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Lithium isotope is potentially useful tracer of continental weathering. However, the factors affecting Li isotope composition in highly weathered saprolites are still largely unclear. In the present study, Li and Nd isotope compositions in saprolites developed on granite from Huizhou, southern China, were analyzed and Li isotope composition in quartz samples separated from the saprolites was determined. The Nd isotope composition of saprolites (eNd = −6.1 ± 0.4, 1σ) was almost identical to that of parent granite (eNd = −5.7), suggesting the eolian deposition in this profile is negligible. The δ7Li value in saprolites varied greatly from −7.7‰ to +14.0‰. Below a depth of 3 m, almost all saprolites were isotopically lighter than the parent granite (+1.0‰). However, above 3 m, δ7Li values were higher in saprolites (+2.2‰ to +14.0‰, average + 7.6‰) than in the parent granite and showed a significant increasing trend toward the surface. Moreover, the δ7Li value showed a negative correlation with the CIA value below 3 m, but a positive correlation above 3 m. Compared with the parent granite, quartz separates had a higher Li concentration (1.1–28.9 mg/kg, average 9.5 mg/kg) and δ7Li value (+12.1‰ to +13.9‰). As weathering progressed, the formation of secondary minerals (such as kaolinite) led to the incorporation of lighter 6Li, which may have contributed significantly to the low δ7Li value in saprolites below 3 m. However, this mechanism could not explain the relative enrichment of heavy 7Li in the upper layer saprolites. The relative enrichment of quartz may contribute significantly to the increase of δ7Li in saprolites. The direct evidence was that Li was abundant and distinctly isotopically heavier in quartz separates. Moreover, quartz content correlated positively with Li concentration (R2 = 0.90, p

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.

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.

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.

The consumption of CO 2 due to carbonate weathering is thought to be an important terrestrial sink for atmospheric CO 2 . However, the reaction and fate of weathering products may significantly affect the magnitude of the sink. Carbon mass balances were determined in Hongfeng Lake, a small artificial lake located in the carbonate plateau of SW China. This was accomplished by measuring the concentrations of DIC (dissolved inorganic C), DOC (dissolved organic C), POC (particulate organic C), and CO 2 partial pressure in lake waters, inflows and outflows, and in surrounding spring waters. Results show that maximum DIC (mainly HCO 3 - derived from carbonate weathering by CO 2 ) to DOC ratios in the catchment export load reach ∼21, implying that as much as ∼80% of the exported primary production is in the form of HCO 3 - , and, therefore, the CO 2 consumed by carbonate weathering and subsequent DIC export is a critical component of the C balance in this ecosystem. This exported HCO 3 - subsidizes C cycling of aquatic ecosystems in the catchment, and 32% (excluding carbonate-derived C) returns to the atmosphere as CO 2 evasion through the fluvial and lacustrine water–air interface and 10% is stored in lake sediment. This lake has a small CO 2 emission rate (13.2 ± 3.9 mmol m −2 d −1 , or 0.097 mol m −2 a −1 relative to catchment area) compared to mean values for many reservoirs found in temperate and tropical climatic zones. This is likely due in part to low organic C loads supplied by the karst-dominated catchment, and low lake water DOC concentrations. The estimate indicates that more C (39%) returns to the atmosphere and much less (13%) is stored in sediments, implying that the C sink of carbonate weathering may not be as significant as once thought.

Economic reform in China since 1978 has accelerated economic development nationwide hugely, but has also brought about some environmental pollution. In order to identify the primary Pb source to the atmosphere in the central Guizhou region, Pb isotopic ratios in the acid soluble fraction of sediment from Hongfeng Lake were investigated. Lead isotopes in the lake sediments record the history of regional atmospheric Pb pollution. Before the economic reform in 1978, the 208Pb/206Pb and 206Pb/207Pb ratios in the leachates of lake sediments were constant, with a range of 2.0060 to 2.0117 and of 1.2314 to 1.2355, respectively. In the early period of economic reform (1978 to 1988), with the rapid industrial growth in Guizhou province, the acid soluble Pb isotope ratios in the lake sediments changed sharply: the 208Pb/206Pb ratios increased from 2.0212 to about 2.05, while the 206Pb/207Pb ratios decreased from 1.2251 to 1.2060. Emissions from Pb-ore-related industries are suggested to be the major pollution source of Pb in this period. Due to output from a local power plant since 1988, the isotope ratios of the acid soluble Pb in sediments in 1990s are characterized by a little higher radiogenic Pb (208Pb/206Pb = 2.0340–2.0400; 206Pb/207Pb = 1.2122–1.2158) than for the 1980s.

