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Sources and cycling of phosphorus in the sediment of inflow rivers (FL, TY and QY) along the eutrophic Chaohu lake, China were discussed by using the oxygen isotope compositions of phosphorus fract...

With the population growth, urbanization and industrialization, China has become a hotspot of atmospheric deposition nitrogen (ADN), which is a threat to ecosystem and food safety. However, the impacts of increased ADN on rice growth and grain metal content are little studied. Based on previous long-term ADN studies, greenhouse experiment was conducted with four simulated ADN rates of 0, 30, 60 and 90 kg N ha−1 yr−1 (CK, N1, N2 and N3 as δ15N, respectively) to assess rice growth and metal uptake in a red soil ecosystem of southeast China during 2016–2017. Results showed that simulated ADN could promote rice growth and increase yields by 15.68–24.41% (except N2) and accumulations of cadmium (Cd) or copper (Cu) in organs. However, there was no linear relationship between ADN rate and rice growth or Cd or Cu uptake. The 15N-ADN was mainly accumulated in roots (21.31–67.86%) and grains (25.26–49.35%), while Cd and Cu were primarily accumulated in roots (78.86–93.44% and 90.00–96.24%, respectively). 15N-ADN and Cd accumulations in roots were significantly different between the two growing seasons (p

The typhoon process has a significant influence on the distribution of heavy metals in sediments. Based on the heavy metal (V, Cr, Co, Ni, Cu, Zn, Pb, and Mn) contents in surface sediments collected under normal conditions and post-typhoon Matmo in Quanzhou Bay in 2014, the distributions, sources, and impacts of typhoon processes on heavy metals and pollution conditions were studied and discussed. The results showed that the heavy metals can be divided into two categories: Class I metals (Cu, Zn, Pb, and Mn) were mainly distributed in the estuary and significantly increased after the typhoon, and Class II metals (V, Cr, Co, and Ni) were distributed in the coastal intertidal zone and estuary and remained unchanged or decreased after the typhoon. The heavy metal assessment showed that heavy metal pollution in Quanzhou Bay was serious and tended to increase after the typhoon. The increased metal supply and enhanced riverine and tidal hydrodynamics after the typhoon may be the main factors influencing the variations in heavy metal content and distribution. This study provided a basis for the accurate evaluation and scientific management of heavy metal pollution caused by typhoon processes in Quanzhou Bay.

Fifty-seven riverine samples in three typical regions, namely, upper mountainous (zone 1), middle hilly (zone 2), and lower plain (zone 3) regions, were collected in May (low flow) and August (high flow) of 2016, and chemical parameters and isotopes were analyzed to enrich the knowledge of riverine nitrate sources and transformations in the Taizi River basin. Results showed that NO3- concentrations in zone 3 were the highest, followed by zones 2 and 1. NO3-/Cl- molar ratios and nitrate dual isotopes indicated that NO3- was mainly from chemical fertilizer (CF) in zones 1 (57.0%) and 2 (43.1%) according to a Bayesian mixing model (SIAR) and mixed sources of CF, nitrification of soil organic nitrogen (SON), and manure and sewage (M&S) in zone 3 (92.8%), during the high-flow season. NO3- was mainly from CF and SON in zones 1 (76.7%) and 2 (74.0%), during the low-flow season. NO3-sources were different in the three rivers of zone 3 mainly due to various urban inputs. Contributions of CF, SON, and M&S increased by 13%, 8.3%, and 7.5% in zones 1, 2, and 3, respectively, from the low-flow to the high-flow season. NO3- in the Taizi River was mainly influenced by nitrification in soils, while no significant denitrification was found in the three zones. Measures for reducing NO3- inputs to rivers should be considered by improving effectively utilizing rate of chemical fertilizer and inhibit nitrification.

