The Taiwan Environmental Protection Administration (EPA) conducted investigations of farmlands with high heavy metal contamination potential from 2010 to 2017. Additionally, a policy of farmland pollution prevention and management was also implemented by EPA in 2018. According to a survey on farmland pollution, farmlands were contaminated with low-concentration heavy metal through irrigation water over long periods. Moreover, factories in industrial and agricultural mixed areas illegally discharge large amounts of wastewater with heavy metal concentrations exceeding the irrigation water quality standard into unknown ditches and road gutters at last contaminating the irrigation water and farmlands. Besides the irrigation water, groundwater overexploitation, industrial air pollution, and waste disposal cause soil heavy metal pollution in farmland.
To establish long-term effective precaution and prevention procedures to avoid soil heavy metal pollution in farmlands, the “Management Project for Pollution Source in Farmland Soils (II)” is progressing. Firstly, this project focuses on selecting four demonstration zones with high pollution potential for the environmental site assessments and soil screening survey to ensure the soil pollution increment model is precise enough. Secondly, 750 samples of time-lapse capsules for heavy metal monitoring were placed in the ditch around the industrial zone to trace the pollution source according to 14 site assessment results, and 148 factories were included in the pollution source inspection list with high priority. Thirdly, 10 site assessment zones for pollution transport pathway patterns of groundwater, air, and waste disposal were selected, and three response measures were also proposed by 6 zone investigation results.
Because releasing irrigation water with high-concentration heavy metal into the ditch would cause farmland soil pollution, monitoring of irrigation water quality and soil screening investigations at regular times were also necessary. According to the management status of the soil pollution hot spot zone, 8 ditch watersheds with pollution potential were selected for site investigation and soil screening survey. As farmland soil, systematic pollution was not found in the 8 ditch watershed, and the principle of regular screening of farmland soil was unideal for the environmental protection bureau to implement, depending on the reflection from local, irrigation water monitor measure improvement suggestion and farmland pollution potential zoning and precautionary measure amendment were also proposed. During the execution of this project, the team also regularly upgraded the “National Farmland Soil Management System” and assisted the EPA in farmland pollution sites and integrating data.