This paper presents hydrogeochemical and S isotopic characteristics of karstic surface and ground water in the karstic aquifers of Zunyi city of Guizhou Province, SW China. The average δ34S value of SO4 is +2.2‰ (n = 28) in ground waters and +7.0‰ (n = 15) in surface waters in the low flow season, while in the high flow season it is +1.0‰ in ground waters and +2.8‰ in surface waters. Natural and anthropogenic sources of the dissolved SO 4 2 - can be discriminated by a combined approach using water chemistry and stable S isotope data. A pollutant source of SO4 is estimated to have very high TDS contents and a narrow range of δ34S values (0‰ to +5.0‰). The water with a distinctively high δ34S value of +30.5‰ originates from an evaporite (gypsum and anhydrite)-bearing aquifer, and the δ34S values lower than −10‰ suggest an origin by oxidation of sulfide minerals in coal seams with intermediate TDS contents.

Land use and land cover changes can cause variations in terrestrial energy, water balance and availability of nutrients. To understand the role of vegetation in regulating the hydrochemistry of karst hillslopes, overland flow and soil seepage water from two hillslopes covered with and without vegetation were studied in the Huanjiang Observation and Research Station for Karst Ecosystems, Guangxi, SW China. Dissolved major ions, as well as isotopic compositions of dissolved inorganic C (DIC) were examined. Water from the vegetated control slope had higher solute concentrations (except NO 3 - ) and lower δ13C values than water from the disturbed slope. The dynamics of K+ and NO 3 - in soil water sampled in time-sequence from the control slope was different from the disturbed slope. Specifically, K+ and NO 3 - concentrations of the control slope decreased gradually over time, while K+ and NO 3 - concentrations of the disturbed slope increased, and other ionic concentrations increased in both of the slopes.

Two reservoirs in series in a Karst area were investigated in this study to understand the impact of river damming on riverine C cycling. Monthly sampling strategy was performed in Hongfeng and Baihua reservoirs, from July, 2007 to June, 2008. DIC and its isotopic compositions were determined. pCO2, and calcite saturation index (SIc) were then calculated. Results show that δ13C-DIC in surface water of these reservoirs responded clearly to the transformation between photosynthesis and respiration, which also changes the inorganic C equilibrium. Based on monthly monitoring data, the major biogeochemical processes along the water column in these reservoirs, was also discussed. It is noted that hypoliminion introduction for hydropower generation and then release can lead to the discontinuity of water chemistry along a river course, and has adverse effects on the downstream environment.

The dual isotopic compositions of dissolved SO 4 2 - in aquatic systems are commonly used to ascertain SO 4 2 - sources and possible biogeochemical processes. In this study, the physical parameters, major anions and isotopic compositions of SO 4 2 - in water samples from Changjiang River (Nanjin) to the East Sea in Changjiang Estuary were determined. The salinity ranged from 0‰ to 32.3‰ in the estuary water samples. The Cl - , SO 4 2 - concentrations and δ18O–H2O values followed the salinity variations from freshwater to seawater, which indicated that mixing processes might be a major factor involved in the distribution of water and solutes. The contents and isotopic compositions of SO 4 2 - suggested that atmospheric deposition, evaporite dissolution and sulphide oxidation were the major sources of dissolved SO 4 2 - in the freshwater of Changjiang River. In addition, the mixing model calculated by contents and isotopic compositions of SO 4 2 - indicated that the mixing of freshwater and sea water was the major factor involved in SO 4 2 - distribution in Changjiang Estuary. However, slightly elevated δ18O–SO4 values were observed in the turbidity maximum zone, which suggested that biological processes might affect the O isotopic compositions of SO 4 2 - there.

