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Geoscience ›› 2024, Vol. 38 ›› Issue (02): 509-519.DOI: 10.19657/j.geoscience.1000-8527.2023.052

• Hydrogeology, Engineering Geology and Environmental Geology • Previous Articles     Next Articles

Thallium (Tl) Migration Between Rice Grains and Root Soils and an Assessment on Human Health Risk in the Pearl River Delta

WEN Riyang(), HOU Qingye(), YANG Zhongfang, YU Tao, WANG Jiaxin   

  1. School of Earth Sciences and Resources, China University of Geosciences (Beijing), Beijing 100083, China
  • Received:2022-11-20 Revised:2023-07-14 Online:2024-04-10 Published:2024-05-22

Abstract:

Thallium (Tl) is a typical toxic heavy metal element, and its environmental behavior and effects on human health recently have attracted more attentions. However, only a few studies have been conducted previously on the geochemical characteristics, influencing factors, biological enrichment capacity, and assessment on human health risk of soil Tl in the river delta. Totally, 243 samples of rice grains and root soils from three parent material areas in the Pearl River Delta were collected and measured. The concentrations, bio-concentration characteristics, and influencing factors of the Tl in the root soil were futher investigated. A human health risk assessment model recommended by the United States Environmental Protection Agency (USEPA) was used to evaluate the human non-carcinogenic health risk. The results show that the Tl concentration in the root soil is significantly higher than the values of Chinese soil background and Guangdong soil background. 18.1% of rice root soil samples exceed the standard values of Canadian Tl environmental quality and the Swiss agricultural soil Tl (1×10-6). The excess rate of Tl in the root soil in quaternary sediments and acid magmatic rocks is significantly higher than that in terrigenous clastic rocks. The Tl concentration in root soil is closely correlated with the K2O, Al2O3, Pb, and Zn contents. The main reason for the enrichment of soil Tl and other heavy metal elements in the lower Pearl River plain is due to the weathering denudation and mining activities of sulfide deposits in the Pearl River catchment. The average Tl concentration of rice grains is 0.35×10-3, which is far lower than the edible standard value of Tl in German food safety regulations. The bioconcentration coefficient of Tl in rice grains is closely correlated with the contents of Na2O, Zn, and Pb in the root soil. HQ values of each sample show that 68% of children had moderate health risk; 46% of adults have moderate health risks, indicating children have significantly higher health risks than adults in the study area.

Key words: Pearl River Delta, rice grain, root soil, thallium, parent material, assessment on human health risk

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