carbon transformation in the soil of the cultivated plots against the forest (reference soil), the Carbon Management Index (CMI) was used. The decay rate of soil organic matter in a natural forest was lower than in the agricultural fields. A long-term tillage of Brunic Arenosols contributed to the degradation of the pool of organic carbon in sandy-textured soil.

Soil aggregate degradation by medium and high intensity fires is often attributed to loss of soil organic matter, whereas low intensity fires are often considered benign to soil aggregate degradation because organic and inorganic binding agents are relatively stable at these low temperature burns. Because of this, there are limited studies specifically focusing on the effect of low intensity fires on soil aggregation. However, recent long-term studies have reviewed that aggregate breakdown can occur long periods of time after low intensity burns. The aggregate breakdown could not be explained by loss of soil binding agents. Previous studies have indirectly tested the hypothesis that stress exerted by rapid vaporization of soil pore water during low intensity burns could lead to aggregate breakdown in the long term. I further explore this mechanism of soil aggregate degradation in a forest sandy loam and shrubland loam soil. In this work, I (1) provide direct proof of the hypothesis by measuring the pressure inside individual moist soil aggregates burned at 175°C and (2) show that soil aggregate degradation by this mechanism can expose physically protected soil organic carbon to decomposition. The pore pressure increase in both the forest and the shrubland aggregates increased with increasing soil water content. Furthermore, tensile strength of both types of soil aggregates decreased with increase in soil water content, suggesting that moist soil aggregates may be more susceptible to breakdown by this mechanism. Additionally, I provide a model predicting that strain on aggregates from rapidly vaporized soil water is maximized in initially wetter soil aggregates. The degradation of soil aggregates by rapidly vaporized soil pore water was observed in forest soils that experienced increase in rate of decomposition of soil organic following low intensity fires. Increase in decomposition of soil organic carbon in shrubland soil aggregates were observed for all burn treatments, and was linked to increase in dissolved organic carbon likely due to loss of cytoplasmic organic compounds from lysis of soil microbes. The results provided in this thesis suggest that low intensity burns can negatively affect soil aggregation in ways that were not studied before since low intensity burns are often considered benign to soil aggregation, and that more research should focus on low intensity fires’ effects on soil aggregates as the number of these burns have been increasing over the last few decades.

Interactions between organic and detrital mineral phases strongly influence both the dispersal and accumulation of terrestrial organic carbon (OC) in continental margin sediments. Yet the complex interplay among biological, chemical, and physical processes limits our understanding of how organo-mineral interactions evolve during sediment transfer and burial. In particular, diverse OC sources and complex hydrodynamic processes hinder the assessment of how the partnership of organic matter and its mineral host evolves during supply and dispersal over continental margins. In this study, we integrate new and compiled sedimentological (grain size, surface area), organic (%OC, OC-δ13C, OC-F14C), and inorganic isotopic (εNd, 87Sr/86Sr) geochemical data for a broad suite of surface sediments spanning the Western Arctic Ocean from the Bering Sea to the Mackenzie River Delta that capture diverse sources and ages of both terrestrial and marine material deposited in contrasting shelf and slope settings. Spatial gradients in sediment properties were used to delineate regional sources and transport processes influencing the dispersion and persistence of OC-mineral particle associations during export and burial. We found strong relationships between physical parameters, aluminum content, and OC-14C suggesting that terrestrial OC remains tightly associated with its detrital mineral carrier during source-to-sink transport. Notably, carbon and neodymium isotopic data yield consistent information regarding organic matter provenance. Results obtained highlight the potential for coupled organic-inorganic tracer measurements to elucidate sediment sources and to constrain physical and geochemical processes during sediment mobilization and transport in the Western Arctic Ocean. Tandem measurements of carbon and Nd isotopes may provide a new way to identify large-scale biogeochemical and ecological changes in the sources, nature, and fate of OC stemming from predicted increases in sea ice loss and fluvial inputs of dissolved and particulate OC to this complex and dynamic high latitude marginal sea. ISSN:0016-7037 ISSN:1872-9533

The extensive anthropogenic activities and their potential impacts on lakes during the Anthropocene could be recorded in the sediments. In this study, the composition of biomarkers (i.e., n-alkanes and n-fatty acids), total organic carbon (TOC), and particle size in 210Pb-dated sediment cores from West Dongting Lake were investigated to trace the historical trend of anthropogenic inputs and their environmental significance. The TOC content was in the range of 3.15–27.32 mg g−1. The n-alkanes and n-fatty acids were distributed from C11–C33 and C12:0–C34:0, respectively. The short- and long-chain biomarkers accounted for a significant proportion of the total. Aquatic plants and algae living in West Dongting Lake were the main source (short-chain) followed by leaf waxes derived from terrestrial C3 plants (long-chain), as demonstrated by their concentrations. The variations of the key indicators i.e., the carbon preference index (CPI), aquatic plant n-alkane proxy (Paq), vascular plant n-alkane proxy (Pwax), and the ratio of unit short- to long-chain n-alkanes (L/H) also indicated that the aliphatic hydrocarbon fractions were mainly composed of short- and long-chain biomarkers. The sedimentary biomarkers had a significant temporal heterogeneity, which was controlled by different factors and sedimentary processes. Fine particles (

Lack of a systematic and environmentally efficient approach to exploitation of bays of Sevastopol (Kruglaya and Kazachya bays) resulted in their severe pollution. The combination of natural and anthropogenic factors led to the deterioration of the benthic communities living conditions. The purpose of this work was a complex research of Kruglaya and Kazachaya bays’ ecosystems to study features of redox conditions formation in the bottom sediments and the bottom waters and their influence on the characteristics of macrozoobenthos. Samples of bottom sediments were taken by diver in plexiglass tubes, hermetically closed above and below, it allowed to save a fine structure of bottom sediments and the bottom layer of water. To study benthic communities, samples were taken in the same place using a manual sampler. To obtain the chemical composition of pore waters with high vertical resolution, the voltammetry analysis was used. Calculation of the oxygen flux at the boundary and in the upper part of the bottom sediments was carried out according to the vertical profile of oxygen concentration in pore waters and geochemical analyzes using the equation for the first Fick law taking into account the concentration gradient and molecular diffusion of oxygen in pore waters. Standard hydrobiological methods were used for the analysis of benthic material. When calculating the values of the Shannon diversity index (H'), the base 2 logarithm was used. The data analysis showed that a high level of anthropogenic impact and restricted water dynamics led to siltation of the bottom sediments of the investigated water areas, which made it difficult for oxygen penetration, and the accumulation of organic carbon contributed to its active consumption. Stratification of the water column due to limited water exchange, high temperature of the bottom waters, accompanied by a decrease in oxygen solubility, and finely dispersed nature of bottom sediments contributed to the fact that the rate of oxygen intake was lower than the rate of oxygen consumption for the oxidation of organic matter, which was accompanied by the development of oxygen deficiency zones and the appearance of reduced compounds, in particular hydrogen sulfide. It was noted that suboxic conditions prevailed in the upper layer of bottom sediments, and anaerobic conditions prevailed below. This had led to the fact that the main forms of macrozoobenthos were species tolerant to oxygen deficiency and organic pollution. Thus, in some parts of the Kazachaya Bay were marked only polychaetes. At the same time, it was noted that in the area of exit from Kruglyaya Bay, intense water dynamics and morphological features of the bottom sediments contribute to saturation of the upper layer of sediments with oxygen. Based on the oxygen concentration data in the surface (0 - 5 mm) sediment layer (pore water), and the geochemical composition of bottom sediments, the oxygen flux at station 4 was calculated. Its value was 0.73 M·m-2·year-1. Taking into account the concentration of oxygen in the bottom layer of water (259 μM), the time for complete exhaustion of oxygen or its renewal taking into account only biogeochemical processes was about 5 months. Thus, it can be assumed that the ecosystems of the Kruglaya and Kazachaya bays are in the stage of degradation. Its further exploitation without a developed systematic approach and rational use will lead to a critical deterioration of its ecosystem - the emergence and spread of environmental risk zones. This will reduce the recreational and socio-economic attractiveness of these areas.