The Xijiang River, the mainstream of the Zhujiang (Pearl) River, which is the second largest river in China in terms of discharge, flows through a large carbonate rock region in South China. The chemical and Sr isotopic compositions of the Xijiang waters were determined during the high-flow season in order to understand the chemical weathering processes, associated CO2 consumption and anthropogenic influences within the carbonate-dominated basin. The major ion compositions of the river waters are characterized by the dominance of Ca2+, Mg2+, HCO 3 - and are significantly rich in SO 4 2 - . The SO 4 2 - is mainly derived from the oxidation of sulfide minerals and acid precipitation caused by coal combustion. Chemical and Sr isotopic compositions of the river waters indicate that four reservoirs (carbonates, silicates, evaporites and anthropogenic inputs) contribute to the total dissolved loads. The chemical weathering rates of carbonates and silicates for the Xijiang basin are estimated to be approximately 78.5 and 7.45 ton km−2 a−1, respectively. The total chemical weathering rate of rocks for the Xijiang basin is approximately 86.1 ton km−2 a−1 or 42 mm ka−1, which is much higher than global mean values. The budgets of CO2 consumption by carbonate and silicate weathering are estimated to be 284 × 109 and 54.3 × 109 mol a−1, respectively. It would appear that H2SO4 is involved as a proton donor in weathering reactions in the Xijiang basin; calculated results show that the contribution of cations from rock weathering induced by H2SO4 accounts for approximately 11.2%. Results from this study show that the flux of CO2 released into the atmosphere is approximately 0.1 × 106 mol C km−2 a−1 or 0.41 × 1012 g C a−1 produced by H2SO4-induced carbonate weathering in the basin. When extrapolated to the entire surface area of carbonate in SW China, the flux of CO2 released to the atmosphere by H2SO4-induced carbonate weathering is about 1.41 × 1012 g C a−1.

Elemental (C/N ratio) and C isotope composition ( δ 13 C) of particulate organic C (POC) and organic C content (OC) of total suspended solids (TSS) were determined for two subtropical karstic tributaries of the Yangtze River, the Wujiang (the eighth largest tributary) and Yuanjiang (the third largest tributary). For the latter, two headwaters, the karstic Wuyanghe and non-karstic Qingshuijiang were studied. The Wujiang catchment is subject to intensive land use, has low forest coverage and high soil erosion rate. The δ 13 C of POC covered a range from −30.6‰ to −24.9‰, from −27.6‰ to −24.7‰, and from −26.2‰ to −23.3‰ at the low-water stage, while at the high-water stage varied in a span between −28.6‰ and −24.4‰, between −27.7‰ and −24.5‰, and between −27.6‰ and −24.2‰ for the Wujiang, Wuyanghe, and Qingshuijiang, respectively. The combined application of C isotopes, C/N ratio, OC, and TSS analyses indicated that catchment soil was the predominant source of POC for the Wujiang while for the Wuyanghe and Qingshuijiang, in-stream processes supplied the main part of POC in winter and summer. A significant increase in δ 13 C value (1.4‰) of POC was found in the Wujiang during summer, and was attributed to the enhanced soil erosion of the dry arable uplands close to the riverbanks of the main channel. Based on a conservative estimate, POC fluxes were 3.123 × 10 10 , 0.084 × 10 10 , and 0.372 × 10 10 g a −1 while export rates of POC were 466, 129, and 218 mg m −2 a −1 for the Wujiang, Wuyanghe, and Qingshuijiang, respectively. The POC export rate for the karstic Wujiang, with intensive land use, was 2–3 higher than that of the karstic Wuyanghe or of the non-karstic Qingshuijiang where soil erosion was minor. Such high values imply rapid degradation of related karstic ecosystems impacted by intensive land use activities, and pose a potential threat to the health of the Three Gorges Reservoir.

Tissue N contents and δ 15 N signatures in 175 epilithic mosses were investigated from urban to rural sites in Guiyang (SW China) to determine atmospheric N deposition. Moss N contents (0.85–2.97%) showed a significant decrease from the urban area (mean = 2.24 ± 0.32%, 0–5 km) to the rural area (mean = 1.27 ± 0.13%, 20–25 km), indicating that the level of N deposition decreased away from the urban environment, while slightly higher N contents re-occurred at sites beyond 30 km, suggesting higher N deposition in more remote rural areas. Moss δ 15 N ranged from −12.50‰ to −1.39‰ and showed a clear bimodal distribution (−12‰ to −6‰ and −5‰ to −2‰), suggesting that there are two main sources for N deposition in the Guiyang area. More negative δ 15 N (mean = −8.87 ± 1.65‰) of urban mosses mainly indicated NH 3 released from excretory wastes and sewage, while the less negative δ 15 N (from −3.83 ± 0.82‰ to −2.48 ± 0.95‰) of rural mosses were mainly influenced by agricultural NH 3 . With more negative values in the urban area than in the rural area, the pattern of moss δ 15 N variation in Guiyang was found to be opposite to cities where N deposition is dominated by NO x –N. Therefore, NH x –N is the dominant N form deposited in the Guiyang area, which is supported by higher NH x –N than NO x –N in local atmospheric deposition. From the data showing that moss is responding to NH x –N/NO x –N in deposition it can be further demonstrated that the variation of moss δ 15 N from the Guiyang urban to rural area was more likely controlled by the ratio of urban-NH x /agriculture-NH x than the ratio of NH x –N/NO x –N. The results of this study have extended knowledge of atmospheric N sources in city areas, showing that urban sewage discharge could be important in cities co-generic to Guiyang.

