The coexistence of di (2-ethylhexyl) phthalate (DEHP), Cd, and Zn poses a serious challenge to soil ecosystems. This study aimed to evaluate the phytoremediation potential of rice assisted with a plant growth promoting rhizobacteria (PGPR) consortium for the remediation of DEHP, Cd, and Zn co-contaminated soil. The consortium consisted of four bacterial strains, all of which exhibited Cd–Zn resistance and DEHP degradability. The results showed that the rice assisted by the bacterial consortium dissipated 86.1% DEHP while removing 76.0% Cd²⁺ and 92.2% Zn²⁺ from soil within 30 d. The presence of the PGPR consortium promoted plant growth and improved soil enzymatic activity, which may have helped enhance the removal of DEHP and heavy metals from the soil. Moreover, the application of the consortium modified the bacterial community and increased the relative abundance of bacteria related to DEHP degradation (Sphingomonas, Xanthobacteraceae), heavy metal immobilization (Massilia), and soil nutrient cycling (Nitrospira, Vicinamibacterales), which promoted plant growth and the removal of DEHP and heavy metals from soil. Notably, the DEHP and heavy metal contents in rice decreased substantially during the phytoremediation process. Therefore, the PGPR consortium could be beneficial for enhancing the removal of DEHP and heavy metals from the soil, without inducing the accumulation of these pollutants in rice. In general, this study confirmed that the combined use of rice and the PGPR consortium could remedy DEHP and heavy metal co-contaminated soil economically and ecologically without simultaneously posing risks for rice consumption.

4-nitrobenzaldehyde (4-NBA) is a widely used chemical intermediate for industrial application and an important photodegradation product of chloramphenicol. This compound represents a substantial threat to human health and ecosystem due to its genotoxic and mutagenic effect. In this study, the 4-NBA detoxification by transgenic rice overexpressing a bacterial nitroreductase gene, ElNFS1, from Enterobacter ludwigii were investigated. The cytosol-targeted ElNFS1 transgenic plants were selected to comprehensively examine their physio-biochemical responses and phytoremediation potential to 4-NBA. Our results showed that the transgenic plants exhibited strong tolerance to 4-NBA. Overexpression of ElNFS1 could significantly alleviate 4-NBA-induced damages of photosynthetic apparatus and reactive oxygen species overproduction in transgenic plants. The phytoremediation assay revealed that transgenic plants could remove more 4-NBA from the medium than wild-type plants. HPLC and LC-MS assays showed that 4-aminobenzaldehyde was found in the reductive products of 4-NBA. Altogether, the function of ElNFS1 during 4-NBA detoxification was characterized for the first time, which provides a strong theoretical support for the application potential of ElNFS1 transgenic plants on the phytoremediation of 4-NBA.

Long-term change and shorter-term variability in the atmospheric deposition of pollutants and marine salts can have major effects on the biogeochemistry and ecology of soils and surface water ecosystems. In the 1980s, at the time of peak acid deposition in the UK, deposition loads were highly dependent on prevailing weather types, and it was postulated that future pollution recovery trajectories would be partly dependent on any climate change-driven shifts in weather systems. Following three decades of substantial acidic emission reductions, we used monitoring data collected between 1992 and 2015 from four UK Environmental Change Network (ECN) sites in contrasting parts of Great Britain to examine the trends in precipitation chemistry in relation to prevailing weather conditions. Weather systems were classified on the basis of Lamb weather type (LWT) groupings, while emissions inventories and clustering of air mass trajectories were used to interpret the observed patterns. Concentrations of ions showed clear differences between cyclonic-westerly-dominated periods and others, reflecting higher marine and lower anthropogenic contributions in Atlantic air masses. Westerlies were associated with higher rainfall, higher sea salt concentrations, and lower pollutant concentrations at all sites, while air mass paths exerted additional controls. Westerlies therefore have continued to favour higher sea salt fluxes, whereas emission reductions are increasingly leading to positive correlations between westerlies and pollutant fluxes. Our results also suggest a shift from the influence of anthropogenic emissions to natural emissions (e.g., sea salt) and climate forcing as they are transported under relatively cleaner conditions to the UK. Westerlies have been relatively frequent over the ECN monitoring period, but longer-term cyclicity in these weather types suggests that current contributions to precipitation may not be sustained over coming years.

