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The driving forces, kill and recovery mechanisms for the end-Permian mass extinction (EPME), the largest Phanerozoic biological crisis, are under debate. Sedimentary records of mercury enrichment and mercury isotopes have suggested the impact of volcanism on the EPME, yet the causes of mercury enrichment and isotope variations remain controversial. Here, we model mercury isotope variations across the EPME to quantitatively assess the effects of volcanism, terrestrial erosion and photic zone euxinia (PZE, toxic, sulfide-rich conditions). Our numerical model shows that while large-scale volcanism remains the main driver of widespread mercury enrichment, the negative shifts of Δ199Hg isotope signature across the EPME cannot be fully explained by volcanism or terrestrial erosion as proposed before, but require additional fractionation by marine mercury photoreduction under enhanced PZE conditions. Thus our model provides further evidence for widespread and prolonged PZE as a key kill mechanism for both the EPME and the impeded recovery afterward.

Ferric ions can bind strongly with dissolved organic matter (DOM), including humic acids (HA), fulvic acids (FA), and protein-like substances, whereas isolation of Fe-DOM precipitates (Fe-DOMP) and their biochemical characteristics remain unclear. In this work FeCl3 was used to isolate DOM components from various sources, including river, lake, soil, cow dung, and standard tryptophan and tyrosine, through precipitation at pH 7.5–8.5. The Fe-DOMP contribute to total DOM by approximately 38.6–93.8% of FA, 76.2% of HA and 25.0–30.4% of tryptophan and tyrosine, whilst fluorescence spectra allowed to monitor/discriminate the various DOM fractions in the samples. The relative intensity of the main infrared peaks such as 3406‒3383 cm−1 (aromatic OH), 1689‒1635 cm−1 (‒COOH), 1523–1504 cm−1 (amide) and 1176–1033 cm−1 (‒S=O) show either to decline or disappear in Fe‒DOMP. These results suggest the occurrence of Fe bonds with various functional groups of DOM, indicating the formation of π–d electron bonding systems of different strengths in Fe‒DOMP. The novel method used for isolation of Fe-DOMP shows promising in opening a new frontier both at laboratory and industrial purposes. Furthermore, results obtained may provide a better understanding of metal–organic complexes involved in the regulation of the long-term stabilization/sequestration of DOM in soils and waters.

Atmospheric ammonia (NH3) and ammonium (NH4+) can substantially influence air quality, ecosystems, and climate. NH3 volatilization from fertilizers and wastes (v-NH3) has long been assumed to be the primary NH3 source, but the contribution of combustion-related NH3 (c-NH3, mainly fossil fuels and biomass burning) remains unconstrained. Here, we collated nitrogen isotopes of atmospheric NH3 and NH4+ and established a robust method to differentiate v-NH3 and c-NH3. We found that the relative contribution of the c-NH3 in the total NH3 emissions reached up to 40 ± 21% (6.6 ± 3.4 Tg N yr−1), 49 ± 16% (2.8 ± 0.9 Tg N yr−1), and 44 ± 19% (2.8 ± 1.3 Tg N yr−1) in East Asia, North America, and Europe, respectively, though its fractions and amounts in these regions generally decreased over the past decades. Given its importance, c-NH3 emission should be considered in making emission inventories, dispersion modeling, mitigation strategies, budgeting deposition fluxes, and evaluating the ecological effects of atmospheric NH3 loading.

A large number of gases are releasing from the medium-high temperature geothermal fields distributed along the large-scale strike-slip fault zones in the southeastern margin of the Tibetan Plateau. In this study, 11 hot spring water and the associated bubbling gas samples were collected along the Xianshuihe-Anninghe fault zones (XSH-ANHFZ) and analyzed for chemical and isotopic compositions. The $${\delta ^{18}}{{\rm{O}}_{{{\rm{H}}_2}{\rm{O}}}}$$ and $$\delta {{\rm{D}}_{{{\rm{H}}_2}{\rm{O}}}}$$ values indicate that hot spring waters are predominantly meteoric origin recharged from different altitudes. Most water samples are significantly enriched in Na+ and HCO3− due to the dissolution of regional evaporites, carbonates and Na-silicates. 3He/4He ratios of the gas samples are 0.025–2.73 times the atmospheric value. The 3He/4He ratios are high in the Kangding region where the dense faults are distributed, and gradually decrease with increasing distance from Kangding towards both sides along the Xianshuihe fault zones (XSHFZ). Hydrothermal fluids have dissolved inorganic carbon (DIC) concentrations from 2 to 42 mmol L−1, δ13CDIC from −6.9‰ to 1.3‰, $${\delta ^{13}}{{\rm{C}}_{{\rm{C}}{{\rm{O}}_2}}}$$ from −7.2‰ to −3.6‰ and Δ14C from −997‰ to −909‰. Combining regional geochemical and geological information, the CO2 sources can be attributed to deep-sourced CO2 from mantle and metamorphism of marine carbonate, and shallow-sourced CO2 from the dissolution of marine carbonate and biogenic CO2. The mass balance model shows that 11±6% of the DIC is sourced from the dissolution of shallow carbonate minerals, 9±8% formed by pyrolysis of sedimentary organic matter, 80±9% derived from deep metamorphic origin and mantle-derived CO2. Among them, the deep-sourced CO2 in Anninghe fault zones (ANHFZ) is merely metamorphic carbon, whereas ca. 12% and ca. 88% of the deep-sourced CO2 in the XSHFZ are derived from the mantle and metamorphic carbon, respectively. The average deep-sourced CO2 flux in the Kangding geothermal field is estimated to be 160 t a−1. If all the hot springs in various fault zones in the southeastern margin of the Tibetan Plateau are taken into account, the regional deep-sourced CO2 flux would reach ca. 105 t a−1. These results show that the deep-sourced CO2 released from non-volcanic areas might account for a considerable proportion of the total amount of global deep-sourced carbon degassing, which should be paid more attention to.

