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Experiments involving boron incorporation into brucite (Mg(OH)2) from magnesium-free artificial seawater with pH values ranging from 9.5 to 13.0 were carried out to better understand the incorporation behavior of boron into brucite and the influence of it on Mg/Ca-SST proxy and δ11B-pH proxy. The results show that both the concentration of boron in deposited brucite ([B]d) and its boron partition coefficient (Kd) between deposited brucite and final seawater are controlled by the pH of the solution. The incorporation capacity of boron into brucite is almost the same as that into corals, but much stronger than that into oxides and clay minerals. The isotopic compositions of boron in deposited brucite (δ11Bd) are higher than those in the associated artificial seawater (δ11Bisw) with fractionation factors ranging between 1.0177 and 1.0569, resulting from the preferential incorporation of B(OH)3 into brucite. Both boron adsorptions onto brucite and the precipitation reaction of H3BO3 with brucite exist during deposition of brucite from artificial seawater. The simultaneous occurrence of both processes determines the boron concentration and isotopic fractionation of brucite. The isotopic fractionation behaviors and mechanisms of boron incorporated into brucite are different from those into corals. The existence of brucite in corals can affect the δ11B and Mg/Ca in corals and influences the Mg/Ca-SST proxy and δ11B-pH proxy negatively. The relationship between δ11B and Mg/Ca in corals can be used to judge the existence of brucite in corals, which should provide a reliable method for better use of δ11B and Mg/Ca in corals to reconstruct paleo-marine environment.

Nitrate (NO

A combination of microbial flocculant (MBF) and ferric trichloride (FeCl3) was applied to aggregate and harvest algae. The orthogonal experiment was designed to optimize conditions of flocculation. Mechanism of flocculation was observed through determining the zeta potential and observing the morphology of algal floc using stereo and scanning electron microscope. The results showed that the optimum combination of flocuulants was 0.175 g of FeCl3 with 10 mL MBF per liter, which exhibited the highest flocculation efficacy (95.12%) and lowest chemical oxygen demand (10.44 mg/L). The flocculation mechanism was charge neutralization, where the MBF first adhered and coated algae. Due to its high affinity to iron-hydroxy ions and long-chain molecules, the MBF attracted positively charged hydroxyl irons generated by FeCl3 hydrolysis and interacted with the iron-hydroxy ions to form a larger floc by bridging. The coat made of MBF formed a thin film which protected algae from being destroyed, and trapped th...

The variation in chemical compositions of regolith along a weathering profile developed on a granite substrate in Jiangxi province, in southern China, was investigated in this paper, with the aim to characterize the speciation of redox-sensitive elements and to evaluate their mobility and redistribution during chemical weathering. Mass balance calculations indicate titanium (Ti) is the most immobile element in this weathering profile. A new method, X-ray absorption fine structure (XAFS) spectroscopy, was used to determine the speciation of Fe and Mn along the profile. Fe K-edge X-ray absorption near edge structure (XANES) spectra show Fe in saprolith is stabilized mainly in the state of Fe(III), suggesting Fe is as immobile as conservative elements during granite weathering. Mn K-edge XANES spectra show Mn (III/IV) oxides are reduced to Mn(II) in surface soil, where soil organic matter (SOM) acts as an important reductant. Although Ce, Co and V were unable to be analysed by XAFS, their concentrations have significant correlations with that of Mn, indicating that the mobilization and redistribution of Ce, Co and V may also be governed by redox condition. All in all, the results suggest that redox process impacts significantly on the redistribution of Mn, Ce, Co and V along the profile. The successful application of XAFS in the study on migration of redox-sensitive elements during granite chemical weathering has provided valuable information for the understanding and evaluating the geochemical behavior of elements in the environment.

Biological degradation of terrestrially derived macromolecules including lignin and cellulose has been shown to produce a large number of environmentally relevant phenolic compounds. It has demonstrated that extracellular superoxide (O2  ) is produced by heterotrophic bacteria that are common in lakes, soil, hydrothermal vents, marine sediments, estuaries and oceans. Rates of superoxide production normalized to the proportion of metabolically active cells vary between 0.02  0.02 amol cell −1 hour −1 (mean ± standard error) and 19.4  5.2 amol cell −1 hour −1 . Such findings provide insights into the mechanism of two key and yet unclear processes, including the biological degradation of particulate organic matter (POM) that can form dissolved organic substances, and the structural diversification of dissolved organic substances originated from POM such as plant material or algal biomass.

It is generally difficult to measure atmospheric gaseous ammonia concentration and to identify its sources by isotopic technique due to the isotopic fractionation after it enters the atmosphere. In this study, Rayleigh model was successfully used to quantify atmospheric concentration and isotopic composition of gaseous ammonia based on sampling of 20 rain events from October 1st, 2008 to September 30, 2009 in Guiyang, southwest China. The estimated gaseous ammonia concentration was 25.7 ± 36.3 μg/m 3 and estimated isotopic composition was − 16.8 ± 4.9‰ in Guiyang. The study also showed that estimated enrichment factor was + 10.4 ± 4.3‰, inferring that large nitrogen isotopic fractionation occurred during exchange reactions in most of the rain events. The atmospheric ammonium deposition was further estimated to be 38.1 kg/ha/year. However, there is no validation for the approach from an actual gas phase NH 3 measurement to examine the model in this study.