The concentrations of Cr, Ni, Cu, Zn, As, Cd, Pb, and Al in suspended particles were measured, and temperature, salinity, flow velocity and direction during a tidal cycle were observed before and after Typhoon Fung-wong at six stations in Quanzhou Bay, respectively. The comparison results show that, after the typhoon, the salinity in Quanzhou Bay decreased, whereas the concentrations of heavy metals increased by a factor of between 2 and 10, and the high heavy metal concentration corresponded to the low value of ratio between heavy metals and Al (HMs/Al), suggesting that these increased heavy metals were mainly from natural sources. Instantaneous unit width flux calculations for heavy metals at different stations indicate that sediments are an important source of heavy metals in suspended particles under the influence of typhoon, which has significantly contribution to understanding the impact of typhoons on the heavy metal pollution in the coastal area.

The sulfate reduction process plays an important role in the early diagenesis of organic matter in the estuarine and coastal sediments. In this study, the sulfate reduction rates (SRR) were determined by the 35SO42− radioactive tracer method, and the SO42−, CH4, Cl− of sediment porewater and total organic carbon (TOC), temperature, and redox potential (Eh) of sediment were determined simultaneously at three stations (QA, HQ, and GS) in different sedimentary environments of the Pearl River Estuary to study the sulfate reduction process and its important role in organic matter mineralization. The results show that SRR was mainly controlled by the content and availability of organic matter in sediments of the Pearl River Estuary. The consumption of sulfate mainly included the organic matter mineralization on the upper sediments and the anaerobic oxidation of methane (AOM) driven by sulfate in the sulfate-methane transition zone (SMT), which formed two peaks in the SRR profile, respectively (stations HQ and GS). Affected by physical disturbance, there was only one SRR peak formed above the SMT at station QA. The results of flux calculations for AOM and sulfate reduction show that the contributions of AOM to total sulfate reduction were 7.04 %, 5.46 %, and 42.0 % at stations QA, HQ, and GS, respectively, which were also controlled by the content and availability of organic matter in sediments. The depths of SMT in sediments of stations QA, HQ, and GS were 25, 30, and 213 cm, respectively, which were controlled by the input of organic matter and sulfate concentration in sediments. The calculation results show that total fluxes of sulfate reduction were 22.7, 35.3, and 3.9 mmol m−2 d-l at stations QA, HQ, and GS, respectively, and the rates of organic carbon mineralization by sulfate reduction were 45.4, 70.6, and 7.8 mmol m−2 d-l. In the estuarine mouth (station GS) with relatively weak hydrodynamic force and deep water, the burying efficiency of organic matter in sediment was higher than that in the brackish coast (station HQ); whereas the burial efficiency of organic matter in sediment cannot be comprehensively estimate in the upper estuary (station QA) due to the existence of the fluid mud layer. These findings contribute to a comprehensive understanding of the biogeochemical cycling process of sulfate and methane in sediments of the Pearl River Estuary.

The 18O/16O of lignin at bulk, molecular and positional levels can be used to extract valuable information about climate, plant growth environment, plant physiology, and plant metabolism. Access to the individual oxygen isotope compositions (δ18O) in the lignin monomeric units is, however, challenging as depolymerization of lignin to release the monomeric units may cause isotope fractionation. We have developed a novel method to measure the δ18O of the three oxygens (O-3, O-4 and O-5) attached to the aromatic ring of the monomeric units (bearing no oxygen in their side chains) releasable by highly selective W2C/AC (tungsten carbide supported by activated carbon)-catalyzed hydrogenolysis of lignin. O-4 is obtained by measuring the δ18O of H-type monomeric unit, while O-3 and O-5 can be calculated following isotope mass balance between H, G and S-type monomeric units measurable simultaneously with GC/Py/IRMS (gas chromatography-pyrolysis-isotope ratio mass spectrometry). The measurement precisions are better than 1.15 mUr and 4.15 mUr at molecular and positional levels, respectively. It was shown that there were a δ18OH > δ18OG > δ18OS isotopic order in the herbaceous plant lignin and an (inclusive) opposite order in woody plant lignin. Such differences in isotopic order is likely to be caused by the fact that both L-tyrosine, which carries an 18O-enriched leaf water signal, and L-phenylalanine, which carries mainly a molecular O2 isotopic signal, serve as the precursors for lignin biosynthesis in herbaceous plants while only the latter serves as precursor for lignin biosynthesis in woody plants. We have highlighted the potential application of such molecular and positional levels isotopic signals in plant physiological, metabolic, lignin biosynthetic and climate studies.