Adopting agroforestry practices in many developing countries is essential to combat climate change and diversify farm incomes. This study investigated the above and below-ground biomass and soil carbon of a citrus-based intercropping system in six sites (subdivisions: Bhalwal, Kot Momin, Sahiwal, Sargodha, Shahpur and Silanwali) of District Sargodha, Southeast Pakistan. Tree biomass production and carbon were assessed by allometric equations through a non-destructive approach whereas, soil carbon was estimated at 0–15 cm and 15–30 cm depths. Above and below-ground biomass differed significantly, and the maximum mean values (16.61 Mg ha−1 &amp, 4.82 Mg ha−1) were computed in Shahpur due to greater tree basal diameter. Tree carbon stock fluctuated from 6.98 Mg C ha−1 to 10.28 Mg C ha−1 among selected study sites. The surface soil (0–15 cm) had greater bulk density, organic carbon, and soil carbon stock than the subsoil (15–30 cm) in the whole study area. The total carbon stock of the ecosystem ranged from 25.07 Mg C ha−1 to 34.50 Mg C ha−1 across all study sites, respectively. The above findings enable us to better understand and predict the carbon storage potential of fruit-based agroforestry systems like citrus. Moreover, measuring carbon with simple techniques can produce trustworthy outcomes that enhance the participation of underdeveloped nations in several payment initiatives such as REDD+.

Peatlands are unique ecosystems but when they are drained for agriculture or peat mining, stored carbon is released to the atmosphere as CO2. The aim of the study was to assess the influence of siltation on secondary humification basing on humification indicators (C/N ratio, humification degree, humification index, E4/E6 ratio). It is essential to examine to what extent siltation hampers soil organic matter (SOM) oxidation. The study revealed that after drainage the amount of humus fractions, both acid and alkali soluble, were increasing at the expense of non-soluble carbon pool (residuum). Siltation hampered the transformation of organic matter and the quantities of OC and N in humus fractions were lower in silted soil samples than in not silted ones. The carbon extracted in acid-soluble fraction was not related to the state of siltation and was associated with the depth. The nitrogen content in this fraction did not change after drainage or siltation. The siltation did not affect C/N ratios. In unaltered peats these ratios were typical for fen soils (lowland peats) but in other studied soil samples the values of the C/N ratios suggested secondary transformation. The humification indicators (HI, HD and E4/E6) also revealed that secondary humification was more advanced in strongly silted soils, i.e. the stability of SOM in these soils is lower and the values of these indicators were dependent on the state of siltation. The study revealed that both drainage and siltation of soils changed the relations in SOM fractions. Drainage of peatlands resulted in initiation of the secondary humification of SOM and increase of chemically extractable humus fractions as well as increase of the humification degree. Stable SOM, which can have a mean residence time of centuries, became a potential source of CO2. However, siltation which led to a 50% decrease in SOM, hampered oxidation of SOM and had a stabilizing effect on SOM quality. These findings provide new insights into possibilities of mitigation of C losses from agricultural areas and may serve as a guidance for soil C management.

The Everglades Stormwater Treatment Areas (STAs) are a complex of large constructed wetlands that are an integral component of the State and Federal efforts to restore the Everglades ecosystem. The overall objective of this study was to determine the accumulation rates of macro‐elements including carbon (C), nitrogen (N), phosphorus (P), sulfur (S), and associated secondary elements including calcium (Ca), magnesium (Mg), aluminum (Al), and iron (Fe) in two Everglades STAs over their periods of operation. The study was conducted in STA‐2 with parallel flow‐ways consisting of emergent aquatic vegetation (EAV) and submerged aquatic vegetation (SAV) and the Western flow‐way of STA‐3/4 with EAV and SAV cells operated in series. Elemental accumulation rates were determined in the unconsolidated surficial sediments (floc) and recently accreted soil (RAS) that have accumulated on top of the antecedent soil over the 14‐ and 10‐yr periods of operation for STA‐2 and STA‐3/4, respectively. Flow‐ways with SAV were more efficient than EAV in accreting mineral matter, resulting in increased bulk density and higher accumulation rates of elements. Average C accumulation in the floc and RAS of SAV flow‐ways was 320 g·m−2·yr−1 with approximately equal proportions of inorganic and organic C, while in the EAV flow‐ways accumulation rates of C ranged from 116 to 147 g·m−2·yr−1 with mostly organic C. Phosphorus accumulation rates were approximately 2–3 times higher in SAV than in EAV flow‐ways. Differences in accumulation of elements between SAV and EAV were largest for Ca with 17–42 times more Ca in SAV than EAV systems. This suggests that in the SAV systems, possible occlusion of macro‐elements and metals during CaCO3 precipitation facilitated accretion of material with high mineral content. In EAV, biomass turnover and associated biotic processes regulated organic matter accumulation rates. The spatial accumulation patterns of P, C, and N in the EAV areas of STA‐2 and STA‐3/4 were similar to those observed in the EAV areas of the natural wetlands in Water Conservation Areas, suggesting that constructed wetland systems function similarly to natural wetlands dominated by EAV areas in retaining and storing macro‐ and secondary elements.

Land-ocean interactions play an important role in transporting and accumulating organic carbon (OC) in marine sediments. Understanding sources (terrestrial, marine and anthropogenic contributions) of sedimentary OC are important to better evaluate the processes controlling the OC distribution in coastal zones. In this study, we present bulk parameters of total organic carbon (TOC), total nitrogen (TN), stable carbon isotopic composition (δ13Corg) and biomarker contents in surface sediments from the Dagu River-estuary-marine system in the Jiaozhou Bay. Comparison between OC/N ratios and δ13Corg indicated significant C4 plant contribution to the sedimentary OC, which was approximately equal to C3 plant contribution in this study. Generally, terrestrial biomarkers contents were high in the river and showed a decreasing trend towards the estuary and inner bay. Marine biomarkers displayed opposite spatial distribution patterns with terrestrial biomarkers except for the brassicasterol that also has a terrestrial/fluvial source. The universal detection of petroleum and sewage biomarkers revealed the significant anthropogenic influence on the sedimentary OC in our study. Principal component analysis-multiple linear regression (PCA-MLR) was performed to quantitatively estimate the OC contributions in the Jiaozhou Bay, showing that anthropogenic activities contributed 77.6% and 29.9% to the sedimentary OC in Dagu River and outside the Dagu River (the estuary and the inner Bay), respectively. Further studies need to be carried out to test this approach in broader regions.

Restoration aimed at rewetting the valley floor has the potential to increase organic carbon stock in the form of floodplain soil carbon, downed wood, and riparian vegetation. The primary goal of stream restoration is typically to restore habitat or maintain balance between natural ecosystem function and human land use. Although many benefits result from stream restoration, the carbon sequestration potential of different restoration approaches in diverse geographic settings has not yet been quantified. We investigate the carbon storage potential of restored stream segments (known as treatment segments) relative to otherwise analogous degraded and reference segments. We develop a conceptual framework to identify the conditions that maximize carbon storage in relation to characteristics of the river corridor and specific restoration practices and propose response surfaces for carbon storage. We illustrate application and quantification of the conceptual framework using data from a pilot study of treatment, degraded, and reference stream segments along two streams in Oregon, United States. The conceptual model is designed to help managers identify levels of hydrologic connectivity, channel and floodplain dynamics, floodplain vegetation, and other variables that may optimize carbon storage at a treatment site.