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.

The analysis of stable isotopes of sulfur (δ34S) is a useful tool for identifying sources of sulfur in soils. Concentrations and sulfur (S) isotopes of water-soluble sulfate (WSS), adsorbed sulfate (AS), residual sulfur (RS), and total sulfur (TS) in uncultivated surface soils of four Chinese provinces were systematically analyzed for identifying sources of S in the soils. Green and healthy mosses (Haplocladium microphyllum) were sampled as bioindicators. The mean WSS concentration (27.8 ± 23.4 mg kg−1) in the surface soils was lower than those of AS (101.4 ± 57.0 mg kg−1) and RS (381.5 ± 256.7 mg kg−1). The mean δ34S values of WSS and AS were very similar (about 2.0%), lower than those of RS (8.0%) and TS (6.1%). A significant linear correlation was found between the δ34S values of AS and WWS (y = 1.0002x – 0.0557, P < 0.0001), indicating that sulfate adsorption in the soils did not markedly fractionate S. All S species in the soils of Guizhou Province were characterized by the lowest δ34S values, consistent with the most 34S-depleted rainwater sulfate reported at Guiyang of Guizhou Province. The δ34S values of sulfate in mosses and rainwater previously reported were significantly linearly correlated with those of both WWS and AS in surface soils, suggesting that atmospheric S input was an important source for soil WSS and AS. However, there were no significant correlations between isotopic composition of rainwater sulfate and RS or TS. The slopes of all these significant linear correlations (soil/rainwater or soil/moss isotopic ratio) were 0.4–0.6, indicating that inorganic sulfate in the surface soils should be a result of mixing of deposited atmospheric sulfate with a more 34S-depleted sulfate component possibly from mineralization of RS.

This paper investigated the sources and behaviors of sulfate in groundwater of the western North China Plain using sulfur and oxygen isotopic ratios. The groundwaters can be categorized into karst groundwater (KGW), coal mine drainage (CMD) and pore water (subsurface saturated water in interstices of unconsolidated sediment). Pore water in alluvial plain sediments could be further classified into unconfined groundwater (UGW) with depth of less than 30 m and confined groundwater (CGW) with depth of more than 60 m. The isotopic compositions of KGW varied from 9.3‰ to 11.3‰ for δ 34 S SO4 with the median value of 10.3‰ ( n = 4) and 7.9‰ to 15.6‰ for δ 18 O SO4 with the median value of 14.3‰ ( n = 4) respectively, indicating gypsum dissolution in karst aquifers. δ 34 S SO4 and δ 18 O SO4 values of sulfate in CMD ranged from 10.8‰ to 12.4‰ and 4.8‰ to 8.7‰ respectively. On the basis of groundwater flow path and geomorphological setting, the pore water samples were divided as three groups: (1) alluvial–proluvial fan (II 1 ) group with high sulfate concentration (median values of 2.37 mM and 1.95 mM for UGW and CGW, respectively) and positive δ 34 S SO4 and δ 18 O SO4 values (median values of 8.8‰ and 6.9‰ for UGW, 12.0‰ and 8.0‰ for CGW); (2) proluvial slope (II 2 ) group with low sulfate concentration (median values of 1.56 mM and 0.84 mM for UGW and CGW, respectively) and similar δ 34 S SO4 and δ 18 O SO4 values (median values of 9.0‰ and 7.4‰ for UGW, 10.2‰ and 7.7‰ for CGW); and (3) low-lying zone (II 3 ) group with moderate sulfate concentration (median values of 2.13 mM and 1.17 mM for UGW and CGW, respectively) and more positive δ 34 S SO4 and δ 18 O SO4 values (median values of 10.7‰ and 7.7‰ for UGW, 20.1‰ and 8.8‰ for CGW). In the present study, three major sources of sulfate could be differentiated as following: sulfate dissolved from Ordovician to Permian rocks (δ 34 S SO4 = 10–35‰ and δ 18 O SO4 = 7–20‰), soil sulfate (δ 34 S SO4 = 5.9‰ and δ 18 O SO4 = 5.8‰) and sewage water (δ 34 S SO4 = 10.0‰ and δ 18 O SO4 = 7.6‰). Kinetic fractionations of sulfur and oxygen isotopes as a result of bacterial sulfate reduction (BSR) were found to be evident in the confined aquifer in stagnant zone (II 3 ), and enrichment factors of sulfate–sulfur and sulfate–oxygen isotopes calculated by Rayleigh equation were −12.1‰ and −4.7‰ respectively along the flow direction of groundwater at depths of 60–100 m. The results obtained in this study confirm that detailed hydrogeological settings and identification of anthropogenic sources are critical for elucidating evolution of δ 34 S SO4 and δ 18 O SO4 values along with groundwater flow path, and this work also provides a useful framework for understanding sulfur cycling in alluvial plain aquifers.

