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In order to better understand the spatiotemporal variations and interrelationships of greenhouse gases (GHG), monthly surface fluxes and profile concentrations of GHG (CO, NO and CH) in karst areas in the Guizhou Province, southwest China, were measured from June 2006 to May 2007. GHG fluxes showed high variability, with a range of 460.9-1,281.2 mg m h for CO, −25.4 to 81.5 μg m h for NO and −28.7 to −274.9 μg m h for CH, but no obvious seasonal change trends of the fluxes existed. Profile concentrations of CO, NO and CH varied between 0.5 and 31.5 mL L, 0.273 and 0.734, and 0.1 and 3.5 μL L, respectively. In general, concentrations of CO and NO increased with depth, while CH had an inverse trend. However, in October, November and January, the reversal of depth patterns of GHG concentrations took place below 15 cm, close to the soil-rock interface. The spatiotemporal distribution of CO in soil profile was significantly positively correlated with that of NO ( p < 0.05-0.01) and negatively correlated with that of CH ( p < 0.01). The correlation analysis showed that soil temperature and moisture may be responsible for GHG dynamics in the soils, rather than the exchange of GHG between land and atmosphere. [ABSTRACT FROM AUTHOR]

Nanming River, the largest urban river in Guizhou Province, southwestern China plateau, has been severely polluted for decades. This study characterizes the organic materials and their sources in the upstream and downstream waters by dissolved organic carbon (DOC), excitation emission matrix (EEM) spectroscopy, parallel factor (PARAFAC) analysis and photo-microbial experiments. DOC concentrations were low (47–120 μM C) upstream and relatively high (146–462 μM C) downstream. The PARAFAC studies on the sample EEM spectra demonstrated that the upstream dissolved organic matter (DOM) was mostly composed of one component that had a fulvic acid-like substance; downstream DOM was composed of two components with mixtures of tryptophan-like and fulvic acid-like substances. From the results of the sewerage drainage samples collected along the bank of the river, it is evident that both household detergent-like and protein-like or tryptophan-like substances are predominantly present, indicating that untreated sewerage effluents are the major sources of organic matter pollution in Nanming River. The degradation experiments conducted on river, sewerage drainage and commercial detergent samples demonstrated that the detergent-like and tryptophan-like substances are both photochemically and microbiologically more decomposable than fulvic acid-like materials under sunlight and dark incubations. These results suggest that the input of the untreated sewerage effluents along the streams is the major pollution source in Nanming River, and the fluorescent DOM was efficiently affected by both photochemical and microbial processes. [ABSTRACT FROM AUTHOR]

Nitrate (NO3 −) is major pollutant in groundwater worldwide. Karst aquifers are particularly vulnerable to nitrate contamination from anthropogenic sources due to the rapid movement of water in their conduit networks. In this study, the isotopic compositions (δ15N–NO3 −, δ15N–NH4 +) and chemical compositions(e.g., NO3 −, NH4 +, NO2 −, K+) were measured in groundwater in the Zunyi area of Southwest China during summer and winter to identify the primary sources of contamination and characterize the processes affecting nitrate in the groundwater. It was found that nitrate was the dominant species of nitrogen in most of the water samples. In addition, the δ15N–NO3 − values of water samples collected in summer were lower than those collected in winter, suggesting that the groundwater received a significant contribution of NO3 − from agricultural fertilizer during the summer. Furthermore, the spatial variation in the concentration of nitrate and the δ15N–NO3 − value indicated that some of the urban groundwater was contaminated with pollution from point sources. In addition, the distribution of δ15N–NO3 − values and the relationship between ions in the groundwater indicated that synthetic and organic fertilizers (cattle manure) were the two primary sources of nitrate in the study area, except in a few cases where the water had been contaminated by urban anthropogenic inputs. Finally, the temporal and spatial variation of the water chemistry and isotopic data indicated that denitrification has no significant effect on the nitrogen isotopic values in Zunyi groundwater. [ABSTRACT FROM AUTHOR]