Landscape evolution is modulated by the regional tectonic uplift, climate change, and river dynamics. However, how to distinguish these mechanisms through the research of surface exhumation and fluvial incision remains controversial. In this study, cosmogenic 10Be, 26Al, and 21Ne concentrations in quartz from cave deposits, modern river sediments, and bedrocks were measured to constrain the applicability of cosmogenic 21Ne and discuss Quaternary landscape evolution history in the Guizhou Plateau, southeast China. Using the 26Al-10Be and 21Ne-10Be pairs to distinguish the cosmogenic 21Ne concentration from the excess 21Ne, we found that the nucleogenic 21Ne produced by the U and Th decay in quartz is significant in the samples although there is the possibility of inherited cosmogenic 21Ne. Combining with previous studies, we suggest that the precise approach for applying the cosmogenic 21Ne could be reached by (1) estimating the contribution from nucleogenic 21Ne, (2) avoiding samples with complex burial histories to exclude inherited cosmogenic 21Ne, and (3) combining the 10Be-26Al-21Ne nuclides method for the Quaternary samples. In addition, both pre-burial basin denudation rates and burial ages derived from the 26Al-10Be pair were used to determine the different timescale surface denudation rate and fluvial incision rate in relation to previous work. The consistency of the different timescales pre-burial basin denudation rate, 36Cl surface denudation rate, and modern basin denudation rate indicates that the landscape-scale surface denudation has been likely stabilized since the Quaternary in the Guizhou Plateau area. The slightly higher river incision rates than the local surface denudation rate show that the river dynamics may not have reached a steady-state due to the regional tectonic uplift in the Guizhou Plateau.

Exploring the source, transformation pathways, and the fate of natural organic matter (NOM) is critical to understanding the regional/global carbon cycle and carbon budget. The dissolved fraction of NOM, i.e., dissolved organic matter (DOM), is a complex mixture resulting from the transformation of plant, animal and microbial matter and plays a crucial role in many biogeochemical processes at the land-ocean-atmosphere interfaces. The advance of Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) makes the detailed characterization of DOM at the molecular level possible. On the other hand, elucidation of complex DOM sample also presents significant analytical challenges, and these challenges also act as a driving force for the instrumentation and methodology development on FT-ICR MS. This review article has been written to aid those working in biogeochemistry, environmental and atmospheric chemistry, and related areas which investigate elemental cycles and DOM transformations. First, the fundamental theory, historical perspective, and recent advances in the field have been introduced. The detailed molecular characterization of environmental and geological samples continues to present significant analytical challenges, and it also has become a driving force for the development of the instrumentation and experimental methods. These achievements in DOM analysis have had an impact upon the fields of environmental science, geochemistry, and analytical chemistry. Next, varieties of applications of FT-ICR MS have also been described, followed by our view of the future of this technique in earth science research. We believe that this review covers the essential pairing of FT-ICR MS and collectively offers environmental and geochemical scientists a substantial resource for their research. Graphical abstract

Hydroelectric reservoirs are highly regulated ecosystems, where the understanding on bacterioplankton has been very limited so far. In view of significant changes in river hydrological conditions by dam construction, hydraulic load (i.e., the ratio of mean water depth to water retention time) was assumed to control bacterioplankton diversity in cascading hydropower reservoirs. To evaluate this hypothesis, we investigated bacterioplankton composition and diversity using high-throughput sequencing and related environmental variables in eleven reservoirs on the Wujiang River, Southwest China. Our results showed a decrease of bacterioplankton diversity index with an increase of reservoir hydraulic load. This is because hydraulic load governs dissolved oxygen variation in the water column, which is a key factor shaping bacterioplankton composition in these hydroelectric reservoirs. In contrast, bacterioplankton abundance was mainly affected by nutrient-related environmental factors. Therefore, from a hydrological perspective, hydraulic load is a decisive factor for the bacterioplankton diversity in the hydroelectric reservoirs. This study can improve the understanding of reservoir bacterial ecology, and the empirical relationship between hydraulic load and bacterioplankton diversity index will help to quantitatively evaluate ecological effects of river damming.

2,5-substituted-6-(4-nitrophenyl)-5H-thiazolo[3,2-a]pyrimidin-7-amines. This method, optimized under microwave conditions, was highly efficient and environmentally benign and delivered the desired products in good yields (89–96%) in short reaction time (

Zn isotope is a useful tool for tracing biogeochemical processes as zinc plays important roles in the biogeochemistry of natural systems. However, the Zn isotope composition in the lake ecosystems has not been well characterized. In order to resolve this problem, we investigate the Zn isotope compositions of suspended particulate matter (SPM) and biological samples collected from the Aha Lake and Hongfeng Lake, and their tributaries in summer and winter, aiming to explore the potential of this novel isotope system as a proxy for biogeochemical processes in aqueous environments. Concentration of dissolved Zn ranges from 0.65 to 5.06 μg/L and 0.74 to 12.04 μg/L for Aha Lake and Hongfeng Lake, respectively, while Zn (SPM) ranges from 0.18 to 0.70 mg/g and 0.24 to 0.75 mg/g for Aha Lake and Hongfeng Lake, respectively. The Zn isotope composition in SPM from Aha Lake and its main tributaries ranges from -0.18‰ to 0.27‰ and -0.17‰ to 0.46‰, respectively, and it varies from -0.29‰ to 0.26‰ and -0.04‰ to 0.48‰, respectively in Hongfeng Lake and its main tributaries, displaying a wider range in tributaries than lakes. These results imply that Zn isotope compositions are mainly affected by tributaries inputting into Aha Lake, while adsorption process by algae is the major factor for the Zn isotope composition in Hongfeng Lake, and ZnS precipitation leads to the light Zn isotope composition of SPM in summer. These data and results provide the basic information of the Zn isotope for the lake ecosystem, and promote the application of Zn isotope in biogeochemistry.

Since the industrial revolution, it has been assumed that fossil-fuel combustions dominate increasing nitrogen oxide (NOx) emissions. However, it remains uncertain to the actual contribution of the non-fossil fuel NOx to total NOx emissions. Natural N isotopes of NO3− in precipitation (δ15Nw-NO3−) have been widely employed for tracing atmospheric NOx sources. Here, we compiled global δ15Nw-NO3− observations to evaluate the relative importance of fossil and non-fossil fuel NOx emissions. We found that regional differences in human activities directly influenced spatial-temporal patterns of δ15Nw-NO3− variations. Further, isotope mass-balance and bottom-up calculations suggest that the non-fossil fuel NOx accounts for 55 ± 7% of total NOx emissions, reaching up to 21.6 ± 16.6Mt yr−1 in East Asia, 7.4 ± 5.5Mt yr−1 in Europe, and 21.8 ± 18.5Mt yr−1 in North America, respectively. These results reveal the importance of non-fossil fuel NOx emissions and provide direct evidence for making strategies on mitigating atmospheric NOx pollution., This study investigates in the importance of non-fossil fuel NOx emissions in the surface-earth-nitrogen cycle. The study shows how changes of regional human activities directly influence δ15N signatures of deposited NOx to terrestrial environments and that emissions have largely been underestimated.

