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[Display omitted] • Adjusting different reaction temperatures of HTL, platform chemical and bio-oil fuel were produced. • The bio-oil yield of paper mill sludge reaches 44 wt% at 340℃. • The main composition aldehyde and ketone substances accounted for more than 40 %. As a kind of industrial hazardous solid waste, paper mill sludge (PMS) was hard to treated by conventional process because of its high moisture, high organic content and and high environmental risk. The hydrothermal liquefaction (HTL) shows excellent potential for the conversion to a wide variety of organic matter with high water contents including various kinds sludge into fuels or value-added chemicals. In this paper, the liquefaction potential for PMS under different reaction temperatures were investigated, and the products were classified into several main components based on the results of GC-MS. The results showed that the highest yield of bio-oil was 44 % (wt/wt dry PMS without ash) at 340 °C with simply compound composition. And the bio-oil product has above 26 % long chain hydrocarbon and 22 % cycloketones. It has potential for conversion to biomass platform compounds. It can be used as bio-fuel for heat recovery of alkali recovery system of paper mill. So, adjusting different reaction temperatures of HTL, the properties of products can meet the different requirements for platform chemical and/or bio-oil fuel. [ABSTRACT FROM AUTHOR]

The improvement of batch photofermentative biohydrogen production was investigated using ultrasonication pre-treatment on a combined effluent of palm oil and pulp and paper mills. The effects of the amplitude (30–90%) and ultrasonication duration (5–60 min) were investigated in terms of their influences on the biohydrogen yield and chemical oxygen demand (COD) removal. The recommended ultrasonication parameters were found at the higher ranges of amplitude and duration (A70T45). Using A70T45 ultrasonication, the production of biohydrogen at 30 °C could be enhanced up to 8.72 mL H 2 /mL medium , with a total COD removal of 36.9%. During pre-treatment at A70T45, an energy input of 775 J/mL was supplied to disintegrate complex compounds into simpler structures. As a result, an increase in the soluble organic matter concentration was achieved, which led to enhanced biohydrogen production. On the other hand, the lowest biohydrogen yield (4.67 mL H 2 /mL medium ) and total COD removal (28.8%) were obtained in the control without pre-treatment. The enthalpy of the photofermentation process was estimated to be 141.1 kJ/mol with a threshold temperature of 30.9 °C based on a modified Arrhenius approach. [ABSTRACT FROM AUTHOR]

The paper industry is one of the most significant industrial branches that contributes to water pollution. Recent studies regarding the chemical composition of wastewaters from modern paper production sites are sparse, and organic contaminants originating from this source may remain undetected and uncontrolled. Therefore, for this study, non-target screening analyses of wastewaters from five different paper production sites were performed, including an extended analysis of one facility, for the identification of volatile non-polar to semi-polar organic contaminants. The identified contaminants were also traced in the adjacent river. Several specific agents related to paper production, including photoinitiators, ink and thermal paper constituents, were present in most wastewaters and were therefore considered to be characteristic paper industry contaminants. A couple of contaminants identified in this study are being reported for the first time and might be toxic, but have been neglected in previous studies. Bisphenol A and 2,4,7,9-tetramethyl-5-decyne-4,7-diol were found in untreated wastewaters, treated wastewater and in river water. Bisphenol A was present in river water downstream from where the paper industry discharges at a concentration that was reported to affect the reproduction of gastropods. Thus, our findings imply that paper industry discharges pose a risk to the populations of sensitive macroinvertebrates. [ABSTRACT FROM AUTHOR]

Several dengue epidemics recently occurred in La Reunion, an island harboring two dengue viruses (DVs) vectors: Aedes albopictus, and Ae. aegypti, the former being the main local DV vector. Aedes aegypti shows a peculiar ecology, compared to other tropical populations of the same species. This study aimed to provide researchers and public-health users with locally validated oviposition traps (ovitraps) to monitor Aedes populations. A field experiment was performed in Saint-Joseph to assess the effect of different settings on the detection probability and apparent density of Aedes mosquitoes. Black plastic ovitraps were identified as the best choice. Vacoa trees (Pandanus utilis) were the only observed breeding sites for Ae. aegypti, shared with Ae. albopictus. They were the experimental units in a Latin square design with three factors: trap position in the trees (ground vs canopy), oviposition surface in the trap (blotting paper vs. vacoa leaf), and addition of organic matter to the trap water. The latter factor was found unimportant. On the ground, Ae. aegypti eggs were only found with vacoa leaves as the oviposition surface. Their detection and apparent density increased when ovitraps were located in the tree canopy. The main factor for Ae. albopictus was the oviposition surface, with a preference for blotting paper. In all trap settings, their detection was close to 100%. Larval survival was lower for a high egg density, combined with blotting paper as the oviposition surface. When monitoring mixed Aedes populations in La Reunion, we recommend using black plastic ovitraps, placed at 1.50-to-2.00-m high in vacoa trees, with vacoa leaves as the oviposition surface. [ABSTRACT FROM AUTHOR]

The sea surface microlayer (SML) is an important biogeochemical system whose physico-chemical analysis often necessitates some degree of sample storage. However, many SML components degrade with time so the development of optimal storage protocols is paramount. Using freshwater and saline SML samples from a river-estuary, we interrogated temporal changes in surfactant activity (SA) and the absorbance and fluorescence of chromophoric dissolved organic matter (CDOM) over four weeks, following selected sample treatment and storage protocols. Some variability in the effectiveness of individual protocols most likely reflects sample provenance. None of the various protocols examined performed any better than dark storage at 4°C without pre-treatment. We thus recommend this as the optimal strategy, coupled with minimal storage times as far as practicable. Future studies of SML properties should validate their chosen storage protocols independently. [ABSTRACT FROM AUTHOR]

Abstract: Here we report multiple parameters used to describe the diagenetic state of sediments, including total hydrolyzable amino acid (THAA), amino acid enantiomer, chlorin (CI) and amino acid degradation (DI, RI) indices, along a transect between the Upper St. Lawrence Estuary and the Gulf of St. Lawrence, Canada. The study area is characterized by gradients in water oxygen concentration, water depth, organic matter (OM) source, primary productivity, and sedimentation rate. Both CI and DI indicate a decline in OM reactivity, with the transition from a more terrestrial to a more marine-dominated sedimentation regime as one moves from the shallow Upper Estuary (23–95 m) to the hypoxic, mid-depth Lower Estuary and to the deep (>400 m), well-oxygenated Gulf. Whereas the CI more accurately reflected OM reactivity in surface sediments and sediments down to 5 cm, the amino acid-based degradation indices (DI and RI) better described degradation in sediments down to 35 cm. Systematic variations in the amino acid composition along the Laurentian Channel confirmed the increased diagenesis of OM with distance from the Upper St. Lawrence Estuary. The ratio of d/l-stereoisomers of alanine increased along the transect, and the co-variation between DI and the d/l-Ala suggest a close coupling between the extent of diagenesis and the accumulation and selective preservation of bacterially-derived cell wall material in the sediments. The same patterns that we observed along the estuarine transect were present down-core in two sediment cores, confirming the robustness of our reactivity indices. Oxygen exposure time of the sediments appears to strongly determine sediment OM reactivity in the St. Lawrence Estuary. The sediment oxygen regime itself is related to the interplay between water column depth, vertical OM flux, and reactivity of settling OM. [Copyright &y& Elsevier]

Coastal peatlands in Southeast Asia release large amounts of organic carbon to rivers, which transport it further to the adjacent estuaries. However, little is known about the fate of this terrestrial material in the coastal ocean. Although Southeast Asia is, by area, considered a hotspot of estuarine CO2 emissions, studies in this region are very scarce. We measured dissolved and particulate organic carbon, carbon dioxide (CO2) partial pressure and carbon monoxide (CO) concentrations in two tropical estuaries in Sarawak, Malaysia, whose coastal area is covered by peatlands. We surveyed the estuaries of the rivers Lupar and Saribas during the wet and dry season, respectively. The spatial distribution and the carbon-to-nitrogen ratios of dissolved organic matter (DOM) suggest that peat-draining rivers convey terrestrial organic carbon to the estuaries. We found evidence that a large fraction of this carbon is respired. The median pCO2 in the estuaries ranged between 618 and 5064 μatm with little seasonal variation. CO2 fluxes were determined with a floating chamber and estimated to amount to 14-272molm-2 yr-1, which is high compared to other studies from tropical and subtropical sites. In contrast, CO concentrations and fluxes were relatively moderate (0.3- 1.4 nmol L-1 and 0.8-1.9 mmolm-2 yr-1) if compared to published data for oceanic or upwelling systems. We attributed this to the large amounts of suspended matter (4- 5004mgL-1), limiting the light penetration depth. However, the diurnal variation of CO suggests that it is photochemically produced, implying that photodegradation might play a role for the removal of DOM from the estuary as well. We concluded that unlike smaller peat-draining tributaries, which tend to transport most carbon downstream, estuaries in this region function as an effcient filter for organic carbon and release large amounts of CO2 to the atmosphere. The Lupar and Saribas mid-estuaries re25 lease 0.4±0.2 TgCyr-1, which corresponds to approximately 80% of the emissions from the aquatic systems in these two catchments. [ABSTRACT FROM AUTHOR]

