Simulation of the long-term transfer and fate of DDT in Lanzhou, China.

A level IV fugacity model is used to simulate the fate and transfer of DDT in the Lanzhou area over a 67-year period from their introduction into agricultural field until 2019. The established model is successfully applied to simulate the transfer processes and the concentration distribution of DDT in four environmental compartments: air, water, soil, and sediment in Lanzhou area under non-steady state assumptions. Furthermore, the calculated results agree well with monitoring data from the literature in same period of time. We assume 20% of the total usage of DDT enters into air and 80% enters the soils. The results indicate that the main source of DDT in the area is agricultural application, the biggest bulk sink is soil (accounting for 99.8% of total amount in the environment). Among all the transfer processes, the deposition from air to soil, deposition from air to water, soil erosion, and sedimentation from water to sediment are the primary processes, and the degradation in soil and air are the key process of DDT disappearance.