The transport and fate of hydrophobic organic contaminants (HOCs) in the marine environment are closely linked to organic carbon (OC) cycling processes. We investigated the influence of marine versus terrestrial OC origin on HOC fluxes at two Baltic Sea coastal sites with different relative contributions of terrestrial and marine OC. Stronger sorption of the more than four-ring polycyclic aromatic hydrocarbons and penta-heptachlorinated polychlorinated biphenyls (PCBs) was observed at the marine OC-dominated site. The site-specific partition coefficients between sediment OC and water were 0.2–1.0 log units higher at the marine OC site, with the freely dissolved concentrations in the sediment pore-water 2–10 times lower, when compared with the terrestrial OC site. The stronger sorption at the site characterized with marine OC was most evident for the most hydrophobic PCBs, leading to reduced fluxes of these compounds from sediment to water. According to these results, future changes in OC cycling because of climate change, leading to increased input of terrestrial OC to the marine system, can have consequences for the availability and mobility of HOCs in aquatic systems and thereby also for the capacity of sediments to store HOCs., The authors wish to thank the Tvärminne zoological research station and staff: Alf Norkko, Joanna Norkko, Göran Lundberg, Jostein Solbakken, and Noora Haavisto for kind assistance with the field sampling. Christoph Humborg, the entire Baltic Bridge team and Crew of R/V Electra: Thomas Strömsnäs, Mattias Murphy, and Carl-Magnus Wiltén are acknowledged for their valuable help with the sediment–water probe retrieval. The authors wish to thank the following people for their help with the sample processing and analytics: Marcus Sundbom, Cipriano Carrero-Carralero, Ulla Sellström, Ulla Erikson, and Heike Siegmund. Flett Research Ltd. is acknowledged for performing the sediment core dating and Prof F Wania for providing air samplers. This research was funded by Vetenskapsrådet (BiogeoPOP project nr 2015-04900), with additional funding from the Research Council of Norway (FANTOM project nr 231736/F20).

Three combined investigations were conducted to examine the sources of PM2.5 in agricultural areas. The first was the measurement of PM2.5 and gaseous compounds in the greenhouse, which is a relatively closed system, while the second was the analysis of pesticide components used in agricultural areas. Finally, the physical and chemical properties of PM2.5 were analyzed in an orchard area and compared with the results of the greenhouse and agricultural chemical analyses. As a result, this research was able to confirm the source of emission and characteristics of PM2.5 originating from the agricultural area. Volatile organic compounds (VOCs) in agricultural areas are emitted by agricultural chemicals, and the discharged agricultural chemicals are first absorbed into the soil, and then released into the air by evaporation. Finally, the secondary products of PM2.5 in agricultural areas were estimated to have positive relationships with the VOCs from agricultural chemicals, and NH3 from fertilizers. The photochemical reactions of VOCs and NH3 were responsible for the impact on secondary products.

Applying pruning residues in the lanes of olive groves has become a popular practice because it is economical and accrues benefits for soil and water management. This study presents an analysis of the impact of different rates of pruning residue on soil properties, in particular related with soil quality. Over 4 annual campaigns, chopped pruning residues used as a mulch were analyzed in terms of composition, coverage and moisture content to evaluate their effects on the amount of soil organic carbon (−10 cm and −20 cm) and CO2 emissions, temperature and moisture. The experiment was carried out in a super-intensive olive orchard in Cordoba (SE, Spain) and used four amounts of fresh pruning residue: 7.5 t ha⁻1(T1), 15.0 t ha⁻1 (T2) and 30.0 t ha⁻1 (T3), with a control T0 = 0.0 t ha1. Mulch mean leaf fraction was 46.0 ± 17.5% (±SD) and initial water content, 24.8 ± 8.6%. The mulching benefits for soil moisture were observed in amounts of pruning residue >7.5 t ha⁻1, which are only produced in super-intensive olive groves or in orchards with high tree densities. The low impact of the treatments on soil moisture was explained by the dramatic annual variations in residue moisture contents, caused by the regimes of high temperatures and rainfall-evapotranspiration deficits inherent to the Mediterranean Basin climate. Thus, the mulching capacity only resulted efficient when the residues were still humid in spring. In addition, 15.0 t ha⁻1 of pruning residues was the threshold to provide significant increases in soil organic carbon at depths of 0–20 cm. Thus, accumulating pruning residue in lanes at rates of over 15 t ha⁻1 (T2 and T3) is more convenient than a uniform distribution with lower amounts, due to the low mineralization rates occurring during warm seasons and the larger inputs of OM increasing the annual balance of SOC., This research was supported by the research projects CGL 2015-64284-C2-2-R, funded by the MINECO-FEDER (Spanish Ministery of Economy and Competitiveness).

We assess the 40-year climatological clear-sky global direct radiative effect (DRE) of five main aerosol types using the MERRA-2 reanalysis and a spectral radiative transfer model (FORTH). The study takes advantage of aerosol-speciated, spectrally and vertically resolved optical properties over the period 1980–2019, to accurately determine the aerosol DREs, emphasizing the attribution of the total DREs to each aerosol type. The results show that aerosols radiatively cool the Earth’s surface and heat its atmosphere by 7.56 and 2.35 Wm−2, respectively, overall cooling the planet by 5.21 Wm−2, partly counterbalancing the anthropogenic greenhouse global warming during 1980–2019. These DRE values differ significantly in terms of magnitude, and even sign, among the aerosol types (sulfate and black carbon aerosols cool and heat the planet by 1.88 and 0.19 Wm−2, respectively), the hemispheres (larger NH than SH values), the surface cover type (larger land than ocean values) or the seasons (larger values in local spring and summer), while considerable inter-decadal changes are evident. These DRE differences are even larger by up to an order of magnitude on a regional scale, highlighting the important role of the aerosol direct radiative effect for local and global climate.

The impact of crop residue burning in northeastern China on South Korean PM2.5 concentrations was assessed via weather conditions, air quality modeling (AQM), and PM2.5 composition data during two cases exceeding 35 µg·m−3 in November 2015. PM2.5 concentration simulations of Case 1 differed from observations by 3.7–17.6 µg·m−3, overestimating the levels by 6–36%, however, Case 2 varied by 20.0–59.8 µg·m−3 from observations, with a 53–91% underestimation. Case 1 was generally well simulated, whereas the Case 2 simulation failed because the emissions of crop residue burning in northeastern China, as confirmed through satellite analysis (MODIS fires and thermal anomalies) and previous research, were not considered. The portion of organic/elemental carbon ratio during Case 2 was 1.6–2.3 times higher than that of Case 1. These results suggest that it is necessary to consider the effects of crop residue burning in northeast China to establish countermeasures to improve air quality and air quality forecasting in South Korea.

The ‘4 per 1000’ initiative aims to increase soil organic carbon stocks to offset carbon dioxide emissions. For a French case study, this graphic offers evidence of the links between carbon stocks and agricultural productions at the territorial level: stocks are positively associated with animal loads, whereas soils with arable crops have much lower stocks despite a higher storage potential. Territorial mapping of both storage capacities and organic resources is needed to optimize soil carbon storage.

