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Ocean acidification, a complex phenomenon that lowers seawater pH, is the net outcome of several contributions. They include the dissolution of increasing atmospheric CO2 that adds up with dissolved inorganic carbon (dissolved CO2, H2CO3, HCO-3, and CO2-3) generated upon mineralization of primary producers (PP) and dissolved organic matter (DOM). The aquatic processes leading to inorganic carbon are substantially affected by increased DOM and nutrients via terrestrial runoff, acidic rainfall, increased PP and algal blooms, nitrification, denitrification, sulfate reduction, global warming (GW), and by atmospheric CO2 itself through enhanced photosynthesis. They are consecutively associated with enhanced ocean acidification, hypoxia in acidified deeper seawater, pathogens, algal toxins, oxidative stress by reactive oxygen species, and thermal stress caused by longer stratification periods as an effect of GW. We discuss the mechanistic insights into the aforementioned processes and pH changes, with particular focus on processes taking place with different timescales (including the diurnal one) in surface and subsurface seawater. This review also discusses these collective influences to assess their potential detrimental effects to marine organisms, and of ecosystem processes and services. Our review of the effects operating in synergy with ocean acidification will provide a broad insight into the potential impact of acidification itself on biological processes. The foreseen danger to marine organisms by acidification is in fact expected to be amplified by several concurrent and interacting phenomena. [ABSTRACT FROM AUTHOR]

Using isotope mixing model (IsoSource) and natural δ15N method, this study evaluated contributions of major sources to N of PM2.5 at Beijing (collected during a severe haze episode of January 22nd-30th, 2013) and a background site (Menyuan, Qinghai province; collected from September to October of 2013) of China. At Beijing, δ15N values of PM2.5 (-4.1 - +13.5 ‰; mean = +2.8 ± 6.4 ‰) distributed within the range reported for major anthropogenic sources (including NH3 and NO2 from coal combustion, vehicle exhausts and domestic wastes/sewage). However, δ15N values of PM2.5 at the background site (+8.0 - +27.9 ‰; mean = +18.5 ± 5.8 ‰) were significantly higher than that of potential sources (including NH3 and NO2 from biomass burning, animal wastes, soil N cycle, fertilizer application, and organic N of soil dust). Evidences from molecular ratios of NH4+ to NO3- and/or SO42- in PM2.5, NH3 to NO2 and/or SO2 in ambient atmosphere suggested that the equilibrium of NH3 ↔ NH4+ caused apparent 15N enrichment only in NH4+ of PM2.5 at the background site due to more abundant NH3 than SO2 and NO2. Therefore, a net 15N enrichment (33 ‰) was assumed for NH3 sources of background PM2.5 when fractional contributions were estimated by IsoSource model. Results showed that 41 %, 30 % and 14 % of N in PM2.5 of Beijing originated from coal combustion, vehicle exhausts and domestic wastes/sewage, respectively. Background PM2.5 derived N mainly from biomass burning (58 %), animal wastes (15 %) and fertilizer application (9 %). These results revealed the regulation of the stoichiometry between ammonia and acidic gases on δ15N signals in PM2.5. Emissions of NO2 from coal combustion and NH3 from urban transportation should be strictly controlled to advert the risk of haze episodes in Beijing. [ABSTRACT FROM AUTHOR]

The contents and stable S isotope ratio (δ34S) values of total S, organic S, SO42--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 δ34S 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 δ34S values differed in limesto\ne soil and yellow soil, indicating the different geochemical responses of these soils to acid deposition. The deposited SO42- was retained as organic S in both soils. The depletion in 34S of TRS relative to SO42- and the parallel increasing δ34S values of TRS and SO42- 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 SO42-, 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. [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]