Enhanced ammonia (NH3) emissions and deposition caused negative effects on air quality and ecosystems. Precipitation is an efficient pathway to remove NH3 and particulate ammonium (p-NH4+) from the atmosphere into ecosystems. However, precipitation scavenging of p-NH4+ in chemical transport models has often considered fine p-NH4+, with inadequate constraints on NH3 and coarse p-NH4+. Based on distinct δ15N values between NH3 and NH4+ in PM2.5 (particulate matters with aerodynamic diameters ≤ 2.5 μm) or TSP (total suspended particulates), this paper interpreted intra-event variations of precipitation NH4+ concentrations and δ15N values (δ15N-NH4+ values) at Guiyang (Xiao et al., 2015). Generally decreased NH4+ concentrations across rain events reflected decreasing scavenging of NH3 and p-NH4+. Using a Bayesian isotope mixing model, we found that differing contributions between 15N-depleted NH3 and 15N-enriched p-NH4+ were responsible for the three-stage variations of intra-event δ15N-NH4+ values. The decreases of δ15N-NH4+ values across the first and third stages indicated more decreases in scavenging p-NH4+ than NH3, while the increases of δ15N-NH4+ values across the second stage were resulted primarily from more increases in scavenging p-NH4+ (particularly fine p-NH4+) than NH3. These results stressed influences of differing scavenging between NH3 and p-NH4+ on precipitation δ15N-NH4+ values, which should be considered in modeling precipitation scavenging of atmospheric p-NH4+.

Radiocarbon (14C) has been measured in single tree ring samples collected from the southwest of the Fukushima Dai-ichi Nuclear Power Plant. Our data indicate south-westwards dispersion of radiocarbon and the highest 14C activity observed so far in the local environment during the 2011 accident. The abnormally high 14C activity in the late wood of 2011 ring may imply an unknown source of radiocarbon nearby after the accident. The influence of 14C shrank from 30 km during normal reactor operation to 14 km for the accident in the northwest of FDNPP, but remains unclear in the southwest.

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.

Sediment pore waters were examined in four Chinese lakes (Bosten, Qinghai, Chenghai and Dianchi) to characterise the sources of dissolved organic matter (DOM) and their microbial changes in the sediment depth profiles. Parallel factor (PARAFAC) modelling on the sample fluorescence spectra confirmed that the pore water DOM was mostly composed of two components with a mixture of both allochthonous and autochthonous fulvic acid-like substances in three lakes, except Lake Dianchi, and protein-like components in Lake Bosten. However, DOM in Lake Dianchi was composed of three components, including a fulvic acid-like, and two unidentified components, which could originate from mixed sources of either sewerage-impacted allochthonous or autochthonous organic matter (OM). Dissolved organic carbon (DOC) concentrations were typically high (583–7410 μM C) and fluctuated and increased vertically in the depth profile. The fluorescence intensity of the fulvic acid-like substance and absorbance at 254 nm increased vertically in the sediment pore waters of three lakes. A significant relationship between DOC and the fluorescence intensity of the fulvic acid-like component in the sediment pore waters of three lakes, except Lake Dianchi, suggested that the fulvic acid-like component could significantly contribute to total DOM and could originate via complex microbial processes in early diagenesis on OM (ca. phytoplankton, terrestrial plant material) in these lakes. Pore water DOM components could therefore be a useful indicator to assess the DOM sources of the lake sediment during sedimentation over the past several decades, which have been heavily affected by ambient terrestrial vegetation and human activities.

This study established the hydrochemistry and stable isotope variations in three lakes, namely brackish Zigetang Co, freshwater Cona and Ranwu lakes located in the central and southeastern Tibetan Plateau of China. Vertical profile fluctuations in the water column, such as temperature and dissolved oxygen (DO) concentration, displayed significant differences which were linked to the thermocline. The hydrochemistry of the three lakes showed that [Formula: see text] as the dominant anion, whereas Na

Moss nitrogen (N) concentrations and natural 15N abundance (δ15N values) have been widely employed to evaluate annual levels and major sources of atmospheric N deposition. However, different moss species and one-off sampling were often used among extant studies, it remains unclear whether moss N parameters differ with species and different samplings, which prevented more accurate assessment of N deposition via moss survey. Here concentrations, isotopic ratios of bulk carbon (C) and bulk N in natural epilithic mosses (Bryum argenteum, Eurohypnum leptothallum, Haplocladium microphyllum and Hypnum plumaeforme) were measured monthly from August 2006 to August 2007 at Guiyang, SW China. The H. plumaeforme had significantly (P < 0.05) lower bulk N concentrations and higher δ13C values than other species. Moss N concentrations were significantly (P < 0.05) lower in warmer months than in cooler months, while moss δ13C values exhibited an opposite pattern. The variance component analyses showed that different species contributed more variations of moss N concentrations and δ13C values than different samplings. Differently, δ15N values did not differ significantly between moss species, and its variance mainly reflected variations of assimilated N sources, with ammonium as the dominant contributor. These results unambiguously reveal the influence of inter-species and intra-annual variations of moss N utilization on N deposition assessment.

