Rice growing in flooded paddy soil often accumulates considerable levels of inorganic and organic arsenic (As) species, which may cause toxicity to plants and/or pose a risk to human health. The bioavailability and toxicity of As in soil depends on its chemical species, which undergo multiple transformations driven primarily by soil microbes. However, the role of endophytes inside rice roots in As species transformation remains largely unknown. We quantified the abundances of microbial functional genes involved in As transformation in the endosphere and rhizosphere of rice roots growing in three paddy soils in a pot experiment. We also isolated 46 different bacterial endophytes and tested their abilities to transform various As species. The absolute abundances of the arsenate reductase gene arsC and the dissimilatory arsenate reductase gene arrA in the endosphere were comparable to those in the rhizosphere, whereas the absolute abundances of the arsenite methylation gene arsM and arsenite oxidation gene aioA in the endosphere were lower. After normalization based on the bacterial 16S rRNA gene, all four As transformation genes showed higher relative abundances in the endosphere than in the rhizosphere. Consistent with the functional gene data, all of the 30 aerobic endophytic isolates were able to reduce arsenate, but only 3 strains could oxidize arsenite. Among the 16 anaerobic endophytic isolates, 4 strains belonging to Desulfovibrio, Terrisporobacter or Clostridium could methylate arsenite and/or methylarsenite. Six strains of aerobic endophytes could demethylate methylarsenite, among which three strains also could reduce and demethylate methylarsenate. None of the isolates could demethylate dimethylarsenate. These results suggest that diverse endophytes living inside rice roots could participate in As species transformation and affect As accumulation and species distribution in rice plants.

In this study, an interval two-stage fuzzy fractional programming (TFFP) method is developed to facilitate collaborative governance of economy and water resources. Methods of interval programming, fuzzy programming, two-stage programming, and fractional programming are integrated within a general system optimization framework. The main contribution of TFFP is simultaneously addressing various uncertainties and tackling trade-offs between environmental and economic objectives in the optimized schemes for water resources allocation. A case study of a highly urbanized coastal city (i.e., Shenzhen) in China is provided as an example for demonstrating the proposed approach. According to the results, industrial sectors should receive 34.8% of total water supply, while agricultural sectors should receive 1.5%. For the spatial allocation of water resources, Bao An, Long Gang, and Fu Tian districts should be allocated 21.6%, 20.5%, and 14.8% water to promote the economic development. The discharge analysis indicates that chemical oxygen demand (CODcᵣ) and total phosphorus (TP) would be key pollutants. Moreover, the optimized seawater desalination volume would be negligibly influenced by price, while the upper bounds of desalination would be increased with the raising acceptable credibility levels in the period of 2031–2035. Analysis of desalination prices also reveals that the decision-makers should increase the scale of desalination in the period of 2021–2025. In addition, the effectiveness and applicability of TFFP would be evaluated under economic maximization scenarios. The result showed that the economic maximization scenario could obtain higher economic benefits, but it would be accompanied by a larger number of pollutant discharges. It is expected that this study will provide solid bases for planning water resources management systems in coastal regions.

Sediment denitrification plays an important role in nitrogen removal in aquatic systems. However, the importance in nitrogen removal in reservoirs, with a focus on seasonal differences of conditions such as macrophyte beds and environmental factors, is less well understood. This study examined sediment denitrification rate (Dₙ), and their potential controlling factors were determined in both macrophyte beds and deeper waters in the subtropical reservoir. The mean Dₙ in the reservoir annually was 18.0 ± 6.3 (mean ± S.E.) mmol N m⁻² d⁻¹, with significant seasonal variation (p < 0.01), i.e. 43.2 ± 12.8, 6.7 ± 6.3, and 4.0 ± 2.2 mmol N m⁻² d⁻¹ in winter, spring and summer respectively. There were no statistical differences in Dₙ between shallow waters with macrophyte beds and deeper waters without macrophyte beds, although macrophyte beds had higher denitrification rates in summer. The Dₙ rates were significantly correlated with temperature, conductivity, dissolved oxygen, pH, nitrate-nitrogen concentration (NO₃⁻-N) (p < 0.01) and turbidity (p < 0.05). Linear regression models demonstrated environmental variables explained between 36% and 76% of the variation in Dₙ. The correlation with NO₃⁻-N concentrations suggests that it may be a limited factor for Dₙ. Annual nitrogen removal of the reservoir by a combination of sediment and water denitrification was totally estimated to be 370 t N with an annual removal efficiency of approximately 11%. Nitrogen removal was much higher in winter than other seasons, with about 305 t N removed, accounting for 12% of the total nitrogen inputs. Therefore, denitrification appears to play a minor role throughout much of the year, but in winter months when nitrate accumulates, it may play a more major role.

