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 NH 4 + -N, NO 3 - -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 NO 3 - -N in the treatments of urea plus DEHP 10 and urea plus DEHP 100 , 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.