In this work, three sulfur-iron materials (sulfide-modified nanoscale zerovalent iron (S-nZVI), ferrous sulfide (FeS), and pyrite (FeS₂)) were employed to enhance the Fenton process for naphthalene (NAP) degradation. The enhancement performance and mechanisms of S-nZVI, FeS, and FeS₂ were investigated and compared. The results showed that NAP removal was enhanced from 56.4% in the H₂O₂/Fe(II) system to 88.6%, 83.0%, and 89.1% with the addition of S-nZVI, FeS, and FeS₂, respectively. Three sulfur-iron materials could all reduce Fe(III) produced in aqueous solution, regenerate Fe(II), and slow down the precipitation of dissolved iron. In addition, the addition of sulfur-iron materials could promote the generation of hydroxyl radical (HO•), thus intensifying the degradation of NAP. The results of scavenging tests indicated that HO• was the dominant reactive oxygen species (ROS) for NAP removal, while superoxide radical (O₂⁻•) also participated. The effect of complex water matrices on NAP degradation was evaluated, showing that sulfur-iron material-enhanced techniques had a wide pH application range and had great tolerance to inorganic ions and humic acid. Moreover, NAP degradation intermediates and their toxicity were elucidated. Finally, the obvious removal of various pollutants in sulfur-iron material-enhanced systems demonstrated that these technologies could be used to remediate organic-polluted groundwater.

Natural attenuation is a potential way to reduce total petroleum hydrocarbons (TPH) contamination, but the microbial mechanisms that explain differences in attenuation performance between soil and groundwater remain unclear. In this study, field investigation and metagenomic analysis were conducted at a decommissioned refinery site with more than 20 years of operation. Over a four-year period, the average TPH degradation rate in the soil attenuation zone reached 307.7 ± 135.2 mg kg⁻¹ year⁻¹, whereas the groundwater attenuation group showed an average degradation rate of 5.2 ± 3.6 mg L⁻¹ year⁻¹. Metagenomic results showed that TPH attenuation in soil and groundwater was associated with two different microbial consortia adapted to local conditions. In soil, the attenuation zone was characterized by a possibly sessile and cooperative consortium dominated by Pseudomonadota and Actinomycetota, with Sphingomonas and Nocardioides as representative genera. The consortium showed broader amino acid metabolic potential (e.g., ko00250, ko00260, and ko00310) and a higher abundance of functions related to biofilm formation and quorum sensing, which may promote stable and surface-attached growth. In groundwater, the attenuation zone was characterized by a possibly motile and more specialized consortium dominated by Pseudomonadota, including Novosphingobium, Sphingorhabdus, and Tabrizicola. The consortium possessed a less complex catabolic network for TPHs and intermediates (e.g., ko01220/ko00621/ko00624; nahAc/catE/fadA/pcaD/atoB), coupled with stronger potential for motility and secretion. In both soil and groundwater, attenuation was associated with lower eukaryotic activity and enrichment of prokaryotic functions related to oxidative stress defenses and high-yield respiration. These results showed that natural attenuation of TPHs in soil and groundwater involved different microbial features, which could improve the evaluation of natural attenuation in heterogeneous environments.

This study investigated the characteristics and interrelationships of polycyclic aromatic hydrocarbons (PAHs), phthalate esters (PAEs), and microbial communities in coastal river sediments and benthic mollusks collected from an e-waste recycling area in Taizhou, Zhejiang Province. In sediments, 16 PAHs and six PAEs were detected, with concentrations ranging from 2.66 to 379.99 μg/kg and 76.5 to 3426.57 μg/kg, respectively. Four-ring PAHs (particularly fluoranthene and pyrene) and Bis(2-ethylhexyl) phthalate (DEHP) were dominant, with DEHP posing a potential risk, especially at site 10, warranting further attention. In contrast, only eight PAHs and four PAEs were detected in mollusks, with concentrations of 60.14–523.10 μg/kg and 144.55–3005.71 μg/kg, respectively. Two-ring PAHs (particularly naphthalene) and Dibutyl phthalate (DBP) were dominant, likely derived directly from the overlying water. The PAHs in sediments primarily originated from fossil fuel combustion, biomass burning, and coal combustion, while PAEs were likely derived from the release of plastic waste from solid waste recycling. Lower concentrations and fewer PAH and PAE species were observed in the sediments near the ocean and at greater distances from the e-waste recycling sites. Significant differences were observed in microbial communities between sediment and mollusk samples. Dominant phyla shared by both sample types include proteobacteria, bacteroidetes, firmicutes, and acidobacteria. The concentration of low-ring PAHs was correlated with the microbial communities, particularly in mollusk samples. Relationships were also identified between microbial communities and DEHP concentrations in sediments or DBP concentrations in mollusks.