Bacterial communities in antimony (Sb) polluted soils have been well addressed, whereas the important players fungal communities are far less studied to date. Here, we report different responses of bacterial and fungal communities to Sb contamination and the ecological processes controlling their community assembly. Soil samples in the Xikuangshan mining area were collected and subjected to high through-put sequencing of 16S rRNA and ITS1 to investigate bacterial and fungal communities, respectively, along an Sb gradient. Sb speciation in the soil samples and other physicochemical parameters were analyzed as well. Bacterial communities were dominated by Deltaproteobacteria in the soil with highest Sb concentration, whereas Chloroflexi were dominant in the soil with lowest Sb concentration. Fungal communities in high-Sb soils were predominated by unclassified Fungi, whilst Leotiomycetes were dominant in low-Sb soil samples. Multivariate analysis indicated that Sb, pH and soil texture were the main drivers to strongly impact microbial communities. We further identified Sb-resistant microbial groups via correlation analysis. In total, 18 bacterial amplicon sequence variants (ASVs) were found to potentially involve in biogeochemical cycles such as Sb oxidation, sulfur oxidation or nitrate reduction, whereas 12 fungal ASVs were singled out for potential heavy metal resistance and plant growth promotion. Community assembly analysis revealed that variable selection contributed 100% to bacterial community assembly under acidic or high Sb concentration conditions, whereas homogeneous selection dominated fungal community assembly with a contribution over 78.9%. The community assembly of Sb-resistant microorganisms was mainly controlled by stochastic process. The results offer new insights into microbial ecology in Sb-contaminated soils, especially on the different responses of microbial communities under identical environmental stress and the different ecological processes underlining bacterial and fungal community assembly.

We quantify for the first time marine aerosol properties and their differences in the offshore and remote ocean in the mid-latitude South Asian waters, low-latitude South Asian waters, and equatorial waters of the Western Pacific Ocean, based on shipboard cruise observations conducted by the Western Pacific Ocean Scientific Observation Network in winter 2018, and further investigate the effects of long-range transport of continental aerosols on the marine environment. During the overall observation period, the average number concentration of particle matter which aerodynamic diameters<2.5 μm (PM₂.₅N) was 35.1 ± 87.4 cm⁻³ and the mass concentration (PM₂.₅M) was 12.3 ± 9.1 μg/m³. The PM₂.₅N and PM₂.₅M during the continental air mass transport period were 7.2 and 1.3 times higher than those during the non-transport period (109.2 ± 169.3 cm⁻³, 15.9 ± 14.9 μg/m³), respectively. Excluding transport period, the average PM₂.₅N and PM₂.₅M are reduced by 120% and 7%. Coarse mode particle number concentration (PM₂.₅–₁₀N) and mass concentration (PM₂.₅–₁₀M) are not significantly influenced by continental air masses (only a reduction of 7% and 2%). The variation of marine aerosol concentrations in different latitudes zones is greatly influenced by continental aerosol transport. The offshore PM₂.₅M/PM₁₀M was 30%, 21%, and 22% in the mid-latitude sea of South Asia, a low-latitude sea of South Asia, and the equatorial sea, respectively. In comparison, in the remote ocean, the distribution ratio of PM₂.₅M/PM₁₀M tended to be steady (22%–23%), and the background characteristics of marine aerosols were clearly represented. The aerosol concentration decreases with the increase of wind speed during the transport period, and the wind speed reflects the scavenging effect on aerosol. In the non-transport period, the wind speed at the sea surface promotes the generation of marine aerosols, and the impact in wind speed is strongest in the PM₂.₅–PM₅ particle size range.