The geochemical compositions of sediments in the Dongshan Bay, a semi-enclosed bay on the southeast coast of China, were obtained to identify pollutant sources and evaluate the anthropogenic impacts over the last 100 years. The results indicated that the metal flux had been increasing since the 1980s. Enrichment factor values (Pb, Zn and Cu) suggested only slight enrichment. The proportion of anthropogenic Pb changed from 9% to 15% during 2000-2014. Coal combustion might be an important contamination source in the Dongshan Bay. The historical variation in the metal flux reflected the economic development and urbanization in the Zhangjiang drainage area in the past 30 years. According to the Landsat satellite remote sensing data, the urbanization area expanded approximately three times from 1995 to 2010. The δ13C values (-21‰ to -23‰) of the organic matter (OM) in the sediments indicated that the OM was primarily sourced from aquatic, terrigenous and marsh C3 plants. Nitrogen was mainly derived from aquatic plants and terrigenous erosion before the 1980s. However, the total organic carbon (TOC) contents, total nitrogen (TN) contents and δ15N had been increasing since the 1980s, which suggested that the sources of nitrogen were soil erosion, fertilizer and sewage. In addition, the TOC and TN fluxes in the Dongshan Bay had significantly increased since the 1980s, which reflected the use of N fertilizer. However, the TOC and TN fluxes significantly decreased in the past decade because environmental awareness increased and environmental protection policies were implemented.

The chemical linkage between α-cellulose and lignin in plant cell walls has long been a controversial topic and crucial to devising effective strategies for sustainable biomass and bioenergy utilization. In this new contribution, we surveyed 80 Poaceae (Gramineae) species grown in tropical Hainan Island (China) to test the hypothesis that the presence of oxygen-containing chemical linkage in Poaceae species is widespread. Our innovative natural abundance oxygen isotopic analysis allowed us to infer that more than 1/3 of the species investigated has chemical (ether) linkages between α-cellulose and lignin in their leaf cell walls, with a species-specific 2–89 oxygen-containing bonds for every 1000 glucose units. However, the presence of such linkage appears to be phylogeny-dependent. On average, species of C3 photosynthetic mode are found to have more extensive oxygen-containing linkages than those of C4 photosynthetic mode. Our finding challenges the conventional view that no chemical bonds between α-cell...

Extreme weather events occur frequently under global warming scenarios and have an important impact on the global carbon cycle. Compared to large rivers, small rivers are more sensitive to extreme weather events (such as typhoons). This paper reports the results of a study carried out in the Quanzhou Bay to explore the evolution of small river estuarine sedimentary organic matter after typhoon process using measurements of the grain-size, total organic carbon (TOC), total nitrogen (TN) and δ13C of surface sediment samples collected 2–3 days and a month, respectively, after typhoon Matmo landing in 2014. The results show that the contents of TOC and TN in the sediments, which gradually decrease from the estuary to the outer sea of Quanzhou Bay, decreased approximately 13% and 16%, respectively, a month later compared with 2–3 days after typhoon landing. The significant decrease occurred in the Jinjiang River estuary and along the South Channel of Quanzhou Bay, while the North Channel and Luoyangjiang River estuary retained high levels of TOC and TN. The results of δ13C values and TOC/TN ratios show that the organic matter in the sediment of the Quanzhou Bay was a mixture derived from C3 terrestrial plants and marine algae. The terrestrial organic matter was mainly deposited in the Jinjiang River estuary 2–3 days after typhoon landing and then spread along the tidal channel to the outer sea a month later. It indicates that the hydrodynamic forces stirred sedimentary organic matters that were input and settled during typhoon, and transported later along the North and South Channel to the outer sea. Some of those organic matters were accumulated in the North Channel during the transport process. The results provide significant meaning for the carbon cycle and material flux study on the coastal and margin seas.

