The promotion of the atrazine degradation mechanism by humic acid in a soil microbial electrochemical system

Abstract

The enhancing effects of anodes on the degradation of the organochlorine pesticide atrazine (ATR) in soil within microbial electrochemical systems (MES) have been extensively researched. However, the impact and underlying mechanisms of soil microbial electrochemical systems (MES) on ATR degradation, particularly under conditions involving the addition of humic acids (HAs), remain elusive. In this investigation, a soil MES supplemented with humic acids (HAs) was established to assess the promotional effects and mechanisms of HAs on ATR degradation, utilizing EEM-PARAFAC and SEM analyses. Results revealed that the maximum power density of the MES in soil increased by 150%, and the degradation efficiency of ATR improved by over 50% following the addition of HAs. Furthermore, HAs were found to facilitate efficient ATR degradation in the far-anode region by mediating extracellular electron transfer. The components identified as critical in promoting ATR degradation were Like-Protein and Like-Humic acid substances. Analysis of the microbial community structure indicated that the addition of HAs favored the evolution of the soil MES microbial community and the enrichment of electroactive microorganisms. In the ATR degradation process, the swift accumulation of Hydrocarbyl ATR (HYA) was identified as the primary cause for the rapid degradation of ATR in electron-rich conditions. Essentially, HA facilitates the reduction of ATR to HYA through mediated bonded electron transfer, thereby markedly enhancing the efficiency of ATR degradation.

Keywords: Atrazine; Extracellular electron transfer; Humic acids; Soil microbial electrochemical system.