Assessment On Heavy-metal Contamination For Bed Sediments In Changsha-Xiangtan Section Of The Xiangjiang River, China

The Xiangjiang River has been one of the most severely polluted rivers by heavy metals in China. The research work for this project was done by collecting nine sediment samples from the riverbed of Xiangjiang River in the Changsha-Xiangtan segment. The author analyzed the main elements, heavy metal elements and other trace elements systematically of45samples out of the240samples by using ICP-MS, and also evaluated the heavy metal pollution of the sediments by using the Geoaccumulation Index(Igeo) method, Enrichment Factors method, Potential Ecological Risk Index (RI) method, Heavy Metal Pollution Load Index method and Nemerow Comprehensive Index method.By analyzing the main elements in the sediment, the author learned that the main elements of the samples are SiO2、Al2O3、LOI、Fe2O3、 K2O and MgO. Compared with the average level of soil in China, the samples are rich in Al2O3、Fe2O3、K2O、MgO and SiO2while lacking CaO、MnO and P2O5. In XW1、XW4、and SG1, there is a high SiO2level and low Al2O3level, but in the other sediments, there is a low SiO2level and high Al2O3level. Therefore, it shows that in XW1、XW4、and SG1the size of the particulate is bigger, the quartz detritus mineral level is high, and the clay mineral level is low.By analyzing the heavy metal elements and other trace elements in the sediment from the riverbed of the Xiangjiang River’s Changsha-Xiangtan segment, the author learned that there is an obvious enrichment of heavy metals like Mn、Cu、Pb、Zn etc and there is also a high enrichment of trace elements like Nb、Cs、Y、Ge、Rb, but there is a lack of Sr, Hf、and Ta compared with the average levels in the soil of China.By estimating the heavy metal pollution in the sediment from the riverbed of the Xiangjiang River’s Changsha-Xiangtan segment, it shows that the two elements which caused the most serious pollution are Mn and Zn, followed by Pb and Cu. These four elements have caused medium level or even intense level pollution.After using Geoaccumulation Index (Igeo) method, Enrichment Factors method, Heavy Metal Pollution Load Index method and Nemerow Comprehensive Index method, it turns out that the results of the Heavy Metal Pollution Load Index Method and the Nemerow Comprehensive Index method are not fit for this particular study. the result of Heavy Metal Pollution Load Index method and Nemerow Comprehensive Index method shows that it has been seriously polluted, which probably is because the background differences caused by different contaminations and the exaggeration of effects of the enriched elements are not considered. Geoaccumulation Index(Igeo) method and Enrichment Factors method are fit for evaluating the heavy metal pollution in the sediment from the riverbed of Xiangjiang River’s Changsha-Xiangtan segment, and in order to have a more objective result, it is better to combine these two methods together for this study.