Exploring the relationship between weathering and erosion is essential for understanding the evolution of landscapes and formation of soil under the influence of climate, tectonics, and topography. We measured the bulk chemistry of regoliths and calculated their weathering rates and intensity in three locations in China: Inner Mongolia in the mid-temperate semi-humid zone; Jiangxi Province, in the mid-subtropical humid zone; and Hainan Province, in the tropical humid zone. These profiles exhibited increased weathering with increasing temperature and precipitation. The low-gradient profile exhibited stronger weathering of saprolite than of soil, whereas the high-gradient profile showed a more constant weathering pattern. The regolith in the cold climate was the product of easily weatherable minerals, whereas weathering of K-feldspar and even secondary minerals occurred in hot and humid climates. The weathering of subtropical profiles was both supply- and kinetic-limited, controlled by weathering and erosion. The tropical profile experienced supply-limited weathering, indicating slow erosion and an intense weathering profile; the mid-temperate profile was not classifiable due to weak erosion and weathering. Long-term weathering fluxes of these profiles show that Si, Na, and K (or Mg) represent the bulk of the mass lost through weathering. This study underscores that weathering of granitic regolith is controlled by both climatic conditions and landscape.

The distribution and anomalies of rare earth elements (REEs) of granitic regolith were studied in Inner Mongolia and Hainan Island, China. One profile showed slight REE enrichment of an upper layer and no obvious light REE/heavy REE (LREE/HREE) fractionation (LaN/YbN of 0.9). The second profile was significantly enriched in REEs and enriched in LREEs in the upper portion (LaN/YbN > 1.8). Eu, Ce, and Gd anomalies of the two profiles are different. Slightly negative Eu, Ce, and Gd anomalies in NMG-3-1 indicate slow dissolution of primary minerals and little secondary products; in contrast, a positive Eu anomaly in HN-2 suggests the vegetation cycle may contribute to soil. The Ce anomaly of HN-2 reflects oxidation of Ce and coprecipitation by Fe- and Mn-oxides and organic matter. Correlation between Ce and Gd anomalies in HN-2 suggests Ce and Gd are both influenced by redox-reduction.

Rare earth elements (REEs) can record geologic and geochemical processes. We studied two granitic regolith profiles from different climatic zones in eastern Tibetan Plateau and found that (1) ΣREEs ranged from 119.65 to 275.33 mg/kg in profile ND and 5.11–474.55 mg/kg in profile GTC, with average values of 205.79 and 161 mg/kg, respectively. ΣREEs was higher in accumulation horizon and semi-regolith; (2) Influenced by climate, the fractionation of light and heavy REEs (LREEs and HREEs) varied during weathering. The ratio of LREEs/HREEs in pedosphere was higher than semi-regolith in tropical profile; (3) A negative Eu anomaly in both profiles was the result of bedrock weathering. A positive Ce anomaly was observed in all layers of profile ND, and only in the upper 100 cm of profile GTC. This indicates that redox conditions along the regolith profile varied considerably with climate. (4) Normalized by chondrite, LREEs accumulated much more than HREEs; REE distribution curves were right-leaning with a V-type Eu anomaly in both profiles.

Carbon stable isotope techniques were extensively employed to trace the dynamics of soil organic carbon (SOC) across a land-use change involving a shift to vegetation with different photosynthetic pathways. Based on the isotopic mass balance equation, relative contributions of new versus old SOC, and SOC turnover rate in corn fields were evaluated world-wide. However, most previous research had not analyzed corn debris left in the field, instead using an average corn plant δ 13C value or a measured value to calculate the proportion of corn-derived SOC, either of which could bias results. This paper carried out a detailed analysis of isotopic fractionation in corn plants and deduced the maximum possible bias of SOC dynamics study. The results show approximately 3‰ isotopic fractionation from top to bottom of the corn leaf. The 13C enrichment sequence in corn plant was tassel > stalk or cob > root > leaves. Individual parts accounting for the total dry mass of corn returned distinct values. Consequently, the average δ 13C value of corn does not represent the actual isotopic composition of corn debris. Furthermore, we deduced that the greater the fractionation in corn plant, the greater the possible bias. To alleviate bias of SOC dynamics study, we suggest two measures: analyze isotopic compositions and proportions of each part of the corn and determine which parts of the corn plant are left in the field and incorporated into SOC.

This study investigated the impact of topography and vegetation on distribution of rare earth elements (REEs) in calcareous soils using methods of single extraction and mass balance calculation. The purposes of the study were to set a basis for further research on the biogeochemical REE cycle and to provide references for soil–water conservation and REE-containing fertilizer amendments. The results show a generally flat Post-Archean Average Australian Shale—normalized REE pattern for the studied calcareous soils. REE enrichment varied widely. The proportion of acid-soluble phases of heavy REEs was higher than that of light REEs. From top to bottom of the studied hills, dominant REE sources transitioned from limestone in-situ weathering to input from REE-containing phases (e.g., clay minerals, amorphous iron, REE-containing fluids). Our results indicate that the REE content of calcareous soils is mainly controlled by slope aspect, while the enrichment degree of REEs is related to geomorphological position and vegetation type. Furthermore, the proportion of acid-soluble phases of REEs is mainly controlled by geomorphological position.

Biological dissimilatory reduction of selenite (SeO32−) to elemental selenium (Se0) is common, but the mineral formation and the biogenic process remain uncertain. In this study, we examined the Se0 formation during the selenite bioreduction by Bacillus licheniformis SeRB-1 through transmission electron microscope (TEM), energy-dispersive spectrometry (EDS) and X-ray absorption fine structure (XAFS) techniques. Results showed that the reduction process occurred mostly during the exponential phase and early stationary phase, whilst the elemental selenium was produced in these periods. From the TEM images and polyacrylamide gel electropheresis, it is known that the Se0 granule formation is a biologically-induced type, and the cell envelopes are the main biomineralization positions, and particles may go through a process from nucleation to crystallization, under the control of microbes. In fact, the minerals are spherical nanoparticles, occurring as a microcrystal or amorphous form. It is vital to recognize which kinds of proteins and/or polysaccharides act as a template to direct nanoparticle nucleation and growth? This should focus for further studies. This study may shed light on the process of formation of Se(0) nanosphere.

