Land disposal of olive mill wastewater enhances ability of soil to sorb diuron: Temporal persistence, and the effects of soil depth and application season

Abstract

Disposal of olive mill wastewater (OMW) is a well-recognized environmental and agricultural problem. Spreading on agricultural lands and roads, which is one way of discharging OMW, may result in multiple effects on soil environment, including changes in the potential of the soil to interact with organic compounds. There is a lack of knowledge regarding the persistence and temporal dynamics of effects of prior OMW land application on the sorption of organic compounds to soil, and the role of application season. This knowledge is also important for better understanding of dynamics of organic matter in soil environments. Therefore, in this work sorption of diuron, an urea pesticide, was determined in lab batch experiments on soil sampled from two depths (0–5 and 5–10cm) in the field, in different time intervals (up to 18 months) following OMW application in various seasons (Spring, Summer and Winter), where Summer application was carried out in “dry” and “wet” (with previous moistening) regimes. The application of typical (local) OMW to the field (in Bait Reema village in Palestinian Authority) enhanced diuron-soil interactions. A greater enhancement effect was on the soil samples from the 5–10cm layer as compared with that on the samples from the 0–5cm layer. Larger extents of diuron sorption enhancement, following the prior OMW-soil interactions, were observed at higher diuron concentrations in soil solution. The enhancement effect of OMW on soil sorption of diuron mitigated with time. It was also “season”- dependent such that the OMW field application when carried out in summer led to smaller impacts on diuron sorption, as compared with the application in spring and winter. This work emphasized the importance of long-term observations in understanding the environmental fate of organic compounds in areas affected by OMW disposal and experiencing the “pressure” of anthropogenic organic contaminants.