Aromatic compounds releases aroused by sediment resuspension alter nitrate transformation rates and pathways during aerobic-anoxic transition

Aromatic compounds (ACs) releases aroused by sediment resuspension would certainly change the concentrations of suspended sediment (SPS) and organic carbon, which may alter nitrate-N transformation during aerobicanoxic transition. To prove this, three typical ACs (aniline, nitrobenzene, and methylbenzene) with different octanol-water partition coefficients (Kow) were selected to investigate the effects of ACs releases aroused by sediment resuspension on nitrate-N transformation during aerobic-anoxic transition. ACs releases aroused by sediment resuspension accelerated nitrate-N transformation and enhanced the potential for dissimilatory nitrate reduction to ammonium (DNRA), compared to that without sediment resuspension. With sediment resuspension, methylbenzene releases affected nitrate-N transformation rates and pathways more significantly than aniline and nitrobenzene releases. Microbial analysis indicated that sediment resuspension created complicated microbial cooccurrence networks and changed the associations among bacteria; dominant bacteria abundance varied with different ACs releases. Further analysis revealed that ACs distributed in SPS, which increased with logKow, indirectly affected nitrate-N transformation rates and pathways via altering dominant bacteria abundance and electron transport system activity (ETSA). Especially, ETSA, which was positively associated with ACs distributed in SPS, affected nitrate-N transformation most directly. Overall, ACs release fate played important roles in nitrate-N transformation, causing ammonia-N retention and alterations in nitrogen cycle during aerobic-anoxic transition.

Automated summary

Aromatic compounds released by sediment resuspension can accelerate nitrate-N transformation, with methylbenzene having a more significant impact compared to aniline and nitrobenzene. Microbial analysis revealed changes in microbial cooccurrence networks and associations among bacteria due to sediment resuspension, with dominant bacteria abundance varying with different ACs releases. Analysis also showed that ACs distributed in suspended sediment indirectly affected nitrate-N transformation rates and pathways through altering bacteria abundance and electron transport system activity.