توصيفگر ها :
نانومواد , معدني شدن كربن , مواد آلي خاك , فراهمي عناصر غذايي گياه , نيتروژن , فسفر , پتاسيم
چكيده انگليسي :
In recent years, nanoparticles have been widely used in various industrial, health, cosmetic, and agricultural products. The extensive use of these nanoparticles has caused them to enter water and soil resources. Silver nanoparticles (Ag-NPs) are one of the most widely used nanomaterials in the world, and therefore their release into the soil is highly probable. After entering the soil, these particles will have negative effects on microbial communities and soil biochemical processes. One of the important processes in the carbon cycle is the decomposition of organic matter and carbon mineralization, which is carried out by various soil microorganisms. The presence of pollutants, including nanoparticles, in the soil may negatively affect this process and consequently the nutrient cycle in the soil, leading to ecosystem instability. The present study aimed to investigate the effect of Ag-NPs on the decomposition kinetics of wheat and alfalfa plant residues and the available concentration of nitrogen, phosphorus, and potassium nutrients in two soils from Saman and Meymeh. For this purpose, 10 g/kg of carbon was added to soil samples in three replicates using wheat and alfalfa residues, and then silver nanoparticles were added to the samples at concentrations of 0, 10, 100, and 400 mg/kg. The soil samples' moisture was brought to 60% of water holding capacity and incubated at 25°C for 60 days. During this period, carbon dioxide resulting from microbial respiration was measured on days 1, 2, 3, 5, 6, 8, 10, 12, 14, 16, 20, 24, 28, 32, 36, 40, 44, 48, 50, and 60. Subsequently, the cumulative mineralized carbon was plotted against time, and kinetic models including first-order, double first-order, first-order-E, and specific models were fitted to the data. In an incubation experiment, microbial biomass carbon, microbial respiration index, metabolic quotient, as well as mineral nitrogen concentration and plant-available phosphorus and potassium in soil samples treated with residues and Ag-NPs were measured after 28 and 58 days of incubation. The results showed that the double first-order and first-order models are the best models for fitting carbon mineralization kinetics data of plant residues in Saman and Meymeh soils, respectively. With increasing Ag-NPs concentration, carbon mineralization showed a decreasing trend, and the rate of this process decreased further over time. Also, the microbial respiration index and microbial biomass carbon decreased with increasing Ag-NPs concentration, while the soil metabolic quotient increased. With increasing Ag-NPs concentration and contact time with soil, the concentration of mineral nitrogen and plant-available phosphorus and potassium decreased. Overall, the results of this study indicate that Ag-NPs at high concentrations can have a negative impact on soil microbial populations and consequently on the process of carbon mineralization and release of nutrients to the soil.