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.

Straw return is becoming a routine practice in disposing of crop residues worldwide. However, the potential effect of such operation on the chemistry of local groundwater is not well documented. Here, shallow groundwater in an area where wheat-maize straw return is practiced was analyzed, and the seasonal changes in the nitrate concentration and the isotope compositions of NO3- and H2O were determined along two flow paths. Measured δD and δ18O in waters indicated that the groundwater was mainly recharged by atmospheric precipitation, while measured δ15N and δ18O in nitrate suggested that the sources for groundwater NO3- included urea fertilizer, soil nitrogen, and sewage/manure. Reduced NO3- concentrations coincided with an enrichment of organic matter in the groundwater of the straw return area, revealing an environmental condition that facilitates nitrate reduction, whereas increased δ15N-NO3- and δ18O-NO3- along the flow path suggested the occurrence of denitrification. Further analyses showed that, compared to the cases in the absence of straw return, as much as 80% and 90% of groundwater nitrate was removed in low and high water seasons in the straw return area, pointing to a potential positive effect of straw return to groundwater quality.

This study established the hydrochemistry and stable isotope variations in three lakes, namely brackish Zigetang Co, freshwater Cona and Ranwu lakes located in the central and southeastern Tibetan Plateau of China. Vertical profile fluctuations in the water column, such as temperature and dissolved oxygen (DO) concentration, displayed significant differences which were linked to the thermocline. The hydrochemistry of the three lakes showed that as the dominant anion, whereas Na+ is the main cation in Zigetang Co and Cona lake and Ca2+ is the prevailing cation in Ranwu lake. In Zigetang Co, K+ and Na+ concentrations decreased by 42 % from 1999 to 2012, caused by the enlargement of the lake area, documented by field investigations carried out in 1998, 2002, 2006 and 2012. The δ13CDIC and δ18OH2O values analysed from the three lakes varied from −6.0 to 2.0 ‰, and from −14.8 to −6.4 ‰, respectively. The closed Zigetang lake showed higher δ13CDIC and δ18OH2O values compared to those of the rivers, the semi-closed Cona and open Ranwu lakes. The δ13CDIC values of lake water in Zigetang Co were mainly controlled by CO2 exchange between lake water and atmosphere; the δ18OH2O values were dominated by the evaporation/freshwater input ratios.

Sulfate concentrations and sulfur isotopic compositions were measured in rainwater in Guiyang city in Southwest China between October 2008 and September 2009 to identify sulfur sources and their impacts on sulfur isotopic composition. The delta S-34 values of 1235 samples collected during this period ranged from - 12.0 to + 9.4 parts per thousand, with a volume-weighted mean of - 2.8 +/- 9.8 parts per thousand, suggesting that rainwater sulfate in Guiyang was mainly derived from SO2 produced during coal combustion. The delta S-34 values of rainwater sulfate increased from 1987 to 2009, with an increment of about + 0.16 parts per thousand per year, reflecting a gradual reduction in S-34-depleted SO2 emitted during coal combustion. Seasonal variations in delta S-34 values were pronounced, with higher values in winter than in summer. Long-distance transport of SO2 from coal burned in northern cities (which was higher than the component from southern cities), and more importantly, the aqueous oxidation of SO2 during transport affected the seasonal variation of rainwater delta S-34 values in Guiyang. Temperature-dependent aqueous oxidation of SO2 suggested that lower rainwater delta S-34 coincides with higher temperature. (C) 2014 Elsevier B.V. All rights reserved.

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.

The concentration and isotopic composition of nitrate were analyzed to improve an understanding of nitrate sources and transformation processes in a typical karstic agricultural field in the Houzhai catchment, Guizhou Province, Southwest China. The results revealed that no distinct spatial pattern of content and isotopic composition of nitrate exists in this karst catchment. Nitrate in surface stream (SFS) had slightly lighter isotopic composition and lower concentration compared with nitrate in subterranean stream (STS) during the dry season. Concentrations of SFS nitrate increased to concentrations similar to those of STS during the wet season. The isotopic values indicated that nitrate were mainly impacted by manure sources during the dry season and influenced by a mix of chemical fertilizer and manure during the wet season. The denitrification rates were roughly estimated based on the isotopic compositions of nitrate after considering volatilization and ignoring assimilation. The calculated result showed that approximately one fifth of nitrate load was removed by denitrification in the catchment. Annual nitrate flux from the outlets accounted for 14.2% of applied total fertilizers used in the catchment, approximately 85% of total transported flux from the catchment in the wet season. Furthermore, chemical weathering processes were enhanced by using nitrogen fertilizer because liberated protons and enhanced HCO3− flux were produced through by nitrification. Copyright © 2014 John Wiley & Sons, Ltd.