The relationship between soil carbon fractions in Chernozem soils was assessed in soil samples of three different environments: arable soil, grassland and oak for­est. Grassland and oak forest had higher soil organic carbon (SOC), carbon soluble in hot water (HWC), particulate organic carbon (POC) and mineral-associated carbon (MOC) than the arable soil. The POC/MOC ratio was lowest in arable soil, indicating a smaller carbon pool for microbial turnover. POC increases with higher total SOC, indicating that the pres­ervation of organic matter depends on the renewal of labile fractions. Our results showed that fertilization had active role in soil carbon stabilization, while crop rotation had less effect on a soil carbon turnover. Our result could contribute to the better understanding of SOC fractions composition and relevance in Chernozem soil, thus could help in selection of cropping management systems for SOC preservation. [Projects of the Serbian Ministry of Education, Science and Technological Development, Grant no. TR031072 and Grant no. TR031073]

The oil well drilling and oil processing industries are globally the main contaminants of environmental condition caused by human economic activities. Oil spills have a negative impact on the environment, economy, and society. In this research, the effects of oil with different chemical contents on soil types formed in two soil-climatic conditions have been studied. The purpose of this research is to study the change of soil properties by oil pollution. The experiments have been conducted in irrigated and non-irrigated soils of the desert region of the Kashkadarya and Surkhandarya (Uzbekistan). The results have shown that aggregates (0.25; 0.5; 1; 2; 3; 5; 7; 10 mm) which are the important of soil fertility have changed by oil and oil production, and the changes have proven to be temporary. The effect of the 5% and 15% concentrations of oil, engine oil, petrol, kerosene has been studied. The aggregates 0.25 mm and 0.5 mm have the biggest change among aggregates, in fact, aggregates of 0.25 mm at the level of 5% of oil decreased by 27.02%, at the level of 15% of oil decreased by 99.8%, at the level of 5% of kerosene decreased by 2%, at the level of 15% of oil decreased by 98.1%. Aggregates of 0.5 mm at the level of 5% of oil decreased by 6.44%, at the level of 15% of oil decreased by 67.14%, at the level of 5% of kerosene decreased by 12.75%, at the level of 15% of oil decreased by 92.8%. Engine oil and Petrol at levels 5 and 15 have relatively rare changed. Also, as a result of oil and oil pollution, the total carbon dioxide in the soil has grown briefly, which is an anthropogenic carbon and insignificant for soil fertility and humus. As a result, an anthropogenic carbon increased in gray-brown soil (Durisols Technic, WRB) at 0 – 35 cm layer by 0.22%, irrigated meadow-alluvial soil (Fluvisols, WRB) by 0.31%, irrigated gray-brown soil (Durisols Technic, WRB) by 0.44%, irrigated Takyr-meadow soil (Calsisols, WRB) by 0.25%, Takyr soil (Calsisols, WRB) by 0.32%, sandy Desert soil (Durisols Technic, WRB) by 0.21%.

The effects of five conservation tillage drills with crop residue levels covering between 17% and 79% of the soil, and tillage depths ranging from 25 mm to 200 mm, were examined over three years. The tillage systems ranged from a relatively disruptive Farm System to a Low Disruption system, with three intermediate treatments labelled Sumo DTS, Claydon, and Mzuri. The study involved field sites on a clay or clay loam soil, where winter wheat and oilseed rape were grown in rotation. In the clay field, the Mzuri and Low Disruption treatments, which produced the highest residue coverage, showed the greatest increase in surface total soil organic carbon (1.1 and 0.48 Mg C ha−1 respectively) between year 1 and 3. The least disruptive tillage system also resulted in the highest density of earthworms (181‐228 m−2), and the most disruptive system produced the lowest densities (75‐98 m−2). In the third year, the least disruptive system also showed a higher proportion of water stable aggregates (29.8%) than the other treatments (22.7‐25.3%). Linear regressions showed positive relationships of both soil organic carbon and earthworm density with surface residue cover, and of the proportion of water stable aggregates with soil organic carbon.

Hummocks develop by cryoturbation in fine-grained frost-susceptible soils and their stage of maturity may affect the translocation of organics in Cryosols. This study examines the distribution and morphology of hummocks in the Chuck Creek Trail Valley (northern British Columbia) and determines the quantity, distribution, and composition of organic matter in their soils. Hummocks occupy about 5%–20% of the valley and their morphology is largely affected by their silt content. Cryoturbated intrusions, radiocarbon dated to 2814 and 1648 cal year B.P., suggest that hummock development was initiated during the cooler late Holocene. Hummocks have an average soil organic carbon density of 16.3 kg m−2 in the uppermost 1 m, with 62% stored in the top 25 cm. Organics are mainly present as particulate organic matter in the O-horizon (25%–80%), characterized by degradable alkyl C and O/N-alkyl groups, but occur as mineral-associated organic matter (96%–98%) composed of recalcitrant aromatic and aliphatic C groups in the underlying B and C horizons. Minor differences in organic content and composition occur between hummock tops and troughs, and between hummocks showing different stages of maturity. In the absence of an observed frost table, contemporary hummock activity is attributed to seasonal freezing and thawing.

ISSN:0148-0227 ISSN:2169-8953 ISSN:2169-8961

International audience; The export of organic carbon export by the rivers to the oceans either as particulate organic carbon (POC) or dissolved organic carbon (DOC) is very sensitive to climate change especially in permafrost affected catchments where soils are very rich in organic carbon. With global warming, organic carbon export in both forms is expected to increase in Arctic regions. It should affect contemporary biogeochemical cycles in rivers and oceans and therefore modify the whole food web. This study tries to understand complex processes involved in sediment, POC and DOC riverine transport in the Yenisei River basin and to quantify their respective fluxes at the river outlet. The SWAT (Soil and Water Assessment Tool) hydrological model is used in this study to simulate water and suspended sediment transfers in the largest Arctic river. POC and DOC export have been quantified with empirical models, adapted from literature for the study case. First, the hydrological model has been calibrated and validated at a daily time step for the 2003–2008 and the 2009–2016 periods respectively, and its output has been compared with field data for water and sediment fluxes. Based on conceptualization of transfer processes, calibration on climate and soil properties has been performed in order to correctly represent hydrology and sediment transfer in permafrost basins. Second, calibration of empirical models for DOC/POC transport have been performed by comparing their output with field data, available from 2003 to 2016. Our study reveals that SWAT is capable of correctly representing hydrology, sediment transfer, POC and DOC fluxes and their spatial distribution at a daily timescale, and outlines the links between these fluxes and permafrost features. Our simulation effort results in specific sediment, POC and DOC fluxes of 2.97 t km−2 yr−1, 0.13 t km−2 yr−1 and 1.14 t km−2 yr−1 for the period 2003–2016 which are in the range of previous estimates. About 60% of the total fluxes of sediment, DOC and POC to the Arctic Ocean are exported during the two months of the freshet. Spatial analysis show that permafrost-free areas have returned higher daily organic carbon export than permafrost affected zones, highlighting the thawing permafrost effect on carbon cycle in climate change feedback.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior Wetlands have become a focus of international attention since 1971, with the first global conference dedicated exclusively to this topic. Since then, it has consolidated as an important area of research, thanks to its transdisciplinarity and complexity, which allows a contribution of various branches of modern science. The pedology in this context aims to understand the dynamic that contribute to the genesis and evolution of soils in these landscapes, seeking ways to rational use and methodologies to ensure minimal impact of anthropogenic use in the surrounding areas. The soil organic carbon is used as an important indicator of ecosystem sustainability, being very sensitive to short-term changes caused by changes in the middle, either natural or anthropogenic origin. The objective of this research was to identify the standard accumulation of organic carbon within the wetland, analyzing both vertically, with different depths of analysis, or horizontally, with the points distributed from the toposequence, relating them to the dynamics of groundwater and soil physical properties. The survey was conducted on the upper course plateau of Uberabinha River, located between the cities of Uberlândia and Uberaba. Minas Gerais, administrative region of Triângulo Mineiro and Alto Paranaíba. Brazil. The organic carbon was quantified from the combustion method, while the humic fractions were quantified by the differential solubility and titration method. Six points were distributed in topossequence, with four collection depths: 0-10; 10-20; 20-30; and 30-50 cm. Carbon percentage found in the study area ranged from 1.7% to 17.7%, preferably concentrating on points downstream and closer to the surface. As groundwater moves away from the surface and the oxidation condition of organic matter is taken up, the carbon content decreases. In humin fraction, organic carbon has shown a similar dynamics to the total organic carbon, concentrating more on the surface and decreasing according to the groundwater debasement; in the fraction of humic acid, the organic carbon percentage ranged from 0.4% to 2 7%, with a different dynamic observed in the total organic carbon, due to its solubility conditions; and in the fraction of fulvic acid, organic carbon ranged from 0.1% to 2.4%. Through research, it was evident the influence of humidity on the decomposition of organic matter, showing that any change in average levels of groundwater have a major impact on the dynamics and processes involving the mineralization of organic carbon in plateau wetlands. As áreas úmidas se tornaram foco da atenção internacional desde 1971, com a primeira conferência mundial voltada exclusivamente para esse tema. Desde então, vem se consolidando como uma importante área de pesquisa, graças principalmente à sua transdisciplinaridade e complexidade, o que permite a contribuição de diversos ramos da ciência moderna. A pedologia nesse contexto visa compreender as dinâmicas que contribuem para a gênese e evolução dos solos nessas paisagens, buscando formas de utilização racional e metodologias para assegurar o mínimo impacto do uso antrópico nas áreas circundantes. O carbono orgânico do solo é utilizado como um importante indicador de sustentabilidade do ecossistema, sendo bastante sensível a mudanças de curto prazo provocadas por mudanças no meio, sejam elas de origem natural ou antrópica. O objetivo desta pesquisa foi identificar os padrões de acumulação de carbono orgânico dentro da área úmida, analisando tanto na vertical, com as diferentes profundidades de análise, quanto na horizontal, com os pontos distribuídos a partir da topossequência, relacionando-os com a dinâmica do lençol freático e as propriedades físicas do solo. A pesquisa foi realizada na chapada do alto curso do Rio Uberabinha, localizada entre os municípios de Uberlândia e Uberaba/MG, na região administrativa do Triângulo Mineiro e Alto Paranaíba. O carbono orgânico foi quantificado a partir do método de combustão, enquanto as frações húmicas foram quantificadas por meio do método de solubilidade diferencial e titulação. Foram distribuídos seis pontos em topossequência com quatro profundidades de coleta: 0-10; 10-20; 20-30; e 30-50 cm. Os teores de carbono encontrados na área de estudo variaram de 1,7% a 17,7%, concentrando preferencialmente nos pontos mais à jusante e mais próximos à superfície. Conforme o lençol freático se distancia da superfície e a condição de oxidação da matéria orgânica é retomada, os teores de carbono decrescem. Na fração humina, o carbono orgânico apresentou uma dinâmica semelhante à do carbono orgânico total, concentrando mais em superfície e decrescendo de acordo com o rebaixamento do lençol; na fração do ácido húmico, o teor de carbono orgânico variou de 0,4% a 2,7%, com uma dinâmica diferente da observada no carbono orgânico total, devido às suas condições de solubilidade; e na fração do ácido fúlvico, o carbono orgânico variou de 0,1% a 2,4%. Com a pesquisa, ficou clara a influência da umidade sobre a decomposição da matéria orgânica, mostrando que qualquer alteração nos níveis médios do lençol freático tem grande impacto nas dinâmicas e nos processos envolvendo a mineralização do carbono orgânico das áreas úmidas da chapada. Mestre em Geografia

