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Zhao H.,Sun Yat Sen University | Zhao H.,Guilin University of Technology | Xia B.,Sun Yat Sen University | Qin J.,Guangdong Provincial Academy of Environmental Science | Zhang J.,Sun Yat Sen University
Journal of Environmental Sciences (China) | Year: 2012

Dabaoshan Mine, the largest mine in south China, has been developed since the 1970s. Acid mine drainage (AMD) discharged from the mine has caused severe environmental pollution and human health problems. In this article, chemical characteristics, mineralogy of ocher precipitations and heavy metal attenuation in the AMD are discussed based on physicochemical analysis, mineral analysis, sequential extraction experiments and hydrogeochemistry. The AMD chemical characteristics were determined from the initial water composition, water-rock interactions and dissolved sulfide minerals in the mine tailings. The waters, affected and unaffected by AMD, were Ca-SO4 and Ca-HCO3 types, respectively. The affected water had a low pH, high SO4 2- and high heavy metal content and oxidation as determined by the Fe2+/Fe3+ couple. Heavy metal and SO4 2- contents of Hengshi River water decreased, while pH increased, downstream. Schwertmannite was the major mineral at the waste dump, while goethite and quartz were dominant at the tailings dam and streambed. Schwertmannite was transformed into goethite at the tailings dam and streambed. The sulfate ions of the secondary minerals changed from bidentate- to monodentate-complexes downstream. Fe-Mn oxide phases of Zn, Cd and Pb in sediments increased downstream. However, organic matter complexes of Cu in sediments increased further away from the tailings. Fe3+ mineral precipitates and transformations controlled the AMD water chemistry. © 2012 The Research Centre for Eco-Environmental Sciences, Chinese Academy of Sciences. Source

Lu H.,Guangdong Provincial Academy of Environmental Science | Lu H.,Sun Yat Sen University | Zhang W.,Sun Yat Sen University | Zhang W.,Guangdong Key Laboratory of Environmental Pollution Control and Remediation Technology | And 6 more authors.
Journal of Analytical and Applied Pyrolysis | Year: 2013

The surface characteristics of sludge-derived biochar (SDBC) made from three feedstocks of wastewater sludge under different pyrolysis temperatures were investigated. Results showed that the sludge from Waste Water Treatment Plant (WWTP) with pure domestic wastewater influent and less mixed industrial wastewater produced the highest biochar yield, and these SDBC samples have the highest isoelectric point (IEP) and the most uniform charge distribution, compared with other sources. For different pyrolysis temperatures, 400 C tend to achieve more uniform surface charge distribution of SDBC, due to the oxidation process more occurred on the external surface than internal matrix at this temperature. In addition, a pyrolysis temperature of 300 C resulted in the most reduction in DTPA-extractable metals of SDBCs, owing to the organo-metallic complex formed with the abundant presence of functional groups and available phosphorus content, which were easily decomposed or degraded at higher temperatures. © 2013 Elsevier B.V. All rights reserved. Source

Zhao P.,Sun Yat Sen University | Xia B.,Sun Yat Sen University | Qin J.,Guangdong Provincial Academy of Environmental Science | Zhao H.,Sun Yat Sen University | Zhao H.,Guilin University of Technology
Shengtai Xuebao/ Acta Ecologica Sinica | Year: 2012

Water quality variation is generally linked to the change of landscape pattern in watershed, which represents the main impact of human activities in macroscopic view. Therefore, identifying the crucial landscape factors that affect water quality variation is valuable for understanding the mechanism that landscape may affect water quality. Multivariate analysis tools are effective methods to deal with complex correlations between landscape pattern and water quality. Besides, advances of remote sensing (RS) and geographic information systems (CIS) technologies have made regional and watershed scale studies much more feasible. This study was conducted along Danshui River watershed, a branch of Dongjiang River in Cuangdong Province. The correlation between landscape pattern and water quality of Danshui River was represented by using spatial analysis and multivariate analysis methods base on ALOS satellite image and water quality monitoring data in 2007. Landscape metrics, including information of landscape composition and spatial configuration, were used to represent landscape pattern. In order to cover overall landscape information, landscape metrics on both watershed scale and riparian scale were used. Spearman's rank correlation analysis, multiple linear regression models with step-wise and canonical correlation analysis (CCA) were used to reveal the linkage between landscape metrics and water quality. The results show that forest, urban and agriculture land use are accounted for more than 90% of the total area in Danshui River watershed, while the area proportion of urban land exceeds 20%. Results of multiple linear regression models with step-wise and CCA showed that water quality indicators were affected by more than one landscape metric. The variation of water quality was influenced by landscape pattern significantly. The landscape metrics in watershed scale revealed more information of water quality variation than landscape metrics in riparian scale. The proportion of urban land use proportion had the greatest impact on water quality. Spearman's rank correlation analysis and multiple linear regression models showed the proportion of urban land use was the most important contributing factor to cause variation of oxygen consuming pollutants and nutrients. However, forest and agriculture land use had less influence on water quality. On the other hand, landscape metrics about landscape fragmentation were crucial factors to affect indicators of water quality, such as pH, DO and heavy metals. The result of CCA indicated that the first ordination axis could explain 54. 0% of the correlations between landscape metrics and water quality indicators, and the first two ordination axes could cumulatively explain 87. 6% of the correlations between landscape metrics and water quality. The result of CCA revealed that water quality had an obvious trend with the varying landscape gradient. The first two ordination axes mainly represented urbanization gradient and landscape fragmentation gradient respectively. Landscape characteristics in the study area showed a gradient of urban, urban-rural fringe, rural from upstream to downstream of Danshui River watershed. The distribution of pollutants concentration was corresponded with the gradient of landscape pattern in the watershed. Land use and cover change is an integrated result due to human activities, and change the state of eco-system of river and watershed significantly. It's highly reasonable that the water quality must correspond to the change of watershed landscape. Source