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.

Molecular mechanisms and gene regulation are of interest in the area of geomicrobiology in which the interaction between microbes and minerals is studied. This paper focuses on the regulation of the expression of carbonic anhydrase (CA) genes in Bacillus mucilaginosus and the effects of the expression product of the B. mucilaginosus CA gene in Escherichia coli on calcite weathering. Real-time fluorescent quantitative PCR (RT-qPCR) was used to explore the relationship between CA gene expression in B. mucilaginosus and promotion of calcite dissolution under condition of Ca2+ deficiency. The results showed that adding calcite to the medium, which lacks Ca2+, can up-regulate the expression of the bacterial CA genes to accelerate calcite dissolution for bacterial growth. CA genes from B. mucilaginosus were transferred into E. coli by cloning. We then employed crude enzyme extract from the resultant E. coli strain in calcite dissolution experiments. The enzyme extract promoted calcite dissolution. These finding...

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.

To better understand chemical weathering and controlling processes in the Yalong River of the eastern Tibetan Plateau, this study presents major ion concentrations and stable isotopes of the dissolved loads. The isotopic compositions (δ13C-DIC, δ34S and δ18O-SO4) of the dissolved loads are very useful to quantify solute sources and define the carbon budget related with chemical weathering in riverine systems. The isotopic composition of sulphate demonstrates that most of the sulphate is derived from sulphide oxidation, particularly in the upper reach of the Yalong River. The correlations between δ13C-DIC, water chemistry and isotopes of sulphate, suggest that the carbon dynamics are mainly affected by carbonate weathering by sulphuric acid and equilibration processes. Approximately 13% of the dissolved inorganic carbon in the Yalong River originates from carbonate weathering by strong acid. The CO2 consumption rates are estimated to be 2.8 × 105 mol/km2/yr and 0.9 × 105 mol/km2/yr via carbonate and silicate weathering in the Yalong River, respectively. In this study, the influence of sulphide oxidation and metamorphic CO2 on the carbon budget is estimated for the Yalong River draining the eastern Tibetan Plateau.

The adsorption of hexavalent chromium (Cr(VI)) was improved by using organic bentonite (OB) modified with iron(III) chloride. The adsorption mechanisms and characteristics of OB and organic bentonite modified by FeCl3 (FMOB) were studied by using X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and energy dispersive X-ray spectroscopy (EDS). It was found that hydroxyl-iron replaced some of the calcium and magnesium contained in the FMOB, but no significant change in its structure was shown even though the adsorption experiments proved that FMOB had a better Cr(VI) adsorption ability compared to OB. The coated material was prepared by mixing FMOB and 4A molecular sieves in a coated pot for the adsorption experiments in the test column. The relevant results showed that the adsorption of the coated material retained its high adsorption ability and maintained that ability after desorption and regeneration, which implied a potential for further application.

The contents and stable S isotope ratio (δS) values of total S, organic S, SO-S, and total reduced inorganic S (TRS) in typical limestone soil and yellow soil were analyzed in this study to examine the general distributions of S forms and their δS values in soils in karst areas of southwest China. Under a similar level of acid deposition, the vertical profiles of the S forms and their δS values differed in limesto\ne soil and yellow soil, indicating the different geochemical responses of these soils to acid deposition. The deposited SO was retained as organic S in both soils. The depletion in S of TRS relative to SO and the parallel increasing δS values of TRS and SO indicate a bacterial reduction process of sulfate in both soils. The different extents of C-bonded S mineralization and organic sulfate transport explain the different vertical profiles of total S and organic S contents in both soils. Sulfate adsorption in limestone soil was negligible because of high pH values. Sulfate adsorption in yellow soil was another important S retention process in addition to biological S retention to form organic S and TRS because of low pH values. The effect of acid deposition on yellow soil appeared more serious because of the accumulation and leaching of deposited SO, which can result in soil acidification and accelerate the loss of basic cations from yellow soil. However, compared with yellow soil, limestone soil released more S into rivers by organic S mineralization after a large decrease in annual S deposition rate.

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.

The knowledge of the impacts of environmental factors on actual evapotranspiration (ETa) and evaporative fraction (EF) is important for understanding a range of land surface processes and for estimating ETa. However, rare attempts have been made to quantitatively assess various controls on ETa and EF. To this end, a comprehensive dataset was obtained from four study sites with different land cover conditions within an arid region from northwest China. The boosted regression tree (BRT) method was applied to assess the relative controls of different factors (e.g., net radiation-Rn, soil water content-SWC, leaf area index-LAI, relative humidity-RH, air temperature-Ta, and wind speed-WS) on ETa and EF. In general, the importance of SWC in controlling ETa increased with decreasing SWC across the sites; however, the BRT analysis revealed that although an arid climate was prevalent in the study region, Rn might outweigh SWC in affecting ETa at both irrigated and rain-fed sites. In addition, RH also played a nonnegligible role in affecting ETa at rain-fed sites, while the relative control of LAI varied with SWC. Moreover, EF at the irrigated site was mainly controlled by LAI and SWC when SWC was low, while by Ta when SWC was higher; RH was the most important in explaining the variability in EF at the rain-fed sites, which was followed by LAI and SWC. This study underscores the importance of available energy and other environmental factors (e.g., RH and LAI) in modulating ETa and EF in water-limited regions, which has important implications for parameterizing hydrological and land surface models for simulating ETa and for identifying EF regimes more accurately.