Plastic additives (PAs) are chemical compounds incorporated into the plastic during the manufacturing process. Phthalate acid esters, bisphenols, and nonylphenols are all PAs found in marine environments and associated with endocrine-disrupting processes. However, our knowledge regarding the impact of endocrine-disrupting PAs on coral-reef organisms is limited. As reef population structure is directly linked to reproduction and larval settlement processes, interference with hormonal systems can impact coral-reef community structure, particularly if the effects of PAs differ among species. In the current study we exposed the reproductive products of four tropical coral-reef invertebrates to environmentally-relevant concentrations of four prevalent PAs in seawater: dibutyl phthalate (DBP), dimethyl phthalate, (DMP), 4-nonylphenol (4-NP), and bisphenol A (BPA), as well as to 10³ higher laboratory concentrations of these PAs. Our results revealed that apart from the significant negative effect of the 1 μg/L of 4-NP on the settlement of the soft coral Rhytisma fulvum, none of the other tested materials demonstrated a significant effect on the exposed organisms at environmentally-relevant concentrations in seawater. The 4-NP high laboratory concentration (1000 μg/L), however, had significant negative effects on all the examined species. The high laboratory BPA concentration (1000 μg/L) significantly reduced fertilization success in the solitary ascidian Herdmania momus, up to its complete failure to reproduce. Moreover, the high laboratory DMP concentration (100 μg/L) had a significant negative effect on planulae settlement of the stony coral Stylophora pistillata. Our findings demonstrate the negative and selective effects of PAs on the development and reproduction of coral-reef organisms; and, specifically, the significant effect found following exposure to 4-NP. Consequently, if we aim to fully understand the impact of these contaminants on this endangered ecosystem, we suggest that the actual concentrations within the living organism tissues should be tested in order to produce relevant risk assessments for brooding-coral species.

Contamination of microcystins (MCs) in plant-soil system have become a serious problem worldwide, however, it remains largely unknown how to alleviate the potential risk of consuming MCs-contaminated plants. In the present study, attapulgite, biochar and peat were used as soil amendments to reduce MCs bioaccumulation in lettuce. Lettuce irrigated with 10 μg L⁻¹ microcystin-LR (MC-LR) were growing in two different kinds of soils with or without soil amendments. Results showed that all soil amendments effectively reduced MC-LR bioaccumulation in lettuce roots and leaves. Compared with the control treatment, the MC-LR concentrations in leaves in treatments with attapulgite, biochar and peat decreased by 41.5%, 30.6%, 57.0% in soil A and 38.9%, 43.2%, 54.7% in soil B, respectively. Peat application was most effective in reducing MC-LR bioaccumulation. The decreased soil free MC-LR concentrations were positively correlated with MC-LR concentrations in lettuce, indicating decreased bioavailability of MC-LR by soil amendments. It is noteworthy that soil total MC-LR concentration in peat treatment significantly decreased by 33.3% and 29.4% in soil A and soil B, respectively, compared with the controls. According to the results from high-throughput sequencing, peat amendment increased the α-diversity of soil bacterial community and boosted the abundance of Sphingomonas and Methylobacillus (dozens of MC-degrading bacteria belong to these genera). This was in line with the results of soil total MC-LR concentration. It can be speculated that peat application directly and/or indirectly promoted microbial degradation of MC-LR in soils. This work proposed an effective way to alleviate the potential risks of MCs contamination in plant-soil system.

