Journal of Environmental Sciences-china最新文献

Benzo[a]pyrene (B[a]P) is a carcinogenic environmental pollutant widely present in the environment and can enter the human body through the food chain. It is therefore essential to treat and remediate the B[a]P-contaminated environment. Microbial remediation of B[a]P-contaminated environments is considered to be one of the most effective strategies, and the addition of biostimulants is a feasible method to further improve the effectiveness of microbial remediation. In this study, we used Bacillus subtilis MSC4 to screen for the stimulation of sodium gluconate, which promoted B[a]P degradation. Based on biochemical and transcriptomic analyses, Sodium gluconate was found to significantly increase the biomass of MSC4 and the expression of most genes involved in B[a]P degradation. Activities of central carbon metabolism, fatty acid β-oxidation and oxidative phosphorylation were all promoted. The significant increase in acid-induced oxalate decarboxylase expression indicates a decrease in intracellular pH, which promoted the synthesis of acetoin and lactate. Genes involved in the nitrogen cycle, especially nitrification and denitrification, were significantly up-regulated, contributing to B[a]P degradation. Genes involved in the synthesis of enzyme cofactors, including thiamine, molybdenum cofactors, NAD and heme, were up-regulated, which contributes to increasing enzyme activity in metabolic pathways. Up-regulation of genes in flagella assembly, chemotaxis, and lipopeptide synthesis is beneficial for the dissolution and uptake of B[a]P. Genes related to the sugar transport system were upregulated, which facilitates the transport and absorption of monosaccharides and oligosaccharides by MSC4. This study provides a theoretical basis for the further application of sodium gluconate in the treatment of PAH-contaminated sites.

As an energy and carbon saving process for nitrogen removal from wastewater, the partial nitrification and denitrification process (PN/D) has been extensively researched. However, achieving stable PN in municipal wastewater has always been challenging. In this study, a gel immobilized PN/D nitrogen removal process (GI-PN/D) was established. A 94d pilot-scale experiment was conducted using real municipal wastewater with an ammonia concentration of 43.5 ± 5.3 mg N/L at a temperature range of 11.3–28.7℃. The nitrogen removal performance and associated pathways, shifts in the microbial community as well as sludge yield were investigated. The results were as follows: the effluent TN and COD were 0.6 ± 0.4 mg/L and 31.1 ± 3.8 mg/L respectively, and the NAR exceeding 95 %. GI-PN/D achieved deep nitrogen removal of municipal wastewater through stable PN without taking any other measures. The primary pathways for nitrogen removal were identified as denitrification, simultaneous nitrification-denitrification, and aerobic denitrification. High-throughput sequencing analysis revealed that the immobilized fillers facilitated the autonomous enrichment of functional bacteria in each reactor, effectively promoting the dominance and stability of the microbial communities. In addition, GI-PN/D had the characteristic of low sludge yield, with an average sludge yield of 0.029 kg SS/kg COD. This study provides an effective technical for nitrogen removal from municipal wastewater through PN.

Global warming caused by the emission of CO₂ in industrial flue gas has attracted more and more attention. Therefore, to fix CO₂ with high efficiency and environmentally friendly had become the hot research field. Compared with the traditional coal-fired power plant flue gas emission reduction technology, carbon fixation and emission reduction by microalgae is considered as a promising technology due to the advantages of simple process equipment, convenient operation and environmental protection. When the flue gas is treated by microalgae carbon fixation and emission reduction technology, microalgae cells can fix CO₂ in the flue gas through photosynthesis, and simultaneously absorb NO_x and SO_x as nitrogen and sulfur sources required for growth. Meanwhile, they can also absorb mercury, selenium, arsenic, cadmium, lead and other heavy metal ions in the flue gas to obtain microalgae biomass. The obtained microalgae biomass can be further transformed into high value-added products, which has broad development prospects. This paper reviews the mechanisms and pathways of CO₂ sequestration, the mechanism and impacts of microalgal emission reduction of flue gas pollutants, and the applications of carbon sequestration in industrial flue gas by microalgae. Finally, this paper provides some guidelines and prospects for the research and application of green emission reduction technology for industrial flue gas.

