Di-(2-ethylhexyl) phthalate (DEHP) exposure significantly decreased soil nitrification through inhibiting ammonia-oxidizing bacteria and destabilizing their co-occurrence networks

Di-(2-ethylhexyl) phthalate (DEHP) has increasingly accumulated in soils due to DEHP-containing plastic film has been extensively used in agriculture. However, the exposure of DEHP on calcareous soil nitrification potential, ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) are poorly investigated. Here, an incubation experiment was established containing four treatments:(ⅰ) unfertilized blank control, (ⅱ) urea addition alone, (ⅲ) urea plus DEHP (10 mg kg-1), (ⅳ) urea plus DEHP (100 mg kg-1). The influences of DEHP exposure on soil NH4+-N, NO3--N, soil potential nitrification rate (PNR), ammonia monooxygenase (AMO) activity, AOA and AOB were analyzed. We found that DEHP exposure (10 and 100 mg kg-1) lowered NO3--N in the treatments of urea plus DEHP10 and urea plus DEHP100, and it significantly decreased soil PNR and AMO activity. Also, the exposure of DEHP reduced the numbers of AOA and AOB gene copies, and decreased AOB community's α-diversity. Moreover, DEHP exposure destabilized AOB community's co-occurrence network and decreased key module abundance, but its influences on AOA community was not significant. Taken together, the exposure of DEHP inhibited PNR in a calcareous soil through decreasing AOB gene copies and weakening the co-occurrence network of AOB community. Our findings provide a novel insights into microbial mechanisms about the detrimental effects of DEHP pollution on soil PNR and nitrification process in calcareous soil.