Interactions between aromatic pollutants (APs) and porphyrin nucleus as physiological receptors have a significant effect on biological functions of porphyrin-based systems in organism. However, the details on the interaction at molecule level are still elusive. Herein, interaction mechanisms between two typical APs (methylene blue, MB and benzo[a]pyrene, B[a]P) and meso-tetra (4-carboxyphenyl) porphine (TCPP) as physiological receptors were systematically investigated. Adsorption behaviors of TCPP to B[a]P was dominated by pi-pi interaction, while interaction between TCPP and MB coupled with a multi-force field including hydrophobic, pi-pi, electrostatic, and H-bonding interactions. The relative contributions of these four forces obeyed an order: H-bonding > pi-pi > electrostatic > hydrophobic, regardless of the pH value and the initial concentration of MB. H-bonding assisted by hydrogen/hydroxide ion was the most influential force. According to the effect of pH and temperature, organisms exposed to cellular environment with high alkalinity and high temperature might uptake more APs molecules with chemical properties similar to MB and suffered greater health risks. In detail, APs might replace amino acid molecules surrounding porphyrin and change the distortion type of porphyrin molecule, and then affect biological functions of porphyrin and related proteins. This study facilitates a better understanding of potential toxicity of organisms in contaminated environment.

This study developed a process of genetically engineered bacteria Rhodococcus erythropolis expressing Nirs and AMO combined with membrane bioreactor (MBR), nanofiltration (NF) and reverse osmosis (RO) membrane (pRho-NA-MNR) for advanced treatment of landfill leachate. Results demonstrated that pRho-NA-MNR presented higher removal rate of chemical oxygen demand (COD), biological oxygen demand (BOD), ammonia nitrogen (N–NH₄), total nitrogen (TN) and total organic carbon (TOC) than activated sludge (AS-MNR) system. Administration of pRho-NA increased nitrification by converting N–NH₄ to nitrite (N–NO₂) and Nitrate (N–NO₃), and promoting denitrification by converting N–NO₂ to nitrogen (N₂) in the landfill leachate treatment, promoted the pH control, increased sludge activity and effluent yield, shortened phase length adaptation under alternating aerobic-anoxic conditions. pRho-NA increased the nitration and denitrifying rate in the aerobic and anaerobic stage in the system by increasing Cyt cd1 and Cyt c expression in the activated sludge. Nitrogen removal by nitrification and denitrification was positively correlated to the concentration of Nirs and AMO expression. Treatment with pRho-NA promoted pollutant removal efficiency of membrane bioreactor, nanofiltration and reverse osmosis membrane processes in landfill leachate. In conclusion, data suggest that pRho-NA-MNR facilitates the formation of granular sludge and enhances comparable removal of nitrogen and organic compounds, indicating the practice of this process should be considered in landfill leachate treatment system.

Australian tropical freshwaters can experience extreme seasonal variability in rainfall and run off, particularly due to pulse events such as storms and cyclones. This study investigated how seasonal variability in dissolved organic matter (DOM) quality impacted the chronic toxicity of copper to a tropical green alga (Chlorella sp.) in the presence of two concentrations of DOM (low: ∼2 mg C/L; high: ∼10 mg C/L) collected from three tropical waters. Copper speciation and lability were explored using diffusive gradients in thin-films (DGT) and modelled maximum dynamic concentrations (cᵈʸⁿₘₐₓ) using data derived from the Windermere Humic Aqueous Model (WHAM VII). Relationships between copper lability and copper toxicity were assessed as potential tools for predicting toxicity. Copper toxicity varied significantly with DOM concentration, source and season. Copper toxicity decreased with increasing concentrations of DOM, with 50% growth inhibition effect concentrations (EC₅₀) increasing from 1.9 μg Cu/L in synthetic test waters with no added DOM (0.34 mg C/L) up to 63 μg Cu/L at DOM concentrations of 9.9 mg C/L. Copper toxicity varied by up to 2-fold between the three DOM sources and EC₅₀ values were generally lower in the presence of wet season DOM compared to dry season DOM. Linear relationships between DGT-labile copper and dissolved copper were significantly different between DOM source, but not concentration or season. Modelled cᵈʸⁿₘₐₓ consistently under-predicted labile copper in high DOM treatments compared to DGT measurements but performed better in low DOM treatments, indicating that this method is DOM-concentration dependent. Neither speciation method was a good surrogate for copper toxicity in the presence of different sources of natural DOM. Our findings show that DOM source and season, not just DOM concentration, affect copper toxicity to freshwater biota. Therefore, DOM quality should be considered as a toxicity-modifying factor for future derivation of bioavailability-based site-specific water quality guideline values.

