International audience | Assessing the ecological risk of combined pollution, especially from a holistic perspective with the consideration of the overarching functions of soil ecosystem, is crucial and beneficial to the improvement of ecological risk assessment (ERA) framework. In this study, four soils with similar physicochemical properties but contrasting heavy metals contamination levels were selected to explore changes in the integrated functional sensitivity (MSI), resistance (MRS) and resilience (MRL) of soil microbial communities subjected to herbicide siduron, based on which the ecological risk of the accumulation of siduron in the four studied soils were evaluated. The results suggested that the microbial biomass carbon, activity of denitrification enzyme and nitrogenase were indicative of MSI and MRS, and the same three parameters plus soil basal respiration were indicative of MRL. Significant dose-effect relationships between siduron residues in soils and MSI, MRS and MRL under combined pollution were observed. Heavy metal polluted soils showed higher sensitivity and lower resistance to the additional disturbance of herbicide siduron due to the lower microbial biomass, while the resilience of heavy metal polluted soils was much higher due to the pre-adaption to the chemical stresses. The quantifiable indicator microbial functional stability was incorporated in the framework of ERA and the results showed that the accumulation of siduron in the studied soils could exhibit potential harm to the integrated functional stability of soil microbial community. Thus, this work provides insights into the application of integrated function of soil microbial community into the framework of ERA.

One attraction of using hydrochar (HC) and biochar (BC) in soil is their intrinsic affinity for organic contaminants. Oxidative ageing is likely to induce changes in physicochemical properties and functionality. To explore the long-term potential trajectories for corn stalk HC and BC to adsorb organic pollutants, we employed HC and BC exposure in 5% H2O2 to simulate oxidative ageing and get insights into mechanisms of atrazine adsorption on fresh and artificially aged materials. The physicochemical properties of fresh and aged materials were systematically compared using elemental analysis, SSA, FTIR, XPS and SEM-EDS, alongside K2Cr2O7/H2SO4 treatment to assess chemical oxidation stability. Atrazine is a typical herbicide chemical and hydrophobic organic pollutant. Adsorption isotherms of atrazine were used to reveal differences in mechanisms of sorption to BC and HC, by assessment before and ageing. BC freshly produced at 650 °C displayed higher capacity for atrazine sorption than BC produced at 500 °C, with a dominant role for π-π EDA interactions. The sorption capacity of HC freshly produced at 250 °C was higher than for HC produced at 200 °C HC, owing to higher C content and atrazine partitioning into the organic phase. Ageing increased the surface abundance of oxygenated functional groups for BC and HC and diminished bulk aromaticity. After ageing, atrazine sorption by high temperature BC was lower, but for HC it was increased. Such divergent effects must be considered when developing strategies to co-manage contaminants and carbon through the addition of carbonized materials to land.

The production and soil accumulation of nanoparticles (NPs) from the industrial sector has increased concerns about their toxic effects in plants which needs the research to explore the ways of reducing NPs toxicity in pants. The gibberellic acid (GA) has been found to reduce abiotic stresses in plants. However, the effect of GA in reducing zinc oxide (ZnO) NPs-mediated toxicity in plants remains unclear. In this study, foliar application of GA was used to explore the possible role in reducing ZnO NPs toxicity in wheat (Triticum aestivum L.) plants. The plants were grown in pots spiked with ZnO NPs (0, 300, 600, 900, 1200 mg/kg) and GA (0, 100, 200 mg/L) was foliar sprayed at different times during the growth period under ambient environmental conditions. Our results demonstrated that GA inhibited the toxicity of ZnO NPs in wheat especially at higher levels of NPs. The GA application improved the plant biomass, photosynthesis, nutrients, and yield under ZnO NPs stress. The GA reduced the Zn accumulation, and reactive oxygen species generation in plants caused by toxicity of NPs. The protective effect of GA in decreasing ZnO NPs-induced oxidative stress was related to GA-mediated enhancement in antioxidant enzymes in plants. The role of GA in enhancing tolerance of wheat against ZnO NPs was further confirmed by the enhancement in nutrient contents in shoots and roots of wheat. Overall, our study provides the evidence that GA can reduce ZnO NPs-induced toxicity in wheat and probably in other crops which needs further in-depth investigation.