Abstract  Natural and anthropogenic impacts on karst ground water, Zunyi, Southwest China, are discussed using the stable isotope composition of dissolved inorganic carbon and particulate organic carbon, together with carbon species contents and water chemistry. The waters can be mainly characterized as HCO3–Ca type, HCO3 · SO4–Ca type, or HCO3 · SO4–Ca · Mg type, according to mass balance considerations. It is found that the average δ13CDIC values of ground waters are higher in winter (low-flow season) than in summer (high-flow season). Lower contents of dissolved inorganic carbon (DIC) and lower values of δ13CDIC in summer than in winter, indicate that local rain events in summer and a longer residence time of water in winter play an important role in the evolution of ground water carbon in karst flow systems; therefore, soil CO2 makes a larger contribution to the DIC in summer than in winter. The range of δ13CDIC values indicate that dissolved inorganic carbon is mainly controlled by the rate of carbonate dissolution. The concentrations of dissolved organic carbon and particulate organic carbon in most ground water samples are lower than 2.0 mg C L−1 and 0.5 mg C L−1, respectively, but some waters have slightly higher contents of organic carbon. The waters with high organic carbon contents are generally located in the urban area where lower δ13CDIC values suggest that urbanization has had an effect on the ground water biogeochemistry and might threaten the water quality. [ABSTRACT FROM AUTHOR]

Abstract  The concentrations of rare earth elements in the dissolved, acid-soluble and residual phases in surface waters of the Changjiang Estuary were determined using ICP-MS. The main purposes of the study are to understand the estuarine geochemistry of rare earth elements and to explore water-particle interactions in the Changjiang estuarine mixing zone. The results show that there are two distinct processes operating on dissolved rare earth elements in the estuary: large scale removal at low salinities due to salt-induced coagulation and remarkable release at mid to high salinities. These processes result in modification of the effective river water flux and the systematical fractionation of the dissolved rare earth elements toward the East China Sea. The increase in concentration of dissolved rare earth elements in the mid to high salinity waters of the Changjiang Estuary suggests a sediment source in the mixing zone of the estuary, which is located over a shallow, broad shelf where there is extensive physical contact between bottom sediment and estuarine waters. Acid-soluble rare earth elements, the concentrations of which also dropped sharply in the low salinity region, appear to be controlled by salt-induced coagulation process and intense deposition of suspended particulate matter in the low salinity region. In the mid to high salinities, all acid-soluble rare earth element concentrations increase slightly with increasing salinity, suggesting that resuspension of sediments occurred. In contrast, the residual rare earth element concentrations are relatively constant with salinity variation in the Changjiang estuarine surface waters. [ABSTRACT FROM AUTHOR]

Sediment and water from the Meiliang Bay of Lake Taihu were analyzed to examine the historical relation between the accumulation of biogenic silica (BSi) and total phosphorus (TP). The results indicate that BSi accumulation in the northern part of Lake Taihu had been controlled by diatom production and phosphorus loading since the 1950s. BSi accumulation increased with the growing agricultural activity since the 1950s, up to a maximum level in the 1960s. After that, BSi accumulation decreased due to the diatom dissolution till the 1980s, and then the diatom biomass decreased with BSi accumulation increased. Lake Taihu came into an accelerated eutrophication periods since the 1990s, while BSi accumulation began to increase but the proportion of diatom decreased. Although the onset of silica depletion cannot be confirmed in the present work, it is clear that BSi accumulation was restrained by the input of TP. [ABSTRACT FROM AUTHOR]

Abstract  The amount of pollution from nonpoint sources flowing in the streams of the Wujiang River watershed in Guizhou Province, SW China, is estimated by a geographic information system (GIS)-based method using rainfall, surface runoff and land use data. A grid of cells of 100 m in size is laid over the landscape. For each cell, mean annual surface runoff is estimated from rainfall and percent land use, and expected pollutant concentration is estimated from land use. The product of surface runoff and concentration gives expected pollutant loading from that cell. These loadings are accumulated going downstream to give the expected annual pollutant loadings in streams and rivers. By dividing these accumulated loadings by the similarly accumulated mean annual surface runoff, the expected pollutant concentration from nonpoint sources is determined for each location in a stream or river. Observed pollutant concentrations in the watershed are averaged at each sample point and compared to the expected concentrations at the same locations determined from the grid cell model. In general, annual nonpoint source nutrient loadings in the Wujiang River watershed are seen to be predominantly from the agricultural and meadow areas. The total annual loadings through the outlet of the watershed are 40,309 and 2,607 tons for total nitrogen (TN) and total phosphorus (TP), respectively. [ABSTRACT FROM AUTHOR]