The Changjiang River is the largest freshwater river in China. Here, the sources and variability in nitrate of the Changjiang River are assessed for the first time using dual isotopic approach. Water samples were collected once in August 2006 from the main channel of the Changjiang and its major tributaries. The concentrations and isotopic composition of nitrate were then analyzed for the waters in the Changjiang River. The δ15N and δ18O of NO3- ranges from 7.3‰ to 12.9‰ and 2.4‰ to 11.2‰ in the Changjiang River waters, respectively. The ranges of isotopic compositions of nitrate suggested that nitrification (including "modified fertilizer") and urban sewage effluent are the major sources of nitrate in the Changjiang River. The high δ18O-NO3- values were observed in the water of the upper reaches, indicated that the current drought might be one important reason for shifting of isotopes in the special sampling period. In addition, there was a strong positive relationship between δ15N-NO3- and δ18O-NO3-, which indicated that denitrification added to the enrichment of heavy isotopes of nitrate. [ABSTRACT FROM AUTHOR]

Pseudosections for two sediments and one basalt calculated in the system K2O–Na2O–CaO–MgO–FeO–Fe2O3–Al2O3–TiO2–SiO2–H2O for the P–T range 10 to 35 kbar, 300 to 900°C give useful insights into the amount of H2O released from oceanic crust in subduction zones. In cold subduction zones (20 kbar–300°C to 35 kbar–500°C) hydrous minerals storing 3 to 4 wt% H2O are still present in metasediments at depths of 120 km. In the same environment, metabasite releases 1 wt% H2O in the depth range 100 to 120 km, but 4.5 wt% H2O is transported to greater depths. In hot subduction zones (300°C hotter than the cold subduction zone at 100 km depth), dehydration events of metasediments in the depth range 50 to 80 km correspond to the breakdown of chlorite and paragonite. In the calculations no further water is released at greater depths because the modal content of phengite, the only hydrous mineral phase at these depths, remains almost constant. For the same P–T path, metabasite shows continuous dehydration between 40 and 80 km releasing almost 3 wt% H2O. At 120 km depth less than 0.4 wt% of H2O remains. In an average modern subduction zone (∼6°C/km) most dehydration of sediments occurs at depths of 70 to 100 km and that of basalts at depths of 80 to 120 km. Only 1.3 wt% H2O in metasediments and 1.6 wt% H2O in metabasalt has the potential to be subducted to depths greater than 120 km. The dehydration behavior of sediments concurs with the generally held idea that subduction zone fluids are most effectively transported to great depths by cold subduction. In hot subduction zones, such as those characteristic of early Earth, most H2O carried by oceanic crust is liberated at depths less than 120 km and, thus, would not contribute to island-arc magmatism. [ABSTRACT FROM AUTHOR]

Because of active exchange between surface and groundwater of a karstic hydrological system, the groundwater of Guiyang, the capital city of Guizhou Province, southwest China, has been seriously polluted by anthropogenic inputs of NO3-, SO42-, CI-, and Na+. In this work, δ37CI of chloride and δ34S variations of sulfate in the karstic surface/groundwater system were studied, with a main focus to identify contaminant sources, including their origins. The surface, ground, rain, and sewage water studied showed variable δ37CI and δ34S values, in the range of -4.1 to +2.0%‰ and -20.4 to +20.9‰ for δ37CI and δ34S (SO42-), respectively. The rainwater samples yielded the lowest δ37CI values among those observed to date for aerosols and rainwater. Chloride in the Guiyang area rain waters emanated from anthropogenic sources rather than being of marine origin, probably derived from HCI (g) emitted by coal combustion. By plotting 1/SO42- vs δ34S and 1/Cl- vs δ37CI, respectively, we were able to identify some clusters of data, which were assigned as atmospheric deposition (acid rain component), discharge from municipal sewage, paleo-brine components in clastic sedimentary rocks, dissolution of gypsum mainly in dolomite, oxidation of sulfide minerals in coal-containing clastic rocks, and possibly degradation of chlorine-containing organic matter We conclude that human activities give a significant input of sulfate and chloride ions, as well as other contaminants, into the studied groundwater system through enhanced atmospheric deposition and municipal sewage, and that multiple isotopic tracers constitute a powerful tool to ascertain geochemical characteristics and origin of complex contaminants in groundwater. [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]