Karst systems are important for drinking water supply. Future climate projections indicate increasing temperature and a higher frequency of strong weather events. Both will influence the availability and quality of water provided from karst regions. Forest disturbances such as windthrow can disrupt ecosystem cycles and cause pronounced nutrient losses from the ecosystems. In this study, we consider the time period before and after the wind disturbance period (2007/08) to identify impacts on DIN (dissolvedinorganic nitrogen) and DOC (dissolved organic carbon) with a process-based flow and solute transport simulation model. Calibrated and validated before the disturbance the model disregards the forest disturbance and its consequences on DIN and DOC production and leaching. It can therefore be used as a base-line for the undisturbed system and as a tool for the quantification of additional nutrient production. Our results indicate that the forest disturbance by windthrow results in a significant increase of DIN production lasting 3.7 years and exceeding the pre-disturbance average by 2.7 kg ha-1 a-1 corresponding to an increase of 53%. There were no significant changes of DOC concentrations. With simulated transit time distributions we show that the impact on DIN travels through the hydrological system within some months. But a small fraction of the system outflow (< 5%) exceeds mean transit times of > 1 year. [ABSTRACT FROM AUTHOR]

Thermokarst (thaw) lakes emit methane (CH4) to the atmosphere formed from thawed permafrost organic matter (OM), but the relative magnitude of CH4 production in surface lake sediments vs. deeper thawed permafrost horizons is not well understood. We assessed anaerobic CH4 production potentials from various depths along a 590 cm long lake sediment core that captured the entire sediment package of the talik (thaw bulb) beneath the center of an interior Alaska thermokarst lake, Vault Lake, and the top 40 cm of thawing permafrost beneath the talik. We also studied the adjacent Vault Creek permafrost tunnel that extends through ice-rich yedoma permafrost soils surrounding the lake and into underlying gravel. Our results showed CH4 production potentials were highest in the organic-rich surface lake sediments, which were 151 cm thick (mean ± SD 5.95 ± 1.67 µg C-CH4 g dw-1 d-1; 125.9 ± 36.2 µg C-CH4 gCorg-1 d-1). High CH4 production potentials were also observed in recently-thawed permafrost (1.18 ± 0.61 µg C-CH4g dw-1 d-1; 59.60 ± 51.5 µg C-CH4 g Corg-1 d-1) at the bottom of the talik, but the narrow thicknesses (43 cm) of this horizon limited its overall contribution to total sediment column CH4 production in the core. Lower rates of CH4 production were observed in sediment horizons representing permafrost that has been thawed in the talik for longer periods of time. No CH4 production was observed in samples obtained from the permafrost tunnel, a non-lake environment. Our findings imply that CH4 production is highly variable in thermokarst-lake systems and that both modern OM supplied to surface sediments and ancient OM supplied to both surface and deep lake sediments by in situ thaw as well as shore erosion of yedoma permafrost are important to lake CH4 production. [ABSTRACT FROM AUTHOR]

The average depth in the ocean at which the majority of sinking organic matter particles remineralise is a fundamental parameter in the oceans role in regulating atmospheric CO2. Observed spatial patterns in sinking fluxes and relationships between the fluxes of different particles in the modern ocean have widely been used to invoke controlling mechanisms with important implications for CO2 regulation. However, such analyses are limited by the sparse spatial sampling of the available sediment trap data. Here we explore whether model ocean circulation rates, in the form of a transport matrix, can be used to derive remineralisation rates and sinking particle flux curves from the much more highly resolved observations of dissolved nutrient concentrations. Initially we use the Earth system model GENIE to generate a synthetic tracer dataset to explore the methods and its sensitivity to key sources of uncertainty arising from errors in the tracer observations and in the model circulation. We use a perturbed physics ensemble to generate 54 different estimates of circulation to explore errors associated with model transport rates. We find that reconstructed remineralisation rates are highly sensitive to both errors in observations and our ensemble uncertainty in model circulation rates such that a simple inversion does not provide a robust estimate of particulate flux profiles. Inferred remineralisation rates are particularly sensitive to differences between the "observed" and modelled transport fluxes because remineralisation rates are 3-4 magnitudes smaller than circulation rates. We also find that when inferring particle flux curves from remineralisation rates the cycling of dissolved organic matter also creates biases that have a similar magnitude and spatial variability to flux curves diagnosed using sediment trap data. We end with a discussion on the potential future directions and pitfalls of estimating remineralisation rates using model circulation schemes. [ABSTRACT FROM AUTHOR]

The relationship between the partial pressure of carbon dioxide (pCO2) and dissolved organic carbon (DOC) concentration in Brazilian lakes, encompassing 225 samples across a wide latitudinal range in the tropics, was tested. Unlike the positive relationship reported for lake waters, which was largely based on temperate lakes, we found no significant relationship for tropical and subtropical Brazilian lakes, despite very broad ranges in both pCO2 and DOC. Closer examination showed that the strength of pCO2 vs. DOC relationships declines with increasing water temperature, suggesting substantial differences in carbon cycling in warm lakes, which must be considered when upscaling limnetic carbon cycling to global scales. [ABSTRACT FROM AUTHOR]

In order to realize rapid and accurate evaluation of drinking water quality, a small-scale water quality detection instrument is designed in this paper that can detect two representative water quality parameters: the permanganate index and total dissolved solids (TDS). The permanganate index measured by the laser spectroscopy method can achieve the approximate value of the organic matter in water, and the TDS measured by the conductivity method can obtain the approximate value of the inorganic matter in water. In addition, to facilitate the popularization of civilian applications, the evaluation method of water quality based on the percent-scores proposed by us is presented in this paper. The water quality results can be displayed on the instrument screen. In the experiment, we measured the water quality parameters of the tap water as well as those after the primary and secondary filtration in Weihai City, Shandong Province, China. The testing results show that the instrument can quickly detect dissolved inorganic and organic matter, and intuitively display the water quality evaluation score on the screen. The instrument designed in this paper has the advantages of high sensitivity, high integration, and small volume, which lays the foundation for the popularity of the detection instrument. [ABSTRACT FROM AUTHOR]

Excess nitrogen gas (excess N2) was measured in samples collected at six locations in the eastern and western sub-basins of the Cariaco Basin, Venezuela, in September 2008 (non-upwelling conditions) and March 2009 (upwelling conditions). During both sampling periods, excess N2 concentrations were below detection in surface waters, increasing to ∼22 µmol N kg-1 at the oxic-anoxic interface ([O2] <∼4 µmol kg-1 , ∼250m). Below the oxic-anoxic interface (300-400m), the average concentration of excess N2 was 24.7±1.9 µmolNkg-1 in September 2008 and 27.5±2.0 µmolNkg-1 in March 2009, i.e., excess N2 concentrations within this depth interval were ∼3 µmolNkg-1 higher (p < 0.001) during the upwelling season compared to the non-upwelling period. These results suggest that N-loss in the Cariaco Basin may vary seasonally in response to changes in the flux of sinking particulate organic matter. We attribute the increase in excess N2 concentrations, or N-loss, observed during upwelling to: (1) higher availability of fixed nitrogen derived from suspended and sinking particles at the oxic-anoxic interface and/or (2) enhanced ventilation at the oxic-anoxic interface during upwelling. [ABSTRACT FROM AUTHOR]

The carbon fluxes mediated by planktonic communities in two cyclonic eddies (CEs) and two anticyclonic eddies (AEs) at the Canary Eddy Corridor were studied and compared with the dynamics in two far-field (FF) stations located outside the eddies. We observed favorable conditions and signs for upwelling at the center of CEs and for downwelling and mixing at the centers of AEs. CEs were characterized by higher nutrients concentration and highest chlorophyll a concentration, associated with highest microphytoplankton and diatoms abundance. AEs displayed similar chlorophyll a values and nutrients concentration (except highest ammonium concentration) to those of the FF stations and were characterized by increasing abundance of picophytoplankton and heterotrophic bacteria.While primary production was similar between the systems, the production of dissolved organic carbon (PDOC) was significantly higher at AEs. Phytoplankton cell mortality was lowest in CEs and we found higher cell mortality in AE than FF, despite similar chl a concentration. Environmental changes at the AEs presented significant prejudicial effects on the phytoplankton health as indicated by higher phytoplankton mortality (e.g. 60% of dead diatoms cells) and higher cell lysis rates observed at AEs than at two other systems. The adverse conditions associated to the early-stage anticyclonic systems, mainly triggered by active downwelling, resulted in higher consequent PDOC production, corresponding to forcing of the carbon flux to the dissolved pool and a weakness of the carbon pump. [ABSTRACT FROM AUTHOR]

