Fate of Arsenic in Soil-Plant Environment in Arsenic-tainted Farm
Date Issued
2008
Date
2008
Author(s)
Yao, Pei-Hsuan
Abstract
Over 100 hectares paddy soils were heavily polluted by arsenic (As) pollution at Guan-Du Plain, Beitou, resulting from a long-term irrigated water with high arsenic content mixed with hot spring water from Thermal Valley in the past hundred years. Since arsenic had already exist in soils used for rice (Oryza sativa) cultivation, in this research, a survey of arsenic contents of rice and paddy soils has been conducted. The aim of this study is to figure out the effect caused by arsenic-rich soils, such as the accumulation and distribution of arsenic in soil-plant systems, moreover, the probable dietary arsenic exposure through food chains, that is, the arsenic exposure via the soil-crop-human pathway.he top 15 cm soil and rice samples from 20 arsenic-tainted fields within Guan-Du Plain were collected in July and November, 2007. Paired rice and soil samples were surveyed just before harvest, with four samples set per field sampled. The total arsenic concentrations in soil and different parts of rice that is grains, straws, and roots averaged 153.2±149.6, 203.7±138.0, 4.21±2.01, 0.231±0.075 mg/kg dry weight, respectively. Meanwhile, the mean arsenic contents in ratoon rice were 191.6±160.1 mg/kg in roots, 2.94±1.60 mg/kg in straws (leaves and stems were included), and 0.045±0.013 mg/kg in brown rice. All of the above were determined by field portable X-ray fluorescence (FP-XRF) or hydride generator connected with atomic absorption spectrometer system (HG-AAS).espite the accumulation of arsenic in rice plants attributable to growth on soils contaminated with elevated arsenic levels, there is no significantly statistical relationship between the concentration of arsenic in soils and that in brown rice. However, correlations of soil arsenic levels with roots and straws are statistically significant, while the same in roots and straws, and what’s more, regression of soil arsenic levels with roots is statistically significant. Although the ratoon rice this year contains lower level arsenic due to loose field practice and climate, the arsenic contents in roots from different growing seasons are not significantly different. Finally, based on the typical consumption of Taiwanese people, the daily intake of arsenic from rice has been demonstrated to assess the safety of dietary intake. The result of this demonstration proves to be within and even below the provisional tolerable daily intakes recommended by WHO.
Subjects
Arsenic
Farmland Pollution
Dietary Exposure
Guan-Du Plain
Paddy rice.
SDGs
Type
thesis
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