In order to evaluate the effect of mining activity on the environment of the Qhorveh mining area in the west of Iran, the geological, ecological and environmental data, related to social development and regional economic status, were used. The geological data included seven sub-indices, such as vegetation coverage, land utilization type, and fault activity; ecological data, with two sub-indices, such as degree of ecological environment recovery; and finally, environmental data, with three sub-indices, such as soil and dust pollutions. These were selected based on the literature and expert opinion which were utilized for environmental pollution and geo-ecological (EPGE) risk assessment of the study site. Remote sensing (RS) image, field sampling, digital elevation map, and data retrieved from different government agencies were used to generate layers for the sub-indices in the geographic information system (GIS) environment. In addition, the analytical hierarchy process (AHP) method was used to determine the weight of sub-indices. Five levels consisting of best, good, middle, poor and worst were used to describe the EPGE risk assessment of the Qhorveh mining area. Results showed that worst and poor levels of EPGE risk are in the east and northeast of the study area where the gold and pumice mines are located while best and good levels of EPGE risk are in its center where the stone mines are located. According to the results of this research, the EPGE risk assessment of the Qhorveh mining area is affected by the environmental pollution index with its highest weight (0.3908). It can be concluded that the integration of the RS, GIS and AHP methods proposed in this study improved the evaluation quality of EPGE risk assessment.

Di (2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) are important pollutants that contaminate agricultural soils. We determined the effects of di (2-ethylhexyl) phthalate (DEHP) and di-n-butyl phthalate (DBP) on the production of reactive oxygen species, photosynthesis, and activity of antioxidant enzymes in wheat planted in fluvo-aquic soils. DBP- and DEHP-induced oxidative stress decreased the values of the photosynthetic/fluorescence parameters (except for intercellular carbon dioxide concentration) and chlorophyll content at the seedling, jointing, and booting stages. Moreover, the non-stomatal factor responsible for the net decrease in photosynthetic efficiency was identified as the decrease in fluorescence resulting from the decreased amount of chlorophyll a returning from the excited to the ground energy state. The content of superoxide anions and hydrogen peroxide in wheat leaves and roots increased with increasing DBP and DEHP supplementation, compared to the control. Antioxidant enzyme activities in the leaves and roots at the seedling stage increased at DBP and DEHP levels of 10 and 20 mg kg⁻¹, respectively, and the enzyme activities at the jointing and booting stages increased with increasing concentrations of the chemicals, compared to the control. These results demonstrated that increased levels of antioxidant enzymes play a significant role in protecting plant growth under DBP and DEHP stress.

Natural subsurface environment is a complex heterogeneous system. To investigate the effect of ionic strength (IS) and heterogeneity on the transport and remobilization of graphene oxide (GO)-facilitated uranium (U(VI)) in saturated porous media, column experiments were performed by the injection of U(VI) alone and U(VI)+GO mixtures into homogeneous and heterogeneous porous media under low and high ionic strength (1 and 50 mM) conditions, and then the columns were successively flushed with background solution and DI water. Results showed that when U(VI) only was introduced into the columns, IS had little effect on the migration of U(VI) alone in both media and the presence of preferential flow in heterogeneous media slightly enhanced the mobility of U(VI). As U(VI)+GO mixtures were injected into the columns, GO showed strong mobility at low IS and high released peak at high IS. The appearance of GO significantly enhanced U(VI) transport in both media. Under low IS condition, the mobility of U(VI) was significantly enhanced at the injection phase, and the medium heterogeneity further promoted the amount of GO-sorbed U(VI) transport. At high IS, less GO-sorbed U(VI) was observed during injection phase, and a large amount of retained GO-sorbed U(VI) were released with GO remobilization during water flushing phase, and the release showed the longer-tailing phenomenon and the release amount was more pronounced in heterogeneous media. The findings in this study showed that the coupled effect of solution chemistry and media heterogeneity played important roles on GO-facilitated U(VI) transport and release in soil and groundwater system.

The Deception Island, located in Maritime Antarctica, is a volcanic island with geothermal activity and one of the most visited by tourists. However, the extent of the anthropogenic impact remains largely unknown and the factors shaping the resistance/tolerance mechanisms in the microbiomes from Whalers Bay ecosystems have never been investigated. In this context, this study aimed to reveal the resistome profiles of Whalers Bay sediments and correlate them with environmental factors. Samples were collected at four sites during the summer 2014/2015 along a transect of 27.5 m in the Whalers Bay sediments. DNA isolated from sediment samples was sequenced using the Illumina HiSeq platform. Bioinformatic analyses allowed the assembly of contigs and scaffolds, prediction of ORFs, and taxonomic and functional annotation using NCBI RefSeq database and KEGG orthology, respectively. Microorganisms belonging to the genera Psychrobacter, Flavobacterium and Polaromonas were shown to dominate all sites, representing 60% of taxonomic annotation. Arsenic (As), copper (Cu) and iron (Fe) were the most abundant metal resistance/tolerance types found in the microbiomes. Beta-lactam was the most common class related to antibiotics resistance/tolerance, corroborating with previous environmental resistome studies. The acridine class was the most abundant amongst the biocide resistance/tolerances, related to antiseptic compounds. Results gathered in this study reveal a repertoire of resistance/tolerance classes to antibiotics and biocides unusually found in Antarctica. However, given the volcanic nature (heavy metals-rich region) of Deception Island soils, this putative impact must be viewed with caution.