Chronic impact will last from a sudden pollution accident, however, potential adverse effects of heavy metal(loid)s are overlooked when pollution decreased during years of equilibration. Here, we assessed the potential health risks of heavy metal(loid)s via intake of vegetables from fields affected by the smelting wastewater spill eight years later, basing on site-specific target hazard quotient (STHQ) and cancer risk (SCR) models. Results showed kohlrabi, lettuce and garlic had significant high concentrations of Sb (10.4 mg kg−1), Pb (21.0 mg kg−1), Cd (6.49 mg kg−1), and Zn (441 mg kg−1), and sweet potato and garlic enriched high levels of As (19.6 mg kg−1) and Cu (14.1 mg kg−1), respectively. Transfer factors of metal(loid)s from soil to plants were enhanced by high soluble metal(loid) concentrations, and Sb, As, Pb and Cd in most edible tissues exceeded the contamination limitations for food in China and FAO/WHO. Chinese cabbage had significant high STHQ of As (adult 9.31 and child 19.8) and Sb (adult 0.76 and child 1.61) (p

The concentrations of rare earth elements in the waters and suspended particles from two alkaline lakes in a carbonate drainage basin of the South China Karst region were determined via ICP-MS. Sequential chemical extraction experiments were conducted on the suspended matter to investigate water-particle interaction processes. Due to their high pH, the alkaline lakes have lower concentrations of dissolved rare earth elements than those reported for most other terrestrial surface waters of the world. Linear regressions between pH and the rare earth element (REE) concentrations over a wide pH range show a “three stage model,” implying the geochemical behavior of dissolved REEs in surface waters is mainly controlled by pH. Shale-normalized patterns of dissolved REEs mainly show a marked enrichment in heavy REEs (HREE), while acid-extracted and organic REEs mainly show convex patterns and the residual fractions have flat patterns. Distinct positive La anomalies were observed in the Lake Aha and its river waters, which also exhibit a very high Mn concentration, indicating severe redox and scavenging conditions. Both negative and positive Ce anomalies were clearly observed in the dissolved phase and extracted fractions of suspended particulate matter. The positive correlation of Ce anomalies with Mn indicates that redox reactions control these Ce anomalies.

Algal toxins or red-tide toxins produced during algal blooms are naturally-derived toxic emerging contaminants (ECs) that may kill organisms, including humans, through contaminated fish or seafood. Other ECs produced either naturally or anthropogenically ultimately flow into marine waters. Pharmaceuticals are also an important pollution source, mostly due to overproduction and incorrect disposal. Ship breaking and recycle industries (SBRIs) can also release various pollutants and substantially deteriorate habitats and marine biodiversity. Overfishing is significantly increasing due to the global food crisis, caused by an increasing world population. Organic matter (OM) pollution and global warming (GW) are key factors that exacerbate these challenges (e.g. algal blooms), to which acidification in marine waters should be added as well. Sources, factors, mechanisms and possible remedial measures of these challenges to marine ecosystems are discussed, including their eventual impact on all forms of life including humans.

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.

The Liao River Basin is one of seven primary river Basins in China. The concentration of dissolved inorganic N (DIN), dual isotopes of NO 3 - using the denitrifier method, the N isotopes of NH 4 + and the N flux in the basin were determined to identify the sources of N and their transformation. The results show that NO 3 - ranges from 0.3 μmol/L to 1316 μmol/L. In general, NO 3 - is the dominant inorganic N species during both flow seasons, but the fraction of NO 3 - /DIN is variable and high NH 4 + is present in some waters. Samples collected from the up-stream portion of the Liao River typically had N isotope values of +8‰ during the high flow season. Most water samples had O isotope values of NO 3 - during the high flow season than the low flow season. The isotopic pattern of NO 3 - suggests that wastewater and soil organic N are the sources of NO 4 + during the high flow season, while wastewater is the main source during low flow season. It appears that no intense denitrification occurs in the river according to the isotopic and chemical data. The N flux of the Liao River system entering the Liao Dong Bay annually is nearly 7.0 × 104 tons, which amounts to 5.0% of the N from chemical fertilizers used in this basin.

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.