A heavy load of nitrogenous compounds reflects nutrient loss and influences water quality in large rivers. Nitrogenous concentrations and dual isotopes of nitrate were measured to ascertain the spatial and temporal distributions of nitrate transformation in the Yellow River, the second-longest river in China. Assessment of the long-term record indicates that [NO3−–N] has increased by two-fold over the past three decades. Weekly observation of ammonium over a twelve-year period revealed high concentrations and suggests impairment of water quality, particularly since 2011. The estimated total dissolved nitrogen flux was 7.2 times higher in middle reaches than that at head waters. Anthropogenic nitrogen sources become more important in lower section of the upper reaches and middle reaches because of intensive agricultural activities and urban input. Nitrate in the lower reaches was mainly derived from transportation of upstream nitrate and point sources from cities. The spatial variation of ammonium and nitrate isotopes show that nitrification is a key process governing nitrogen transformation. Riverine biological processes could potentially be responsible for the shift of nitrate isotope signature. The first step to reducing nitrogen load and improving water quality will be containment and careful management of sources from urban input, sewage waste and irrigation runoff.

To better understand the mechanisms that hydrological conditions control chemical weathering and carbon dynamics in the large rivers, we investigated hydrochemistry and carbon isotopic compositions of dissolved inorganic carbon (DIC) based on high-frequency sampling in the Wujiang River draining the carbonate area in southwestern China. Concentrations of major dissolved solute do not strictly follow the dilution process with increasing discharge, and biogeochemical processes lead to variability in the concentration-discharge relationships. Temporal variations of dissolved solutes are closely related to weathering characteristics and hydrological conditions in the rainy seasons. The concentrations of dissolved carbon and the carbon isotopic compositions vary with discharge changes, suggesting that hydrological conditions and biogeochemical processes control dissolved carbon dynamics. Biological CO2 discharge and intense carbonate weathering by soil CO2 should be responsible for the carbon variability under various hydrological conditions during the high-flow season. The concentration of DICbio (DIC from biological sources) derived from a mixing model increases with increasing discharge, indicating that DICbio influx is the main driver of the chemostatic behaviors of riverine DIC in this typical karst river. The study highlights the sensitivity of chemical weathering and carbon dynamics to hydrological conditions in the riverine system.

To better understand the decreases observed in pH levels downstream from the associated hydroelectric dam, the impounded Wujiang River in Southwest China was investigated. Study results indicate that the average pH decrease from upstream to downstream of the hydroelectric dam could be up to 0.47 units, and pH differences were particularly apparent during water thermal stratification. Notably, pH was controlled by [CO2]/[CO3 2−] ratios in this impounded river. The decrease in [CO2]/[CO3 2−] ratios and associated increases in pH at the surface of the reservoirs were mainly due to the prevalence of photosynthesis, while the reverse phenomenon was observed at the bottom due to respiration. The evidence from δ13CDIC clearly demonstrated these processes. The increase in phytoplankton biomass enhanced this pH decrease, while dissolved organic carbon had limited impacts on the pH variation. The decrease in pH downstream from the hydroelectric dam resulted from the development of pH stratification in the water profile and the dam operations that release bottom waters for hydropower generation. Consequently, the cascade in hydropower development could increase the risk of river acidification.

Inland waters, including rivers and lakes, are increasingly recognized as playing significant roles in the transport, mineralization and burial of organic carbon exported from land. However, in many areas, dissolved inorganic carbon (DIC) dominates the carbon export from catchments. Owing to different production processes and turnover times of organic versus inorganic carbon, CO2 emitted from rivers and lakes may have different impacts on global carbon cycling depending on its origin. Here, pCO2 and dissolved oxygen concentrations were determined, and the ratios of excess CO2 to O2 depletion (ΔCO2/ΔO2) were compared in spring water, river water and lake water in a carbonate catchment located in the southwestern plateau region of China. Results show that groundwater CO2 evasion, at 2.0 g C m−2year−1, is insignificant in terms of terrestrial carbon loss compared with soil CO2 emission. In the rivers, calcite precipitation due to oversaturation is an important mechanism for CO2 production in some seasons. In the lake, HCO3 − contributed approximately 75 % of the total carbon supply to organic matter production and calcite deposition during seasons favoring photosynthesis. The seasons which had high ΔCO2/ΔO2 are the main periods of CO2 emission from the lake, and the extra CO2 may be produced from HCO3 − titration by H+. Thus, lake CO2 evasion was controlled primarily by pH, not respiration. The spring, river, and lake waters mainly process DIC exported from the catchment, of which HCO3 − is primarily derived from carbonate weathering by soil CO2 that, with extraordinarily high ΔCO2/ΔO2, may originate from sources including organic matter decomposition, root respiration (autotrophic), and acid dissolution. Therefore, freshwater CO2 emission is a return pathway of catchment soil CO2 to the atmosphere more than that of net primary production and net ecosystem production.

This study quantifies the surface denudation rate of granitic regolith via the application of the in situ cosmogenic 26Al and 10Be depth profile in China. The concentration ranges of 26Al and 10Be in the quartz along the ~3-m granitic regolith profile in Qinhuangdao are (4.9–23.1) × 105 and (2.3–36.6) × 104 atoms/g, respectively. With the exception of the surface sample, both 26Al and 10Be concentrations decrease exponentially with sample depth. The Chi-square best-fitting results revealed a total denudation rate of ~9 m/Ma averaged over a 103–105 a timescale, which is lower than the values observed in global granitic outcrops. Compared with global datasets, the flat terrain due to the lack of tectonic activities is most likely the dominant factor that controls the local denudation process. The surface sample offsets from the theoretical cosmogenic nuclide distribution implies that the denudation rate from river basin sediment could be overestimated because of the bioturbation in the surficial soil layer.

This study analyzed the water-soluble sulfate (SSO4) and total sulfur (ST) concentrations and their isotopic signatures (δ34SSO4 and δ34ST) in needles of Pinus massoniana Lamb collected from Guiyang (seriously affected by acid rain) and Yunnan areas (acid rain did not occur), China SW. The results indicated that the SSO4 concentrations in needles of Pinus massoniana Lamb collected from several Chinese areas were found to be significantly correlated to ambient sulfur dioxide (R2 = 0.9176, p = 0.01), showing that SSO4 concentrations in needles were more reliable to indicate atmospheric sulfur. The average δ34SSO4 (−7.2 ‰) and δ34STS (−5.1 ‰) in needles in Guiyang areas were significantly lower than those in Yunnan areas (+3.9 and +5.7 ‰, respectively), which were in accordance with the lower δ34S of coals in Guiyang areas than in Yunnan areas. The δ34SSO4 and δ34STS in needles became less positive with a distance from a plant combusted 34S-enriched coals while for another plant combusted 34S-depleted coals, more positive was observed. These results indicated that δ34SSO4 in needles was also a good indicator of atmospheric sulfur sources. A very small difference between δ34 ST and δ34 SSO4 for most needle samples suggested that little isotopic fractionation accompanies sulfur assimilation processes.