This article discusses the chemical and isotopic composition of a headwater tributary of the Yangtze River, the Minjiang River in China. According to the authors, the chlorides, nitrates and sulfates increase through the Sichuan Basin as the result of anthropogenic impacts. Sulfur, oxygen and hydrogen isotopic compositions and water chemistry indicate impacts of air pollutants, industrial effluents, domestic wastewater, and agricultural fertilizers. The Minjiang River pollutants appear to be diluted by the cleaner Jinshajiang River as it flows into the Yangtze River.

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]

Nitrate pollution of the karstic groundwater is an increasingly serious problem with the development of Guiyang, the capital city of Guizhou Province, southwest China. The higher content of NO3- in groundwater compared to surface water during both summer and winter seasons indicates that the karstic groundwater system cannot easily recover once contaminated with nitrate. In order to assess the sources and conversion of nitrate in the groundwater of Guiyang, we analyzed the major ions, δ15N-NH4+, δ15N-NO3-, and δ18O-NO3- in surface and groundwater samples collected during both summer and winter seasons. The results show that nitrate is the major dominant species of nitrogen in most water samples and there is a big variation of nitrate sources in groundwater between winter and summer season, due to fast response of groundwater to rain or surface water in the karst area. Combined with information on NO3-/CI-, the variations of the isotope values of nitrate in the groundwater show a mixing process of multiple sources of nitrate, especially in the summer season. Chemical fertilizer and nitrification of nitrogen-containing organic materials contribute nitrate to suburban groundwater, while the sewage effluents and denitrification mainly control the nitrate distribution in urban groundwater. [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]

Secular variations in the carbon isotopic composition of organic and carbonate carbon characterize the Lower to Middle Cambrian transition that is exposed on the Yangtze Platform at Taijiang, Guizhou Province, southern China. δ13C values for organic matter range between -33.4 and -26.5‰. The carbon isotopic composition for carbonate carbon fluctuates between -2.7 and +3.1‰. A progressive decrease in the isotopic difference (Δδ) between these two isotope records reflects a decrease in the proportional contribution of bacterial biomass to the total sedimentary organic matter. In general, the observed changes are interpreted to reflect primary depositional values, notably variations in the burial rates of organic matter. These, in turn, are linked to biological changes across the Lower to Middle Cambrian transition. No distinct shift in the carbon isotopic composition marks the proposed Lower--Middle Cambrian boundary. [ABSTRACT FROM AUTHOR]

Variations in the concentrations and isotopic compositions (δ13CDIC) of dissolved inorganic carbon (DIC) reflect contamination and biogeochemical cycling of the carbon in ground water. In order to understand contamination and biogeochemical cycling of DIC, we carried out research on the geochemistry of ground water of Guiyang, the capital city of Guizhou Province, China. Results show that ground water is mainly characterized by SO₄·HCO₃-Ca·Mg and HCO₃-Ca·Mg chemical compositions. The hydrochemical characteristics of these types of water are mainly controlled by lithology of the aquifers. HCO₃- is the dominant species of DIC in ground water and has lower concentrations and more negative values of δ13CDIC in the high-flow (summer monsoon) season, as compared to the low-flow season. This indicates that DIC is relatively enriched in carbon of biological origin in the high-flow season as compared to the low-flow season and that biological activities are the predominant control on shifts of stable carbon isotope values. The evidence that the δ13CDIC values of ground water decrease with increasing concentrations of anthropogenic species shows that the carbon isotopic composition of DIC can be a useful tracer of contamination, in addition to biogeochemical cycling of inorganic carbon in ground water. Results from this study show that ground water is impacted by significant levels of contamination from human activities, especially in the urban areas, as well as the northeast and west suburbs, in Guiyang city, southwest China. [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]