Pharmaceuticals and analogs of bisphenol A (BPA) are increasingly threatening environmental pollutants. In this study, mixtures of selected pharmaceuticals (diclofenac sodium salt, chloramphenicol, oxytetracycline hydrochloride, fluoxetine hydrochloride, estrone, ketoprofen, progesterone, gemfibrozil and androstenedione) were prepared with BPA and its two analogs (namely, bisphenols F and S) at such ratios to reflect environmentally detectable levels. Then, the mixture solutions were studied with a XenoScreen YES/YAS assay to determine the variations in the initial hormonal response of each pharmaceutical compound due to the presence of a bisphenol analog. The results obtained were modeled with the concentration addition (CA) and independent action (IA) approaches, the trueness of which was studied with model deviation ratios (MDR). The estrogenic agonistic activity of the drugs studied was most strongly affected by the presence of BPA in solution (twenty-one cases of synergy observed for CA models versus twelve cases of antagonism in the case of IA predictions). BPS shows a strong agonistic estrogenic impact on most of the drugs studied at medium and high concentration levels; androgenic agonistic activity was also impaired with elevated concentrations of BPS. Increasing the concentration of BPF in a reaction mixture also increased the number of YES + synergism incidences (for CA modeling). Estrone, progesterone and androstenedione were mostly affected by the highest BPF concentrations studied in the case of androgenic agonistic research performed.

The United States Environmental Protection Agency (US EPA) has recently proposed changes to strengthen the transparency of its pivotal regulatory science policy and procedures. In this context, the US EPA aims to enhance the transparency of dose-response data and models, proposing to consider for the first time non-linear biphasic dose-response models. While the proposed changes have the potential to lead to markedly improved ecological risk assessment compared to past and current approaches, we believe there remain open issues for improving the quality of ecological risk assessment, such as the consideration of adaptive, dynamic and interactive effects. Improved risk assessment including adaptive and dynamic non-linear models (beyond classic threshold models) can enhance the quality of regulatory decisions and the protection of ecological health. We suggest that other countries consider adopting a similar scientific-regulatory posture with respect to dose-response modeling via the inclusion of non-linear biphasic models, that incorporate the dynamic potential of biological systems to adapt (i.e., enhancing positive biological endpoints) or maladapt to low levels of stressor agents.

Dredging is frequently implemented for the reduction of internal nitrogen (N) and phosphorus (P) loadings and the control of eutrophication. Residuals during dredging activities and external pollution loadings after dredging both commonly contribute to influence the effectiveness of dredging and have been widely discussed. In the current study, the exchanges of N and P across the sediment-water interface (SWI) to these two factors were compared in a six-month field incubation experiment. The results showed that the continuous deposition of external suspended particulate matter (SPM) led ammonium nitrogen (NH₄⁺N) and soluble reactive phosphorus (SRP) fluxes across the newly formed SWI to increase by factors of 4.16 and 12.71, respectively, while residual material caused the same fluxes to increase by factors of 2.06 and 5.06. Both the deposition of external SPM and the residual matter led to higher increase of the fluxes of P across the SWI than those of the fluxes of N across the SWI after dredging. The SPM easily adsorbed P in the water due to extensive adsorption of water soluble organic matter (consisting primarily of easily-decomposed humic-like substances), iron, and aluminum. However, the decomposition of organic matter in the SPM after the deposition on the dredged sediment accelerated the dissolution of redox-sensitive P and organic P across the SWI after dredging. Both the increase in the fluxes of N and P across the SWI would further increase the concentrations of N and P in the overlying water and thereby aggravate the eutrophication status in lakes. More frequent dredging operations might be necessary to reduce the fluxes of N and P from the sediment due to the continuous influence of the external SPM and the residual matter.

Solvent stabilizer 1,4-dioxane, an emerging recalcitrant groundwater contaminant, was commonly added to chlorinated solvents such as trichloroethene (TCE), and the impact of co-disposal on contaminant transport processes remains uncertain. A series of batch equilibrium experiments was conducted with variations of 1,4-dioxane and TCE composition to evaluate aqueous dissolution of the two components and their sorption to aquifer sediments. The solubility of TCE increased with increasing amounts of 1,4-dioxane, indicating that 1,4-dioxane acts as a cosolvent causing solubility enhancement of co-contaminants. The solubilization results compared favorably with predictions using the log-linear cosolvency model. Equilibrium sorption coefficients (Kd and Kf) were also measured for different 1,4-dioxane and TCE compositions, and the findings indicate that both contaminants adsorb to aquifer sediments and TCE Kd values increased with increasing organic matter content. However, the Kd for TCE decreased with increases in 1,4-dioxane concentration, which was attributed to cosolvency impacts on TCE solubility. These findings further advance our understanding of the mass-transfer processes controlling groundwater plumes containing 1,4-dioxane, and also have implications for the remediation of 1,4-dioxane contamination.