Extra virgin olive oil is considered worldwide as one of the most important products, a standard bearer of the Mediterranean diet. Despite this, the production chain of extra virgin olive oil generates four times more waste than quantity of oil. For this reason, the disposal of olive mill wastes represents a significant environmental problem in all the Mediterranean countries. In this direction, several innovations and improvement strategies were proposed in the literature to correctly manage these by-products and, in some cases, to valorize them by the recovery of polyphenols and other interesting substances. However, innovations and improvement strategies for the valorization of olive tree leaves are definitely neglected in the literature, thus motivating this work. The aims of this work are as follow: firstly, to develop and test an innovative olive tree leaves shredder prototype to help olive oil millers in the management of waste leaves deriving from pruning and olive oil production; secondly, to test the combination of the minced olive tree leaves with other by-products in the production of high-quality compost. The results showed the effectiveness of the tested olive tree leaves shredder in significantly reducing the volume occupied by the leaves by 40%. Moreover, the mixing of the minced olive tree leaves with other by-products lead to a high-quality compost which, in accordance with Italian legislation, could even be certified and labeled with this denomination. Future research will investigate the quantification of the benefits in terms of environmental impacts using life cycle assessment.

Very little is known about the changes that occur in soil organic carbon (SOC) and total nitrogen (TN) under an intensive rice-based cropping system following the change to minimal tillage and increased crop residue retention in the Gangetic Plains of South Asia. The field experiment was conducted for 3 years at Rajbari, Bangladesh to examine the impact of tillage practices and crop residue retention on carbon (C) and nitrogen (N) cycling. The experiment comprised four tillage practices—conventional tillage (CT), zero tillage (ZT), strip-tillage (ST), and bed planting (BP) in combination with two residue retention levels—increased residue (R50%) and low residue (R20%—the current practice). The TN, SOC, and mineral N (NH4+-N and NO3−-N) were measured in the soil at different crop growth stages. After 3 years, ZT, ST, and BP sequestered 12, 11, and 6% more SOC, and 18, 13, and 10% more TN, respectively than the conventional crop establishment practice at 0–5 cm soil depth. The accumulation of SOC and TN was also higher compared to the initial SOC and TN in soil. Among the tillage practices, the maximum SOC and TN sequestration were recorded with ST and with R50% that might be attributed to reduced mineralization of C and N in soil particularly with increased residue retention, since decay rates of potentially mineralizable C was lower in the ST with both the residue retention practices. Increased residue retention and minimum tillage practices after nine consecutive crops has altered the C and N cycling by slowing the in-season turnover of C and N, reducing the level of nitrate-N available to plants in the growing season and increasing retained soil levels of SOC and TN.

Resumen: Dada la Influencia en la explotación agrícola de los atributos físicos de los suelos, es necesario su estudio geoestadístico, con el fin de conocer la distribución y variabilidad que poseen, y su efecto sobre las restantes características del suelo. Por lo anterior, se realizó la medición de 80 puntos en un transecto de la granja de la Universidad Pedagógica y Tecnológica de Colombia. Se analizó la densidad real (Dr), la densidad aparente (Da), la porosidad total (PT), el contenido de carbono orgánico (CO), el tamaño de las partículas y la infiltración básica (Ib), mediante un análisis descriptivo, geoestadístico y multivariado. Las propiedades físicas que presentaron los menores coeficientes de variación (cv) fueron la Dr (7,50%) y la Da (4,33%). Todas las variables evaluadas mostraron bajo cv, a excepción de la Ib. Los valores de CO de la granja son muy bajos (1,97 %). La Dr, el CO y la PT se ajustaron a semivariogramas lineales y tuvieron los mayores rangos (75 m). La arcilla se correlacionó negativamente con la arena y el limo; mientras que la PT tuvo correlación directa con la Dr, e inversa con la Da. La porosidad y el tamaño de partículas tienen gran influencia en la varianza de las propiedades físicas de los suelos de la granja, de acuerdo con el análisis de componentes principales. Probablemente, la ganadería intensiva practicada allí afecta la porosidad y la Dr, lo que disminuye la Ib y aumenta la compactación del suelo. Abstract: Given the influence on the agricultural exploitation of the physical properties of soils, it is necessary to study its geo-statistics to know their distribution, variability, and their effect on the remaining soil properties. 80 points were measured in a transect of a farm belonging to the Universidad Pedagógica de Colombia. True density (Td), apparent density (Ad), total porosity (Tp), organic carbon content (OC), particle size and basic infiltration (Bi) were analyzed using a descriptive, geostatistical, and multivariate analysis. The physical properties with the lowest coefficients of variation (cv) were Td (7.50 %) and Ad (4.33 %). All variables showed a low cv, saved the Bi. OC farm values are very low (1.97 %). Td, OC and TP were adjusted to linear semi-variograms and showed the highest ranges (75 m). Clay correlated negatively with sand and lime; while the TP correlated directly with Td, and inversely with Ad. Porosity and particle size have a large influence on the variance of the physical properties of the farm soils, as per the analysis of the main components. It is possible that intensive cattle farming affect the porosity and Td, which decreases the Bi and increases soil compaction.