Abstract??Winter seasonal concentrations of dissolved rare earth elements (REE) of two major river systems (the Wujiang River system and the Yuanjiang River system) in karst-dominated regions in winter were measured by using a method involving solvent extraction and back-extraction and subsequent ICP-MS measurements. The dissolved REE concentrations in the rivers and their tributaries are lower than those in most of the large rivers in the world. High pH and high cation (i.e., Na+?+?Ca2+) concentrations of the rivers are the most important factors controlling the concentrations of dissolved REE in the river water.The dissolved load (<0.22??m) REE distribution patterns of high-pH river waters are very different from those of low-pH river waters. The shale (PAAS)-normalized REE patterns for the dissolved loads are characterized by light REE-enrichment and heavy REE-enrichment. Water in the upper reaches of the Wujiang River generally shows light REE-enriched patterns, while that in the middle and lower reaches generally shows heavy REE-enriched patterns. The Yuanjiang River is heavy REE enriched with respect to the light REE in the same samples. Water of the Wuyanghe River draining dolomite-dominated terrains has the highest heavy REE-enrichment. Most river water samples show the shale-normalized REE patterns with negative Ce and Eu anomalies, especially water from Wuyanghe River. Y/Ho ratios show that the water/particle interaction might have played an important role in fractionation between HREE and LREE. [ABSTRACT FROM AUTHOR]

Yulong ore-bearing porphyries, along the northwestern extension of the Red River–Ailao Shan fault system in eastern Tibet, consist of five porphyry deposits, containing a total of more than 8 million tons of copper resources. U–Th–Pb laser inductively coupled plasma mass spectrometry dating of zircon shows that the porphyries were emplaced in Early Tertiary (41.2–36.9 Ma), covering a period of ∼4.3 Ma, with formation ages decreasing systematically from northwest to southeast. The start of porphyry magmatism coincided with the onset of transpressional movement along the Red River–Ailao Shan fault system, implying a close link between these two events. Age sequence in intrusions can be plausibly explained by assuming that a region of melting in the lower northwestern plate moved southeasternward along the Tuoba–Mangkang fault relative to the upper plate. Zircon grains from the Yulong ore-bearing porphyries have higher Ce4+/Ce3+ than those from barren porphyries in the region. This suggests that the ore-bearing porphyries crystallized from a relatively oxidized magma, which has important implications for future ore exploration in the region and other Cu deposits in convergent margin environments in general. [ABSTRACT FROM AUTHOR]

Mine tailings can provide a long-term source of environmental contamination. Lead-zinc mine tailings can represent a source of toxic elements-Pb and Zn through mobilization into surface water, and then into downstream rivers. Previous studies have shown that migration of heavy metals can be mitigated by carbonate rock. This research investigates the characterization of heavy metals and sulphur isotope in a downstream river of the Shanshulin Pb-Zn mine, which is located in Guizhou province in China, a typical carbonate area in the world. A slight alkalinity (pH > 8) of the river water is maintained owing to the carbonate rich country rocks. The results of this study show that heavy metals in water can be strongly adsorbed by suspended solids and therefore decrease more quickly than in sediments. Pb and Zn contents in water close to the waste pile are 6780 μg L-1 and 324 μg L-1 (Pb and Zn in water not affected by mine waste piles are only 3.71 μg L-1 and 11.6 μg L-1) respectively, meaning that the water is severely contaminated by the pile. Thirty kilometers downstream Pb and Zn contents in water drop quickly to 3.15 μg L-1 and 16.4 μg L-1. In contrast, Pb and Zn contents in sediment close to the waste pile are 4553 mg kg-1 and 7971 mg kg-1 respectively, and are still high 30 km downstream with measurements of 3334 mg kg-1 and 7268 mg kg-1 respectively (Pb and Zn contents in sediment not affected by mine waste piles are only 20 mg kg-1 and 120 mg kg-1). This indicates that the impact of tailings on the sediment can be much further than on water. In sediment, Pb exists mostly as carbonate and oxide fractions, Zn mostly as sulfide+organic fraction, and Cu mostly as sulfide+organic, residual and carbonate fractions. Sulphur characteristics indicate that sulphur in sediment originates from mine tailing, soil and suspended solids in other tributaries, whereas sulphur in water originates from mine tailing dissolution, spring water, rain water and dissolution of gypsum. In conclusion, the environmental impact of mine tailing can be indicated by heavy metals content, sulphur content and sulphur isotope of sediment. On the other hand, heavy metal content, sulphur content or sulphur isotope of water are possibly not good indicators for mine impact due to mitigation of carbonate rocks, sorption of heavy metals, as well as interference of gypsum layers. [ABSTRACT FROM AUTHOR]