Microplastic (MP) pollution in agroecosystems is a growing concern with unknown consequences for sustainable agricultural activities. Few studies have revealed MPs in soil as a result of wastewater irrigation, despite the increasing application of wastewater irrigation and inadequacy of conventional wastewater treatment plants in removing microplastics (MPs). In this study, the effect of treated wastewater (TWW) irrigation on MPs accumulation in agricultural soils of Konya City (in Türkiye) and the potential risks on agricultural ecosystem were investigated. For this purpose, 202 soil samples taken from 90 TWW irrigated lands and 11 non-agricultural control lands, at depths of 0–10 cm and 10–20 cm, were analyzed for color, shape, and polymer type. The risk level of MPs pollution was determined by the pollution factor (CF), pollution load index (PLI), and polymer risk index (H). The relationship between some physico-chemical properties of the soil and MPs pollution level was also analyzed. The findings of this study revealed a significant difference (P < 0.0001) in the MP count in the TWW irrigated soils, and control soils. While the average numbers of MPs for control soils were 169 ± 46.8 MPs/kg (100–220 MPs/kg) and 140 ± 44.7 MPs/kg (80–240 MPs/kg) for the 0–10 cm and 10–20 cm soil depths, respectively; 329 ± 139.5 MPs/kg (100–840 MPs/kg) and 295 ± 115.4 MPs/kg (80–660 MPs/kg) were identified for TWW irrigated soil samples taken from the same soil depths. Fiber, film, and fragment type MPs were found to be dominant polymer types in TWW irrigated soil, with 56%, 23%, and 16%, respectively. Transparent colored MPs were predominant. MP decreased from 0–10 cm to 10–20 cm depths. Most of the samples were significantly contaminated with MPs (3 ≤ CF < 6), categorized in hazard category class I (PLI < 10). The findings of this study indicate that TWW irrigation increases the accumulation of MPs in agricultural soils, which poses a higher risk to more fertile soils with higher organic matter, total nitrogen, and available phosphorus content. Hazard index assessments reveal that the soils of Konya, often referred to as the "granary of Türkiye," are at risk of MPs contamination. The findings showed that MPs, a neglected type of pollution for soil, will become an even more important problem with increasing wastewater irrigation.

In this study, the occurrences, temporal concentration variations and ecotoxicological risks were determined for 18 polycyclic aromatic hydrocarbons (PAHs); 7 congeners of polychlorinated biphenyls (PCBs), and 18 selected organochlorine pesticides (OCPs) in the anaerobically digested sewage sludge samples obtained from a conventional wastewater treatment plant (WWTP) in Konya, Turkey. Flowrate of the evaluated WWTP was 200,000 m³/day, with the production of 140 tons/day treated sewage sludge. Total 18 PAHs were in the range of 1,203 – 17,599 μg/kg of dry matter (dm); total PCBs were in the range of 51.26 – 561.37 μg/kg dm, and total OCPs were in the range of 4.90 – 13.11 μg/kg dm. The highest concentrations were determined for fluoranthene among PAHs, with 2445 μg/kg dm, PCB118 congener with 514 μg/kg dm, and δ-HCH among OCPs with 2.44 μg/kg dm. Considering the average daily production amounts of treated sludge, the highest mass loads were 1,785 g/day for total PAHs; 79 g/day for total PCBs; and 1 – 2 g/day for total OCPs, while the annual mass load was estimated to be approximately 7.3 kg. An ecotoxicological risk assessment was performed by estimation of risk quotients (RQs). High risk for soil ecosystem was identified due to PAHs and PCBs ingredient of sludge, while lower risk was determined for OCPs compounds. The highest RQ values were determined for pyrene (RQ: 1337) among PAHs, PCB118 congener (RQ: 7608), and γ-HCH (RQ: 5.23) among OCPs. Findings of this study show that sewage sludge can be an important source in the spread of persistent pollutants to the environment, and may pose a risk for soil ecosystem.

Heavy metals and pharmaceuticals have polluted agricultural soils mainly through wastewater irrigation, fertilizers, and soil amendment with sewage sludge. This study aims to determine the synergetic toxic effect of Cd and the selected macrolide antibiotic, azithromycin (AZI), on ammonia-oxidizing bacteria (AOB) in soil, via analyzing nitrification inhibition. A short-term acute toxicity test was used to measure the formation of Nitrite (NO₂-N) to indicate the nitrification potential of the aerobic nitrosomonas bacteria in the germination period. Potential nitrification rates (PNRs) of five soil samples ranged between 3.782–17.642 mg NO₂-N/kg dm PNRs of soil samples positively correlated with organic matter content and neutral pH. PNRs of the tested soils were significantly affected by Cd and AZI contamination, with interactions exhibited for their simultaneous occurrence and soil pH. A significant difference (p < 0.05) was found when soil samples with pH 6.5–pH 8.5 contaminated with environmentally relevant concentrations of Cd (1 mg/kg–21 mg/kg) and AZI (1 mg/kg–9 mg/kg). 50% PNR inhibition after 11 mg/kg Cd and 5 mg/kg AZI contamination was determined for the soil sample at pH 8.5, with 3.782 mg NO₂-N/kg dm potential. From these outcomes, it was concluded that there was a risk of the soil nitrification process in case of simultaneous occurrence of Cd and AZI.