Microplastics (MPs) have been shown to act as sorbent phases and thus carriers of organic chemicals in the aquatic environment. Therefore, concerns exist that MP ingestion increases the uptake and accumulation of organic chemicals by aquatic organisms. However, it is unclear if this pathway is relevant compared to other exposure pathways. Here we compared the bioconcentration capacity of two hydrophobic organic chemicals (i.e., chlorpyrifos and hexachlorobenzene) in a freshwater fish (Danio rerio) when exposed to chemicals through water only and in combination with contaminated polyethylene MPs. Additionally, a suite of biomarker analyses (acetylcholine esterase, glutathione S-transferase, alkaline phosphatase, catalase) was carried out to test whether MPs can enhance the toxic stress caused by chemicals. Two 14-day semi-static experiments (one for each chemical) were carried out with adult fish. Each experiment consisted of (1) a control treatment (no chemicals, no MPs); (2) a treatment in which fish were exposed to chlorpyrifos or hexachlorobenzene only through water; (3) a treatment in which fish were exposed to the chemicals through water and contaminated polyethylene MPs (100 mg MP/L). Two additional treatments were included for the biomarker analysis. These contained MPs at two different concentrations (5 and 100 mg MP/L) but no chemicals. The presence of contaminated MPs in contaminated water did not enhance but rather decreased the bioconcentration of both chemicals in fish compared to the treatment that contained contaminated water in absence of MPs. This was more pronounced for hexachlorobenzene, which is more hydrophobic than chlorpyrifos. Enzyme activity levels in fish were only significantly altered in the presence of MPs for alkaline phosphatase. This study indicates that MP presence in freshwater ecosystems is not expected to increase the risks associated with chemical bioconcentration in aquatic organisms and that other exposure pathways (i.e., uptake via respiration, skin permeability) may be of higher importance.

Colloid-sized microplastics (MPs) are ubiquitous in aquatic environments and can share the same transport route together with various crystalline, poorly crystalline and freshly formed iron oxides. However, the colloidal interactions between these colloid constituents are not fully understood. This study was designed to investigate the colloidal properties of polystyrene microplastics (PSMPs) under the influence of haematite, goethite, ferrihydrite and freshly formed Fe oxide (FFFO). Dynamic light scattering was coupled with a test tube method to observe changes in the surface charge and colloidal dynamics of suspensions of PSMPs and Fe oxides. The overall effects on the aggregation of PSMPs are found to decrease in the following order: FFFO > ferrihydrite > goethite > haematite. The effects of these Fe oxides are found to strongly depend on pH. While the crystalline oxides play a dominant role in the acidic environment, poorly crystalline oxides show greater effects on PSMP aggregation in an alkaline environment. Heteroaggregation due to decreasing electrostatic interactions is the major mechanism that governs the colloidal dynamics of PSMPs and Fe oxides. It can be inferred that the copresence of Fe oxides and MPs can delay the transport of MPs or even change the destination for MPs.

Microbially induced carbonate precipitation (MICP) is a technique used extensively to address heavy metal pollution but its micro-dynamic process remains rarely explored. In this study, A novel Cd-tolerant ureolytic bacterium DL-1 (Pseudochrobactrum sp.) was used to study the micro-dynamic process. With conditions optimized by response surface methodology, the removal efficiency of Cd²⁺ could achieve 99.89%. Three components were separated and characterized in the reaction mixture of Cd²⁺ removal by MICP. The quantitative-dynamic distribution of Cd²⁺ in different components was revealed. Five synergistic effects for Cd²⁺ removal were found, including co-precipitation, adsorption by precipitation, crystal precipitation on the cell surface, intracellular accumulation and extracellular chemisorption. Importantly, during Cd²⁺ removal by MICP, the phenomenon that crystalline nanoparticles adhere to the cell surface, but without any micrometer-sized precipitation encapsulated bacterial cells was observed. This indicated that the previously studied model of bacterial cells as nucleation sites for metal cation precipitation and crystal growth is oversimplified. Our findings provided valuable insights into the mechanism of heavy metals removal by MICP, and a more straightforward method for studying biomineralization-related dynamic process.