We investigated the abundance of different picophytoplankton groups and the phytoplankton pigment ratio in relation to environmental factors such as nutrients and suspended solids along a salinity gradient in the Changjiang River Estuary. The average numbers of Synechococcus spp. (Syn) and picoeukaryotes (Euk) were (2.7 ± 5.1) ×103 and (1.1±1.4) ×103 cells mL−1, respectively. Prochlorococcus spp. (Pro) was only found in the high-salinity brackish water with the concentration of 3.0×103 cells mL−1. Syn and Euk numbers both tended to increase offshore and Syn showed a larger variation in cell abundance than Euk. The contribution of picophytoplankton to total phytoplankton biomass increased with increasing salinity and decreasing nutrient concentrations from the estuary to the open ocean. The response of different picophytoplankton groups to environmental variables was different. Water temperature was more important in its control over Euk than over Syn, while nutrients were more important in their influence over Syn than over Euk. Phytoplankton pigment ratios were different in the three different ecological zones along the salinity gradient (i.e., freshwater zone with 0–5 range, fresh and saline water mixing zone with 5–20 range, and high-salinity brackish water zone with 20–32 range), where three different phytoplankton communities were discovered, suggesting that phytoplankton pigment ratios can be considered as a complementary indicator of phytoplankton community structure in the Changjiang River Estuary.

Excess nutrient (N and P) loads are recognized as the major cause of serious water quality problems in China. River systems play a very important role in nitrate (NO3 −) transportation and transformation in the aquatic environment. To understand and clarify the sources and processes affecting NO3 − in river basins, we have examined spatial and temporal variations of concentration and dual-isotopic composition of NO3 − in the dam-controlled Jialing River, a major tributary of the Yangtze River where land use is dominated by agriculture. Water samples were collected in July 2008 and February 2009 from the main channel of the Jialing River and its major tributaries. The δ15N and δ18O of NO3 − range from 1.5 to 11.0 ‰ (average 6.2 ‰) and −5.0 to 11.1 ‰ (average, 1.6 ‰), respectively. NO3 − isotope data and δ18O of water interpreted in combination with hydrological and chemical data suggest that most of the NO3 − input is from nitrification during the rainy season, and discharge of sewage and manure in the upper course and from cities accounts for much of the NO3 − load during the dry season. The construction of cascade dams has led to retention of Si and a decrease in the Si/N ratio, implying that assimilation and/or denitrification may significantly affect NO3 − in the dam area, as demonstrated by NO3 − and dissolved Si concentrations, and $$\updelta^{ 1 5} {\text{N}}_{{{\text{NO}}_{3} }}$$ and $$\updelta^{ 1 8} {\text{O}}_{{{\text{NO}}_{3} }}$$ values. This study indicates that dual-isotopic data can be used to identify NO3 − pollution sources and the processes NO3 − has undergone during its retention and transport in the watershed of the dam-controlled Jialing River.

To determine the impact of damming on the geochemical behavior of dissolved inorganic carbon (DIC) in the Wujiang River basin, field measurements and samples were collected semimonthly for a year. The surface waters of the reservoirs contained concentrations of chlorophyll a up to 5.6 times higher than the upstream river. Compared with the entering waters, the contributions of HCO3 − and dissolved CO2 to DIC decreased, and the contribution of CO3 2− to DIC and the carbon isotopic composition of DIC (δ 13CDIC) increased in the surface waters of the reservoirs, while in the waters released, the DIC species showed reverse geochemical behaviors. The δ 13CDIC ranged from −10.2 ‰ to 2.5 ‰, indicating that significant contributions were from carbonate weathering, photosynthesis, and respiration. After the damming of a river, the bioactivity of phytoplankton was enhanced, and this affected the geochemistry of DIC compared to an unimpacted river and δ 13CDIC can be used to discern these changes. High-frequency monitoring of river-reservoir systems is necessary to evaluate the efflux of CO2 and provide a better understanding of the carbon sinks and sources in the impounded river.

The Wujiang River is an important tributary to the Changjiang River that has been intensively impounded for hydropower exploitation. To understand the potential impact of reservoir construction on the riverine inorganic carbon transport, seasonal longitudinal sampling was conducted in four reservoirs Hongjiadu (HJD), Dongfeng (DF), Suofengying (SFY) and Wujiangdu (WJD) along the Wujiang River from April 2006 to January 2007. Results indicated that damming the river induced an obvious discontinuity of water chemistry in the warmer seasons. δ 13C of dissolved inorganic carbon (DIC) ranged from −3 to −11.4 ‰, likely as the results of photosynthesis, respiration and carbonate weathering. During periods of thermal stratification, the addition of CO2 from respiration to hypolimnion and the deep water release for hydropower generation led to higher pCO2 downstream, as well as 13C depletion in DIC and undersaturated to calcite. An estimate of DIC budget indicated that only DF reservoir was the sink for DIC while reservoirs HJD, SFY and WJD were the sources for DIC. However, when the retained water was taken into account, for the reason of water storage occurring mainly in HJD and DF, all reservoirs became the sources for DIC with exporting rates of 26.68, 7.97, 6.22 and 11.80 % for HJD, DF, SFY and WJD, respectively.

Two strains of green microalgae C. reinhardti and C. pyrenoidosa were examined for their biosorption of Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ from aqueous multi-metal solutions. A wide range of biosorption capacities can be observed due to different strains of microalgae and different species of trace metals. This characteristic was ascribed to the distinct components and structures of algal cell walls and the different physicochemical properties of trace metals, such as atomic weight and ion density. C. pyrenoidosa showed higher uptake capacities than C. reinhardti and both of them had a preference for the uptake of cadmium over others in the trace metal solution, suggesting they can be a good biomaterial for biosorption of cadmium. Live microalgal cells displayed a more complex sorption process than dead microalgal cells because of cell assimilation.

