Di-(2-ethylhexyl) phthalate (DEHP) contamination suppressed soil microbial biomass carbon and mitigated CO 2 emissions against the background of alfalfa from different soils

Plastic mulching and organic amendments are prevalent agricultural practices worldwide. Plastic mulching has long been suspected as a significant source of DEHP contamination in terrestrial ecosystems. However, effects of DEHP contamination on greenhouse gas emissions and microbial biomass carbon (MBC) remain unclear. Here, a microcosm experiment was set up to assess the impact of DEHP exposure on MBC and carbon dioxide (CO 2 ) emission in two different soils (acidic and alkaline) with the inclusion of alfalfa straw. The treatment includes: (i) control with no amendment (T 1 ); (ii) alfalfa straw addition (20 g kg −1 ) (T 2 ); (iii) DEHP (10 mg kg −1 ) + alfalfa straw (T 3 ); and (iv) DEHP (100 mg kg −1 ) + alfalfa straw (T 4 ). Against the background of alfalfa inclusion, DEHP exposure led to a potential reduction in cumulative CO 2 emissions by 16.35 % and 6.91 % in alkaline soil and 12.27 % and 13.65 % in acidic soil for T 3 and T 4, respectively. The addition of DEHP triggered CO 2 emissions and manifested a detrimental negative priming effect in both soil types. In both soils, average CO 2 emission fluxes were highest for the T 2 treatment. The MBC fluctuated at around 80 mg kg −1 for the control group, alfalfa straw alone (T 2 ) treatment considerably enhanced MBC contents, whereas DEHP contamination in T 3 and T 4 treatments suppressed the stimulatory effect of alfalfa on MBC in both alkaline and acidic soils. Furthermore, a positive relationship was observed between soil CO 2 emissions and MBC in both soils. Overall, these findings highlight the toxic impact of DEHP on MBC and its role in mitigating CO 2 emissions in diverse soils. DEHP exposure counters the CO 2 emissions induced by alfalfa straw. In addition, the inhibitory effect of DEHP on CO 2 fluxes in alkaline soil is less pronounced than in acidic soil. Therefore, further cutting-edge research is crucial since DEHP contamination poses serious ecological threats to agroecosystems.