Dissolved fluxes of C which are an important component of the global C budget of peatlands may be affected by global change in different ways. The evolution of peatland vegetation is an issue caused by the indirect effect of global change that still needs to be addressed. The aim of this study was to study the temporal and spatial variations in the quantity and the characteristics of dissolved C within in a peatland stream continuum, the peatland being invaded by Molinia caerulea and Betula spp. The study highlighted the following key points: (i) Vegetation change tends to increase the DOC concentration of peat surface water. (ii) DOC exports were in the range of those found in the literature, and it was clearly established that peatland DOC can reach second order streams. (iii) Peat water was supersaturated in CO2 especially in summer during the peak of microbial activity. (iv) the CO2 critical layer at the surface of the soil may promote CO excess build-up in the peat water. This critical layer may promote CO2 export out of the peatland. The effect of vegetation change on the DOC content of peat water deserves further attention as it may have a deep impact on downstream river water quality. In particular, it is necessary to clarify whether the concentration of C dynamics is affected by the invading species. More attention should be paid to hydrological processes (e.g. pumping capacity of the different plants) and the microbial activity in the rhizosphere of the invading plants. Also, the relation between the CO2 critical zone at the surface of the soil and the CO2 concentration in water should be studied in detail. [ABSTRACT FROM AUTHOR]

Anthropogenic carbon dioxide (CO2) emissions are causing severe changes in the global inorganic carbon balance of the oceans. Associated ocean acidification is expected to impose a major threat to marine ecosystems worldwide, and it is also expected to be amplified in the Baltic Sea where the system is already at present exposed to relatively large natural seasonal and diel pH fluctuations. The response of organisms to future ocean acidification has primarily been studied in single-species experiments, whereas the knowledge of community-wide responses is still limited. To study responses of the Baltic Sea pelagic community to a range of future CO2-scenarios, six ~ 55 m³ pelagic mesocosms were deployed in the northern Baltic Sea in June 2012. In this specific study we focused on the tolerance, development and subsequent settlement process of the larvae of the benthic key-species Macoma balthica when exposed to different levels of future CO2. We found that the settling of M. balthica was delayed along the increasing CO2 gradient of the mesocosms. Also, when exposed to increasing CO2 levels larvae settled at a larger size, indicating a developmental delay. With on-going climate change, both the frequency and extent of regularly occurring high CO2 conditions is likely to increase, and a permanent pH decrease will likely occur. The strong impact of increasing CO2 levels on early-stage bivalves is alarming as these stages are crucial for sustaining viable populations, and a failure in their recruitment would ultimately lead to negative effects on the population. [ABSTRACT FROM AUTHOR]

Floodplains are important biogeochemical reactors during fluvial transport of carbon and nutrient species towards the oceans. In the tropics and subtropics pronounced rainfall seasonality results in highly dynamic floodplain biogeochemistry. Massive construction of hydropower dams, however, has significantly altered the hydrography and chemical characteristics of many (sub)tropical rivers. In this study, we compare organic matter and nutrient biogeochemistry of two large, contrasting floodplains in the Zambezi River Basin in Southern Africa, the Barotse Plains and the Kafue Flats. Both systems are of comparable size, but differ in anthropogenic influence: while the Barotse Plains are still relatively pristine, the Kafue Flats are bordered by two hydropower dams. While the Barotse Plains retain particles during the wet season, annual yields of particulate organic carbon and nitrogen are higher than previously reported for the Zambezi and other tropical rivers. Enhanced wet-season runoff adds soil-derived dissolved organic carbon and nitrogen to the Zambezi River, with a corresponding increase in the Barotse Plains. Soil-derived organic matter dominates the particulate phase year-round in the Barotse Plains, and a varying influence of C3- and C4-plant vegetation can be observed throughout the year. In contrast to the Barotse Plains, net export of particulate matter from the Kafue Flats has been observed during the wet season, but over an annual cycle, the Kafue Flats are effectively accumulating dissolved carbon and nutrients. In the Kafue Flats, the runoff-induced increase in dissolved organic carbon and nitrogen concentrations is delayed by the upstream dam operation. The dam reservoir also causes a shift in the source of the particulate organic matter - from soil-derived during the dry season to aquatically produced in the wet season - in the downstream Kafue Flats. Spatial zonation in vegetation and temporal flooding dynamics in the Kafue Flats result in mostly C3-derived particulate organic matter during wet season, and a dominance of C4-derived material during dry season. This pattern results from dam-induced changes in vegetation, as dam construction along the Kafue River has led to encroachment of woody plant species onto the Kafue Flats. The two systems exhibit different flooding dynamics, with a~larger contribution of floodplain-derived water in the Kafue Flats and a stronger peak flow in the Barotse Plains. Differences in the biogeochemistry of the two systems that can be linked to the dams are the timing of the runoff-driven dissolved organic carbon and nitrogen pulses in the wet season and the origin and inputs of particulate organic matter. This study reveals clear effects of dam construction on organic matter and nutrient dynamics on the downstream floodplain. Man-made reservoirs alter the origin of organic matter, and change the timing of precipitation-driven carbon and nitrogen pulses. Environmental assessments of dam impacts should therefore consider changes in water quality. [ABSTRACT FROM AUTHOR]

In spite of the great abundance and ecological importance of headwater streams, managers are usually limited by a lack of information about water chemistry in these headwaters. In this study we test whether river outlet chemistry can be used as an additional source of information to improve the prediction of the chemistry of upstream headwaters (size < 2 km²), relative to models based on map information alone. Between 2000 and 2008, we conducted 17 synoptic surveys of streams within 9 mesoscale catchments (size 32-235 km²). Over 900 water samples were collected from catchments ranging in size from 0.03 to 235 km². First we used partial least square regression (PLS) to model headwater stream total organic carbon (TOC) median and interquartile values for a given catchment, based on a large number of candidate variables including catchment characteristics from GIS, and measured chemistry at the catchment outlet. The best candidate variables from the PLS models were then used in hierarchical linear mixed models (MM) to model TOC in individual headwater streams. Three predictor variables were consistently selected for the MM calibration sets: (1) proportion of forested wetlands in the sub-catchment (positively correlated with headwater stream TOC), (2) proportion of lake surface cover in the sub-catchment (negatively correlated with headwater stream TOC), and (3) whole-catchment river outlet TOC (positively correlated with headwater stream TOC). Including river outlet TOC as a predictor in the models gave 5-15% lower prediction errors than using map information alone. Thus, data on water chemistry measured at river outlets offers information which can complement GIS-based modelling of headwater stream chemistry. [ABSTRACT FROM AUTHOR]

In order to assess whether eroded carbon is a net source or sink of atmospheric CO2, characterisation of the chemical composition and residence time of eroded organic matter (EOM) at the landscape level is needed. This information is crucial to evaluate how fast EOM can be decomposed by soil microbes during its lateral transport. This study considers a continuum of scales to measure the fate of EOM during its transport, across a steep hillslope landscape of the Mekong basin, with intense erosion. Here we show that changes in the chemical composition of EOM (measured by NMR spectroscopy) and in its 13C and 15N isotope composition provide consistent evidence for EOM decomposition during the lateral transport of carbon on time scales of less than 50 yr across distances of 10 km. Between individual soil units (1m²) to a small watershed (107 m²), the observed 28% decrease of the C/N ratio and the enrichment of 13C and 15N isotopes in EOM is of similar magnitude than the enrichment with depth in soil profiles due to soil organic matter "vertical" decomposition. Radiocarbon measurements indicated that these changes are not related to the slow transformation of soil carbon during pedogenesis, but rather to an acceleration of the SOM stabilisation process during its journey through the watershed. [ABSTRACT FROM AUTHOR]

We conducted a shipboard observation over the Chukchi Sea and the Canada Basin in the western Arctic Ocean in September and October 2012 to obtain vertical distributions of four volatile organic iodine compounds (VOIs) in seawater. VOIs are believed to play a role in ozone destruction in the troposphere and lower stratosphere. The VOIs observed in this study were iodomethane (CH3I), iodoethane (C2H5I), diiodomethane (CH2I2) and chloroiodomethane (CH2ClI). Maximum concentrations of the four VOIs were found in the bottom layer water over the Chukchi Sea shelf, in which layer the maximum concentration of ammonium (NH4+) also occurred. A significant correlation was observed between C2H5I and NH4+ (correlate coefficient R = 0.93) and between CH3I and NH4+ (R = 0.77), suggesting production of these VOIs increased with degradation of organic matter. Over the northern Chukchi Sea shelf-slope area, concentration maxima of CH2I2, CH2ClI, and CH3I were found in the subsurface cold, dense water (CDW). A large nitrogen deficit (N-deficit = NH4+ + NO3- + NO2- - 16PO43-) simultaneously occurred in this water, suggesting production of the three VOIs in the sediment or the bottom layer water over the shelf, probably in association with degradation of organic matter. We conclude that VOI production over the Chukchi Sea shelf can be largely attributed to the degradation of organic matter that is produced in the highly productive shelf water. High concentrations of CH2ClI were also found in the Alaskan Coastal Water (ACW) from the Bering Strait to the surface of the northern Chukchi slope. The VOIs that originated at the Chukchi Sea shelf are expected to be laterally transported to the Arctic Ocean Basin though the subsurface CDW and the surface ACW. [ABSTRACT FROM AUTHOR]

