Studies have shown that the mixture toxicity of compounds with similar modes of action (MOAs) is usually predicted by the concentration addition (CA) model. However, due to the lack of toxicological information on compounds, more evidence is needed to determine whether the above conclusion is generally applicable. In general, the same type of compounds with similar chemical structures have similar MOAs, so whether the toxicities of the mixture of these compounds are additive needs to be further studied. In this paper, three types of pesticides with similar chemical structures (three organophosphoruses, two carbamates and two neonicotinoids) that may have similar MOAs were selected and five binary mixture systems were constructed. For each system, five mixture rays with different concentration ratios were designed by the direct equipartition ray design (EquRay) method. The mortality of Caenorhabditis elegans was regarded as the endpoint for the toxicity exposure to single pesticides and binary mixtures. The combined toxicities were evaluated simultaneously using the CA model, isobologram and combination index. The structural similarity of the same type of pesticides was quantitatively analyzed according to the MACCS molecular fingerprint and the slope of dose-response curve at pEC₅₀. The results show that the toxicities of neonicotinoid mixtures and carbamate mixtures are almost antagonistic. The entire mixture system of dichlorvos and dimethoate produced synergism, and four of the five mixture rays of dimethoate and methamidophos induced antagonism, while among the mixture rays of dichlorvos and methamidophos, different concentrations showed different interaction types. The results of structural similarity analysis show that the size of structural similarity showed a certain quantitative relationship with the toxicity interaction of mixtures, that is, the structural similarity of the same type of pesticides may show an additive action in a certain range.

A native strain of Bacillus paramycoides isolated from the leachate of coal mine overburden rocks was investigated for its potential to produce selenium nanoparticles (SeNPs) by biogenic reduction of selenite, one of the most toxic forms of selenium. 16S rDNA sequencing was used to identify the bacterial strain (SP3). The SeNPs were characterized using spectroscopic (UV–Vis absorbance, dynamic light scattering, X-ray diffraction, and Raman), surface charge measurement (zeta potential), and ultramicroscopic (FESEM, EDX, FETEM) analyses. SP3 exhibited extremely high selenite tolerance (1000 mM) and reduced 10 mM selenite under 72 h to produce spherical monodisperse SeNPs with an average size of 149.1 ± 29 nm. FTIR analyses indicated exopolysaccharides coating the surface of SeNPs, which imparted a charge of −29.9 mV (zeta potential). The XRD and Raman spectra revealed the SeNPs to be amorphous. Furthermore, biochemical assays and microscopic studies suggest that selenite was reduced by membrane reductases. This study reports, for the first time, the reduction of selenite and biosynthesis of SeNPs by B. paramycoides, a recently discovered bacterium. The results suggest that B. paramycoides SP3 could be exploited for eco-friendly removal of selenite from contaminated sites with the concomitant biosynthesis of SeNPs.

In the present study, produced water sample collected from the Indian crude oil reservoir is used to enrich the bacterial communities. The impact of these enriched bacterial communities on the biodegradation of crude oil, biofilm formation, and biocorrosion process are elucidated. A crude oil degradation study is carried out with the minimal salt medium and 94% of crude oil was utilized by enriched bacterial communities. During the crude oil degradation many enzymes including alkane hydroxylase, alcohol dehydrogenase, and lipase are playing a key role in the biodegradation processes. The role of enriched bacterial biofilm on biocorrosion reactions are monitored by weight loss studies and electrochemical analysis. Weight loss study revealed that the biotic system has vigorous corrosion attacks compared to the abiotic system. Both AC-Impedance and Tafel analysis confirmed that the nature of the corrosion reaction take place in the biotic system. Very less charge transfer resistance and higher corrosion current are observed in the biotic system than in the abiotic system. Scanning electron microscope confirms that the dense biofilm formation favoured the pitting type of corrosion. X-ray diffraction analysis confirms that the metal oxides formed in the corrosion systems (biotic). From the metagenomic analysis of the V3–V4 region revealed that presence of diverse bacterial communities in the biofilm, and most of them are uncultured/unknown. Among the known genus, Bacillus, Halomonas, etc are dominant in the enriched bacterial biofilm sample. From this study, we conclude that the uncultured bacterial strains are found to be playing a key role in the pitting type of corrosion and they can utilize crude oil hydrocarbons, which make them succeeded in extreme oil reservoir environments.

As ubiquitous, persistent organic pollutants, polycyclic aromatic hydrocarbons (PAHs) have adverse impacts on human health. Phenanthrene (Phe) is one of the most abundant PAHs in the environment. However, the long-term effects of exposure to environmental level of Phe on the kidneys and the potential mechanisms are unclear. T helper (Th) cells, a subtype of CD4⁺ T cells that play a central role in the renal immune microenvironment. In this study, male mice were chronically exposed to 5, 50, and 500 ng/kg bw Phe every other day for total 210 days. Those results indicated that environmental Phe exposure caused kidney hypertrophy, injury and fibrosis in the mice. Chronic, long-term environmental level of Phe exposure did not significantly alter the innate immune response but induced adaptive immune response changes (Th1/Th2 related cytokines release), causing a type 1 immune response in the 5 ng/kg bw Phe group and a type 2 immune response in the high dose groups (50 and 500 ng/kg bw). This study provides novel insights into the roles of adaptive immune response in long-term PAH exposure-induced chronic kidney injury and fibrosis, which is beneficial for further understanding the potential health hazards of PAHs and providing new avenues for immune intervention strategies to alleviate PAHs toxicity.