Emperor penguins (Aptenodytes forsteri) are sensitive to the Antarctic climate change because they breed on the fast sea ice. Studies of paleohistory for the emperor penguin are rare, due to the lack of archives on land. In this study, we obtained an emperor penguin ornithogenic sediment profile (PI) and performed geochronological, geochemical and stable isotope analyses on the sediments and feather remains. Two radiocarbon dates of penguin feathers in PI indicate that emperor penguins colonized Amanda Bay as early as CE 1540. By using the bio-elements (P, Se, Hg, Zn and Cd) in sediments and stable isotope values (δ(15)N and δ(13)C) in feathers, we inferred relative population size and dietary change of emperor penguins during the period of CE 1540-2008, respectively. An increase in population size with depleted N isotope ratios for emperor penguins on N island at Amanda Bay during the Little Ice Age (CE 1540-1866) was observed, suggesting that cold climate affected the penguin's breeding habitat, prey availability and thus their population and dietary composition.

A novel approach for measurement of stable carbon isotopic ratio of atmospheric aerosols was developed by tandem operation of two instruments: a Sunset Organic Carbon-Elemental Carbon (OC-EC) analyzer and an online Carbon Dioxide Stable Isotope Analyzer (LGR, CCIA-36d). Sensitivity, accuracy and measurement uncertainty of the CCIA was comprehensively investigated using the standard reference CO_2 gas with known concentration and isotopic ratio. Drift in CCIA measurement due to varying CO_2 and water vapor concentration was evaluated and a humidity stabilizer was designed and developed to control the water vapor concentration of exhaust gas flow from OC-EC prior to entering the CCIA. A Keeling approach was applied to separate the ratio in the samples from the mixture of PM sample-produced CO_2 and reference gas and we developed a protocol to derive the isotopic composition of the particle samples. A lithium carbonate standard (in powder form) from National Institute of Standards and Technology (NIST) was used to validate measurement of δ^(13)C ratios by CCIA. Offline measurement on ambient aerosol and diesel exhaust aerosols produced comparable results of isotopic ratio with literature values. This study demonstrates the utility of this tandem operation for carbon isotopic measurement of atmospheric particles with better than 1.0 per mille precision as a cost-effective alternative of conventional Isotopic Ratio Mass Spectrometer (IR-MS).

Two sedimentary cores in the Minjiang River estuary (SE China) are documented for grain size, clay minerals, heavy metals, magnetic parameters and Pb isotopes to investigate the source and historical variation of heavy metals. The MJK9 core was collected outside of the Minjiang River estuary, and the core is composed of mixed sediments, of which ~70% from the Yangtze River and 30% from the Minjiang River. It is thus difficult to be used for tracing the human activity along the Minjiang River. In contrast, the sediments of MJK16 core which was collected in a nearshore area are primarily from the Minjiang River. The enrichment factors of the sediments were1.5, indicating minor pollution. The results indicate that the sediments of the MJK16 core have Cu and Pb concentrations increasing since 1980, associated with the increase of magnetic mineral concentration and (206)Pb/(207)Pb and (206)Pb/(208)Pb of the sediments. We compared the Pb isotopic compositions between our results and those for the deposit mining in the Minjiang River basin, and aerosols and coal dust in south China, and considered that Pb in the sediments of the MJK16 core was derived primarily from weathered rocks as well as industrial emission (e.g. coal combustion). The sediments have anthropogenic Pb concentrations ranging from 6% in 1950 to 23.7% in 2010, consistent with the impact of rapid urban and industrial development in China.

