Kentsel Atıksu İle Sulanan Tarım Topraklarında Mikroplastik Kirliliği Ve Risk Değerlendirmesi

Although a high percentage of microplastics (MP) are removed in wastewater treatment plants, a significant portion is released into the environment through wastewater discharges. The use of wastewater for irrigation transports microplastics to agricultural soil. Despite the increasing global use of treated and untreated wastewater for irrigation, especially in arid and semi-arid regions, the burden of microplastics reaching agricultural soils from wastewater has not yet been adequately investigated. Microplastic pollution in soil is a major concern with unknown consequences for sustainable agricultural activities. Within the scope of this study, microplastic accumulation in agricultural soils irrigated with urban wastewater for many years and the potential risks to agricultural ecosystems were investigated. For this purpose, 202 soil samples taken at depths of 0-10 cm and 10-20 cm from 11 control and 90 wastewater-irrigated soils were analyzed for microplastic quantity, color, shape, and polymer type. The risk level of microplastic pollution detected in the soil was determined by the pollution factor (CF), pollution load index (PLI), and polymer risk index (H). In addition, the relationship between some physicochemical properties of the soil and microplastics was analyzed. While the average microplastics counts in the control soils were 169 MP/kg (100-220 MP/kg) and 140 MP/kg (80-240 MP/kg) for soil depths of 0-10 cm and 10-20 cm, respectively, they were determined as 329 MP/kg (100-840 MP/kg) and 295 MP/kg (80-660 MP/kg) in soils irrigated with wastewater taken from the same soil depths. It was found that there was a significant difference (P<0.0001) in terms of microplastic counts between the control and wastewater irrigated soils and that irrigation with wastewater caused an increase in the number of microplastics in the soil. It was observed that the number of microplastics detected decreased as the soil depth increased (P<0.0141). In soils irrigated with wastewater, fiber (56-60%), film (20-23%), and fragment (15-16%) types of microplastics were predominant. Transparent colored microplastics were predominant in control (64-71%) and wastewater-irrigated soils (54-57%). Polyethylene (PE), cellophane (CP), and polypropylene (PP) polymers were predominant in both control and wastewater-irrigated soils. According to the pollution factor (CF) value, 50% of the soils at a depth of 0-10 cm and 64% of the soils taken from a depth of 10-20 cm were contaminated with significant amounts of microplastics. According to both point and regional pollution load index (PLI) values, the hazard category for microplastics is I (PLI<10). As a result of the potential ecological risk assessment based on the types of polymers detected in the soil, 21% of the samples taken at both depths were found to be in the risk level III (100≤H<1000) category, based on the polymer risk index (H) value. No significant change was observed in the number of microplastics with changes in pH and salinity. The number of microplastics detected increased as the amounts of organic matter, total nitrogen, and plant-available phosphorus detected in the soil increased. The study findings indicate that microplastic accumulation increases in agricultural soils irrigated with wastewater, posing a higher risk for more fertile soils with higher organic matter, total nitrogen, and available phosphorus contents. The risk assessment results reveal that agricultural soils irrigated with wastewater are at risk of microplastic contamination. The findings suggest that microplastics, a neglected type of soil pollution, will become an even more significant problem with increasing amounts of wastewater used for irrigation and the additional infiltration of sewage sludge into the soil. Therefore, when planning the reuse of wastewater in irrigation, it is recommended that it should also be evaluated in terms of microplastic pollution