Lake carbon burial is of vital significance in global carbon cycle and carbon budget, particularly in the large deepwater lakes. However, carbon burial in large deepwater lakes is hard to estimate due to the difficulty in obtaining high spatial-resolution samples. In this study, we investigated distributions of total organic carbon (TOC) and inorganic carbon (TIC), two main carbon components in lake sediments, based on dozens of surficial sedimentary samples (n= 26) covering whole Lake Qinghai, the largest saline lake in China. The results showed that the TOC content, with a range of 1.4–4.8%, was significantly higher in the lake area near the northern lakeshore where human activities are concentrated and lower in the lake areas near the Buha River mouth and the eastern lake area. In contrast, the TIC content, ranging from 1.5 to 3.8%, increased from the northwestern and southeastern lake areas toward the lake center, and mainly depended on hydro-chemical and hydraulic characteristics. The inorganic carbon burial (47.77 ± 19.73 Gg C yr−1) was approximately equal to organic carbon burial (47.50 ± 22.68 Gg C yr−1) and accounted for about 50% of the total carbon burial (95.27 ± 37.74 Gg C yr−1), suggesting that saline lakes constitute a large inorganic carbon pool in addition to an organic carbon pool. Because of saline water body type in arid and semiarid regions and alpine Qinghai–Tibet Plateau, lakes in these regions have huge inorganic carbon burial potential and important contributions to the global carbon budget.

Within the content of this thesis, I aim to qualitatively and quantitatively assess the driving mechanisms and consequences of marine deoxygenation and CORG burial in a greenhouse world (Fig. 1.5). The focus lies on instances of locally and globally enhanced deoxygenation (Fig. 1.6): the Holocene Baltic Sea (Chapter 2), three sapropels deposited in the Pliocene and Quaternary Mediterranean Sea (Chapter 3), the PETM (Chapters 3 and 4), OAE2 (Chapters 3 and 5) and Toarcian Oceanic Anoxic Event (Chapter 3). Key questions I aim to answer are the causes of deoxygenation on a local (Chapter 2) and global (Chapter 4) scale, the controls of P mineral formation on P recycling under anoxia (Chapter 3) and the global impact of enhanced redox-driven P recycling (Chapters 3 ‒ 5), and the effect of redox-driven CORG burial on the global carbon cycle (Chapters 4 and 5). In order to unravel the causes of extensive deoxygenation and its impact on CORG burial, I paired new geochemical and palynological sediment analyses, with the analysis of existing data sets and biogeochemical box modelling. In summary, this thesis provides a framework for the causes and consequences of marine deoxygenation and CORG burial. Warming, both regional (Chapter 2) and global (Chapters 3 and 4), promotes the loss of dissolved O2 from ocean waters and the accumulation of CORG in marine sediments. Deoxygenation enhances P recycling relative to CORG. This recycling was more pronounced during greenhouse periods than at present (Chapters 2 – 4). During the PETM (Chapter 4) and OAE2 (Chapter 5), the geochemical cascade leading to the buildup of CORG in marine sediments was caused by increased CO2 emissions. The burial of CORG had a profound effect on the exogenic carbon cycle, resulting in the drawdown of CO2 from the atmosphere. The findings presented in this thesis provide indications for the possible future evolution of marine biogeochemical cycles. The projected increase in temperature (IPCC, 2013) will lead to loss of O2 from open ocean waters, while it may also hinder the recovery of coastal areas (e.g. the Baltic Sea) from deoxygenation, upon nutrient input reductions (Chapter 2). Acidification will not only affect calcifying organisms and marine alkalinity, but may enhance P recycling and, hence, eutrophication (Chapter 3). As the oceans warm and CaCO3 dissolution spreads into more areas of the deep ocean (e.g. Sulpis et al., 2018), P recycling from deep marine sediments may increase. The impact of CORG burial on atmospheric CO2 (Chapters 4 and 5), even during a mild deoxygenation event such as the PETM (Chapter 4), underlines the importance of including this process and its causes in global biogeochemical and climate models when assessing the lifetime of our emissions in the atmosphere.

18 pages, 10 figures, 5 tables, supplementary material https://doi.org/10.1016/j.gca.2021.04.021, Burial fluxes of organic carbon and biogenic silica were determined in 17 continental shelf sediment cores collected from the northern Weddell Sea, the Bransfield Strait, and the southern Drake Passage. Coring sites included open-shelf stations as well as slope and glacial trough environments, with water depths varying from 220 to 760 m. Apparent 210Pb accumulation rates from these cores ranged from 0.04 g m−2y−1 to 0.21 g m−2y−1 (1 to 3 mm y−1), with organic carbon burial rates ranging from 3 to 15 g OC m−2y−1 and biogenic silica accumulation rates ranging from 15 to 126 g SiO2 m−2y−1. OC contents below the surface mixed layer ranged from 0.26 to 1.51 wt. % (avg. 0.64 %). Biogenic silica contents at depth ranged from 2.3 to 11.2 wt. % (avg. 7.5%), with an average bSi/OC ratio (wt. %/wt. %) at depth of 12. Annual OC primary production rates and biogenic silica production rates in the euphotic zone were estimated from satellite chlorophyll-a data in the literature and from a seasonal model for biogenic particle export from surface waters. Based on these biogeochemical data, preservation efficiencies (i.e., mass burial rate/water column production rate) were calculated for organic carbon and biogenic silica. These preservation efficiency values ranged from 2 to 18% (avg. 9%) for OC and 8 to 106% (avg. 54%) for bSi. These relatively high preservation efficiencies resulted from extensive lateral sediment focusing (210Pb Psi (Ψ) values [burial flux/water column production rate] ranging from 2 to 33; avg. of 16), cold bottom water temperatures (2 to −2°C), and relatively high biogenic Si and OC production rates in the euphotic zone. The enhanced preservation efficiency for bSi relative to OC (i.e., 54% vs. 9%) in these Antarctic settings is consistent with the change in the phytoplankton bSi/OC (wt. %/wt. %) value of 2 for this area to the burial bSi/OC value of 12. Excess 210Pb activities in surface sediments varied from 4 to 47 dpm g−1. The surface mixed layer in the seabed varied in thickness from 0 to 4 cm. The penetration of excess 210Pb into these Antarctic Peninsula sediments varied from 6 to 28 cm (avg. 18 cm). The inventory of excess 210Pb in the seabed varied from 13 to 230 dpm cm−2 (avg. 110 dpm cm−2). Although 210Pb was the only radionuclide measured in this study, “apparent” 210Pb sediment accumulation rate (SAR) values from these 17 cores (assuming that deep bioturbation is negligible) are believed to be accurate SAR values because of good agreement between 210Pb and 14C chronologies from nearby cores reported in the literature, This work was funded by the Spanish Ministry of Economy and Competitiveness as part of the project ECOWED (CTM2012-39350-C02-01), With funding from the Spanish government through the ‘Severo Ochoa Centre of Excellence’ accreditation (CEX2019-000928-S)

Offshore windfarms (OWFs) offer part of the solution for the energy transition which is urgently needed to mitigate effects of climate change. Marine life has rapidly exploited the new habitat offered by windfarm structures, resulting in increased opportunities for filter- and suspension feeding organisms. In this study, we investigated the effects of organic matter (OM) deposition in the form of fecal pellets expelled by filtering epifauna in OWFs, on mineralization processes in the sediment. OM deposition fluxes produced in a 3D hydrodynamic model of the Southern Bight of the North Sea were used as input in a model of early diagenesis. Two scenarios of OWF development in the Belgian Part of the North Sea (BPNS) and its surrounding waters were calculated and compared to a no-OWF baseline simulation. The first including constructed OWFs as of 2021, the second containing additional planned OWFs by 2026. Our results show increased total mineralization rates within OWFs (27–30%) in correspondence with increased deposition of reactive organic carbon (OC) encapsulated in the OM. This leads to a buildup of OC in the upper sediment layers (increase by ∼10%) and an increase of anoxic mineralization processes. Similarly, denitrification rates within the OWFs increased, depending on the scenario, by 2–3%. Effects were not limited to the OWF itself: clear changes were noticed in sediments outside of the OWFs, which were mostly opposite to the “within-OWF” effects. This contrast generated relatively small changes when averaging values over the full modeling domain, however, certain changes, such as for example the increased storage of OC in sediments, may be of significant value for national / regional carbon management inventories. Our results add to expectations of ecosystem-wide effects of windfarms in the marine environments, which need to be researched further given the rapid rate of expansion of OWFs.