As one of the most cost-effective and sustainable methods for contaminants' removal, sequestration and/or detoxification, phytoremediation has already captured comprehensive attention worldwide. Nevertheless, the accurate effects of various spatial pattern in enhancing phytoremediation efficiency is not yet clear, especially for the polluted mining areas. This study designed nine planting patterns (monocropping, double intercropping and triple intercropping) of three indigenous plant species (Setaria viridis (L.), Echinochloa crus-galli (L.) and Phragmites australis (Cav.) Trin. ex Steud.) to further explore the effects of plants spatial pattern on phytoremediation efficiency. Considering the uncertainties of the residual contaminants' concentration (RCC) caused by soil anisotropy, permeability and land types, the interval transformation was introduced into the plant uptake model to simulate the remediation efficiency. Then multi-criteria decision analysis (MCDA) were applied to optimal the planting patterns, with the help of criteria of (a) the amount of heavy metal absorption; (b) the concentration of residual contaminant in soil; (c) root tolerance of heavy metals; (d) the total investment cost. Results showed that (1) the highest concentrations of Zn, Cd, and Pb of the polluted area were 7320.02, 14.30, 1650.51 mg kg⁻¹ (2) During the 180 days simulation, the highest RMSE of residue trace metals in soil are 3.02(Zn), 2.67(Pb), 2.89(Cd), respectively. (3) The result of IMCDA shows that the planting patterns of Setaria viridis, Echinochloa crus-galli and Phragmites australis in alternative a9 (269 mg kg⁻¹ year⁻¹) had the highest absorption rate of heavy metals compared with a7 (235 mg kg⁻¹ year⁻¹) and a2 (240 mg kg⁻¹ year⁻¹). After 20 years of remediation, the simulated RCC in a9 is far below the national standard, and the root toxicity is 0.12 (EC ≤ EC₂₀). In general, the optimal alternative derived from interval residual contaminant concentration can effectively express the dynamic of contaminant distribution and then can be effectively employed to evaluate the sustainable remediation methods.

Understanding how mercury (Hg) accumulates in the aquatic food web requires information on the factors driving methylmercury (MeHg) contamination. This paper employs data on MeHg in muscle tissue of three black bass species (Largemouth Bass, Spotted Bass, and Smallmouth Bass) sampled from 21 reservoirs in California. During a two-year period, reservoirs were sampled for total Hg in sediment, total Hg and MeHg in water, chlorophyll a, organic carbon, sulfate, dissolved oxygen, pH, conductivity, and temperature. These data, combined with land-use statistics and reservoir morphometry, were used to investigate relationships to size-normalized black bass MeHg concentrations. Significant correlations to black bass MeHg were observed for total Hg in sediment, total Hg and MeHg in surface water, and forested area. A multivariate statistical model predicted Largemouth Bass MeHg as a function of total Hg in sediment, MeHg in surface water, specific conductivity, total Hg in soils, and forested area. Comparison to historical reservoir sediment data suggested there has been no significant decline in sediment total Hg at five northern California reservoirs during the past 20 years. Overall, total Hg in sediment was indicated as the most influential factor associated with black bass MeHg contamination. The results of this study improve understanding of how MeHg varies in California reservoirs and the factors that correlate with fish MeHg contamination.

Despite their ecological and socioeconomic importance, mangroves are among the most threatened tropical environments in the world. In the past two decades, the world's mangrove degradation and loss were estimated to lie between an 35% and >80%. However, appropriate bioindicators for assessing the impact of external factors, and for differentiating polluted from unpolluted areas are still scarce. Here, we determine the physicochemical profiles of the soils of two mangroves, one exposed to and one not exposed to anthropogenic factors. By metagenomic analysis based on 16S rRNA, we generated the bacterial diversity profiles of the soils and estimated their functional profiles. Our results showed that the two examined mangrove forests differed significantly in the physicochemical properties of the soils, especially regarding organic carbon, phosphorus and metal content, as well as in their microbial communities, which was likely caused by anthropogenic pollution. The physicochemical differences between the soils explained 76% of the differential bacterial composition, and 64% depended solely on gradients of phosphorus, metal ions and potassium. We found two genera JL-ETNP-Z39 and TA06 exclusively in polluted and non-polluted mangroves, respectively. Additionally, the polluted mangrove was enriched in Gemmatimonadetes, Cyanobacteria, Chloroflexi, Firmicutes, Acidobacteria, and Nitrospirae. A total of 77 genera were affected by anthropic contamination, of which we propose 33 as bioindicators; 26 enriched, and 7 depleted upon pollution.