In situ U–Pb dating and Hf isotopic of detrital zircons from beach sediments of Yalong Bay were analyzed to trace sedimentary provenance and reveal the crustal evolution of Hainan Island in South China. The grain size distribution of the sediments displays a clear single-peak feature, indicating the sediments were formed under the same condition of hydrodynamic force. The detrital zircons had Th/U ratios of greater than 0.1, and REE pattern displayed a positive Ce anomaly and a negative Eu anomaly, indicating that these zircons are predominantly of magmatic origin. The U–Pb spectrum of detrital zircons mainly peaked at the Yanshanian (96–185 Ma), Hercynian–Indosinian (222–345 Ma) and Caledonian (421–477 Ma). A portion of the detrital zircons were of Neoproterozoic origin (728–1,003 Ma), which revealed that the basement in the eastern region of Hainan Island was mainly of Neoproterozoic, with rare Archean materials. The positive eHf(t) values (0 to +10.1) of the Neoproterozoic detrital zircons indicated that the juvenile crust grew in the southeastern Hainan Island mainly during the Neoproterozoic period. The Neoproterozoic orogeny in the southeastern part of the island (0.7–1.0 Ga) occurred later than in the northwestern region of the island (1.0–1.4 Ga). Importantly, the Grenvillian orogeny in the southeastern area of Hainan Island shared the same timing with that of the western Cathaysia Block; i.e., both areas concurrently underwent this orogenic event, thereby forming a part of the Rodinia supercontinent. Afterwards, the crust experienced remelting and reworking during the Caledonian Hercynian–Indosinianand Yanshanian accompanied by the growth of a small amount of juvenile crust.

The distribution of methane in the western Pearl River Estuary (PRE) and northern South China Sea (SCS) was investigated during an oceanic cruise in September, 2006. Results show that the methane concentration in surface water ranged from 6.9 to 173.7 nmol L− 1 at the 27 stations sampled in the western PRE. The methane saturation ratio ranged from 329 to 7896%, and the average sea-to-air methane flux was about 63.5 ± 32.2 μmol m− 2 d− 1. The methane concentration in surface water was high in the western margin of the upper estuary, near marshes and shoals. The methane concentration decreased rapidly from the estuarine margin to the open coastal ocean, resulting from salinity (sulfate) increase in the overlying water, increasing water depth, diffusion across the air–sea interface and dilution of seawater during estuarine mixing. The major methane source in the PRE is thought to be methanogenic degradation in organic-enriched sediments. In the northern SCS, the concentration of methane varied from 2.4 to 5.9 nmol L− 1 in surface water at the 55 testing stations. The methane saturation ratio was between 134 and 297 %, and the sea-to-air methane flux was estimated to be 15.6 ± 8.0 μmol m− 2 d− 1. Two stations located at E7 (15° 59.405″; 17° 59.165″) and E6 (115° 0.065″; 17° 0.032″) showed abnormal methane concentrations of 9.5 and 13.8 nmol L− 1 in surface water, respectively, and were probably affected by pollution from allochthonous oil. A subsurface methane maximum (4–5 nmol L− 1) occurred in water that was 150–200 m deep within this area. This maximum may be due to accumulation of plankton productive particulates and limited sea–air exchange in the sea surface layer. Abnormally high methane values of 4.3 and 8.7 nmol L− 1 were measured in the bottom waters of stations B8 and E4, respectively. These can be interpreted as being due to methane seeps from seafloor sediments.

Here the composition of total and active archaeal communities in a sediment core of Jiulong River estuary at Fujian Province, Southern China was reported. Profiles of CH(4) and SO(2-) (4) concentrations from the sediment core indicated the existence of a sulfate-methane transition zone (SMTZ) in which sulfate reduction-coupled anaerobic oxidation of methane (AOM) occurs. Accordingly, three sediment layers (16-18.5 cm, 71-73.5 cm, and 161-163.5 cm) from the 1.2 m sediment core were sectioned and named top, middle and bottom, respectively. Total DNA and RNA of each layer were extracted and used for clone libraries and sequence analysis of 16S rRNA genes, the reverse transcription (RT)-PCR products of 16S rRNA and methyl CoM reductase alpha subunit (mcrA) genes. Phylogenetic analysis indicated that archaeal communities of the three layers were dominated by the Miscellaneous Crenarchaeotal Group (MCG) whose ecological functions were still unknown. The MCG could be further divided into seven subgroups, named MCG-A, B, C, D, E, F, and G. MCG-A and MCG-G were the most active groups in the estuarine sediments. Known anaerobic methanotrophic archaea (ANMEs) were only found as minor components in these estuarine archaeal communities. This study, together with the studies of deep subsurface sediments, would be a very good start point to target and compare the specific active archaeal groups and their roles in the dark, deep subsurface sediment environments.