Although concerns have been raised about co-selection for antibiotic resistance and various antibiotics and non-antibiotic agents, the data on their association in urban sludge is still limited. In addition, antibiotic contamination can result in not only the toxicity but also the antibiotic resistance. In this study, the first large-scale identification of antibiotics and non-antibiotic agents concern for co-selection of resistance against antibiotics was conducted in urban sludge. Co-occurrence analysis showed that antibiotic resistance genes (ARGs) had no significant correlation with the corresponding antibiotics. Therefore, the results of co-occurrence analysis based on antibiotic concentration and ARG abundance were always ambiguous and difficult to interpret. However, antibiotic resistance was positively correlated with highly toxic compounds such as diclofenac, enrofloxacin and nicotine, suggesting that environmental contaminants might influence antibiotic resistance while exerting toxicity through mechanisms such as changes in microbial community and enzyme activity. The close correlation between class 1 integrase gene (intI1) and diclofenac/enrofloxacin indicated that the co-selection scenario between environmental contaminants and ARGs was likely mediated via intI1. In total, the derived co-occurrence patterns improve our understanding of the co-selection between ARGs, antibiotics and non-antibiotic agents, and also reaffirm the importance of potential role of non-antibiotic agents in the global spread of antibiotic resistance.

Exposure to electronic and electrical waste (e-waste) has been related to a few adverse health effects. In this study, sediment samples from an e-waste recycling town in China were collected, and aryl hydrocarbon receptor (AhR) agonists in the samples were identified using an effect-directed analysis (EDA) strategy. The CBG2.8D cell line reporter gene bioassay was used as a toxicity test, while suspect screening against chemical databases was performed for potential AhR agonist identification where both gas chromatography- and liquid chromatography-high resolution mass spectrometry analyses were run. When the original sample extract showed high AhR-mediated activity, sample fractionation was performed, and fractions exhibiting high bioactivity were chemically analyzed again to reveal the corresponding AhR agonists. In total, 23 AhR agonists were identified, including 14 commonly known ones and 9 new ones. Benzo [k]fluoranthene and 6-nitrochrysene were the dominant AhR agonists, covering 16–71% and 2.7–12%, respectively, of the AhR activation effects measured in the parent extracts. The newly identified AhR-active chemicals combined explained 0.13–0.20% of the parent extracts’ effects, with 7,12-dimethylbenz [a]anthracene and 8,9,11-trimethylbenz [a]anthracene being the major contributors. A diagnostic isomer ratio analysis of polycyclic aromatic hydrocarbons suggested that the major source of AhR agonists identified in these e-waste related sediment samples were probably petroleum product combustion and biomass combustion. In the future, for a more comprehensive AhR agonist investigation, in-house chemical synthesis and purification, and, when necessary, a secondary sample fractionation, would be beneficial.

Soil contamination by potentially toxic elements (PTEs) is one of the greatest threats to environmental degradation. Knowing where PTEs accumulated in soil can mitigate their adverse effects on plants, animals, and human health. We evaluated the potential of using long-term remote sensing images that reveal the bare soils, to detect and map PTEs in agricultural fields. In this study, 360 soil samples were collected at the superficial layer (0–20 cm) in a 2574 km² agricultural area located in São Paulo State, Brazil. We tested the Soil Synthetic Image (SYSI) using Landsat TM/ETM/ETM+, Landsat OLI, and Sentinel 2 images. The three products have different spectral, temporal, and spatial resolutions. The time series multispectral images were used to reveal areas with bare soil and their spectra were used as predictors of soil chromium, iron, nickel, and zinc contents. We observed a strong linear relationship (−0.26 > r > −0.62) between the selected PTEs and the near infrared (NIR) and shortwave infrared (SWIR) bands of Sentinel (ensemble of 4 years of data), Landsat TM (35 years data), and Landsat OLI (4 years data). The clearest discrimination of soil PTEs was obtained from SYSI using a long term Landsat 5 collection over 35 years. Satellite data could efficiently detect the contents of PTEs in soils due to their relation with soil attributes and parent materials. Therefore, distinct satellite sensors could map the PTEs on tropics and assist in understanding their spatial dynamics and environmental effects.