Forestry activities in the Canadian Boreal region have increased in the last decades, raising concerns about their potential impact on aquatic ecosystems. Water quality and fluorescence characteristics of dissolved organic matter (DOM) were measured over a three-year period in eight Eastern Boreal Shield lakes: four lakes were studied before, one and two years after forest harvesting (perturbed lakes) and compared with four undisturbed reference lakes (unperturbed lakes) sampled at the same time. ANOVAs showed a significant increase in total phosphorus (TP) in perturbed lakes when the three sampling dates were considered and in DOC concentrations when considering one year before and one year after the perturbation only. At one year post-clear cutting DOC concentrations were about 15% greater in the perturbed lakes at ~15mg C L-1 compared to 12.5 mg C L-1 in the unperturbed lakes. In contrast, absorbance and fluorescence measurements showed that all metrics remained within narrow ranges compared to the range observed in natural waters, indicating that forest harvesting did not affect the nature of DOM characterised with spectroscopic techniques. Multivariate statistical analysis showed lakes to be significantly different one year after the perturbation. These results confirm an impact of forestry activities one year after the perturbation. However, this effect seems to be mitigated two years after, indicating that the system shows high resilience and may be able to return to its original condition. [ABSTRACT FROM AUTHOR]

In order to assess the production of biologically labile photoproducts (BLPs) from nonlabile riverine dissolved organic carbon (DOC), we collected water samples from ten major rivers, removed labile DOC and mixed the residual non-labile DOC with artificial seawater 5 for microbial and photochemical experiments. Bacteria grew on nonlabile DOC with a growth effciency of 11.5% (mean; range from 3.6 to 15.3 %). Simulated solar radiation transformed a part of non-labile DOC into BLPs, which stimulated bacterial respiration and production, but did not change bacterial growth effciency (BGE) compared to the non-irradiated dark controls. In the irradiated water samples, 10 the amount of BLPs stimulating bacterial production depended on the photochemical bleaching of chromophoric dissolved organic matter (CDOM). The apparent quantum yields for BLPs supporting bacterial production ranged from 9.5 to 76 (mean 39) (μmolCmol photons-1) at 330 nm. The corresponding values for BLPs supporting bacterial respiration ranged from 57 to 1204 (mean 320) (μmolCmol photons-1). Accord15 ing to the calculations based on spectral apparent quantum yields and local solar radiation, the annual production of BLPs ranged from 21 (St. Lawrence) to 584 (Yangtze) mmolCm-2 yr-1 in the plumes of the examined rivers. Complete photobleaching of riverine CDOM in the coastal ocean was estimated to produce 10.7 MtCBLPs yr-1 from the rivers examined in this study and globally 38 Mt yr-1 (15% of riverine DOC flux from all rivers), which support 4.1 Mt yr-1 of bacterial production and 33.9 Mt yr-1 20 bacterial respiration. [ABSTRACT FROM AUTHOR]

Rapid changes in the volume and sources of discharge during the spring freshet lead to pronounced variations in biogeochemical properties in snowmelt-dominated river basins. We used daily sampling during the onset of the freshet in the Fraser River (southwestern Canada) in 2013 to identify rapid changes in the flux and composition of dissolved material, with a focus on dissolved organic matter (DOM) and mercury (Hg) dynamics. Previous time series sampling (at twice monthly frequency) of dissolved inorganic species in the Fraser River has revealed smooth seasonal transitions in concentrations of major elements and tracers of water and dissolved load sources between freshet and base flow periods. In contrast, daily sampling reveals a significant increase in dissolved organic carbon (DOC) concentration (200 to 550 µmol L-1) occurring over a matter of days, accompanied by a shift in DOM optical properties, indicating a transition towards higher molecular weight, more aromatic DOM composition. Comparable changes in DOM composition, but not concentration, occur at other times of year, underscoring the role of seasonal climatology in DOM cycling. Concentrations of total and dissolved Hg also varied during the spring freshet period, although dissolved Hg dynamics appear to be driven by factors beyond DOM as characterized here. The time series records of DOC and particulate organic carbon (POC) concentrations indicate that the Fraser River exports 0.25-0.35% of its annual basin net primary productivity. [ABSTRACT FROM AUTHOR]

This study was designed to determine the effects of flooding on plankton community respiration (CR) in the East China Sea (ECS). In July 2010, a devastating flood occurred in the Changjiang River; the mean monthly discharge was 60 527m³ s-1. To compare, the variables were also examined in the low riverine flow of July 2009 (33 955 m³ s-1). During the flooding, the Changjiang diluted water (CDW) zone, the sea surface salinity (SSS) was ≤ 31 psu, covering almost two thirds of the ECS, which was approximately six times that in the non-flooding period. The mean nitrate concentration was higher in 2010 (6.2 µM) than in 2009 (2.0 µM). However, in the 2010 flood, the mean values of Chl a and the bacterial biomass were only slightly higher or even lower than in 2009. Surprisingly, however, the CR was still higher in the flood period than in the non-flood period, with mean values of 105.6 and 73.2mg C m-3 d-1, respectively. The higher CR in 2010 could be attributed to vigorous plankton activities, especially phytoplankton, at stations in the CDW zone, which were not mostly covered by low SSS in 2009. There was a huge amount of fCO2 drawdown in the 2010 flood. These results suggested that the devastating flood in 2010 had a significant effect on the carbon balance in the ECS. This effect might become more pronounced as extreme rainfall events and flooding magnitudes increase dramatically throughout the world. [ABSTRACT FROM AUTHOR]

As high latitudes warm, vast stocks of carbon and nitrogen stored in permafrost will become available for transport to aquatic ecosystems. While there is a growing understanding of the potential effects of permafrost collapse (thermokarst) on aquatic biogeochemical cycles, neither the spatial extent nor temporal duration of these effects are known. To test hypotheses concerning patterns and persistence of elemental export from upland thermokarst, we sampled hydrologic outflow from 83 thermokarst features in various stages of development across the North Slope of Alaska. We hypothesized that an initial pulse of carbon and nutrients would be followed by a period of elemental retention during feature recovery, and that the duration of these stages would depend on feature morphology. Thermokarst caused substantial increases of dissolved organic carbon and other solute concentrations with a particularly large impact on inorganic nitrogen. Magnitude and duration of thermokarst effects on water chemistry differed by feature type and secondarily by landscape age. Most solutes returned to undisturbed concentrations after feature stabilization, but elevated dissolved carbon, inorganic nitrogen, and sulfate concentrations persisted through stabilization for some feature types, suggesting that aquatic disturbance by thermokarst for these solutes is long-lived. Dissolved methane decreased by 90% for most feature types, potentially due to high concentrations of sulfate and inorganic nitrogen. Spatial patterns of carbon and nutrient export from thermokarst suggest that upland thermokarst may be a dominant linkage transferring carbon and nutrients from terrestrial to aquatic ecosystems as the Arctic warms. [ABSTRACT FROM AUTHOR]

Controlled laboratory studies of the physical and chemical properties of sea spray aerosol (SSA) must be underpinned by a physically and chemically accurate representation of the bubble mediated production of nascent SSA particles. Since bubble bursting is sensitive to the physicochemical properties of seawater, any important differences in the SSA production mechanism are projected into SSA composition. Using direct chemical measurements of SSA at the single-particle level, this study presents an inter-comparison of three laboratory-based, bubble-mediated SSA production schemes: gas forced through submerged sintered glass filters ("frits"), a pulsed plunging waterfall apparatus, and breaking waves in a wave channel filled with natural seawater. The size-resolved chemical composition of SSA particles produced by breaking waves is more similar to particles produced by the plunging waterfall than sintered glass filters. Aerosol generated by disintegrating foam produced by sintered glass filters contained a larger fraction of organic enriched particles and a different size resolved elemental composition, especially in the 0.8-2 µm size range. These particles, when dried, had more spherical morphologies compared to the more cubic structure expected for pure NaCl particles, which can be attributed to the presence of additional organic carbon. In addition to an inter-comparison of three SSA production methods, the role of the episodic or "pulsed" nature of the waterfall method utilized in this study on SSA composition was undertaken. In organic-enriched seawater, the continuous operation of the plunging waterfall mechanism resulted in the accumulation of surface foam and an over-expression of organic matter in SSA particles compared to pulsed plunging waterfall. Throughout this set of experiments, comparative differences in the SSA number size distribution were coincident with differences in aerosol composition, indicating that the production mechanism of SSA exerts important controls on both the physical and chemical properties of the resulting aerosol. This study provides insight into the physicochemical differences between each of these bubble-mediated SSA generation mechanisms and serves as a guideline for future laboratory studies of SSA particles. [ABSTRACT FROM AUTHOR]