Seabirds are widely used as indicators of marine pollution, including mercury (Hg), because they track contaminant levels across space and time. However, many seabirds are migratory, and it is difficult to understand the timing and location of their Hg accumulation. Seabirds may obtain Hg thousands of kilometers away, during their non-breeding period, and deposit that Hg into their terrestrial breeding colonies. We predicted that Hg concentration in rectrices reflects exposure during the previous breeding season, in body feathers reflects non-breeding exposure, and in blood collected during breeding reflects exposure during current breeding. To test this hypothesis, we measured total Hg concentration in these three tissues, which reflect different timepoints during the annual cycle of rhinoceros auklets (Cerorhinca monocerata) breeding on both sides of the North Pacific (Middleton Island in Alaska and Teuri Island in Hokkaido), and tracked their wintering movement patterns with biologging devices. We (i) identify the wintering patterns of both populations, (ii) examine Hg levels in different tissues representing exposure at different time periods, (iii) test how environmental Hg exposure during the non-breeding season affects bird contamination, and (iv) assess whether variation in Hg levels during the non-breeding season influences levels accumulated in terrestrial plants. Individuals from both populations followed a figure-eight looping migration pattern. We confirm the existence of a pathway from environmental Hg to plant roots via avian tissues, as Hg concentrations were higher in plants within the auklet colonies than at control sites. Hg concentrations of breast feathers were higher in Alaskan than in Japanese auklets, but Hg concentrations in rectrices and blood were similar. Moreover, we found evidence that tissues with different turnover rates could record local anthropogenic Hg emission rates of areas visited during winter. In conclusion, Hg was transported across thousands of kilometers by seabirds and transferred to local plants.

Understanding the distribution and persistence of the fumigant dimethyl disulfide (DMDS) under different soil conditions would contribute to a more environmentally sustainable use of this gas. We determined the effects of soil type, soil moisture content and soil organic amendment rate on DMDS distribution and persistency using soil columns in the laboratory. The peak concentrations of DMDS at 60 cm soil depth in sandy loam soil, black soil and red loam soil were 1.9 μg cm⁻³, 0.77 μg cm⁻³, 0.22 μg cm⁻³, respectively. The total soil residues of DMDS in sandy loam soil, black soil and red loam soil were 0.4, 1.3 and 1.3%, respectively. The peak concentrations of DMDS at 60 cm soil depth and the total soil residues of DMDS applied decreased from 3.2 μg cm⁻³ to 0.9 μg cm⁻³ and 3.3 to 0.5% when soil moisture content increased from 6 to 18%, respectively. Incremental increases (0–5%) in organic amendment rates decreased DMDS distribution through the soils and increased soil residues. Wait periods were required of 7, 21 and 21 days after polyethylene (PE) film was removed to reduce residues sufficiently for cucumber seed germination in sandy loam soil, black soil and red loam soil with 12% moisture content and 0% organic amendment rate, respectively. However, no wait period was required for successful cucumber seed germination in sandy loam soils (Beijing) with 6, 12 or 18% moisture content or organic amendment rates of 1 or 5%, respectively, but in commercial practice 7 days delay would be prudent. Our results indicated that soil type, soil moisture content and organic amendment rates significantly affected DMDS distribution, persistency and residues in soil. Those factors should be taken into consideration by farmers when determining the appropriate dose of DMDS that will control soil pests and diseases in commercially-produced crops.

In this review, global change processes have been linked to polycyclic aromatic compounds (PACs) in Canada and a first national budget of sources and sinks has been derived. Sources are dominated by wildfire emissions that affect western and northern regions of Canada disproportionately due to the location of Pacific and boreal forests and the direction of prevailing winds. Wildfire emissions are projected to increase under climate warming along with releases from the thawing of glaciers and permafrost. Residential wood combustion, domestic transportation and industry contribute the bulk of anthropogenic emissions, though they are substantially smaller than wildfire emissions and are not expected to change considerably in coming years. Other sources such as accidental spills, deforestation, and re-emission of previous industrial deposition are expected to contribute anthropogenic and biogenic PACs to nearby ecosystems. PAC sinks are less well-understood. Atmospheric deposition is similar in magnitude to anthropogenic sources. Considerable knowledge gaps preclude the estimation of environmental transformations and transboundary flows, and assessing the importance of climate change relative to shifts in population distribution and energy production is not yet possible. The outlook for PACs in the Arctic is uncertain due to conflicting assessments of competing factors and limited measurements, some of which provide a baseline but have not been followed up in recent years. Climate change has led to an increase in primary productivity in the Arctic Ocean, but PAC-related impacts on marine biota appear to be modest. The net effect of changes in ecological exposure from changing emissions and environmental conditions throughout Canada remains to be seen. Evidence suggests that the PAC budget at the national scale does not represent impacts at the local or regional level. The ability to assess future trends depends on improvements to Canada’s environmental measurement strategy and biogeochemical modelling capability.

