Arsenic and other heavy metals in the Sunkoshi and Saptakoshi Rivers, eastern Nepal
| Autor: | Steven H. Emerman, Tara Nidhi Bhattarai, Roshan Raj Bhattarai, M. P. Bunds, Ryan B. Anderson, A. Palmer, Sushmita Bhandari |
|---|---|
| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | Journal of Nepal Geological Society. 43:241-254 |
| ISSN: | 2676-1378 0259-1316 |
| DOI: | 10.3126/jngs.v43i0.25589 |
| Popis: | Since previous research had shown that elevated fl uvial As occurs throughout Nepal outside of the Higher Himalayan Zone, the objective of this study was to determine whether elevated fl uvial As occurs throughout the Ganges River system or, if not, where in the river system As adsorbs onto sediments. Samples were collected during an 11-day 288-km rafting trip down the Sunkoshi River to the Saptakoshi River from Dolalghat to Koshi Barrage. Water samples were collected from the Sunkoshi and Saptakoshi rivers twice daily and from fi ve major tributaries, while sediment samples were collected from sand bars daily. Dissolved concentrations of As, Fe, Cu, Ni, Co, Mn, Zn and Cr were measured with a spectrophotometer. Mobile sediment As was measured by extraction with 1 M HCl. Dissolved transition elements were elevated both upstream of and within the Terai Zone (Indo-Gangetic Plain), while dissolved As was elevated upstream of the Indo-Gangetic Plain, but became uniformly undetectable within the Indo-Gangetic Plain. There was a moderate correlation (R 2 = 0.44) between mobile sediment As and downstream distance. The fl uvial behavior of As can be related to the large mass, volume and valency of the As oxyanion so that, when river velocity is high, the As oxyanion does not have suffi cient residence time in the vicinity of sorption sites to attach to those sites. The implication of this study is that it may be possible to address As contamination of groundwater by addressing deforestation only in the tectonic valleys upstream of the Indo-Gangetic Plain. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|