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Geochemical characteristics of phosphorus in surface sediments of two major Chinese mariculture areas: The Laizhou Bay and the coastal waters of the Zhangzi Island
2014
Zhuang, Wen | Gao, Xuelu | Zhang, Yong | Xing, Qianguo | Tosi, Luigi | Qin, Song
Phosphorus (P) in surface sediments of the Laizhou Bay (LB) and the coastal waters around the Zhangzi Island (ZI) was analyzed. Six forms of P were separated — exchangeable or loosely sorbed P (Ads–P), aluminum-bound P (Al–P), iron-bound P (Fe–P), authigenic apatite plus CaCO3-bound P plus biogenic apatite (Ca–P), detrital apatite plus other inorganic P (De–P) and organic P (OP). The average contents of P in the LB were in the order: De–P>OP>Ca–P>Fe–P>Ads–P>Al–P; in the ZI, the corresponding order was De–P>OP>Fe–P>Ca–P>Ads–P>Al–P. Due to the high nutrient loadings from the surrounding rivers, TP contents in sediments of the LB were higher than in those of the ZI. The potential bio-available P (Ads–P and OP) accounted for 14.7% and 24.2% of TP in sediments of the LB and the ZI, respectively.
اظهر المزيد [+] اقل [-]Geochemistry of Tungsten and Arsenic in Aquifer Systems: A Comparative Study of Groundwaters from West Bengal, India, and Nevada, USA
2014
Mohajerin, T Jade | Neal, Andrew W. | Telfeyan, Katherine | Sasihharan, Sankar M. | Ford, Sophie | Yang, Ningfang | Chevis, Darren A. | Grimm, Deborah A. | Datta, Saugata | White, Christopher D. | Johannesson, Karen H.
Tungsten (W) concentrations were measured along with arsenic (As) in groundwaters from the Murshidabad district of West Bengal, India. Tungsten concentrations range from 0.8 to ~8 nmol kg⁻¹(0.15–1.5 μg kg⁻¹) in the circumneutral pH (average pH ~ 7.3) Murshidabad groundwaters, and attain concentrations as high as 14 nmol kg⁻¹(2.5 μg kg⁻¹) in local ponds (n = 2). Total dissolved As concentrations (AsT) range from 0.013 to 53.9 μmol kg⁻¹(<1 to 4,032 μg kg⁻¹), and As(III) predominates in Murshidabad groundwaters accounting for 70 %, on average, of As in solution. Tungsten concentrations in Murshidabad groundwaters are low compared to alkaline groundwaters (pH > 8) from the Carson Desert in Western Nevada, USA, where W concentrations are reported to reach as high as 4,036 nmol kg⁻¹(742 μg kg⁻¹). Although W is positively correlated with As in groundwaters from the Carson Desert, it is not correlated with AsTor As(III) in Murshidabad groundwaters, but does exhibit a weak relationship with As(V) in these groundwaters. Surface complexation modeling indicates that pH related adsorption/desorption can explain the geochemical behavior of W in Murshidabad groundwaters. However, the model does not predict the high As concentrations observed in Murshidabad groundwaters. The high As and low W concentrations measured in Murshidabad groundwaters indicate that either As and W originate from different sources or are mobilized by different biogeochemical processes within the Murshidabad aquifers. Mobilization of As in Murshidabad groundwaters is presumed to reflect reductive dissolution of Fe(III) oxides/oxyhydroxides and release of sorbed and/or coprecipitated As to the groundwaters. Multivariate statistical analysis of groundwater composition data indicate that W is associated with Mn and Cl⁻, which may point to a Mn oxide/oxyhydroxide, clay mineral, and/or apatite source for W in the Murshidabad sediments.
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