Di-(2-ethylhexyl) phthalate (DEHP) exposure suppressed the community diversity and abundance of ammonia-oxidizers and mitigated NO emissions in an alkaline soil.

Phthalic acid esters (PAEs) pollution has become an increasing issue worldwide, but little is known about its effects on ammonia-oxidizers and nitrous oxide (NO) in the soil environment. Here, a 50-day soil microcosm experiment was conducted using low and high doses bis (2-Ethylhexyl) phthalate (DEHP) to estimate the effect of DEHP exposure on soil NO emissions and the nitrifying community in calcareous soil. The results showed that DEHP exposure at 10 and 100 mg kg doses significantly reduced NO by 67.5% and 73.6%, respectively, relative to the DEHP absent treatment. The microbial biomass carbon and nitrogen (MBC and MBN) were consistently and significantly decreased with DEHP exposure at 5, 22, and 50 days after incubation, especially with high-dose. The bipartite association networks showed that DEHP exposure changed the compositions of both ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) communities. Moreover, the AOA and AOB amoA gene abundances were significantly decreased by DEHP addition to the soil (P < 0.05). Random forest modeling showed that the AOB Shannon index and pH were the most important biotic and abiotic factors affecting NO emissions in the soil with DEHP exposure, respectively. Partial least squares path modeling (PLS-PM) demonstrated that the reduction of NO emissions due to DEHP exposure was mainly ascribed to the changes of the AOB community. The results from this study highlight the toxicity of DEHP on the ammonia oxidizers, and its mitigating effect on NO emissions in the soil where ammonia-oxidation is largely driven by AOB.