This study systematically analyzed the concentrations of cations and anions and determined the pH in the rainwater at Guiyang from Oct. 2008 to Sep. 2009. The pH in the rainwater varied between 3.35 and 9.99 with a volume-weighted mean value of 4.23. The volume-weighted mean concentrations of anions followed the order SO42->Cl->F->NO3-, whereas the volume-weighted mean concentrations of cations followed the order Ca2+>NH4+>Na+>Mg2+>K+. This finding indicates that SO42- was the main anion and that Ca2+ and NH4+ were the main cations. Significant correlations between each pair of ions (SO42-, NO3-, NH4+, Ca2+, and Mg2+) were observed, suggesting that CaSO4, Ca(NO3)2, MgSO4, Mg(NO3)2, NH4NO3, (NH4)2SO4, and/or NH4HSO4 exist in the atmosphere at Guiyang. The soil-derived species (such as Ca2+) played an important role in the neutralization of the acidity in rainwater. The SO42- and NO3- in the rainwater were mainly from anthropogenic sources, and their contributions accounted for 98.1 % and 94.7 %, respectively. NH4+ was also most likely derived from anthropogenic sources, such as domestic and commercial sewage, and played an important role in the neutralization of the rainwater at Guiyang.

Land use changes extensively affect soil erosion, which is a great environmental concern. To evaluate the effect of land use change on soil erosion in fast economic developing areas, we studied land use changes of Guangdong, China, from 2002 to 2009 using remote sensing and estimated soil erosion using the Universal Soil Loss Equation. We calculated the areas and percentage of each land use type under different erosion intensity and analyzed soil erosion changes caused by transitions of land use types. In addition, the impact of land use change on soil erosion in different river catchments was studied. Our results show that forest and wasteland land conversions induce substantial soil erosion, while transition from wasteland to forest retards soil loss. This suggests that vegetation cover changes significantly influence soil erosion. Any conversion to wasteland causes soil erosion, whereas expansion of forests and orchards mitigates it. The most significant increase in soil erosion from 2002 to 2009 was found in the Beijiang catchment corresponding to the transition from forest/orchard to built-up and wasteland. Soil erosion in the Xijiang catchment accelerated in this period due to the enormous reduction in orchard land. In Hanjiang catchment, erosion was alleviated and vegetation coverage greatly expanded owing to considerable transitions from wasteland and cropland to orchards. Field investigations validated our estimations and proved the applicability of this method. Measures including protecting vegetation, strict control of mining as well as reasonable urban planning should be taken to prevent successive soil erosion.

This study quantifies surface denudation of carbonate rocks by the first application of in-situ cosmogenic 36Cl in China. Concentrations of natural Cl and in-situ cosmogenic 36Cl in bare carbonates from Guizhou karst areas were measured with isotope dilution by accelerator mass spectrometer. The Cl concentration varied from 16 to 206 ppm. The 36Cl concentrations were in range of (0.8–2.4)×106 atom g−1, resulting in total denudation rates of 20–50 mm ka−1 that averaged over a 104–105 a timescale. The 36Cl-denudation rates showed roughly a negative correlation with the local mean temperature. This preliminary observation may suggest the variations of proportions of chemical weathering and physical erosion in denudation process, depending upon local climatic conditions.

This study analyzes the biotransformation of earthworms on K in potassium-bearing mineral powder (PBMP) under different PBMP recruitments. A mixture of PBMP (10% to 60% mass fraction) and decaying cow dung was used as feed for breeding the earthworms to study the potassium-releasing ability of earthworms on PBMP in soil. The mixture containing 20% and 30% PBMP resulted in good growth and propagation of the earthworms as well as higher conversion rates of potassium. Therefore, the optimum recruitments of mineral powder are 20% and 30%. The mixture of cow dung and PBMP was compared with the mixture of cow dung and corresponding proportions of quartz powder to analyze the conversion rate of earthworms on PBMP in different combinations. After the earthworms were raised with the mixture of cow dung and PBMP (8 : 2 and 7 : 3) for 30 d, the con- tents of rapidly available K and effective K were 10 824.3±35.9 and 11 688.4±16.1 mg·kg -1 as well as

Carbon (C) and silicon (Si) biogeochemical cycles are important factors in the regulation of atmospheric CO2 concentrations and hence climate change. Theoretically, these elements are linked by chemical weathering and organism stoichiometry, but this coupling has not been investigated in freshwaters. Here we compiled data from global rivers and lakes in the United States of America and the United Kingdom, in order to characterize the stoichiometry between the biogeochemical cycles of C and Si. In rivers this coupling is confirmed by a significant relationship between HCO3−/Na+ and DSi/Na+, and DSi:HCO3− ratio can reflect the mineral source of chemical weathering. In lakes, however, these characteristic ratios of chemical weathering are altered by algal activity. The lacustrine Si:C atomic ratio is negative feedback regulation by phytoplankton, which may result in this ratio in algal assemblages similar to that in water column. And this regulation suggests lacustrine photosynthetic C fixation in this equilibrium state is quantitative and depends on the DSi concentration. These findings provide new insights into the role of freshwaters in global C and Si biogeochemical cycles.

We present major ion compositions for water samples from Jinshajiang, Lancangjiang, and Nujiang drainage basins of China, collected in a water-rich period. This was done to determine natural chemical weathering rates on the eastern Himalayan and Qinghai-Tibet Plateau (HQTP), where anthropogenic impacts are considered small. The major ion distribution of the mainstream samples primarily reflects the weathering of carbonates, which accounts for ~46 % of total cations in the samples of Lancangjiang and Nujiang. Evaporite dissolution prevailed in the mainstream samples of Jinshajiang, as evidenced by high total dissolved solids (TDS) (364–479 mg/L) and Cl, SO4, and Na-dominant major element composition. Silicate weathering contributed

Epikarst water, which is one of the most important water resources in karst mountain areas, is extremely sensitive to mining activities. Acid mine drainage (AMD) with high levels of heavy metals can degrade the water quality. A typical coalfield basin was chosen to research the migration process of heavy metals. It was found that the chemical compositions of the stream water in the research field were controlled by the dissolution of carbonate rocks or/and the weathering and oxidation of pyrite in the mining area. Excluding a few sites in the mining area, As(V) was dominant species of arsenic in the form of H2AsO4 − or HAsO4 2− in the research field. Based on the mass balance concept, it was found that fluxes of As, Zn, Cu and Cd in water from the mining area (site 17) affected by AMD were 18, 871, 281 and 12 kg year−1, respectively. Also, concentrations of Cd, Zn, As and Cu in the stream water decreased along the flow, because these ions deposited from the water to the stream bed as the redistribution processes in environment.