With the upgrade of wastewater treatment plants (WWTPs) to meet more stringent discharge limits for nutrients, dissolved organic nitrogen (DON) is present at an increasing percentage (up to 85%) in the effluent. Discharged DON is of great environmental concern due to its potentials in stimulating algal growth and forming toxic nitrogenous disinfection by-products (N-DBPs). This article systematically reviewed the characteristics, transformation and ecological impacts of wastewater DON. Proteins, amino acids and humic substances are the abundant DON compounds, but a large fraction (nearly 50%) of DON remains uncharacterized. Biological treatment processes play a dominant role in DON transformation (65–90%), where DON serves as both nutrient and energy sources. Despite of the above progress, critical knowledge gaps remain in DON functional duality, relationship with dissolved inorganic nitrogen (DIN) species, and coupling/decoupling with the dissolved organic carbon (DOC) pool. Development of more rapid and accurate quantification methods, modeling transformation processes, and assessing DON-associated eutrophication and N-DBP formation risks should be given priority in further investigations.

Developing low-cost and high-performance biosorbent for water purification continues drawing more and more attention. In this study, cellulose-chitosan composite hydrogels were fabricated via a co-dissolution and regeneration process using a molten salt hydrate (a 60 wt% aqueous solution of LiBr) as a solvent. The addition of chitosan not only introduced functionality for metal adsorption but also increased the specific surface area and improved the mechanical strength of the composite hydrogel, compared to pure cellulose hydrogel. Batch adsorption experiments indicated that the composite hydrogel with 37% cellulose and 63% chitosan exhibited an adsorption capacity of 94.3 mg/g (1.49 mmol/g) toward Cu²⁺ at 23 °C, pH 5, and initial metal concentration of 1500 mg/L, which was 10 times greater than the adsorption capacity of pure cellulose hydrogel. Competitive adsorption from a mixed metals solution revealed that the cellulose-chitosan composite hydrogel exhibited selective adsorption of the metals in the order of Cu²⁺ > Zn²⁺ > Co²⁺. This study successfully demonstrated an innovative method to fabricate biosorbents from abundant and renewable natural polymers (cellulose and chitosan) for removing metal ions from water.

With the implementation of clean air strategies, PM₂.₅ pollution abatement has been observed in the “2 + 26” cities in the Beijing-Tianjin-Hebei (BTH) region (referred to as the BTH2+26) and their surrounding areas. To identify the drivers for PM₂.₅ concentration decreases in the BTH2+26 cites from the 2016/17 heating season (HS1617) to the 2017/18 heating season (HS1718), we investigated the contributions of meteorological conditions and emission-reduction measures by Community Multi-Scale Air Quality (CMAQ) model simulations. The source apportionments of five sector sources (i.e., agriculture, industry, power plants, traffic and residential), and regional sources (i.e., local, within-BTH: other cities within the BTH2+26 cities, outside-BTH, and boundary conditions (BCON)) to the PM₂.₅ decreases in the BTH2+26 cities were estimated with the Integrated Source Apportionment Method (ISAM). Mean PM₂.₅ concentrations in the BTH2+26 cities substantially decreased from 77.4 to 152.5 μg m⁻³ in HS1617 to 52.9–101.9 μg m⁻³ in HS1718, with the numbers of heavy haze (daily PM₂.₅ ≥150 μg m⁻³) days decreasing from 17-77 to 5–30 days. The model simulation results indicated that the PM₂.₅ concentration decreases in most of the BTH2+26 cities were attributed to emission reductions (0.4–55.0 μg m⁻³, 2.3–81.6% of total), but the favorable meteorological conditions also played important roles (1.9–25.4 μg m⁻³, 18.4–97.7%). Residential sources dominated the PM₂.₅ reductions, leading to decreases in average PM₂.₅ concentrations by more than 30 μg m⁻³ in severely polluted cities (i.e., Shijiazhuang, Baoding, Xingtai, and Beijing). Regional source analyses showed that both local and within-BTH sources were significant contributors to PM₂.₅ concentrations for most cities. Emission controls in local and within-BTH sources in HS1718 decreased the average PM₂.₅ concentrations by 0.1–47.2 μg m⁻³ and 0.3–22.1 μg m⁻³, respectively, relative to those in HS1617. Here we demonstrate that a combination of favorable meteorological conditions and anthropogenic emission reductions contributed to the improvement of air quality from HS1617 to HS1718 in the BTH2+26 cities.