This project conducted arsenic concentration investigation of agricultural soil and groundwater in Choushui River Alluvial Fan, Chianan Plain, Pingtung Plain and Lanyang Plain which had high groundwater arsenic concentrations over the years. The results showed that due to the reducing environment in aquifers, high concentrations of Fe, Mn, As were released to groundwater in aforementioned areas. Through intensive use of groundwater for irrigation, lots of arsenic were accumulated in soil. Therefore, agricultural and hydrological analysis database were collected for establishing “Potential influenced areas of paddy soils in geogenic As-rich groundwater irrigation zones,” and potential were classified into high, middle and low levels. Additionally, the management suggestions by competent authorities were already proposed. Agricultural soil arsenic concentration were high for a long period of time at Touciao and Puzih industrial zone in Chiayi County, and Gouzao Village in Yunlin County. The origin of high soil arsenic concentration was concluded to the long-term irrigation of arsenic-rich groundwater by soil, groundwater, and drain sediment data analysis. According to the experience in figuring out the origin of high agricultural soil arsenic concentration, this project had revised “Scientific procedure of evaluating the origin of agricultural soil arsenic concentration” for the purpose of having a better practical implementation. In addition, in order to completely solve the problem of high arsenic concentration in agricultural soil, this project collected in-situ soil and groundwater arsenic removal technologies and case studies. Through evaluating the removal efficiency, cost, operational feasibility, convenience, stakeholders’ expectations, etc., the recommended soil and groundwater arsenic removal technologies were selected. Moreover, these technologies comparisons and experiments were intended for each responsible authority for further demonstrations and promotions.

Potential influenced areas of paddy soils in geogenic As-rich groundwater irrigation zones, Scientific procedure of evaluating the origin of agricultural soil As concentration, In-situ soil and groundwater As removal