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Öğe Assessment of the levels of heavy metal pollution in roadside soils of Termiz – Taskent, Uzbekistan(Polskie Towarzystwo Inzynierii Ekologicznej (PTIE), 2025) Kholikulov, Shodi Turdukulovich; Erdem, Halil; Bobobekov, Isomiddin Nuriddinovich; Demir, Saniye; Gence, Cabir ÇağrıThis study investigates the contamination of roadside soils by heavy metals (Pb, Zn, Ni, and Mo) along the Tashkent- Termiz International M-39 highway, utilizing indices such as the enrichment factor (EF), geo-accumulation index (Igeo), and pollution load index (PLI). Soil samples collected at 21 distances (5–1000 m) indicate that metal concentrations decrease with distance from the road, with rapid reductions observed within the 5–100 m range. Pb levels decline from 24 mg kg-1 at 5 m to 1.4 mg kg-1 at 1000 m, while Zn reduces from 26.3 mg kg-1 to 2.1 mg kg-1. Ni and Mo follow similar trends, but Mo exhibits lower mobility. Pb, Zn, and Ni stand out as indicators of anthropogenic pollution, with high correlation values between their DTPA-extractable and total concentrations (R2: Pb = 0.953, Zn = 0.930, Ni = 0.932). The Igeo values reveal moderate to high contamination near the road, particularly for Pb and Zn. The EF values for Mo (2.06) suggest moderate enrichment due to anthropogenic sources, such as traffic emissions, while Pb (0.76), Zn (0.89), and Ni (0.93) show minimal enrichment. PLI values of 4.24, 4.03, 3.63, and 4.87 for Pb, Zn, Ni, and Mo, respectively, classify the area as “highly polluted” for most metals. These findings highlight the significant anthropogenic contribution to heavy metal accumulation, driven by vehicular emissions, tire wear, and industrial activities. The contamination poses risks to soil health, biodiversity, and human safety through bioaccumulation in the food chain. Sustainable environmental management and pollution mitigation strategies are urgently required to address these concerns and safeguard agricultural productivity and ecosystem functions.Öğe Effect of biochars produced at different pyrolysis temperatures on Ammonium (NH4+) and Nitrate (NO3-) Leaching: Column experiment(Hasan ÖNDER, 2024) Gence, Cabir Çağrı; Erdem, HalilNitrogen (N) leaching from agricultural soils is a global problem with negative effects on both human health and the environment. Efforts should be made to increase the efficiency of use of plant nutrients and minimize N losses from terrestrial ecosystems to aquatic ecosystems. In this study, the effects of different doses (%0, %1 and %2) of biochar obtained from corn cob and rice husk biomass, which are agricultural production residues, at three different temperatures, on ammonium (NH4+) and nitrate (NO3-) leaching in a coarse-textured soil were investigated. Polyethylene (PE) columns with a diameter of 70 mm and a height of 20 cm were used in the study, which was carried out in three replications according to the randomized plots experimental design. Total nitrogen (27 kg N da-1) and water amounts (969 mm) used for 6 tons da-1 yield of sugar beet were applied. Total water was given to each column in equal volume using drip adjustment sets at one-week intervals, simulating 6 irrigation periods, and the leaked water was collected in each irrigation period and NO3- and NH4+ concentrations were determined. Applications of 1 and 2 doses of corn and rice biochars obtained at three different pyrolysis temperatures caused a significant decrease in NH4+ concentrations leaching from the column. Similarly, biochar applications (especially 2% dose) caused a significant decrease in NO3- concentrations leaching from the column. While the total NO3- concentration leaching from the control columns was 149.23 mg kg-1, 2% dose of rice husk biochars at 300, 400 and 500 ? temperature applications caused a decrease in the total NO3- concentrations washed from the column by 51%, 55% and 51%, respectively. The results revealed that biochar applications significantly reduced nitrogen leaching from the soil.Öğe Effects of Nitrogen and Zinc Fertilization on Alleviating Cadmium Accumulation in Durum Wheat Grains(Taylor and Francis Ltd., 2023) Tosun, Yener Kortan; Erdem, Halil; Gence, Cabir ÇağrıCadmium (Cd) accumulation in durum wheat (Triticum durum L.) is of particular concern compared to the other commonly cultivated cereals. This study was conducted to determine the effects of zinc (Zn) and nitrogen (N) applications on grain Cd concentration of durum wheat grown in a Cd contaminated soil. The experimental design consisted of randomized plots with four replications. The treatments included low and adequate (0.05 and 5 mg kg?1) Zn doses, and inadequate, optimal and high (200, 400 and 600 mg kg?1) N doses. Cadmium application rates were 0 and 5 mg kg?1. The findings demonstrated that Cd application caused a significant increase in grain Cd concentrations, and a decrease in straw and grain yields under low and adequate doses of Zn and all N doses. However, increasing N applications with adequate soil Zn caused an increase in the straw and grain yields and a significant decrease in grain Cd concentration. The grain Cd concentration in low Zn and optimum N treatment under Cd application was 6206 µg kg?1, while the grain Cd concentration decreased by 26.3% (4574 µg kg?1) in the Zn and optimum N treatment. In addition, the grain Zn concentration of durum wheat under low soil Zn conditions was decreased in Cd application, whereas the grain Zn concentration increased in Cd application under adequate soil Zn concentration. The results revealed that combined application of N and Zn in Zn deficient soils is highly effective at decreasing Cd accumulation in wheat grains compared to individual applications.Öğe Microplastics in Soil Increase Cadmium Toxicity: Implications for Plant Growth and Nutrient Imbalance(2025) Erdem, Halil; Gence, Cabir Çağrı; Öztürk, Mehmet; Buhan, Ekrem; Kholikulov, Shodi Turdukulovich; Kaya, YağmurThe increasing presence of microplastics (MPs) and cadmium (Cd) in agricultural soils represents an emerging environmental challenge, necessitating urgent investigation due to their potential synergistic effects on soil and plant health. This study investigated how polyethylene microplastics (PE-MPs) affect Cd behavior in soil, focusing on both their individual and combined impacts on soil pH, Cd bioavailability, plant growth, and nutrient dynamics. MPs can act as carriers of Cd, enhancing its mobility within the soil–plant system. To achieve this, a pot experiment was conducted using soils treated with different doses of PE MPs (0%, 1%, and 2%, w/w) and Cd (20 mg Cd kg−1). Soil pH, DTPA-extractable Cd, plant growth parameters, Cd accumulation in roots and shoots, and mineral nutrient concentrations were measured. The results indicated that while Cd alone did not significantly alter soil pH, increasing MP doses statistically reduced soil pH and enhanced Cd bioavailability, with DTPA-extractable Cd rising by 14.4% to 25.4%. The combined application of MPs and Cd resulted in a 38% reduction in root yield and a 32% decrease in above-ground biomass. The presence of MPs exacerbated Cd uptake, leading to significantly higher Cd accumulation in both roots and shoots compared to Cd application alone. Moreover, the combined presence of MPs and Cd disrupted the nutrient uptake mechanisms, as evidenced by significant reductions in nitrogen (N) and phosphorus (P) concentrations in root and shoot tissues. These results indicate that MPs and Cd together disrupt soil chemical stability and compromise plant nutritional status. Thus, our findings emphasize that MPs not only serve as physical pollutants but also as vectors that intensify heavy metal contamination risks in agricultural ecosystems.
