Sediment remediation using submerged plants mitigated the bioaccumulation of organic contaminants in benthic organisms in simulated freshwater aquaculture ponds

Abstract

Few studies have investigated whether growing submerged plants can provide significant mitigation of both polycyclic aromatic hydrocarbons (PAHs) and antibiotics (ATBs) in sediments and cultured aquaculture products. In this study, Corbicula fluminea was selected as the indicator organism in the laboratory simulation experiment, and four remediation systems using Vallisneria natans L. (VN), Hydrilla verticillate L. (HV), Elodea nuttallii P. (EL) and Control Check (CK) were constructed individually. The accumulated concentrations (Cb) and changes in both bioavailability (Cfree) and bulk burden (Cs) of 16 PAHs and four ATBs were analyzed before, during, and after the experiment. Compared with the CK group, the introduction of VN, HV, and EL reduced: Cb of ΣPAHs by 43%, 32%, and 27%, respectively; ΣATBs by 68%, 49%, and 39%, respectively, in Corbicula fluminea; the corresponding cancer risk of ΣPAHs by 19%, 8.9%, and 13%, respectively; and the target hazard quotients of ΣATBs by 73%, 48%, and 41%, respectively. The freely dissolved concentrations of ΣPAHs and ΣATBs (Cfree) in the experimental groups decreased by 38%− 58% and 37%− 70%, respectively. More ATBs than PAHs were reduced in biota, with VN showing the highest efficiency. Reduction in Cfree was more related to reduction in Cb than reduction in Cs. In terms of Cb reduction, Cfree was more indicative for ATBs than PAHs. Analyses of the bacterial community revealed that the introduction of submerged plants significantly increased the abundance of Sphingomonas and Mycobacterium, with specific degradation effects observed for high molecular weight PAHs in the sediment.