Abstract
In this study, the water quality of the irrigation system and concentration of trace metals in the sediments were combined to establish a farmland trace metal contamination and management model (FTM_CMM). The purpose of this model was to clarify the main sources of the trace metals that have caused the contamination of paddy soil in central Taiwan. The results of the model simulation showed that the trace metals in the paddy soil mainly came from the irrigation water and especially from the sediments in the irrigation channels. The contribution of the sediments in the irrigation channel to the individual trace metals in the paddy soil ranged from 56% to 72% as the contributions for Cr, Cu, Ni, and Zn were 72%, 68%, 56%, and 62%, respectively. The trace metal species according to their concentration in the contaminated soil ranked in the order of Zn > Cr ≈ Cu > Ni, which is about the same as in the channel sediment. During the simulation process, Cr, Cu, Ni, and Zn exceeded the control standards for farmlands in the 18th, 12th, 13th, and 17th years, respectively. This highlights that, in addition to the management of irrigation water quality, the management of trace metal contaminated sediment in adjacent canal irrigation systems is also an important part of the prevention of trace metal contamination in farmland.
Highlights
The harmful effects of environmental contamination were often ignored in the past because economic development was always given the first priority
The target paddy soils that were studied are located in central Taiwan and have been heavily contaminated with trace metals (TMs), including Cr, Cu, Ni, and Zn
The irrigation water is supplied by the East–West Second Canal irrigation system, one of the major irrigation systems in Changhua County
Summary
The harmful effects of environmental contamination were often ignored in the past because economic development was always given the first priority. In Taiwan, agricultural soils contaminated with trace metals (TMs) are an obvious example. Due to the negligence of the competent authorities, farmland irrigation and drainage systems in Taiwan used the same channels, which caused TM-containing industrial wastewater to be discharged directly into irrigation channels, contaminating farmlands with TMs [1,2]. Soil contaminated with TMs in agricultural areas is likely to affect people’s health and safety once the TMs have translocated into the edible parts of crops [4,5]. According to data from the Environmental Protection Agency of Taiwan (EPA Taiwan), as of the end of 2018, a total of 1138.5 hectares of farmland sites across Taiwan have been declared as contaminated. A total of approximately USD 60 million has been allocated as expenditures for soil remediation on f-armlands [7]
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