Comparative analysis of organophosphorus esters, novel brominated flame retardants, and organic pesticides on soil eco-enzymatic activity

Abstract

To evaluate the ecological risks of emerging contaminants (ECs) in soils, we systematically investigated the effects of 28 ECs, including organophosphorus esters (OPEs), novel brominated flame retardants (NBFRs), and organic pesticides on five key soil enzyme activities: β-glucosidase, urease, alkaline phosphatase, arylsulfatase (ARS), and fluorescein diacetate hydrolase (FDA-H). Among the enzymes tested, ARS activity was enhanced by nearly half of the ECs (13 out of 28), especially by OPEs. However, enzyme kinetic analyses revealed that reduced substrate affinity offsets the increased maximal reaction velocity, resulting in unchanged or even reduced catalytic efficiency. In contrast, FDA-H activity was generally inhibited, exhibiting the greatest response ratio (0.115), indicating that it was the most sensitive enzyme to pollutant exposure. Notably, 2,4,6-tribromophenol inhibited ARS via linear mixed inhibition mechanism, with ecological dose (ED₁₀) values ranging from 7.53 to 13.9 mg kg⁻¹, whereas isoprocarb suppressed FDA-H via competitive inhibition, with ED₁₀ values of 3.97–6.58 mg kg⁻¹. Based on the average magnitude of effects on soil enzymatic activities (mean score: 0.113) and the functional index (0.148), NBFRs potentially pose greater ecological risks to overall soil functionality than OPEs or the evaluated organic pesticides. These findings highlight the significant and diverse impacts of ECs on critical soil microbial functions and emphasize the urgent need for further investigation into the ecological effects of NBFRs in terrestrial environments.