Microplastics are omnipresent in the terrestrial and aquatic environment, and are considered as a potentially serious threat to the biodiversity and ecosystem. Pollution of plastic debris and microplastics in the inland and marine environment has raised concerns in Bangladesh, which is one of the most densely populated countries in the world. This review summarizes the research progress on separation and characterization of microplastics, as well as their occurrence and sources in Bangladesh. Despite of the first total ban on plastic bags in the world introduced back in 2002, microplastics have been ubiquitously detected in the country's inland and marine environment, with the majority of them coming from secondary sources. The microplastics observed in Bangladesh were dominated by fibers, which were derived mainly from textile sources. Polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polyvinylchloride (PVC) were the most abundant polymers found for microplastics in the marine and freshwater environment of Bangladesh. Along with the identified research priorities to improve the understanding on the ecotoxicological effect and fate of microplastics, extensive and in-depth studies are required to bridge the knowledge gaps to enable comprehensive risk assessment of microplastic pollution on local ecosystems and human health, while effective management of plastic wastes and their recycling are necessary to alleviate this problem in the country.

In this study, the feasibility of using zero-valent iron (ZVI) and Fe₃O₄-loaded biochar for Pb immobilization in contaminated sandy soil was investigated. A 180-day incubation study, combined with dry magnetic separation, chemical extraction, mineralogical characterization, and model plant (ryegrass, namely the Lilium perenne L.) growth experiment was conducted to verify the performance of these two materials. The results showed that both amendments significantly transferred the available Pb (the exchangeable and carbonates fraction) into more stable fractions (mainly Fe/Mn oxides-bound Pb), and ZVI alone showed a better performance than the magnetic biochar alone. The magnetic separation and extended X-ray absorption fine structure (EXAFS) analysis proved that Fe (oxyhydr)oxides on aged ZVI particles were the major scavengers of Pb in ZVI-amended soils. In comparison, the reduced Pb availability in magnetic biochar-amended soil could be explained by the association of Pb with Fe/Mn (oxyhydr)oxides in aged magnetic biochar, also the possible precipitation of soil Pb with soluble anions (e.g. OH⁻, PO₄³⁻, and SO₄²⁻) released from magnetic biochar. ZVI increased ryegrass production while Fe₃O₄-loaded biochar had a negative effect on the ryegrass growth. Moreover, both markedly decreased the Pb accumulation in aboveground and root tissues. The simple dry magnetic separation presents opportunities for the removal of Pb from soils, even though the efficiencies were not high (17.5% and 12.9% of total Pb from ZVI and biochar-treated soils, respectively). However, it should be noted that the ageing process easily result in the loss of magnetism of ZVI while the magnetic biochar tends to be more stable and has high retrievability during the dry magnetic separation application.

Microbial degradation of polycyclic aromatic hydrocarbons (PAHs) is the major channel for their decontamination from different environments. Aerobic and anaerobic biodegradations of PAHs in batch reactors with single or multiple bacterial strains have been intensively studied, but the cooperative mechanism of functional PAH-degrading populations at the community level under field conditions remains to be explored. We determined the composition of PAH-degrading populations in the bacterial community and PAHs in farmland and wasteland soils contaminated by coking plants using high-throughput sequencing and high-performance liquid chromatography (HPLC), respectively. The results indicated that the PAH content of farmland was significantly lower than that of wasteland, which was attributed to the lower content of low molecular weight (LMW) PAHs and benzo [k]fluoranthene. The soil physicochemical properties were significantly different between farmland and wasteland. The naphthalene content was related to the soil organic carbon (SOC) and pH, while phenanthrene was related to the nitrate nitrogen (NO₃⁻-N) and water content (WC). The pH, nitrite (NO₂⁻-N), SOC, NO₃⁻-N and WC were correlated with the content of high molecular weight (HMW) PAHs and total PAHs. The relative abundances of the phyla Actinobacteria, Chloroflexi, Acidobacteria, and Firmicutes and the genera Nocardioides, Bacillus, Lysobacter, Mycobacterium, Streptomyces, and Steroidobacter in farmland soil were higher than those in wasteland soil. The soil physicochemical characteristics of farmland increased the diversities of the PAH degrader and total bacterial communities, which were significantly negatively related to the total PAHs and LMW PAHs. Subsequently, the connectivity and complexity of the network in farmland were lower than those in wasteland, while the module containing a module hub capable of degrading PAHs was identified in the network of farmland soil. Structural equation modelling (SEM) analysis showed that the soil characteristics and optimized abundance and diversity of the bacterial community in farmland were beneficial for the dissipation efficiency of PAHs.