The Study Of Thallium In Sediment From Maba Stream Of Beijiang River Valley Of Guangdong Province

Thallium(Tl) is a highly toxicity and rare heavy metal element. Its mean value is only 0.682 mg/kg in arable soils from Guangdong Province. Tl also is a lithophile and sulphophile element so it usually occurs in numerous mines, for example pyrites and lead-zinc ores. Guangdong north region, known as the hometown of nonferrous metals, has abundant containing Tl mineral resources. So that there were a mass of factories working on metal smelting and iron-steel manufacture in the areas. Tl which released from the process of smelting and treating containing Tl ores will pollute environment. A example is that when Tl was released into rivers, the water and sediment will be polluted in the river, and Tl can enter into biology and human and gather through food chain. It is the main cause of regional Tl poisoning and endemic disease. With the rapid development of economy in our country, those plants production is higher and higher than they need more and more ores resources. As a result of thallium pollution of the environment is becoming more and more obvious. So far, the main survey of thallium pollution in water at home and abroad were researches of thallium from water and surface sediment in the main stream while there has not much attention on the Tl pollution in receiving industrial wastewater rivers, especially Tl pollution in columnar sediments. So the study of Tl geochemical behavior in river sediments after industrial containing Tl wastewater discharge not only has important practical significance, but also has momentous instruct significance for prevent Tl pollution in the industrial wastewater from metals smelting and enriching Tl ores mining.In this study, samples that column sediment cores were collected from the sewage-received river, called Maba river which is a stream of Beijiang River in northern Guangdong, China. Using ICP-MS and BCR sequential extraction procedure to analyze Tl concentrations and forms and assess the pollution degree and the potential ecological risk of Tl and other heavy metals in sediments. The results show that(1) Tl concentrations range 1.03 mg/kg to 3.13 mg/kg with a mean of 1.89 mg/kg which is about three times as many as the Tl average content in local background soil.(2) Tl has a significantly positively relationship with nickel(Ni), copper(Cu), zinc(Zn), lead(Pb) and cadmium(Cd). It indicates that Tl and most common heavy metal elements have the same sources of pollution.(3) About 98 % of Tl exists in natural soil with residue phase while there were about 46 % to 70 % in sediment cores.(4) Though the studied sediments just had been mildly polluted by Tl, its environment around was in a higher potential ecological risk of Tl. What's more, the whole sediment cores had a very serious pollution of Cd and Cd has highly potential ecological risk on environment.Tl in wastewater-received river is directly related to the health and benefit of residents along the river. For this reason, the public should pay more attention to Tl pollution in sediments from the wastewater-received river of mining ores and smelters.