Arsenic Variation in Two Basins of Lake Dianchi

Abstract

The spatial variation of arsenic, including arsenic speciation changes under the influence of water quality parameters in lake Dianchi, China was investigated. The water quality parameters were found to differ between the two basins of the lake (Caohai vs. Waihai), consistent with the eutrophic status. Arsenic in Caohai was greater than that in Waihai, with average values as 9.45 and 6.68 lg L -1 , respectively. Expect redox potential, correlation between various water quality parameters and arsenic forms were found, supporting the hypothesis that arsenic partition in suspended particulates in Lake Dianchi was driven mainly by biota factor.Keywords Arsenic Á Forms Á Arsenite Á Water quality parameters Arsenic (As) is a ubiquitous but toxic element. The range of background As levels in water is 0.1-80 lg L -1 . However, the elevation of As in groundwater due to the reduction and dissolution of As-containing minerals in alluvial strata occurs in some areas of the world, causing serious detriment to human health, mainly in India, Bangladesh and China (Mandal et al. 2007). Arsenic in drinking water has been legally restricted to within 10 lg L -1 by the WHO and China to protect human health (WHO 2003). Lakes act as watershed sinks, receiving both natural and anthropogenic sources of As (Nikolaidis et al. 2004). Arsenic in the water column is equilibrated between suspended particulates and water, with sorption and desorption reactions. These reactions are influenced by various factors, such as changes of temperature, pH and redox potential, organic degradation and other reduction reactions (Couture et al. 2010). The sorption and desorption of As in lake waters have been found to be concomitant with As oxidation/reduction in the outer sphere of particulates, causing the sorption/ desorption of As between the particulate and water phases (Gao et al. 2006). Dianchi, the sixth largest fresh water lake in China, is located near Kunming city, Yunnan province. The lake covers an area of 308.6 km 2 , with an average depth of 4.4 m and an elevation of 1,887.4 m, and is separated by a dam in the north, forming two basins as Caohai and Waihai (Fig. 1). The lake is in a hypereutrophic status, with severe algae blooms occurring annually over the past two decades. The nitrogen and phosphorus contents were found to decrease gradually from the north to south, which is consistent with the eutrophic status of the lake (Hu et al. 2006). Arsenic is a chemical analogue to phosphorus, and the relationship between phosphorus with eutrophication and the interaction of As and phosphorus has been documented in many lakes (Martin and Pedersen 2004;Rahman et al. 2008). Nevertheless, the As behavior in Lake Dianchi, especially its relationship with eutrophication, has rarely been documented to date. An investigation of As in Lake Dianchi may be helpful in understanding As behavior in hypereutrophic lakes. The objective of this study was to elucidate the spatial variation of As in relation to the eutrophic status of Lake Dianchi.

Water Quality Evaluation of Chapurson Valley in Hunza Nagar, Gilgit Baltistan, Pakistan, Based on Statistical Analysis and Water Quality Index

“…The method adopted was the examination of the positive and negative correlation for trends in concentration among water quality measures in the Chapurson Valley that were either significant or not [23]. Only few physico-chemical parameters were found to have a significant positive correlation (r > 0.5) such as pH, Hardness, and Turbidity.…”