Environmental colloids play crucial roles in the transport of environmental pollutants in porous media by acting as pollutant carriers. In this work, the dispersion stability and correlated transport of kaolinite colloid were investigated as a function of solution pH, solution ionic strength, and concentration of humic acid (HA), the roles of kaolinite colloid in driving Eu(III) transport were discussed. The results showed that the dispersion of kaolinite colloid was favorable at alkaline and extremely acidic pH values, the trend of aggregation with varying pH was critically reversed at pH ∼3.2 due to the transformation of surface electrical properties. Cations with higher valence and mineral affinity showed a more significant contribution in inducing colloid aggregation, which was generally in accordance with the Schulze-Hardy rule and Hofmeister series. HA greatly increased the colloid stability by altering the surface electrostatic potential and steric effect. The Derjguin-Landau-Verwey-Overbeek (DLVO) model suggested that the electrostatic force between colloidal particles controlled the aggregation and destabilizing trend of colloid, and the theoretically calculated critical coagulation concentration was consistent with that determined from kinetic aggregation experiments. The roles of kaolinite colloid in driving Eu(III) transport varied under different conditions, and the transport behavior was highly correlated with the dispersion stability trend of colloid. These results can provide an enhanced understanding of the environmental fate of kaolinite colloid as well as commensal pollutants.

Field survey-based ecological risk assessments for trace metals are conducted to examine the necessity and/or effectiveness of management intervention, such as setting of environmental quality standards. Observational datasets often involve confounders that may bias estimation of the effects of intervention (e.g., reduction of trace-metal concentrations through regulation). The field of ecotoxicology lags behind some other research fields in understanding proper analytical procedures for causal inference from observational datasets; there are only a few field survey-based ecotoxicological studies that have explicitly controlled for confounders in their statistical analyses. In the present study, we estimated the effect of intervention in nickel concentrations on Ephemeroptera, Plecoptera, and Trichoptera richness in rivers in Japan. We also provide detailed explanations for the backgrounds of spurious associations derived from confounders and on proper analytical procedures for obtaining an unbiased estimate of the targeted intervention effect by using regression analysis. We constructed a multiple regression model based on a causal diagram for aquatic insects and environmental factors, and on “the backdoor criterion,” that enabled us to determine the set of covariates required to obtain an unbiased estimate of the targeted intervention effect from regression coefficients. We found that management intervention in nickel concentrations may be ineffective compared to intervention in organic pollution, and that analysis ignoring the confounders overestimated the effect of intervention in nickel concentrations. Our results highlight the fact that confounders can lead to misjudging the necessity for management of anthropogenic chemical substances. Confounders should be explicitly specified and statistically controlled to achieve a comprehensive assessment of ecological risks for various substances.

To highlight the levels and distributions and to assess the risk of human exposure of chlorinated paraffins (CPs) in PM₂.₅ in China, the concentrations and homologue patterns of short−chain chlorinated paraffins (SCCPs) and medium−chain chlorinated paraffins (MCCPs) in PM₂.₅ from 10 cities in China were studied in 2013 and 2014. The mean concentrations of ΣSCCPs and ΣMCCPs were 19.9 ± 41.1 ng m⁻³ and 15.6 ± 18.6 ng m⁻³, respectively. Unexpectedly, the highest pollution levels occurred in two central cities (Xinxiang and Taiyuan) rather than in well−known eastern megacities such as Beijing, Nanjing, Shanghai, and Guangzhou. By comparing with earlier research, it has indicated the trend of CPs industry shifting from large eastern cities to small and medium-sized cities in central China to some extent. In addition, the composition pattern of SCCPs demonstrated an obviously differences from previous studies, with C₁₁ and Cl₇ predominating and accounting for 45.1% and 24.9%, respectively. Meanwhile, the ratio of MCCPs/SCCPs in most cities was less than 1.00 except for Guangzhou (1.92), Shanghai (1.29), and Taiyuan (1.11). Combined with the results of correlation analysis and principal component analysis, the observed pollution characteristics of CPs in PM₂.₅ had similar sources, which were more influenced by the ratio of MCCPs/SCCPs than by organic carbon, elemental carbon, temperature, population, and gross domestic product. Overall, the composition of CPs reflected the characteristics of local industrial production and consumption, and also implied efforts of Chinese enterprises to reduce the content of short carbon groups of CPs production. The CPs mainly deposited in head airways during the process of entering the human respiratory system. However, at the present levels, there was no significant carcinogenic effect for human health.

