Risk Assessment of Atrazine polluted Farmland and Drinking Water: A Case Study

Abstract

Atrazine (2-chloro-4-[ethylamino]-6-[isopropylamino]-striazine) is a herbicide widely used for the protection of corn, sugarcane, grain sorghum, tea, and fruit crops. Since the introduction of atrazine to China in the early 1980s, its consumption in China has been increasing by 20% each year (Shu, 2000). Atrazine has been detected in the surface water and groundwater of several European Union countries (Siebers, 1994). The maximum contaminant level of 0.1 lg/L in drinking water has been detected in European Union countries, and 3 lg/L has been detected in the United States and China (Wust et al., 1992). At a low soil pH, protonized atrazine becomes more hydrophilic, with the result that this compound moves downward to groundwater through water infiltration of soil. Furthermore, the higher the organic matter and clay contained in soil, the stronger the atrazine bond to the soil solid phase. An investigation conducted in Nebraska, USA, showed that 0.07% of the total atrazine applied to a sandy loam infiltrated down to 1.5 m below the surface (Capriel et al., 1986). In the case of paddy fields, frequent irrigation facilitates atrazine leaching in soils. It has been proposed that leaching and degradation are the two main pathways of atrazine dissipation in paddy fields, whereas the contribution of surface runoff is less important than these two pathways (Alissara and Thomas, 2001). In late May 1997, a large-scale pollution incident occurred in the rice-growing area of Changtu County, Liaoning Province. During this incident, more than 2,800 ha of rice fields were heavily contaminated by atrazine during a short period of irrigation by atrazine-polluted waters from two rivers across the rice fields: the Tiaozi and Zhaosutai Rivers. An official investigation was conducted subsequently to trace the sources of atrazine in the rivers. It was found that an accidental leakage occurring in Siping City, Jilin Province, located on the upper reaches of the two rivers, resulted in a substantially higher concentration of atrazine upstream in the rivers. Rice seeds died in many of the contaminated fields, leading to a direct loss of about US$ 4.4 million (National Pharmacy Water Pollution Control Center [NPHC], 2005). A 6-month monitoring study was conducted immediately after the accident. According to the report issued by the Pesticides Safety Evaluation Center (PSEC) in July 1997, atrazine concentrations measured around Bamiancheng, one of the major rice-growing regions in Changtu County, ranged from 0.06 to 0.29 mg/L in the Tiaozi River, from 0.23 to 0.36 mg/kg in soils, and from 1.07 to 2.26 mg/kg in young rice shoots. Atrazine concentrations around Baoli, another rice-growing region of the County, was 0.03 to 0.06 mg/L in the Zhaosutai River, up to 0.08 mg/kg in soils, and 0.28 mg/kg in young rice shoots. Given the unusually high concentration and persistence of atrazine in environments, a concern is raised. How long will this accident affect the local ecosystem and environment? The current study aimed to determine atrazine residues in soils, rice grains, and drinking water in the contaminated area from November 1997 to October 2001 after the Q. Li (&) College of Environmental Science and Engineering, Dalian Maritime University, 1, Linghai Road, Dalian, Liaoning 116026, China e-mail: drlqb@yahoo.com.cn