Sattal Lake is one of the important lake of Nainital regions in Uttarakhand state. Physico-chemical characteristics study in the Sattal Lake has been studied. Chemical examination of the water samples collected from the sampling stations of Sattal lake were done for the tests like Total Solids (TS), pH of water, acidity of water, alkalinity of water, hardness of water, sulfate in water, Chlorides in water, Fluorides in water, Dissolved Oxygen in water, biochemical Oxygen Demand in water, chemical oxygen demand in water, total organic carbon / organic matter in water, nitrogen in water, nitrogen, ammonia, Nitrogen, nitrate, nitrogen, nitrite, nitrogen, organic and Metals in water. The study indicates that Sattal Lake is becoming a oligotrophic lake. The data have been reported in the study or present paper. [ABSTRACT FROM AUTHOR]

Although of substantial importance for marine tracer distributions and eventually global carbon, oxygen, and nitrogen fluxes, the interaction between sinking and remineralization of organic matter, benthic fluxes and burial is not always represented consistently in global biogeochemical models. We here aim to investigate the relationships between these processes with a suite of global biogeochemical models, each simulated over millennia, and compared against observed distributions of pelagic tracers and benthic and pelagic fluxes. We concentrate on the representation of sediment-water interactions in common numerical models, and investigate their potential impact on simulated global sediment- water fluxes and nutrient and oxygen distributions. We find that model configurations with benthic burial simulate global oxygen well over a wide range of possible sinking flux parameterizations, making the model more robust with regard to uncertainties about the remineralization length scale. On a global scale, burial mostly affects oxygen in the meso- to bathypelagic zone. While all model types show an almost identical fit to observed pelagic particle flux, and the same sensitivity to particle sinking speed, comparison to observational estimates of benthic fluxes reveals a more complex pattern and may be influenced by the data distribution and methodology. Still, evaluating model results against observed pelagic and benthic fluxes of organic matter can complement model assessments based on more traditional tracers such as nutrients or oxygen. Based on a combined metric of dissolved tracers and biogeochemical fluxes, we here identify two model descriptions of burial as suitable candidates for further experiments and eventual model refinements. [ABSTRACT FROM AUTHOR]

The analysis of the shape of excitation-emission matrices (EEMs) is a relevant tool for exploring the origin, transport and fate of dissolved organic matter (DOM) in aquatic ecosystems. Within this context, the decomposition of EEMs is acquiring a notable relevance. A simple mathematical algorithm that automatically deconvolves single EEM is described, creating new possibilities for the comparison of DOM fluorescence properties and EEMs that are very different from each other. A mixture model approach is adopted to decompose complex surfaces into sub-peaks. The laplacian operator and the Nelder--Mead optimization algorithm are implemented to individuate and automatically locate potential peaks in the EEM landscape. A small heterogeneous data set of 21 EEMs from a human-impacted Mediterranean river is used to describe the model application and to illustrate a strategy that optimises the search for the optimal output. [ABSTRACT FROM AUTHOR]

Surface sediments collected from deep slopes and basins (1018-4087 m depth) of the oligotrophic Eastern Mediterranean Sea have been analysed for bulk elemental and isotopic composition of organic carbon, total nitrogen and selected lipid biomarkers, jointly with grain size distribution and other geochemical proxies. The distribution and sources of sedimentary organic matter (OM) have been subsequently assessed and general environmental variables, such as water depth and currents, have been examined as causative factors of deep-sea sediment characteristics. Lithogenic and biogenic carbonates are the dominant sedimentary fractions, while both bulk and molecular organic tracers reflect a mixed contribution from autochthonous and allochthonous sources for the sedimentary OM, as indicated by relatively degraded marine OM, terrestrial plant waxes and anthropogenic OM including degraded petroleum by-products, respectively. Wide regional variations have been observed amongst the studied proxies, which reflect the multiple factors controlling sedimentation in the deep Eastern Mediterranean Sea. Our findings highlight the role of deep Eastern Mediterranean basins as depocentres of organic-rich fine-grained sediments (mean 5.4 ± 2.4 μm), with OM accumulation and burial due to aggregation mechanisms and hydrodynamic sorting. A multi-proxy approach is hired to investigate the biogeochemical composition of sediment samples, which sheds new light on the sources and transport mechanisms along with the impact of preservation vs. diagenetic processes on the composition of sedimentary OM in the deep basins of the oligotrophic Eastern Mediterranean Sea. [ABSTRACT FROM AUTHOR]

Changes in land use and climate increase the supply of terrestrial sediment (here-after, TS) to coastal waters worldwide but the effects of these sediments on benthic ecosystem functioning are not well known. Past experiments with defaunated, intertidal sediment suggested a link between the de-oxygenation of sediments underlying a thin (mm) layer of TS and reduced burial rates of juvenile macrofaunal recruits. We examined this link predicting that surficial TS deposits will still negatively affect burial when applied to sediments that are initially well oxygenated due to bioturbation (C) or depleted of organic matter (D). We observed the behaviour of post-settlement juveniles of the tellinid bivalve Macomona liliana on the surface of four treatments; C, D, and the same sediments to which we added a thin layer of TS (CTS, DTS). Pore water analyses confirmed that the diffusive impedance of the 1.7-1.9 mm TS deposit decreased the oxygenation of the underlying intertidal sediment (CTS) but not that of the depleted sediment (DTS). Unexpectedly, (1) the application of a TS deposit significantly increased but not decreased the probability of burial, irrespectively of treatment, and (2) juveniles more likely buried into C than into D. We attribute the failure to document a negative effect of TS on the recruits' burial to the activity of the resident macroinfauna (CTS) or the absence of organic matter (DTS). Our results underline the important role of the resident macrofauna in mediating the stress response of benthic ecosystems. [ABSTRACT FROM AUTHOR]

Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of in situ fDOM measurements. Fluorescence must be converted to CDOM absorbance for use in light attenuation calculations and models. However, this fDOM-CDOM relationship varies among and within estuaries.We quantified the variability in this relationship within three estuaries: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD, VA). Land use surrounding these estuaries ranges from urban to developed, with varying sources of nutrients and organic matter. Measurements of fDOM and CDOM absorbance were taken along a terrestrial-to-marine gradient in all three estuaries. The ratio of the absorption coefficient at 340nm (m-1) to fDOM (QSU) was higher in West Falmouth Harbor (1.22) than in Barnegat Bay (0.22) and Chincoteague Bay (0.17). The fDOM-CDOM absorption ratio was variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent between sites within Chincoteague Bay. Stable carbon isotope analysis for constraining the source of dissolved organic matter in West Falmouth Harbor and Barnegat Bay yielded δ13C values ranging from -19.7 to -26.1‰ and -20.8 to -26.7 ‰, respectively. Stable carbon isotope mixing models of DOC in the estuaries indicate contributions from marine plankton, terrestrial plants, and Spartina cordgrass. Comparison of DOC source to fDOM-CDOM absorption ratio at each site demonstrates the influence of source on optical properties. Samples with a greater contribution from marsh (Spartina) organic material had higher fDOM-CDOM absorption ratios than samples with greater contribution from terrestrial organic material. Applying a uniform fDOM-CDOM absorption ratio and spectral slope within a given estuary yields errors in modeled light attenuation ranging from 11-33% depending on estuary. The application of a uniform absorption ratio across all estuaries doubles this error. These results demonstrate that continuous monitoring of light attenuation in estuaries requires some quantification of CDOM absorption and source to refine light models. [ABSTRACT FROM AUTHOR]