Water samples were collected for 23 different stations along a cross section profile of an estuary extending over to adjacent sea. The collected water samples were filtered and analyzed for major–minor ions and strontium isotope using the standard procedure to understand the geochemical behaviors of major and minor elements. The normalized values indicated that all riverine elements were entering to adjacent coastal sea with some significant variations at the estuary. The seawater dilution and regression lines explain about the overall patterns for seven elements. Removal processes were detected on calcium, magnesium, strontium and sulfate in the estuarine region. No significant mineral precipitation observed to release magnesium with respect to calcium. Minor variations of strontium and sulfate ions could be attributed to the presence of organic matter in the study area. Comparing seven elements with total suspended matters revealed that the total suspended matters played crucial role in either adsorption or absorption of all the elements in estuary before it reaches to coastal sea. Mixing patterns of strontium isotope showed minimal non-conservative with an evidence of active geochemical process in the estuary.

Stable isotope tracing and analysis play an important role in interpretation of hydrological and ecological processes at the watershed scale and can provide information regarding the flow path, water source, nutrient loss and biogeochemical cycles of a system. In this study, environmental isotopes (δ18O-H2O, δD, δ15N-NO3−, δ18O-NO3−) and chemical compositions of surface water in Guizhou Province, China, were measured to evaluate the primary sources of nitrate and characterize the processes affecting nitrate as well as its correlation with vegetation cover in karstic areas. The δ15N and δ18O-NO3− levels ranged from +1.3 to +9.8 ‰ and +4.7 to +16.9 ‰, respectively, which indicated that nitrate in water from the investigated area primarily originated from nitrification of soil organic matter during the sampling period. There was also a wide range of isotopes in the water and high contents of nitrate in karstic areas with poor vegetation cover, indicating that water and nutrient loss were serious problems hindering plant growth in the study areas. For example, there was a positive relationship between isotopic composition and nitrate content in the natural forest and negative relationship in Libo County nearby, which suggested that the nitrate fate was affected by land use and human disturbance.

Vicia villosa is an annual legume plant, and is mainly used for green manure by farmers in southwest China. Field growth experiments were performed on six plots. The concentrations of mineral nutrients and soluble sugar, and the changes of carbon and nitrogen isotopic composition within and among organs of Vicia were determined. Significant differences in legume growth were found in response to soil type and its moisture conditions. The Vicia villosa was relatively well adapted to growth in limestone soils than sandstone soils. The distribution of sugar concentrations and δ13C-differences between roots and leaves indicate that the translocation of sugars from leaves to roots may be restricted by soil drought. Therefore, there was an inhibition of Pi distribution from roots to leaves, resulting in over optimum threshold of N/P ratio. Those may originate from the feedback regulation in the legume, where soluble sugar could not be distributed from leaves to roots. The results of δ15N values in tissues suggest that there should be different preferential use of nitrogen resource by legume during the formation of nodules: before nodule formation the legume preferentially utilizes inorganic nitrogen from soils, but afterwards the nitrogen should be mainly from N2-fixation. Our results indicate that the lack of nodulation development, except for S2, should be ascribed to the factor controlling bi-direction nutrient transfer, which should be efficiency of establishment symbiosis with arbuscular mycorrhiza before nodulation formation. It is predicted that the species of Vicia villosa should be a legume associated with dual symbiosis with rhizobia and mycorrhiza.

Nitrate (NO3−) is an important form of nitrogen (N) available to plants. The measurements of NO3− concentration [NO3−] and isotopes (δ15N and δ18O) in plants provide unique insights into ecosystem NO3− availability and plant NO3− dynamics. This work investigated the variability of these parameters in individuals of a broadleaved (Aucuba japonica) plant and a coniferous (Platycladus orientalis) plant, and explored the applicability of tissue NO3− isotopes for deciphering plant NO3− utilization mechanisms. The NO3− in washed leaves showed concentration and isotopic ratios that were much lower than that in unwashed leaves, indicating a low contribution of atmospheric NO3− to NO3− in leaves. Current leaves showed higher [NO3−] and isotopic ratios than mature leaves. Moreover, higher leaf [NO3−] and isotopic enrichments (relative to soil NO3−) were found under higher soil NO3− availability for A. japonica. In contrast, leaves of P. orientalis showed low [NO3−] and negligible isotopic enrichments despite high soil NO3−. Higher [NO3−] was found in both fine and coarse roots of the P. orientalis plant, but significant isotopic enrichment was found only in coarse roots. These results reflect that the NO3− accumulation and isotopic effects decreased with leaf age, but increased with soil NO3− supply. Leaves are therefore identified as a location of NO3− reduction for A. japonica, while P. orientalis did not assimilate NO3− in leaves but in coarse roots. This work provided the first organ-specific information on NO3− isotopes in plant individuals, which will stimulate further studies of NO3− dynamics in a broader spectrum of plant ecosystems.

We have investigated the diurnal variations of the pCO2 and related environmental factors in the cascade reservoirs with different trophic levels along Wujiang River. In surface water the pCO2 was 357±11 μatm in Hongjiadu Reservoir, 338±48 μatm in Dongfeng Reservoir, 682±303 μatm in Wujiangdu Reservoir, and 1677±429 μatm in Liuguang, respectively. The results indicated that these cascade reservoirs had much lower pCO2 values in surface water than river did, and hypereutrophic reservoir showed larger diurnal variations of pCO2 than meso-eutrophic reservoir. In water column, pCO2 tended to increase with the depth. Phytoplankton and the environmental factors such as temperature and pH had different influences on pCO2 diurnal variations due to different trophic levels, and the effect of phytoplankton on pCO2 variation increased with the increase of trophic level in these reservoirs.

The Aha Lake is a seasonal anoxic water system in the southwest of Guiyang City, Guizhou Province, China. Seasonal variations in SO42− concentrations and their isotopic compositions in lake water as well as in the tributaries were investigated in this study. The results showed that sulfate concentrations in river water range from 0.94 to 6.52 mmol/L and their δ34S values range from t14.9‰ and 0.9‰, while lake water has sulfate concentrations ranging from 1.91 to 2.79 mmol/L, and δ34S values from −9.8‰ to −5.9‰. It is suggested that coal mining drainage is the major source of SO42− in the Aha Lake. Rainfall, sewage discharge, sulfide oxidation and gypsum dissolution have made only limited contributions. Different depth-dependent distributions of dissolved SO42− and δ34S were developed for both DB and LJK in summer and winter. Due to water overturn, δ34S values display homogenous vertical distributions in winter and spring. While in summer and autumn, significant positive shifts of δ34S were clearly observed in epilimnion and bottom strata as a result of water stratification. High δ34S values in epilimnion may result from the retention of rainwater during water stratification. Dissimilatory sulfate reduction by bacteria was thought to be responsible for the increase of δ34S value in hypolimnion.