Dissolved organic matter (DOM) in the Nanming River, an urban river in Guiyang City in SW China, and its complexation behavior with Hg(II) were investigated using fluorescence spectroscopy and the quenching titration technique. Three major fluorophores, two humic-like and one protein-like fluorescence, were observed in most of the DOM samples. Significant correlations were observed between the humic-like and protein-like fluorescence intensities, as well as, between them and other water quality parameters such as dissolved organic carbon, PO 4 3 - , chemical oxygen demand and NH 4 + concentrations, suggesting that agricultural and municipal wastewaters may be the source for both protein-like and humic-like fluorescence materials in the river. The fluorescence quenching titration resulted in similar values for the conditional stability constants for Hg(II) complexes with the humic-like and protein-like fluorophores, likely due to the dominance of Hg binding with O-containing function groups at the high Hg(II) concentrations used in the titration. Effects of Cl−, Ca2+, Mg2+ and Cu2+ ions on the binding between Hg(II) and three different fluorophores were also studied. The fluorescence index from the Nanming River was further found to be controlled by pH and Hg(II), cautioning its use in discriminating the sources of DOM.

There is a lack of information in the literature regarding Tl exposure from naturally occurring Tl enrichment. This paper draws attention to the potential health risk posed by high concentrations of naturally occurring Tl in the environment. The inhabitants of a rural area in SW Guizhou Province, China, reside within a natural Tl accumulated environment resulting from Tl-rich sulfide mineralization, and they face ongoing severe Tl exposure. High Tl concentrations were detected in urine of the local residents. Urinary Tl concentrations are as high as 2668 lg/L, with most subjects surpassing the accepted world urinary Tl concentration at

The chemical compositions of the surface/ground water of Guiyang, the capital city of Guizhou Province, China are dominated by Ca2+, Mg2+, HCO3-andSO42-, which have been derived largely from chemical weathering of carbonate rocks (limestone and dolomite). The production of SO42- has multiple origins, mainly from dissolution of sulfate evaporites, oxidation of sulfide minerals and organic S in the strata, and anthropogenic sources. Most ground water is exposed to soil CO2 and, therefore, the H2CO3 which attacks minerals contains much soil C. In addition, the H2SO4 produced as a result of the oxidation of sulfides in S-rich coal seams and/or organic S, is believed to be associated with the chemical weathering of rocks. The major anthropogenic components in the surface and ground water include K+, Na+, Cl−, SO42-andNO3-, with Cl− and NO3- being the main contributors to ground water pollution in Guiyang and its adjacent areas. The seasonal variations in concentrations of anthropogenic components demonstrate that the karst ground water system is liable to pollution by human activities. The higher content of NO3- in ground water compared to surface water during the summer and winter seasons, indicates that the karstic ground water system is not capable of denitrification and therefore does not easily recover once contaminated with nitrates.

The Li isotope geochemistry of the Jinshajiang (upper reach of the Changjiang), Lancangjiang (Meckong) and the Nujiang (Salween) rivers have been studied to better understanding the weathering of continental crust. The three rivers show different water geochemistry, the Jinshajiang followed by the Lancangjiang contains much solute from dissolution of evaporites; the Jinshajiang has the highest average Li content and δ 7 Li values. The relatively low δ 7 Li values (+4.74∼+12.9‰) of the river waters, compared to those of large rivers in the world, probably reflect less weathering intensity in this arid and cold region. The Jinshajiang water has relatively high and constant δ 7 Li values, and is considered to be affected by evaporite dissolution and the high δ 7 Li values indicating that precipitation of salt minerals might have resulted in enrichment of 7 Li in the remaining water. It is thought that H 2 SO 4 has been involved in crustal weathering in the region, especially in the Nujiang basin.