Su Y.,CAS Nanjing Institute of Geography and Limnology | Deng Y.,CAS Nanjing Institute of Geography and Limnology | Deng Y.,Guangdong Provincial Academy of Environmental Science | Du Y.,CAS Nanjing Institute of Geography and Limnology
Journal of Molecular Catalysis A: Chemical | Year: 2013

Microcystins generated by Microcystis aeruginosa are commonly detected in freshwater bodies and their removal becomes an emerging field recently owing to the toxicity. Here we report the structural characterization of degradation products from the photocatalysis of microcystin-LR (MC-LR). To achieve efficient photocatalytic degradation of MC-LR, we fabricated highly ordered TiO 2 nanotubes using anodization method. The surface morphology of TiO2 nanotubes depends primarily on the anodic voltage and the optimum value is 20 V. Under UV irradiation, the concentration of MC-LR decreases by 84.6% when using TiO2 nanotubes anodized at 20 V within 30 min. The degradation intermediates of MC-LR are detected with mass spectrometry (MS) and seven main intermediates are observed in liquid chromatography mass spectrometry (LC/MS) chromatogram. We propose the possible structures of the intermediates of MC-LR and infer its possible degradation pathways. The results indicate that the conjugated double bond and methoxy group in the Adda chain, as well as the conjugated system in the Mdha amino acid, are susceptible to be initially attacked by hydroxyl radicals. In addition, it is deduced that the peptides undergo breakdown from Mdha, then their carboxyl and amino groups are stepwise hydrolyzed and the side chain of the amino acid is oxidized. © 2013 Elsevier B.V. Source

Lu H.,Sun Yat Sen University | Lu H.,Guangdong Provincial Academy of Environmental Science | Zhang W.,Sun Yat Sen University | Zhang W.,Guangdong Key Laboratory of Environmental Pollution Control and Remediation Technology | And 5 more authors.
Water Research | Year: 2012

Lead sorption capacity and mechanisms by sludge-derived biochar (SDBC) were investigated to determine if treatment of acid mine drainage (AMD) containing metals with SDBC is feasible. It was found that the biochar derived from pyrolysis treatment of sewage sludge could effectively remove Pb 2+ from acidic solution with the capacities of 16.11, 20.11, 24.80, and 30.88mgg -1 at initial pH 2, 3, 4 and 5, respectively. Lead sorption processes were pseudo-second order kinetic and faster at a higher pH. Furthermore, the relative contribution of both inorganic mineral composition and organic functional groups of SDBC for Pb 2+ removal mechanisms, was quantitatively studied at pH 2-5. The results showed that Pb sorption primarily involved the coordination with organic hydroxyl and carboxyl functional groups, which was 38.2-42.3% of the total sorbed Pb varying with pH, as well as the coprecipitation or complex on mineral surfaces, which accounted for 57.7-61.8% and led to a bulk of Ca 2+ and Mg 2+ release during sorption process. A new precipitate was solely observed on Pb-loaded SDBC as 5PbO·P 2O 5·SiO 2(lead phosphate silicate) at initial pH 5, confirmed by XRD and SEM-EDX. The coordination of Pb 2+ with carboxyl and hydroxyl functional groups was demonstrated by FT-IR, and the contribution of free carboxyl was significant, ranging from 26.1% to 35.5%. Results from this study may suggest that the application of SDBC is a feasible strategy for removing metal contaminants from acid solutions. © 2011 Elsevier Ltd. Source

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