Global models of the oceanic nitrogen cycle are subject to many uncertainties, among them type and form of biogeochemical processes involved in the fixed nitrogen cycle, and the spatial and temporal scales, on which the global nitrogen budget is regulated. We investigate these aspects using a global model of ocean biogeochemistry, that explicitly considers phosphorus and nitrogen, including pelagic denitrification and nitrogen fixation as sink and source terms of fixed nitrogen, respectively. The model explores different parameterizations of organic matter sinking speed, oxidant affinity of oxic and suboxic remineralization, and regulation of nitrogen fixation by temperature and different stoichiometric ratios. Examination of the initial transient behaviour of different model setups initialized from observed tracer distributions reveal changes in simulated nitrogen inventories and fluxes particularly during the first centuries. Millennial timescales have to be resolved in order to bring all biogeochemical and physical processes into a dynamically consistent steady state, for which global patterns of biogeochemical tracers and fluxes are reproduced quite well. Analysis of global properties suggests that particularly particle sinking speed, but also the parameterization of denitrification determines the extent of oxygen minimum zones, global nitrogen fluxes, and hence the oceanic nitrogen inventory. However, the ways and directions, in which different parameterizations of particle sinking, nitrogen fixation and denitrification affect the global diagnostics, are different, suggesting that these may, in principle, be constrained independently from each other. Analysis of the model misfit suggests a particle flux profile close to the one suggested by Martin et al. (1987). Simulated pelagic denitrification best agrees with the lower values between 59 and 84 TgNyr-1 recently estimated by other authors. [ABSTRACT FROM AUTHOR]

Western Siberia's thermokarst (thaw) lakes extend over a territory spanning over a million km²; they are highly dynamic hydrochemical systems that receive chemical elements from the atmosphere and surrounding peat soil and vegetation, and exchange greenhouse gases with the atmosphere, delivering dissolved carbon and metals to adjacent hydrological systems. This work describes the chemical composition of ~ 130 thermokarst lakes of the size range from a few m² to several km², located in the discontinuous permafrost zone. Lakes were sampled during spring floods, just after the ice break (early June), the end of summer (August), the beginning of ice formation (October) and during the full freezing season in winter (February). Dissolved organic carbon (DOC) and the major and trace elements do not appreciably change their concentration with the lake size increase above 1000m² during all seasons. On the annual scale, the majority of dissolved elements including organic carbon increase their concentration from 30 to 500 %, with a statistically significant (p < 0.05) trend from spring to winter. The maximal increase in trace element (TE) concentration occurred between spring and summer and autumn and winter. The ice formation in October included several stages: first, surface layer freezing followed by crack (fissure) formation with unfrozen water from the deeper layers spreading over the ice surface. This water was subsequently frozen and formed layered ice rich in organic matter. As a result, the DOC and metal concentrations were the highest at the beginning of the ice column and decreased from the surface to the depth. A number of elements demonstrated the accumulation, by more than a factor of 2, in the surface (0-20 cm) of the ice column relative to the rest of the ice core: Mn, Fe, Ni, Cu, Zn, As, Ba and Pb. The main consequences of discovered freeze-driven solute concentrations in thermokarst lake waters are enhanced colloidal coagulation and the removal of dissolved organic matter and associated insoluble metals from the water column to the sediments. The measured distribution coefficient of TE between amorphous organo-ferric coagulates and lake water (< 0.45µm) were similar to those reported earlier for Fe-rich colloids and low molecular weight (< 1kDa) fractions of thermokarst lake waters, suggesting massive co-precipitation of TE with amorphous Fe oxy(hydr)oxide stabilized by organic matter. Although the concentration of most elements is lowest in spring, this period of maximal water coverage of land creates a significant reservoir of DOC and soluble metals in the water column that can be easily mobilized to the hydrological network. The highest DOC concentration observed in the smallest (< 100m²) water bodies in spring suggests their strongly heterotrophic status and, therefore, elevated CO2 flux from the lake surface to the atmosphere. [ABSTRACT FROM AUTHOR]

Coastal areas adjoining rivers are nourished by both the riverborne nutrients and organic matters. Annually, the East China Sea (ECS) receives large quantities of particulate organic carbon transported from the Changjiang (Yangtze River), as well as nutrients, which have brought about high primary production in the ECS. This study evaluated the respective contributions of terrigenous organic matters (allochthonous food source) and nutrient-induced marine production (autochthonous food source) to the ECS benthic ecosystem by analyzing the stable isotope compositions for zooplankton, benthic crustacea and demersal fish. Zooplankton exhibited consistently higher δ13C values (-21.31‰~-19.22‰) in the inner shelf than in the outer shelf. The δ13C signals of fish (-19.64‰~-13.46‰) and crustacea (-18.87‰~-15.00‰) showed strong reliance on the marine production across the ECS continental shelf, regardless of distance from the shore. Moreover, the benthic crustacea and fish exhibited significantly higher δ13C values in the highly productive inshore sites and the δ13C values decreased seawards, implying a higher intrusion of atmospheric CO2 and lower photosynthetic fractionation due to algal blooming in the inner shelf. The δ13C values of fish also showed significant positive correlations with the concentration of surface chlorophyll a and nitrogen. Riverborne nutrients closely linked marine benthic consumers to the terrestrial watershed and tightly coupled the pelagic and benthic ecosystems in the ECS. The stable isotope compositions of benthic consumers can act as an indicator for pelagic trophic status. The future research combining analyses of stable isotope and community structure may improve assessment on the balance between contribution and risk of phytoplankton blooms. [ABSTRACT FROM AUTHOR]

The balance between organic matter production and decay determines how fast coastal wetlands accumulate soil organic matter. Despite the importance of soil organic matter accumulation rates in influencing marsh elevation and resistance to sea-level rise, relatively little is known about how decomposition rates will respond to sea-level rise. Here, we estimate the sensitivity of decomposition to flooding by measuring rates of decay in 87 bags filled with milled sedge peat, including soil organic matter, roots and rhizomes. Experiments were located in field-based mesocosms along 3 mesohaline tributaries of the Chesapeake Bay. Mesocosm elevations were manipulated to influence the duration of tidal inundation. Although we found no significant influence of inundation on decay rate when bags from all study sites were analyzed together, decay rates at two of the sites increased with greater flooding. These findings suggest that flooding may enhance organic matter decay rates even in water-logged soils, but that the overall influence of flooding is minor. Our experiments suggest that sea-level rise will not accelerate rates of peat accumulation by slowing the rate of soil organic matter decay. Consequently, marshes will require enhanced organic matter productivity or mineral sediment deposition to survive accelerating sea-level rise. [ABSTRACT FROM AUTHOR]

Increasing concentrations of atmospheric carbon dioxide are projected to lead to an increase in sea surface temperatures, potentially impacting marine ecosystems and biogeochemical cycling. Here we conducted an indoor mesocosm experiment with a natural plankton community taken from the Baltic Sea in summer. We induced a plankton bloom via nutrient addition and followed the dynamics of the different carbon and nitrogen pools for a period of one month at temperatures ranging from 9.5 °C to 17.5 °C, representing a range of ± 4 °C relative to ambient temperature. The uptake of dissolved inorganic carbon (DIC) and the net build-up of both particulate (POC) and dissolved organic carbon (DOC) were all enhanced at higher temperatures and almost doubled over a temperature gradient of 8 °C. Furthermore, elemental ratios of carbon and nitrogen (C:N) in both particulate and dissolved organic matter increased in response to higher temperatures, both reaching very high C:N ratios of > 30 at + 4 °C. Altogether, these observations suggest a pronounced increase in excess carbon fixation in response to elevated temperatures. Most of these findings are contrary to results from similar experiments conducted with plankton populations sampled in spring, revealing large uncertainties in our knowledge of temperature sensitivities of key processes in marine carbon cycling. Since a major difference to previous mesocosm experiments was the dominant phytoplankton species, we hypothesize that species composition might play an important role in the response of biogeochemical cycling to increasing temperatures. [ABSTRACT FROM AUTHOR]

During the Bonus-GoodHope (BGH) expedition (Jan-Mar 2008) we studied the water column distribution of total 234Th and biogenic particulate Ba (Baxs) in the Atlantic sector of the Southern Ocean. The objective was to assess the export flux of particulate organic carbon (POC) from the surface to the mesopelagic twilight zone along a section between the Cape Basin and Weddell Gyre. Export production of POC was estimated from steady state and non steady state export fluxes of 234Th which were converted into POC ?uxes, using the POC/234Th ratio of large (>53 µm) suspended particles, collected via in-situ pumps. Deficits in 234Th activities were observed at all stations from the surface to the bottom of the mixed- layer. 234Th export fluxes from the upper 100m ranged from 496±57 dpm m-2 d-1 to 1195±120 dpm m-2 d-1 for the steady state model and from 149±18 dpm m-2 d-1 to 1217±146 dpm m-2 d-1 for the non steady state model calculated for a time window of 15 to 22 days preceding the timing of the present cruise. The POC/234Thp ratio of large, potentially sinking particles (>53 µm), was observed to increase with latitude, from 1.9±0.2 µmol dpm-1 and 1.7±0.3 µmol dpm-1 in the Subtropical Zone (STZ) and Subantarctic Zone (SAZ), respectively, to 3.0±0.2 µmol dpm in the Polar Front Zone (PFZ), 4.8±1.9 µmol dpm-1 at the Southern Antarctic Circumpolar Current Front (SACCF) to 4.1±1.7 µmol dpm in the northern Weddell Gyre, in line with an increasing contribution of larger cell diatoms. Steady state and non steady state POC export from the upper 100m ranged from 0.9±0.2mmolC m-2 d to 5.1±2.1mmolC m-2 d-1 and from 0.3±0.0mmolC m-2 d-1 to 4.9±3.2mmolC m-2 d-1 , respectively. From the SAZ to the SACCF, non steady state POC export production represented only 15 to 54% of the steady state POC flux, suggesting that the intensity of export had decreased over time partly due to the fact that regenerated-production based communities of small-sized phytoplankton became predominant. In contrast, for the HNLC area south of the SACCF, we found an excellent agreement between the two modeling approaches indicating that surface POC export remained rather constant there. [ABSTRACT FROM AUTHOR]