With increasing demand for aquaculture products, water reuse is likely to increase for aquaculture operations around the world. Herein, wastewater stabilization ponds (WSP) represents low cost and sustainable treatment technologies to reduce nutrients and various contaminants of emerging concern from effluent. In the present study, we examined bioaccumulation of selected pharmaceuticals from several therapeutic classes by two important fish species in aquaculture with different feeding preferences (Cyprinus carpio and Sander lucioperca) and their common prey to test whether species specific accumulation occurs. Forty and nineteen from 66 selected pharmaceuticals and their metabolites were positively found in water and sediment samples, respectively from the representative WSP. After a six-month study, which corresponds to aquaculture operations, fourteen pharmaceuticals and their metabolites were detected (at a frequency of higher than 50% of samples) in at least one fish tissue collected from the WSP. We observed striking differences for species and organ specific BAFs among study compounds. Though muscle tissues consistently accumulated lower levels of the target analytes, several substances were elevated in brain, liver and kidney tissues (e.g., sertraline) of both species. Low residual concentrations of these target analytes in aquaculture products (fish fillets) suggest WSPs are promising to support the water-food nexus in aquaculture.

Mitigation of air pollution by plants is a well-established phenomenon. Trees planted on the roadside are known to reduce particulate matter pollution by about 25%. In an urban ecosystem, especially in a metropolitan city such as Delhi, roadside trees are constantly exposed to air pollution. We, therefore, evaluated the effect of air pollution on a common Indian roadside tree, Neem (Azadirachta indica), and its associated microbes in areas with high and low levels of particulate matter (PM) pollution in Delhi. We hypothesized that alteration in the air quality index not only influences plant physiology but also its microbiome.A 100-fold increase in the number of epiphytic and 10–100 fold increase in endophytic colonies were found with 1.7 times increase in the level of pollutants. Trees in the polluted areas had an abundance of Salmonella, Proteus and Citrobacter, and showed increased secondary metabolites such as phenols and tannins as well as decreased chlorophyll and carotenoid. The number of unique microbes was positively correlated with increased primary metabolites.Our study thus indicates that, alteration in air quality affects the natural micro-environment of plants. These results may be utilized as sustainable tools for studying plant adaptations to the urban ecosystem.

Persistent organic pollutants (POPs) can undergo long-range atmospheric transport (LRAT) and deposit in remote areas. How persistent are POPs in remote areas? To answer this question, we measured two parent-DDTs and eight metabolites in soil and air along a transect in the Qinghai-Tibet Plateau, China, to quantitatively evaluate the degree of degradation of DDTs. DDTs were ubiquitous in soil and air with the total DDT concentrations (Σ₁₀DDTs) ranging 37.7–70,100 pg g⁻¹ dw and 3.4–175 pg m⁻³, respectively. The air-soil equilibrium status indicated that the forest/basin soil was a source for most DDTs, while the plateau soil was a sink receiving DDTs from the LRAT and photodegradation in the air (for metabolites). The metabolites accounted for avg. 64.1% of Σ₁₀DDTs in soil, with avg. 93.2% from local degradation, implying the overall high degradation of DDTs. With the significant degradation, the continuous input via LRAT was deemed to be the main reason for the stable level (persistence) of POPs in the Qinghai-Tibet Plateau. Therefore, we emphasize the importance of source control for the risk management of POPs. POPs in the environment might decline rapidly due to a reduction in source input and significant degradation as indicated by our study.

Atmospheric halogenated polycyclic aromatic hydrocarbons (Halo-PAHs) and parent PAHs were monitored in Ulsan, South Korea for one year (January‒December 2015) to investigate their seasonal patterns, gas/particle partitioning behavior, and the impact of meteorological conditions. The mean concentrations of 24 chlorinated PAHs, 11 brominated PAHs, and 13 parent PAHs in the gaseous and particulate phases were 8.64 and 9.64 pg/m³, 11.6 and 1.62 pg/m³, and 2.17 and 2.40 ng/m³, respectively. Winter had the highest ClPAH and PAH levels, with significant contributions from poly-chlorine groups and high-molecular-weight compounds. However, BrPAHs showed reverse patterns with the highest concentration in summer and the dominant gaseous fraction throughout the year. This finding could be explained by the strong local sources of BrPAHs, related to automobile and petrochemical industries. In contrast, the effects of the temperature inversion layer and atmospheric transport from the outside of Ulsan were more apparent for ClPAHs and PAHs, particularly in winter and spring. Regarding gas/particle partitioning, Halo-PAHs exhibited different seasonal behaviors from those of parent PAHs. The sorption pathway of Halo-PAHs seemed to shift from absorption as the sole dominant mechanism in winter and spring to both adsorption and absorption in summer and fall, while both partitioning mechanisms contributed equally for parent PAHs during the entire year. This study implies that Halo-PAHs and parent PAHs might not share the same atmospheric behavior, possibly due to different characteristics in atmospheric reactions with other chemicals and particle-size distribution. However, there have been limited studies about the formation of Halo-PAHs and their physicochemical properties; hence, further in-depth investigations are of vital importance.