Mosses, among all types of terrestrial vegetation, are excellent scavengers of anthropogenic nitrogen (N), but their utilization of dissolved organic N (DON) and their reliance on atmospheric N remain uncharacterized in natural environments, which obscures their roles in N cycles. Natural (15) N abundance of N sources (nitrate (NO(3)(-)), ammonium (NH(4)(+)) and DON in deposition and soil) for epilithic and terricolous mosses was analyzed at sites with different N depositions at Guiyang, China. Moss NO(3)(-) assimilation was inhibited substantially by the high supply of NH(4)(+) and DON. Therefore, contributions of NH(4)(+) and DON to moss N were partitioned using isotopic mass-balance methods. The N contributions averaged 56% and 46% from atmospheric NH(4)(+), and 44% and 17% from atmospheric DON in epilithic and terricolous mosses, respectively. In terricolous mosses, soil NH(4)(+) and soil DON accounted for 16% and 21% of bulk N, which are higher than current estimations obtained using (15) N-labeling methods. Moreover, anthropogenic NH(4)(+) deposition suppressed utilization of DON and soil N because of the preference of moss for NH(4)(+) under elevated NH(4)(+) deposition. These results underscore the dominance of, and preference for, atmospheric NH(4)(+) in moss N utilization, and highlight the importance of considering DON and soil N sources when estimating moss N sequestration and the impacts of N deposition on mosses.

The limestone and yellow sandstone soil profiles from SW China were measured for chemical and Sr isotope compositions of the bulk soils and their sequential leachates (labile, carbonate, and residue or silicate fraction), aiming to characterize the parent materials of the soils, to understand the soil weathering and formation processes, and to discuss the origin of the red residua (terra rossa). The studied yellow sandstone soil, yellow limestone soil, and black limestone soil show different pH values, SiO 2 contents, Rb/Sr abundance ratios, and 87 Sr/ 86 Sr ratios. The sequential leachates of different soil types also have different 87 Sr/ 86 Sr and Ca/Sr ratios. The major chemical compositions of the studied soil profiles suggest that all the sandstone and limestone soils are developing at a stage that feldspar is exhausting and the clay minerals are changing from smectite to kaolinite and gibbsite. As compared with the red residua distributed in the karst region, the soils studied here show lower CIA values (58–84), but both higher Na 2 O/K 2 O (0.9–2.7) and Na 2 O/Al 2 O 3 concentration ratios (0.07–0.26) on average, suggesting a lower weathering intensity than that of the red residua. The depth profiles of soil CIA values, Na 2 O/K 2 O and Rb/Sr ratios, and 87 Sr/ 86 Sr ratios indicate that the weathering intensity is slightly lower for the upper and higher for the deeper soils, which suggest that the sandstone and limestone soil profiles were formed through both accumulation and weathering of in situ weathering residue and input of external detritus or soil from upper land. During weathering of the soils, preferential release of Ca and retention of Sr in soil result in higher Ca/Sr ratios in both labile and carbonate fractions than those in the residue fractions of all soil profiles. The co-variations of Hf/Nb and Zr/Nb ratios, together with those Rb/Sr and 87 Sr/ 86 Sr ratios of limestone soils, sandstone soils, and the red residua, demonstrate that their parent materials are distinct, and support the point that the widely distributed red residua is originated from the weathering residua of both carbonate and silicate clastic rocks, and further weathering of the weathering residua resulted in intensive release of Si, Na, Ca and relative enrichment of Al, K and other immobile elements in the red residua.

For the first time, the river water geochemistry of the Songhuajiang Basin, the third largest river system in China, has been studied in order to understand chemical weathering and associated CO2 consumption rate in a mid- to cool temperate and monsoon-controlled climatic zone. The major ion compositions of the river waters are characterized by the dominance of Ca2+ and HCO 3 - , accounting for 46% and 74% of major cations and anions, respectively. The average total dissolved solids (TDS, 116 mg L−1) and total cation concentration (TZ+, 1388 μEq L−1) of the river waters are similar to those of global major rivers. The chemical weathering rates of carbonate, silicate and evaporites in the whole Songhuajiang Basin are estimated to be approximately 5.15, 2.23 and 0.40 t km−2 a−1, respectively. The total rock weathering rate for the whole Songhuajiang Basin is approximately 7.78 t km−2 a−1, which is at the lower end of the spectrum for global major rivers, and is comparable with that of the Amur and the Congo-Zaire River. The estimated CO2 consumption rates for the whole Songhuajiang Basin are 53.4 × 103 mol km−2 a−1 and 66.6 × 103 mol km−2 a−1 by carbonate and silicate weathering, respectively. As a sub-basin, the 2nd Songhuajiang has the highest (18.9 t km−2 a−1) while the Nenjiang River Basin has the lowest total rock weathering rate (5.03 t km−2 a−1), which indicates important controls of regional climate and lithology. Compared to the large rivers of China, total rock weathering rates increase from north to south, supporting the idea that the climate acts as major control on global chemical weathering. The CO2 consumption rate by silicate weathering within the whole Songhuajiang River Basin, though under mid- to cool temperate climate, is in the same order of magnitude as that of Huanghe (82.4 × 103 mol km−2 a−1) and is not much lower than that of Changjiang (112 × 103 mol km−2 a−1), which suggests that the role of Songhuajiang River weathering in long-term climate change cannot be neglected compared to those of the large rivers of China.