A comprehensive spatio-vertical survey of short-chain (SCCPs, C10-13) and medium-chain (MCCPs, C14-17) chlorinated paraffins (CPs) was performed in surface and core soils from Chinese nation-wide agricultural lands in 2016, and a total of 48 congener groups were measured. The shorter carbon chain C10-11 in SCCP and C14-15 in MCCP homologue groups, and the lower chlorinated congeners (Cl5-7) for both CP groups were predominant. The ∑SCCP and ∑MCCP concentrations in surface soils ranged from 39 to 1609 ng/g and 127–1969 ng/g, dry weight (dw), respectively. The spatial distribution trend showed that SCCP congener groups with relatively low octanol-water partition coefficient (KOW) and octanol-air partition coefficient (KOA) are uniformly distributed across surface soils compared to MCCP congener groups. Significant relationships were observed between the spatial variation of SCCP concentrations and the driving factors responsible for dispersion and deposition. The distribution behavior of SCCPs and MCCPs in highland and plain surface soils showed an increasing trend of MCCP concentrations with elevation, indicating the “mountain cold-trapping effect”. Vertical distribution profile revealed similar homologue group composition patterns of SCCP and MCCP congener groups as those of surface soils. Furthermore, the penetration potential ratios (r) of chlorine and carbon atoms of CPs demonstrated that the lower chlorinated (Cl5-7) and the shorter carbon chain (C10-13) congener groups are more prone to vertical movement into deeper soil layers compared to the longer carbon chain (C14-17) and highly chlorinated (Cl8-10) congener groups.

Pollution caused by antibiotics has been highlighted in recent decades as a worldwide environmental and health concern. Compared to traditional physical, chemical and biological treatments, constructed wetlands (CWs) have been suggested to be a cost-efficient and ecological technology for the remediation of various kinds of contaminated waters. In this review, 39 antibiotics removal-related studies conducted on 106 treatment systems from China, Spain, Canada, Portugal, etc. were summarized. Overall, the removal efficiency of CWs for antibiotics showed good performance (average value = over 50%), especially vertical flow constructed wetlands (VFCWs) (average value = 80.44%). The removal efficiencies of sulfonamide and macrolide antibiotics were lower than those of tetracycline and quinolone antibiotics. In addition, the relationship between the removal efficiency of antibiotics and chemical oxygen demand (COD), total suspended solids (TSS), total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH₃-N) concentrations showed an inverted U-shaped curve with turning points of 300 mg L⁻¹, 57.4 mg L⁻¹, 40 mg L⁻¹, 3.2 mg L⁻¹ and 48 mg L⁻¹, respectively. The coexistence of antibiotics with nitrogen and phosphorus slightly reduced the removal efficiency of nitrogen and phosphorus in CWs. The removal effect of horizontal subsurface flow constructed wetlands for antibiotic resistance genes (ARGs) had better performance (over 50%) than that of vertical wetlands, especially for sulfonamide resistance genes. Microorganisms are highly sensitive to antibiotics. In fact, microorganisms are one of the main responsible for antibiotic removal. Moreover, due to the selective pressure induced by antibiotics and drug-resistant gene transfer from resistant bacteria to other sensitive strains through their own genetic transfer elements, decreased microbial diversity and increased resistance in sewage have been consistently reported. This review promotes further research on the removal mechanism of antibiotics and ARGs in CWs.

A sediment core was obtained from Moira Lake to study the legacy of contamination and remediation at the Deloro industrial site which includes 95-years of operations involving gold mining, mineral processing, and arsenic-based pesticide production resulting in high levels of arsenic, cobalt, and nickel. A timeline for the sediment core was established by ²¹⁰Pb dating and used to evaluate the geochemical record and the impact on primary production and subfossil cladocerans. In the early 1800s, there was an initial increase in the arsenic, cobalt and nickel concentrations due to industrial development. By the 1850s, the rate of enrichment increased due to the conglomeration of small-scale operations. In the 1960s, the concentrations of those metal(loid)s decreased following the cessation of the industrial activity at Deloro and the initiation of a clean-up effort. Primary production, inferred by chlorophyll-a concentrations, initially decreased as the metal(loid)s concentrations increased. This was followed by a recovery of the chlorophyll-a concentrations and further increases in production to higher levels than recorded prior to the Deloro years. Secondary production, inferred by cladoceran assemblage structure, was initially dominated by bosminids. The assemblage then changed to one dominated by chydorids and daphnids with the change occurring contemporaneous with the change in chlorophyll-a. However, the changes in primary and secondary production occurred during the period of accelerated metal(loid) enrichment, suggesting limited impact of contamination on primary and secondary producers. Loss on ignition results revealed that during the period of accelerated arsenic enrichment, the carbonate content of the sediments increased while the percent organic content decreased. This work contributes to ongoing research to establish the environmental legacy of historical industrial activities within complex ecosystems. Furthermore, the combination of geochemical (i.e. ²¹⁰Pb, ICP-OES, XANES) and ecological analysis provides a more complete picture of the complex interactions that have occurred in Moira Lake.

