DOM-mediated interaction of DOM-enzyme-pollutants affected the toxicity of combined aged tire wear particles (aged-TWPs) and polyfluoroalkyl substances (PFASs) in soil under successive extreme weather stress.

Extreme weather stress is posing growing threats to ecosystems, as they directly disturb soil moisture and affect the toxicity of pollutants, thereby increasing ecological risks. This study investigated how successive extreme climate stress (heatwave, heatwave-drought, and flood) affected the toxicity of co-exposed aged tire wear particles (aged-TWPs) and polyfluoroalkyl substances (PFASs). Results revealed that the combined contamination (COM) significantly altered bacterial diversity and community composition, with the responses varying across the three successive extreme weather stress. Under three extreme weather stress, compared to the control group, the COM did not significantly induce the oxidative stress and cellular membrane damage caused by the individual contamination. The COM increased the aromaticity, hydrophobicity, and humification degree of dissolved organic matter (DOM), particularly under flood stress. The terrestrial esters within DOM significantly shifted the bacterial community. Under three extreme weather stress, the COM increased activities of selected C/N/P cycling enzymes. Interaction of DOM-Enzyme-Pollutants analysis confirmed that DOM, particularly from COM under flood stress, counteracted pollutants-induced conformational loosen of extracellular enzymes in C/N/P cycles and restored enzyme activities. This study provided novel insights into effects of co-exposure of PFASs and aged-TWPs on soil ecosystem under successive extreme weather stress.