Geochemical studies on REE, trace elements and oxygen isotopes from metamorphic veins and their host metasedimentary rocks in the Zhoutan Group at two localities, Xiangshan and Yihuang, in central Jiangxi Province have been conducted in this paper. The results show that the metamorphic quartz veins inherited the REE and oxygen isotope geochemical characteristics from their host rocks, suggesting that the vein-forming fluids were derived from the host rocks. Additionally, fractionation degrees of the trace element pairs Zr-Hf, Nb-Ta, Y-Ho and U-Th in the veins are different from those of their host rocks. It is also indicated that the veins are the products of the fluids. The metamorphic veins within the Zhoutan Group metasedimentary rocks were formed principally as a result of lateral diffusion of the metamorphic fluids.

Lead, Zn, and Cd in vegetables/crops were investigated in a zinc smelting region in China, and their daily dietary intake by local residents was estimated. It is observed that Pb, Zn, and Cd were in 34.7-91.1, 242-575, and 0.199-2.23 μg g(-1) dry weight in vegetables/crops with their greatest concentrations in leafy vegetable. The daily dietary intake of Pb, Zn, and Cd by adult residents reached 3, 646, 59,295, and 186 μg day, respectively, and lettuce and cabbage together contributed 75% of the Pb, 50% of the Zn, and 70% of the Cd.

For establishing rational farming mechanism, it is essential to know the relative contribution of different geological background and anthropogenic activities to trace elements in agricultural soil. In this paper, 282 surface soil samples were collected based on the different geological background. Five harmful trace elements (As, Cd, Cr, Hg and Pb) were analyzed. The results indicated most of trace elements contents were far beyond the threshold of uncultivated soil background, which indicate anthropogenic input strongly influenced on trace elements in agricultural soil. In addition, correlation analysis showed trace element contents exhibited high relationships with soil pH, C/N and physical clay (

One-year-old seedlings of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) are not colonized with ectomycorrhizal (EM) fungi, but often colonized with arbuscular mycorrhizal (AM) fungi. The AM fungi could be important for nutrient acquisition in Chinese fir seedlings. Previous studies show that feedbacks between aboveground and belowground plant tissues play a fundamental role in controlling the interaction between plants and AM fungi. Our results indicate significant feedback in seedlings grown on shrubland soils, but not on plowed soils. The amounts of sugar in fir leaves in the shrubland soils were significantly lower than those in plowed soils. Leaf zinc (Zn) and nitrogen (N) concentrations were significantly higher in seedlings in shrubland soils than in plowed soils. In mycorrhizal seedlings growing in shrubland soils, leaf N:P ratios were significantly higher than those in plowed soils, likely because of enhanced N absorption through AM-mediated process. Leaf N:P ratios in seedlings grown on plowed soils were below the threshold levels, because of low metabolic activity of feedback in AM-mediated process. The results suggested that the presence of feedback between Chinese fir seedlings and AM fungi should be benefit in transplanting Chinese fir seedlings.

The quality changes of shallow groundwater from karst hilly areas in Guiyang region of China impacted by the urbanization were investigated. The results show that the major ions in shallow groundwater from the karst hilly areas are mainly composed of HCO3−, SO42−, Ca2+ and Mg2+, and the concentrations scopes of NO3−, Cl−, K+ and Na+ of the groundwater in agricultural, residential and industrial areas are 4.5–9.6, 2.8–7.1, 3.9–6.3 and 2.5–4.9 times higher than those in the forest areas, respectively. The concentrations of As, Pb and Cd of shallow groundwater in the industrial areas are also significantly enhanced, followed by those in the residential areas and the agricultural areas. The concentrations of NO3−, SO42−, As, Pb and Cd of the groundwater in the industrial areas and those of NO3−, SO42−, As and Cd of shallow groundwater in the residential areas reach grade III of the Groundwater Quality Standard of China (GB/T 14848-93), while the concentration of NO3− in the groundwater from the industrial areas exceeds grade V. With the process of urbanization, NO3− is the key factor to influence the groundwater quality in karst hilly areas, followed by SO42−, As, Pb and Cd.

Dissolved inorganic carbon (DIC) is a primary constituent of the aquatic geochemistry of terrestrial ecosystems. Changes in DIC concentration and its isotopic composition are closely associated with environmental changes in the drainage basin. Thus, a better understanding of DIC may lead to improved characterization of environmental changes. Corbicula fluminea (Muller 1774), a bivalve native to southeast Asia and a dominant invasive species in many aquatic environments around the world, has the potential to record DIC information, particularly because of its sequential skeletal deposition. Analysis of the stable carbon isotope composition (δ13C) of the shell and the aquatic DIC in the Xijiang River drainage basins in southern and western China allowed us to determine that changes in δ13C in the skeleton significantly correlated with those of DIC (P < 0.01, r = 0.63). These results indicate that the isotopic signature of the shell reflects that δ13C of the DIC in ambient water. The temporal resolution was at the seasonal scale. Metabolic effect does not change the co-variation, even though it makes the shell δ13C 1.4‰ lower statistically than that of DIC. δ13C of DIC in creeks of some watershed areas may experience large temporal changes characterization of these changes requires high sampling resolution of the shell. This problem makes the clams in these areas less preferable for reconstruction of environmental changes. The present findings provide the basis for recovering paleoenvironmental changes and carbon cycles in a watershed through analysis of fossil shells of C. fluminea, which are common in some lacustrine and/or riverine sediment sequences.

Vicia villosa is an annual legume plant. Field-growing experiments were performed on six plots under different soil conditions. Variations in the concentrations of Zn and Cd in tissues were investigated. Differences in distribution patterns between Zn and Cd appeared during growing: the concentrations of Zn in roots in sandstone-derived soils were relatively higher than those in limestone-derived soils, and the uptake patterns of Zn by roots should be similar to those of iron (Fe). However, the concentrations of Cd in roots in limestone-derived soils were higher than those in sandstone-derived soils, and the uptake patterns of Cd by roots should be similar to those of manganese (Mn). On the contrast, the distribution patterns of Zn were similar to those of Mn, while the distribution patterns of Cd were similar to those of Fe in tissues, indicating that the uptake patterns of Zn and Cd were different from distribution patterns.

There is considerable discussion and uncertainty in the literature regarding the importance of fresh litter versus older soil organic matter as sources of soil dissolved organic carbon (DOC) in forest floor. In this study, the differences of organic carbon concentration and stable isotope composition were analyzed under different background conditions to identify the origins of DOC in forest soil. The data show that there is no significant difference in SOC content between these collected soil samples (P > 0.05), but the litter-rich surface soils have relatively higher DOC concentration than the litter-lacking (P