Estuaries are dynamic ecosystems which vary widely in loading of the contaminant methylmercury (MeHg), and in environmental factors which control MeHg exposure to the estuarine foodweb. Inputs of organic carbon and rates of primary production are important influences on MeHg loading and bioaccumulation, and are predicted to increase with changes in climate and land use pressures. To further understand these influences on MeHg levels in estuarine biota, we used a field study approach in sites across different temperature regions, and with varying organic carbon levels. In paired comparisons of sites with high vs. low organic carbon, fish had lower MeHg bioaccumulation factors (normalized to water concentrations) in high carbon sites, particularly subsites with large coastal wetlands and large variability in dissolved organic carbon levels in the water column. Across sites, MeHg level in the water column was strongly tied to dissolved organic carbon, and was the major driver of MeHg concentrations in fish and invertebrates. Higher primary productivity (chlorophyll-a) was associated with increased MeHg partitioning to suspended particulates, but not to the biota. These findings suggest that increased inputs of MeHg and loss of wetlands associated with climate change and anthropogenic land use pressure will increase MeHg concentrations in estuarine food webs.

Abandoned nonferrous metal(loid) tailings sites are anthropogenic, and represent unique and extreme ecological niches for microbial communities. Tailings contain elevated and toxic content of metal(loid)s that had negative effects on local human health and regional ecosystems. Microbial communities in these typical tailings undergoing natural attenuation are often very poorly examined. The diversity and inferred functions of bacterial communities were examined at seven nonferrous metal(loid) tailings sites in Guangxi (China), which were abandoned between 3 and 31 years ago. The acidity of the tailings sites rose over 31 years of site inactivity. Desulfurivibrio, which were always coupled with sulfur/sulfide oxidation to dissimilate the reduction of nitrate/nitrite, were specific in tailings with 3 years abandonment. However, genus beneficial to plant growth (Rhizobium), and iron/sulfur-oxidizing bacteria and metal(loid)-related genera (Acidiferrobacter and Acidithiobacillus) were specific within tailings abandoned for 23 years or more. The increased abundance of acid-generating iron/sulfur-oxidizing and metal(loid)-related bacteria and specific bacterial communities during the natural attenuation could provide new insights for understanding microbial ecosystem functioning in mine tailings. OTUs related to Sulfuriferula, Bacillus, Sulfurifustis, Gaiella, and Thiobacillus genera were the main contributors differentiating the bacterial communities between the different tailing sites. Multiple correlation analyses between bacterial communities and geochemical parameters indicated that pH, TOC, TN, As, Pb, and Cu were the main drivers influencing the bacterial community structures. PICRUSt functional exploration revealed that the main functions were related to DNA repair and recombination, important functions for bacterial adaptation to cope with the multi-contamination of tailings. Such information provides new insights to guide future metagenomic studies for the identification of key functions beyond metal-transformation/resistance. As well, our results offers novel outlooks for the management of bacterial communities during natural attenuation of multi-contaminated nonferrous metal(loid) tailings sites.

To better understand the toxicological activities of perfluorooctanoic acid (PFOA), we examined the effects of PFOA on apoptosis and its molecular mechanism in SMMC-7721 hepatoma cells. Cell viability was evaluated by MTT assay and apoptosis was determined by flow cytometry. Western blot and quantitative real-time PCR were used to examine the protein and gene expressions of Bax and Bcl-2. Our results showed that PFOA inhibited SMMC-7721 cell growth and induced apoptosis. PFOA treatment increased Bax expression and increased Bcl-2 expression at both gene and protein levels. Our study demonstrated that PFOA had toxic effects on SMMC-7721 cells, such as inhibiting cell proliferation and inducing apoptosis. Furthermore, we showed that PFOA-mediated induction of apoptosis involved inducing Bax and decreasing Bcl-2 expression as a molecular mechanism of its toxicological effects.