Impacts of different emitter layouts on the accumulation of Pharmaceuticals And Personal Care Products (PPCPs) in soil and tomato under reclaimed water irrigation

Abstract: Pharmaceuticals and Personal Care Products (PPCPs) have emerged in recent years as prevalent environmental pollutants subjected to the ever-growing global population and occurrence of new diseases. PPCPs can easily enter the soil-plant system via reclaimed wastewater irrigation and sludge application in modern agriculture. A multitude of biotic and abiotic processes directly determine the PPCPs metabolism in soil. However, the effects of soil moisture on PPCPs accumulation still remain unclear. In this study, a new irrigation arrangement was proposed to facilitate the PPCPs degradation while retard the root uptake during translocation in plants. Three typical PPCPs were taken as research materials, including carbamazepine (CBZ), gemfibrozil (GEM), and triclosan (TCS), under different dripper arrangements (at the root of tomato and between two tomatoes), with conventional border irrigation (CK) as the control. Subsequently, the soil at different depths was selected to measure the PPCPs contents of plant tissues, physicochemical properties, and microflora. The results showed that there was no significant difference in the cumulative amounts of CBZ and TCS in the 0-5, >5-10, and >10-15 cm soil layers under each treatment. The cumulative amount of GEM under CK and the treatment of emitters placed at root (DR) were lower than the treatment of emitters placed between two plants (DM) (P<0.05). The cumulative amount of CBZ in leaves under DM reduced by 38.90% and 32.23% compared with CK and DR respectively (P<0.05). In terms of the cumulative amount of GEM in tomato roots, DM decreased by 49.07% and 55.61% compared with CK and DR treatment separately, the cumulative amount of GEM in leaves under DM treatment was reduced by 53.40% compared with DR (P<0.05). The cumulative amount of TCS in roots under DM was 32.17% lower than that under CK (P<0.05). The correlation analysis indicated that the distribution of CBZ in the soil was positively correlated with Proteobacteria, Nitrospirae, and Elusimicrobia (P<0.05), whereas negatively correlated with Actinobacteria (P<0.05). GEM was positively correlated with the soil pH and Patescibacteria (P<0.05). TCS was also positively correlated with Proteobacteria, Nitrospirae, Nitrospirae, Elusimicrobia, and Verrucomicrobia (P<0.05). DM treatment in reclaimed water irrigation made a great contribution to the accumulation of GEM in the 0-5 cm soil layer, significantly higher than other treatments (P<0.05), and where there was a significant reduction in accumulative amount of CBZ in tomato leaves and the accumulation of GEM in roots (P<0.05). The small border irrigation significantly reduced the accumulation of CBZ in fruits, as well as GEM in tomato stems, leaves and fruits. The main reason was that CBZ and TCS were decomposed by Proteobacteria and Nitrospirae whereas Actinobacteria was used to degrade CBZ. Substitution reactions under acidic conditions dominated the degradation of GEM with relation to the soil pH. The finding can contribute to better understanding the common processes of PPCPs transport and distribution in soil-vegetable systems using reclaimed water irrigation in agriculture.