Highlights • Participation of local stakeholders is important part of sustainability assessments. • Scale of implementation can determine whether the benefits to outweigh the costs. • Implementation of innovations can be less sustainable than current systems. • Stakeholders did not prioritize technical performance of innovations. Sustainability assessments can be a powerful tool in decision-making regarding technical innovations. In this study, a sustainability assessment of technical systems for recovering nutrients and carbon from domestic wastewater is presented. Multi-criteria analysis was used to calculate a sustainability score of three different technical systems compared to a baseline in two case-studies: the Fyriså river catchment in Sweden and the Słupia river catchment in Poland. Two participatory workshops with local stakeholders were held in each case-study, the first to co-develop the system alternatives and sustainability criteria and the second to collect stakeholder weighting of the criteria. Although the systems assessed in both case studies were similar, the resulting sustainability scores were different. In Fyris, although the differences in scores was small, the preferred alternative was introduction of source-separation followed by a large redesign of the treatment and phosphorus extraction from incinerated sludge was the least sustainable alternative. For the Słupia systems the scores varied more, and the preferred system was a large redesign of the wastewater treatment followed by ammonia stripping of the reject water and the source-separation alternative received the lowest score. In both case-studies, the more costly system received highest sustainability score indicating the large potential benefits of enhancing resource recovery from domestic wastewater. Stakeholders did not prioritize technical aspects over the other sustainability criteria, yet most of research on resource recovery interventions is focused on technical performance.

The off-site effects of agricultural organic soils include the leaching of N, P, and organic carbon (OC) to watercourses and CO2, CH4, and N2O emissions into the atmosphere. The aim of this study was to quantify how the thickness of organic layers affects these loads. A 19.56-ha experimental field drained by subsurface pipes was established in Ruukki, northwestern Finland. Three plots had a 60–80 cm-thick sedge peat layer and three others had a thickness of 20 cm or less. The drainage pipes lie in mineral soil that, in this field, contains sulfidic material. This study documents the experimental settings and reports on the leaching of substances in the first two years, as well as CO2, CH4 and N2O emissions during eight weeks in one summer. Total N (TN) and OC loads were higher from the thicker peat plots. The mean TN loads during a hydrological year were 15.4 and 9.2 kg ha-1 from the thicker and thinner peat plots, respectively, with organic N representing 36% of TN load. Total P (TP) load averaged 0.27 kg ha-1 yr-1. Dissolved P load represented 63 and 36% of TP in the thicker peat area and only 23 and 13% in the thinner peat area, and was thus increased upon peat thickness. These N and P loads through the subsurface drainage system represented roughly 83% of TN and 64% of TP loads from this field. There were no clear differences in greenhouse gas emissions among the plots during the eight-week monitoring period. Slowly oxidizing sulfide in the subsoil resulted in annual leaching of 147 kg S ha-1, almost ten times that of non-sulfidic soils. Our first results emphasize the effect of the peat thickness on the leaching of substances and warn about considering all organic soils as a single group in environmental assessments.

The aim of this work was to evaluate the effect of the land use change (CUS) of a Ñadi soil (Aquands) from secondary forest to naturalised grassland, on the aggregate stability (tensile strength and shrinkage capacity) and its relationship with the soil water tension (drying effect), the wetting capacity and the soil organic carbon. The site belongs to the Alerce soil series. The research unit consists of four land uses: Renewal Alerce Forest (BN1), a secondary native forest (BN2), naturalised pasture 1 (PN1, without mole drainage), and naturalised pasture 2 (PN2, with mole drainage). Four soil depths were sampled at each site. Total porosity (PT), plant available water (ADP), air capacity (CA), aggregate shrinkage capacity (COLE), mechanical resistance (Crushing Test method), repellency index (Sorptivity) and soil organic carbon (CO) were determined. CUS in Aquands alters the water regime causing a loss of PT (down to 28% in H1) and 30% of ADP in the surface horizons (H1 and H2), which restricts the shrinkage capacity of aggregates. Although all the aggregates in every site shrink due to water loss, PN1 and PN2 show less shrinkage (COLE > 0.15) due to lower PT and higher bulk density (0.53 Mg m-3). The intensification of land use causes changes in the CO content of the soil, which decreases as the depth increases (27% to 5%) in all soil uses evaluated., El cambio de uso de suelo (CUS) de bosque nativo a pradera naturalizada reduce el volumen de macroporos e incrementa la resistencia mecánica de los Aquands (Ñadi). El objetivo de este trabajo fue evaluar el efecto del CUS sobre la estabilidad de los agregados y su relación con la capacidad de humectación y el contenido de carbono orgánico en un suelo Ñadi (Duric Histic Placaquands). Cuatro usos de suelo fueron evaluados: Renoval de bosque de Alerce (BN1), bosque nativo secundario (BN2), pradera mejorada sin drenaje topo (PN1) y pradera mejorada con drenaje topo (PN2). Se colectaron agregados a cuatro profundidades de muestreo por cada sitio. Se determinaron: la porosidad total (PT), el agua disponible para las plantas (ADP), la capacidad de aire (CA), la contracción de los agregados (COLE), la resistencia mecánica (Crushing test), el índice de repelencia (Sortividad), y el carbono orgánico (CO) del suelo. El CUS en Aquands, altera el régimen hídrico provocando una pérdida de la PT (hasta un 28% en H1) y de un 30% del ADP en los horizontes superficiales (H1 y H2), lo que restringe la capacidad de contracción de los agregados. Si bien todos los agregados de todos los sitios se contraen debido a la pérdida de agua, PN1 y PN2 presentan una menor contracción (COLE > 0,15) debido a una menor PT y a una mayor densidad aparente (0,53 Mg m−3). La intensificación de uso de suelo provoca cambios en el contenido del CO del suelo, la cual disminuye conforme aumenta la profundidad (27% a 5%) en todos los usos de suelos evaluados.

Anthropogenic land use change (LUC) affects soil quality and the global carbon (C) pool. Such LUC is a potential threat for forest ecosystems because it can alter soil biome and increases the emission of greenhouse gasses (GHGs). Here, we investigated the changes in soil quality and CO2 emission following afforestation of reclaimed coal mine land and agriculture land created in a tropical dry deciduous forest of Jharkhand, India. Soil samples were collected from afforested mined soil (AMS), agriculture soils (AGS), and the natural forest soils (NFS) and analyzed for physicochemical and biological properties. Soil infiltration rate and CO2 efflux were recorded in situ, and C balance and emission coefficient (Ci) were calculated to determine soil C dynamics. Our results demonstrated significant alteration in soil quality parameters (decreases/increases based on the individual parameter) in converted land use. Compared to NFS, soil organic carbon (SOC) stocks decreased by 84% in AMS and 50% in AGS, soil CO2 efflux increased by 35% in AGS and decreased by 43% in AMS, attributed to differences in vegetation and microbial activities among sites. Principal component analysis showed soil infiltration rate, total nitrogen, and clay content were highly influenced by the LUC and explicitly indicate soil quality. The 4-year old AMS was C negative and had a greater Ci value than AGS and NFS, probably due to the lesser vegetation cover and adverse soil properties. We concluded that the conversion of tropical forests to different lands altered soil quality that can be assessed using indicator parameters like soil infiltration rate, total nitrogen, and clay content. Such LUC tends to switch the forest from a sink to a source of CO2 whether the end use is afforestation or agriculture. However, land degradation due to surface mining activities had a greater impact on soil quality and C sequestration potential than agriculture. © 2021 The Author(s) The authors are thankful to the Indian Institute of Technology (Indian School of Mines) Dhanbad India for providing research facilities and Central Coalfield Limited, Ranchi for providing a site to study. AK acknowledges the work support by RFBR, Russia (Project No. 19-516-45006) and the Ministry of Science and Higher Education of the Russian Federation (Agreement no. 02.A03.21.0006). We are also thankful to the Editor and anonymous reviewers for thoughtful suggestions and comments on this article.