Unlike conventional reservoirs, shale is particularly complex in its mineral composition. As typical components in shale reservoirs, clay and organic matter have different pore structures and strong interactions with fluids, resulting in complex fluid occurrence-states in shale. For example, there are both free water and adsorbed water in clay, and both free oil and ad/absorbed oil in organic matter. Key properties such as fluid content, organic/inorganic porosity, and permeability in clay-rich shale have been poorly characterized in previous studies. In this paper, we used a vacuum-imbibition experimental method combined with nuclear magnetic resonance technique and mathematical modeling to characterize the fluid content, organic/inorganic porosity, saturation, and permeability of clay-rich shale. We conducted vacuum-imbibition experiments on both shale samples and pure clay samples to distinguish the adsorbed oil and water in clay and organic matter. The effects of clay content and total organic matter content (TOC) on porosity and adsorbed-fluid content are then discussed. Our results show that, for the tested samples, organic porosity accounts for 26–76% of total porosity. The oil content in organic matter ranges from 29% to 69% of the total oil content, and 2% to 58% of the organic oil content is ad/absorbed in kerogen. The inorganic porosity has a weak positive correlation with clay content, and organic porosity increases with rising levels of organic matter content. The organic permeability is 1–3 orders of magnitude lower than the inorganic permeability. [ABSTRACT FROM AUTHOR]

Climate change will lead to prolonged droughts in various regions of the world, which may significantly affect agricultural production. This is particularly problematic for soils with low water retention capacity, which cannot store sufficient water for crops. In this paper, we investigate how a change in the water‐holding capacity of the soil material, as could be achieved by increasing the soil organic carbon (SOC) amount, affects the components of the soil water balance (evaporation, transpiration, and groundwater recharge). Specifically, we state the hypothesis that an increased water‐holding capacity in a shallow soil layer, as it is achieved through SOC enrichment at the soil surface, will result in more water being stored near the soil surface and lost to unproductive evaporation, thereby reducing the amount of water available to plants and groundwater recharge. The hypothesis was tested by numerical simulations, employing the Hydrus‐1D program package to model the water balance in a soil–plant–atmosphere system for an arable crop in hydrologically contrasting years. The study considered soils with varying textures and different depths of a soil layer with increased SOC content. The soil hydraulic properties (SHP) of the soil material, including the effect of SOC on the SHP, were determined using a recently developed pedotransfer model based on data from over 500 samples. We showed that both the improved water retention by SOC and its vertical distribution affect the soil water balance in a complex manner. In sandy soils, increasing the water‐holding capacity in shallow layers up to 0.1 m led to enhanced evaporation and thus a decrease in water availability for crops. However, deeper incorporated SOC could ameliorate these negative effects. Our findings suggest that not only the amount but also the vertical SOC distribution should be considered if enrichment of SOC shall be applied to mitigate the effect of droughts. Core Ideas: Addition of soil organic carbon (SOC) alters soil material's hydraulic properties.This, in turn, impacts the water balance of soils under agricultural use.The depth at which SOC is incorporated into soils plays a crucial role in the partitioning of evapotranspiration (ET) into evaporation (E) and transpiration (T).Deeper incorporation of SOC results in greater water availability for plants. [ABSTRACT FROM AUTHOR]

Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model. The objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000-2006, with differences of order 0. 9 Pg C yr-1 over the region south of 45°S. Wind stirring impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other species associated with ocean biogeochemistry. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong sensitivity of nutrient concentrations exported in Subantarctic Mode Water (SAMW) to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry, through its impact over the Southern Ocean. [ABSTRACT FROM AUTHOR]

Analysis of dissolved organic and inorganic carbon (DOC and DIC, respectively), pH, Na, K, Ca, Mg, Cl, SO4 and Si in ~ 100 large and small rivers (< 100 to = 150 000 km²) of western Siberia sampled in winter, spring, summer and autumn over a more than 1500 km latitudinal gradient allowed for establishing the main environmental factors controlling the transport of dissolved river components in this environmentally important region, comprising continuous, discontinuous, sporadic and permafrost-free zones. There was significant latitudinal trend consisting in general decrease of DOC, DIC, SO4, and major cation (Ca, Mg, Na, K) concentrations northward, reflecting the interplay between groundwater feeding (detectable mostly in the permafrost-free zone, south of 60° N) and surface flux (in the permafrost-bearing zone). The trend of inorganic components was mostly pronounced in winter and less visible in spring, whereas for DOC, the trend of concentration decrease with latitude was absent in winter, and less pronounced in the spring flood than in the summer baseflow. The latitudinal trends persisted over all river watershed sizes, from < 100 to > 10 000 km². This suggested that in addition to groundwater feeding of the river, there was a significant role of surface and shallow subsurface flow linked to plant litter degradation and peat leaching. Environmental factors are ranked by their increasing effect on DOC, DIC, d13CDIC, and major elements in western Siberian rivers as the following: watershed area < season < latitude. Seasonal fluxes of dissolved components did not significantly depend on the river size and as such could be calculated as a~function of watershed latitude. Unexpectedly, the DOC flux remained stable around 3 t km-2 yr-1 until 61° N, decreased two-fold in the discontinuous permafrost zone (62-66° N), and increased again to 3 t km-2 yr-1 in the continuous permafrost zone (67° N). The DIC, Mg, K and Ca followed this pattern. The total dissolved cation flux (TDS_c) ranged from 1.5 to 5.5 t km-2 yr-1, similar to that in central Siberian rivers of the continuous permafrost region. While Si concentration was almost unaffected by the latitude over all seasons, the Si flux systematically increased northward, suggesting a decreasing role of secondary mineral formation in soil and of vegetation uptake. The dominating effect of latitude cannot however be interpreted solely in terms of permafrost abundance and water flow path (deep vs. surface) but has to be considered in the context of different climate, plant biomass productivity, unfrozen peat thickness and peat chemical composition. It can be anticipated that, under climate warming in western Siberia, the maximal change will occur in small (< 1000 km² watershed) rivers DOC, DIC and ionic composition, and this change will be mostly pronounced in summer and autumn. The wintertime concentrations and spring flood fluxes and concentrations are unlikely to be appreciably affected by the change of the active layer depth and terrestrial biomass productivity. Assuming a conservative precipitation scenario and rising temperature over next few centuries, the annual fluxes of DOC and K in the discontinuous permafrost zone may see a maximum increase by a factor of 2, whereas for DIC and Mg, this increase may achieve a factor of 3. The fluxes of Ca and TDS_c may increase by a factor of 5. At the same time, Si fluxes will either remain constant or decrease two-fold in the permafrost-bearing zone relative to the permafrost-free zone of western Siberia. [ABSTRACT FROM AUTHOR]

A basin-wide study was conducted in the Tana River Basin (Kenya), in February 2008 (dry season), September-November 2009 (wet season), and June-July 2010 (end of the wet season) to assess the dynamics and sources of dissolved inorganic carbon (DIC) as well as to quantify CO2 fluxes, community respiration (R), and primary production (P). Samples were collected along the altitudinal gradient (from 3600 m to 8 m) in several headwater streams, reservoirs (Kamburu and Masinga), and main Tana River. DIC concentrations ranged from 0.2mmolL-1 to 4.8mmolL-1 but with exceptionally high values (3.5 ± 1.6 mmolL-1) in Nyambene Hills tributaries. The wide range of δ13CDIC values (-15.0% to -2.4%) indicate variable sources of DIC with headwater streams recording higher signatures compared to main Tana River. With few exceptions, the entire riverine network was supersaturated in CO2, implying the system is a net source of CO2, to the atmosphere. pCO2, values were generally higher in the lower main Tana River compared to headwater tributaries, opposite to the pattern typically observed in other river networks. This was attributed to high suspended sediment in the main Tana River fuelling in-stream community respiration and net heterotrophy. This was particularly evident during 2009 wet season campaign (median pCO2, of 1432ppm) compared to 2010 end of wet season (1002ppm) and 2008 dry season (579 ppm). First-order estimates show in-stream community respiration was responsible for the bulk of total CO2, evasion (59% to 89%) in main Tana River while in tributaries respiration accounted for 4% to 52% of total CO2, evasion, suggesting CO2, evasion in tributaries was sustained by processes than respiration, such as CO2,-oversaturated groundwater input. While sediment loads increase downstream and thus light availability decreases in the water column, both chlorophyll a (0.2µgl-1 to 9.6 µg L-1) and primary production (0.004 µmol L-1 h-1 to 7.38 µmol L-1 h-1) increased consistently downstream. Diurnal fluctuations of biogeochemical processes were examined at three different sites along the river continuum (headwater, reservoir, and mainstream), and were found to be substantial only in the headwater stream, moderate in the reservoir and not detectable at main Tana River. The pronounced diurnal fluctuations observed in the headwater stream were largely regulated by periphyton as deduced from the low chlorophyll a in the water column. [ABSTRACT FROM AUTHOR]

