Impact Of Technical Elements Of Trickle Irrigation On The Transformation And Accumulation Of Typical Pharmaceuticals And Personal Care Products In Soil-plant System Under Reclaimed Water Irrigation

Pharmaceuticals and personal care products(PPCPs)have emerged as a new prevalent contaminant and could enter soil-plant system through reclaimed wastewater irrigation or sludge amendment.As metabolization of PPCPs in soil is a multifaceted process modulated by soil moisture,we conjecture that irrigation method affects PPCPs degradation and their uptake by roots and translocation in plants.PPCPs in water can enter the soil-plant system through reclaimed water irrigation,sludge reuse,etc.,and cause chronic toxic damage to humans through the food chain.The environmental hazards and human health risks of PPCPs are increasingly concerned and become research hotspots.To investigate the effects of drip irrigation and its irrigation elements on the transport and accumulation of PPCPs in the soil-plant system under reclaimed water irrigation conditions and the driving mechanisms,three typical PPCPs with high environmental detection and different hydrophobicity,namely carbamazepine,gemfibrozil and triclosan,were selected as target pollutants.The study was carried out on the accumulation of typical PPCPs in different soil layers and different organs of the plant(tomato)by different drip head arrangements(drip head at the root of the plant,drip head in the middle of the two plants)and different drip head flow rates(2,4 and 8 L/h).By analyzing the changes in the physicochemical properties,heavy metal content and microbial community structure of the soil in different treatments,as well as the correlation between each factor and the migration and accumulation patterns of PPCPs,the mechanisms driving the migration and accumulation of typical PPCPs in soil-plant systems were explored.It will provide a theoretical basis for the safe agricultural use of reclaimed water based on the effective prevention and control of the emerging pollutant PPCPs.The main achievements are as followed.(1)The arrangement of emitters and emitter flow can affect the accumulation of carbamazepine and triclosan in the soil,while gemfibrozzi is affected by the interaction of emitter flow,emitter arrangement and emitter flow.When the dripper was medium(4 L/h)and high flow(8 L/h),placing the dripper on the root of the plant can reduce the accumulation of carbamazepine in the soil,and the cumulative amount was 0.07～0.41 μg/g.The accumulation of carbamazepine in soil did not pose a risk when the emitter was at a medium flow rate(4 L/h)and placed at the root of the plant.When the emitter was at a high flow rate(8 L/h),the accumulation of gemfibrozil in the soil was reduced.The drip irrigation reduced the abundance of Nitrospirae,which led to the higher accumulation of gemfibrozil in the soil.When the drip tip was low(2 L/h)and high flow rate(8 L/h),placing the drip tip on the root of the plant can increase the accumulation of triclosan in the soil,and the cumulative amount is 0.35～1.36 μg/g.Medium(4 L/h)and low(2 L/h)flows emitters reduced the accumulation of triclosan in the soil.Medium(4 L/h)flow emitters and placement in the root increased the abundance of Actinobacteria,leading to a decrease in the accumulation of triclosan in the soil.Under each drip irrigation treatment,the accumulation of gemfibrozil and triclosan would pose a risk to the soil.(2)By detecting the accumulation of PPCPs in tomato organs under different emitter arrangement and emitter flow,the accumulation rule and risk of PPCPs in tomato organs were studied.The emitter arrangement could affect the accumulation of carbamazepine and triclosan in different organs of tomato,while gemfibrozil was affected by emitter arrangement,emitter flow and their interaction.The treatment with emitter placed in the middle of two plants could reduce the accumulation of carbamazepine and triclosan in tomato plants,cumulative amounts are 0.10～5.83 μg/g and 0.21～0.51 μg/g respectively.The content of carbamazepine in the fruits treated with emitter flow rate of 4 L/h did not pose a risk to human health.Meanwhile,the content of gemfibrozil and triclosan in tomato fruits treated with each drip irrigation did not pose a risk to human health.(3)Enrichment coefficients of carbamazepine,gemfibrozil and triclosan in different tomato organs were affected by emitter arrangement,emitter flow and their interaction.Low(2 L/h)and medium(4 L/h)flows emitter were arranged between the two plants,which could increase the content of soil organic matter and the abundance of Proteobacteria,reduce the abundance of Actinobacteria,and thus reduce the enrichment coefficient of carbamazepine in tomato roots.The emitter with medium flow(4 L/h),the emitter with high flow(8 L/h)and placed between the two plants,and the emitter with low flow(2 L/h)and placed at the root of the plant could reduce the enrichment coefficient of the tomato organs to the soil gemfibrozil to a certain extent.When emitter flow was medium(4 L/h)and high(8 L/h),emitter placement between the two plants could effectively inhibit triclosan enrichment in tomato roots by increasing soil electrical conductivity and reducing the abundance of Actinobacteria.