Red mud (bauxite residue) is the main waste product of the alkaline extraction of alumina from bauxite with high amounts of metals. In this study, bioleaching of heavy metals from red mud by using the fungus Aspergillus niger was investigated. Bioleaching experiments were examined in batch cultures with the red mud at various pulp densities (1–5%, w/v) under various bioleaching conditions (one-step, two-step and spent medium bioleaching). It was shown that the main lixiviant excreted by A. niger was citric acid. The highest leaching ratios of most various heavy metals were achieved under spent medium leaching at 1% pulp density. The increase in red mud pulp densities resulted in a general decrease in leaching ratios under all bioleaching conditions. However, in the case of the spent medium leaching the decrease in leaching ratios was lowest. The Toxicity Characteristic Leaching Procedure (TCLP) tests showed that the leaching toxicity of the bioleaching residue was far below the levels of relevant regulations. The micromorphology of the red mud particles were changed by the fungal activity during bioleaching process.

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.

Anhydrosugars (galactosan, mannosan and levoglucosan), sugars (xylose, fructose, glucose, sucrose and trehalose) and sugar alcohols (erythritol, arabitol, mannitol and inositol) were measured in the aerosol samples collected in a remote island (Chichi-Jima, Japan) in the western North Pacific from 1990 to 1993 and from 2006 to 2009. Total concentrations of anhydrosugars, the biomass burning tracers, were 0.01–5.57 ng m−3 (average 0.76 ng m−3) during 1990–1993 versus 0.01–7.19 ng m−3 (0.64 ng m−3) during 2006–2009. Their seasonal variations were characterized by winter/spring maxima and summer/fall minima. Such a seasonal pattern should be caused by the enhanced long-range atmospheric transport of biomass burning products and terrestrial organic matter (such as higher plant detritus and soil dust) from the Asian continent in winter/spring seasons, when the westerly or winter monsoon system prevails over the western North Pacific. Sugars and sugar alcohols showed different seasonal patterns. The monthly mean concentrations of erythritol, arabitol, mannitol, inositol, fructose, glucose and trehalose were found to be higher in spring/summer and lower in fall/winter during both 1990–1993 and 2006–2009 periods, indicating an enhanced biogenic emission of aerosols in warm seasons. Interestingly, saccharides showed a gradual decrease in their concentrations from 1991 to 1993 and an increase from 2006 to 2009. In addition, the monthly averaged concentrations of sugars and sugar alcohols showed maxima in early summer during 1990–1993, which occurred about 1–2 months earlier than those during 2006–2009. Such a clear seasonal shift may be attributable to the changes in the strength of westerly and trade wind systems during two periods.

Early Cambrian black shales of South China not only host important sponge, arthropod and other soft-bodied fossils that have helped to trace early metazoan diversification, but also show extreme enrichments of a number of trace metals in particular Ni, Mo and V. In this study, we use a new approach by analyzing rare earth elements in kerogen extracted from the black shales, together with a number of redox-sensitive trace element compositions and total organic carbon (TOC) concentrations in an early Cambrian black shale sequence in Zunyi, Guizhou province, South China, to place better constraints on the oceanic redox conditions and the origin of the extreme metal enrichment. Our data show significant negative Ce anomalies (Ce/Ce* as low as 0.4) occurring in kerogen, which indicate an oxygenated surface environment of primary productivity in consistent with the concept that the organic matter is mainly derived from organisms in the euphotic zone. Mass balance calculation suggests that the kerogen-associated REE can dominate the measured black shale REE budget, while similarity between our measured REE patterns and those of similarly aged phosphorites indicates that the REE content of ancient phosphorites may have also derived initially from organic matter. The redox-sensitive trace elements, such as U, V, Mo, and their ratios of U/Al, V/Al and Mo/Al in black shales show different correlation patterns with TOC contents. The upper black shales show a good metal/TOC correlation, but such a correlation is absent in the lower part. The lower black shales exhibit much higher metal enrichments compared to Black Sea sulphidic (euxinic) sediment. This is taken to indicate the presence of sulphidic bottom waters during the deposition of the lower black shales, including the Ni–Mo ore layer. In contrast, anoxic, non-sulphidic conditions occurred during the deposition of the upper black shales. Taking all these geochemical data together, we suggest that the early Cambrian South China seaway was strongly stratified and stagnant, and that euxinic bottom water conditions may have led to enrichment of the redox-sensitive metals such as U, V and Mo in the lower black shales, and in one case the occurrence of a polymetallic Ni–Mo sulphide ore bed bearing an extraordinarily extreme metal enrichment, which, according to the Mo/TOC and Ni/TOC ratios and much other geochemical evidence, may have been additionally influenced by hydrothermal input of metals within the rift basin as suggested by a number of previous studies.