The paper discusses the distribution and origin of organic matter in natural waters with regard to the latitudinal geographic zoning in the European territory of Russia (ETR) and Western Siberia (WS) and demonstrates how conditions on the catchments and climate affect the content of autochthonous and allochthonous organic matter. Conditional coefficients of the ratios of these forms are calculated. The influence of the temperature factor on the content of autochthonous organic matter in the waters of the southern territories of the ETR and WS was proved by multivariate statistical methods of analysis. General trends and relations are identified in the distribution of lipids, proteins, and carbohydrates of the autochthonous and allochthonous organic compounds. The mechanism of biochemical transformation of bound carbohydrates of allochthonous organic compounds into free autochthonous ones via the microbial decomposition is demonstrated, which is more typical of waters in the southern regions of WS. The paper discusses how natural and climatic conditions can influence changes in concentrations of organic compounds in the lake waters and structural characteristics of these compounds (contents of aromatic and aliphatic fragments). [ABSTRACT FROM AUTHOR]

Leachate is a major problem in landfills due to the type and amount of pollutants. In Croatia, the usual way of handling leachate is recirculation back to the landfill body. However, this method poses a danger of pollutant leakage into the environment, especially during periods of increased precipitation. Leachate is heavily polluted with organic matter, and its spillage into the environment can cause environmental incidents. This paper presents a model for the efficient treatment of landfill water contaminated with organic matter based on the operating parameters of the existing water treatment system. This scientific research aims to develop a model for landfill water treatment and to design a methodology suitable for significant patterns of organic matter pollution behaviour. The developed conceptual model is a computer-based model that uses randomly selected values from the theoretical probability distribution of the applied variables. The mathematical model is based on a system of differential equations solved by the Runge-Kutta method. A non-parametric test was applied to validate the model, given that the distributions are asymmetric non-Gaussian. The methodology proposed in this paper is based on simulation modelling as a useful method in environmental protection. The developed and validated model has proven that landfill water can be effectively and economically purified. Simulation modelling and environmental informatics can effectively contribute to solving environmental problems on the computer without unnecessary environmental risk. [ABSTRACT FROM AUTHOR]

The coal pillar dam of underground reservoirs and residual coal in goaves have a direct impact on the quality of mine water. In this paper, the coal pillar dam of an underground reservoir and residual coal in the goaf and mine water in the Daliuta coal mine are used as research objects. The adsorption mechanism of residual coal with respect to NO 3 − in mine water was analyzed by carrying out adsorption experiments. The composition and variation of organic matter in mine water at different times were simulated using three-dimensional fluorescence spectrum analysis. The influence of residual coal and microorganisms in underground reservoirs on the change in NO 3 − contents in mine water was explored. Moreover, the mechanism of NO 3 − changes in the water body was clarified. The results showed that the concentration of NO 3 − in the water first decreased and then increased, showing a downward trend as a whole. The adsorption of NO 3 − by residual coal led to a decrease in its concentration, which conformed to a pseudo-second-order kinetic model and Freundlich isothermal adsorption model, indicating that the adsorption process of NO 3 − by residual coal is mainly carried out via chemical adsorption and multi-layer adsorption. The increase in NO 3 − concentration was caused by the hydrolysis of tryptophan and other protein-like substances in the water into nitrate under the action of microorganisms. [ABSTRACT FROM AUTHOR]

Determining the potential sources of water that eventually become organic matter that make up the bulk of tree biomass has been facilitated by using the stable isotope composition of waters. Until recently these water sources were thought to only be taken up by roots from soils and other subsurface reservoirs. However, there is a growing body of evidence that now shows that water taken up directly by leaves and stems can not only be significant but can also dominate as the water source used in organic matter synthesis. In this commentary, I review and discuss these issues and point to an important paper by Akira Kagawa in this issue of Tree Physiology that provides a new experimental method and some striking evidence that foliar water uptake can be the primary water source that makes up tree biomass. [ABSTRACT FROM AUTHOR]

The spatial distribution of the air-sea flux of carbon dioxide is a poor indicator of the underlying ocean circulation and of ocean carbon storage. The weak dependence on circulation arises because mixing-driven changes in solubility driven and biologicallydriven air-sea fluxes largely cancel out. This cancellation occurs because mixing driven increases in the poleward residual mean circulation results in more transport of both remineralized nutrients and heat from low to high latitudes. By contrast, increasing vertical mixing decreases the storage associated with both the biological and solubility pumps, as it decreases remineralized carbon storage in the deep ocean and warms the ocean as a whole. [ABSTRACT FROM AUTHOR]

The cores of the subtropical anticyclonic gyres are characterized by their oligotrophic status and minimal chlorophyll concentration, compared to that of the whole ocean. These zones are unambiguously detected by space borne ocean color sensors thanks to their typical spectral reflectance, which is that of extremely clear and deep blue waters. Not only the low chlorophyll (denoted [Chl]) level, but also a reduced amount of colored dissolved organic matter (CDOM or "yellow substance") account for this clarity. The oligotrophic waters of the North and South Pacific gyres, the North and South Atlantic gyres, and the South Indian gyre have been comparatively studied with respect to both [Chl] and CDOM contents, by using 10-year data (1998-2007) of the Sea-viewing Wide field-of-view Sensor (SeaWiFS, NASA). Albeit similar these oligotrophic zones are not identical regarding their [Chl] and CDOM contents, as well as their seasonal cycles. According to the zone, the averaged [Chl] value varies from 0.026 to 0.059 mg m-3, whereas the ay(443) average (the absorption coefficient due to CDOM at 443 nm) is comprised between 0.0033 and 0.0072 m-1. The CDOM-to-[Chl] relative proportions also differ between the zones. The clearest waters, corresponding to the lowest [Chl] and CDOM concentrations, are found near Easter Island and near Mariana Islands in the western part of the North Pacific Ocean. In spite of its low [Chl], the Sargasso Sea presents the highest CDOM content amongst the six zones studied. Except in the North Pacific gyre (near Mariana and south of Hawaii islands), a conspicuous seasonality appears to be the rule in the other 4 gyres and affects both [Chl] and CDOM; both quantities vary in a ratio of about 2 (maximum-to-minimum). Coinciding [Chl] and CDOM peaks occur just after the local winter solstice, which is also the period of the maximal mixed layer depth in these latitudes. It is hypothesized that the vertical transport of unbleached CDOM from the subthermocline layers is the main process enhancing the CDOM concentration within the upper layer in winter. In summer, the CDOM experiences its minimum which is delayed with respect to the [Chl] minimum; apparently, the solar photo-bleaching of CDOM is a slower process than the post-bloom algal Chl decay. Where they exist, the seasonal cycles are repeated without notable change from year to year; long term (10 years) trends have not been detected in these zones. These oligotrophic gyres can conveniently be used for in-flight calibration and comparison of ocean color sensors, provided that their marked seasonal variations are accounted for. [ABSTRACT FROM AUTHOR]

The lidar ratio of seawater is an essential quantity related to both lidar retrieval and water constituent. However, few studies discuss its spatial–temporal characteristics and ecological significance, which limits its applications in lidar remote sensing and marine science. This paper investigates the spatial–temporal characteristics and ecological significance of the lidar ratio of seawater using satellite passive remote sensing, which is validated by in situ measurements. Spatially, nearshore lidar ratio values are higher than offshore, mainly owing to the high concentration of colored dissolved organic matter in nearshore water. Temporally, the lidar ratio in each hemisphere exhibits lower values in summer than in winter due to the annual boom–bust cycle of phytoplankton. Furthermore, the variability patterns of the lidar ratio are nearly consistent with those of the chlorophyll-to-carbon ratio, implying the high ecological significance of phytoplankton physiology. These findings will provide the foundation for the application of lidar ratio in marine science and lidar remote sensing. [ABSTRACT FROM AUTHOR]