The rice–wheat cropping system (RWCS) has substantially contributed in making India self-sufficient in food grain production; however, rice residue management is of great concern, threatening the sustainability of this system. Rice residue is invariably disposed of by farmers through open burning. In addition to environmental pollution, residue burning of rice also leads to loss of soil nutrients. One of the alternatives to overcome these problems and sustain the RWCS is managing the rice residues in the field itself. Rice residue retention has variable effects on agricultural pests (namely, weeds, insect pests, diseases, and rodents) in the RWCS. High weed infestation in the RWCS results in high consumption of herbicides, which leads to several ecological problems and evolution of herbicide resistance. The shift from intensive tillage to conservation tillage causes major changes in weed dynamics and herbicide efficacy. Incorporation of rice residue reduces weed density and helps in improving soil physical, chemical, and biological properties. Rice residue retention on the surface or mulching reduces weed density and the biomass of both grass and broadleaf weeds in wheat crop as compared to its removal. Long-term field studies involving the use of rice residue as a component of integrated weed management strategies are needed to be done in the RWCS.

This work was supported by Marine Scotland through the Blue Carbon Forum. Additional support from the NERC Life Sciences Mass Spectrometry Facility (CEH_L_115_05_2018) allowed additional analytical work to be undertaken. BGS provided access to samples through their In-kind sample loan scheme (Loan: 273227). Continental shelf sediments are recognized as long-term stores of globally significant quantities of carbon (C) and potentially provide an important, yet largely overlooked climate regulation service via the Earth’s C cycle. Current understanding of the spatial distribution of sedimentary C across continental shelves remains poor, inhibiting the targeted management and potential inclusion of these globally significant C stores into national C budgets. Further understanding of the spatial heterogeneity of continental shelf sediments and associated C provides a foundation to quantify the organic carbon (OC) stock and better understand the role that marine sediments play in regulating the global climate and the potential for CO2 to be released through anthropogenic disturbance of these C stores. Utilizing a spectrum of available marine data, we have created bespoke sediment maps that quantify the surficial (top 10 cm) OC stock and highlight significant spatial heterogeneity in the distribution of sediments and their associated C content across the United Kingdom’s Exclusive Economic Zone (EEZ). The surficial sediments within the UK EEZ are estimated to store 524 ± 68 Mt of organic carbon (OC) and 2,582 ± 168 Mt of inorganic carbon (IC). The spatial mapping of this C highlights well-defined OC accumulation hotspots in fjords, estuaries and coastal muds, while large accumulations of IC are found in the tidally swept areas around Orkney, Shetland and the South West of England. Within the well-defined OC hotspots, muddy sediments store the greatest quantity of OC; the muds offer potentially valuable opportunities for targeted future management and protection of sedimentary C stores within the UK EEZ. In the future, if areas of the seafloor were to be managed to include the protection of these valuable sedimentary C resources, we recommend an initial focus on hotspots of high sedimentary OC density. Publisher PDF

Streams and rivers integrate and transport particulate organic carbon (POC) from an array of aquatic and terrestrial sources. Storm events greatly accelerate the transport of POC. The sequences by which individual POC inputs are mobilized and transported are not well-documented but are predicted to be temporally transient and spatially dependent because of changes in forcing functions, such as precipitation, discharge, and watershed morphology. In this study, the 3rd−4th order agricultural stream network, Clear Creek in Iowa, U.S.A., was sampled at a nested series of stations through storm events to determine how suspended POC changes over time and with distance downstream. Carbon and nitrogen stable isotope ratios were used to identify changes in POC. A temporal sequence of inputs was identified: in-channel algal production prior to heavy precipitation, row crop surface soils mobilized during peak precipitation, and material associated with the peak hydrograph that is hypothesized to be an integrated product from upstream. Tile drains delivered relatively 13C- and 15N-depleted particulate organic carbon that is a small contribution to the total POC inventory in the return to baseflow. The storm POC signal evolved with passage downstream, the principal transformation being the diminution of the early flush surface soil peak in response to a loss of connectivity between the hillslope and channel. Bank erosion is hypothesized to become increasingly important as the signal propagates downstream. The longitudinal evolution of the POC signal has implications for C-budgets associated with soil erosion and for interpreting the organic geochemical sedimentary record.

The burial of organic carbon (OC) in the river-dominated margin plays an important role in global carbon cycle, but its accumulation mechanism is not well understood. Here, we examined the concentration and distribution of water-extractable organic matter (WEOM) and base-extractable organic matter (BEOM) in surface sediments from the lower Yangtze River, estuary, and the East China Sea. Chemical characteristics of the WEOM and BEOM were described by multiple ultraviolet-visible and fluorescence spectral indicators. Concentrations of both WEOM and BEOM showed significant correlations with sediment grain size, suggesting that mineral surface area is a key factor for OC loadings on sediments. Three components (C1, C2, and C3) extracted from fluorescence excitation emission matrices-parallel factor analysis were assigned as terrigenous humic-like substance, mixed terrigenous/aquatic humic-like substance, and microbial protein-like substance, respectively. From the lower Yangtze River to the East China Sea, the C1%, specific UV absorbance at 254 nm (SUVA254), and humification index (HIX) of the WEOM decreased, while the C3%, fluorescence index (FI), and biological index (BIX) of the WEOM increased. This suggested the loss of terrigenous OC and addition of microbial OC in the WEOM. While for BEOM, the overall increase of C1% and HIX and the decrease of C3% and FI suggested selective removal of microbial OC and preferential preservation of terrigenous OC. Our study demonstrates complex behaviors of sediment organic matter (OM) during the land-to-sea transport that is largely controlled by the binding strength of OM–sediment association, and that the formation of BEOM is an important pathway for accumulation of terrigenous OM in the river-dominated margin.

Carbonaceous matter, including organic carbon (OC) and black carbon (BC), is an important climate forcing agent and contributes to glacier retreat in the Himalayas and the Tibetan Plateau (HTP). The HTP – the so-called “Third Pole” – contains the most extensive glacial area outside of the polar regions. Considerable research on carbonaceous matter in the HTP has been conducted, although this research has been challenging due to the complex terrain and strong spatiotemporal heterogeneity of carbonaceous matter in the HTP. A comprehensive investigation of published atmospheric and snow data for HTP carbonaceous matter concentration, deposition and light absorption is presented, including how these factors vary with time and other parameters. Carbonaceous matter concentrations in the atmosphere and glaciers of the HTP are found to be low. Analysis of water-insoluable organic carbon and BC from snowpits reveals that concentrations of OC and BC in the atmosphere and glacier samples in arid regions of the HTP may be overestimated due to contributions from inorganic carbon in mineral dust. Due to the remote nature of the HTP, carbonaceous matter found in the HTP has generally been transported from outside the HTP (e.g., South Asia), although local HTP emissions may also be important at some sites. This review provides essential data and a synthesis of current thinking for studies on atmospheric transport modeling and radiative forcing of carbonaceous matter in the HTP.