Generally speaking, the precursors of ozone (O₃), nitrogen oxides and volatile organic compounds are very low in desert areas due to the lack of anthropogenic emissions and natural emissions, and thus O₃ concentrations are relatively low. However, high summer background concentrations of about 100 µg/m³ or 60 ppb were found in the Alxa Desert in the highland of northwest China based on continuous summer observations from 2019 to 2021, which was higher than the most of natural background areas or clean areas in world for summer O₃ background concentrations. The high O₃ background concentrations were related to surface features and altitude. Heavy-intensity anthropogenic activity areas in desert areas can cause increased O₃ concentrations or pollution, but also generated O₃ depleting substances such as nitrous oxide, which eventually reduced the regional O₃ baseline values. Nitrogen dioxide (NO₂) also had a dual effect on O₃ generation, showing promotion at low concentrations and inhibition at high concentrations. In addition, sand-dust weather reduced O₃ clearly, but O₃ eventually stabilized around the background concentration values and did not vary with sand-dust particulate matter.

Majority of carbon emissions originate from fossil energy consumption, thus necessitating calculation and monitoring of carbon emissions from energy consumption. In this study, we utilized energy consumption data from Sichuan Province and Chongqing Municipality for the years 2000 to 2019 to estimate their statistical carbon emissions. We then employed nighttime light data to downscale and infer the spatial distribution of carbon emissions at the county level within the Chengdu-Chongqing urban agglomeration. Furthermore, we analyzed the spatial pattern of carbon emissions at the county level using the coefficient of variation and spatial autocorrelation, and we used the Geographically and Temporally Weighted Regression (GTWR) model to analyze the influencing factors of carbon emissions at this scale. The results of this study are as follows: (1) from 2000 to 2019, the overall carbon emissions in the Chengdu-Chongqing urban agglomeration showed an increasing trend followed by a decrease, with an average annual growth rate of 4.24%. However, in recent years, it has stabilized, and 2012 was the peak year for carbon emissions in the Chengdu-Chongqing urban agglomeration; (2) carbon emissions exhibited significant spatial clustering, with high-high clustering observed in the core urban areas of Chengdu and Chongqing and low-low clustering in the southern counties of the Chengdu-Chongqing urban agglomeration; (3) factors such as GDP, population (Pop), urbanization rate (Ur), and industrialization structure (Ic) all showed a significant influence on carbon emissions; (4) the spatial heterogeneity of each influencing factor was evident.

The Northeast Plain in China ranks among the top five regions that have been significantly impacted by haze pollution. To effectively control pollution, it is crucial to accurately assess the effects of emission reduction measures. In this study, we analyzed surveillance data and found substantial decreases (ranging from 19.0% to 50.1%) in average annual mass concentrations of key pollutants (such as CO, SO₂, NO₂, and PM_2.5) in the Northeast Plain from 2016 to 2020. To precisely determine the contributions of meteorological conditions and emission reductions to the improvement of air quality in the Northeast Plain, we conducted three scenario simulations. By comparing source emissions in December 2016 and 2020 using the WRF-Chem model (except for SO₂), we observed significant reductions of 21.3%, 8.8%, and 9.8% in mass concentrations of PM_2.5, NO₂, and CO, respectively, from 2016 to 2020. This highlights the essential role that meteorological conditions play in determining air quality in the Northeast Plain. Moreover, further reducing source emissions by 30% in December 2016 resulted in subsequent reductions of 25.3%, 29.0%, 4.5%, and 30.3% in mass concentrations of PM_2.5, SO₂, NO₂, and CO, respectively, under the same meteorological conditions. Notably, source emission reduction was effective for PM_2.5, SO₂, and CO, but not for NO₂. The improvement in air quality in the Northeast Plain from 2016 to 2020 can be attributed to the combined effects of improved meteorological conditions and reduced pollution sources.

As important precursors of ozone (O₃) and secondary organic aerosol (SOA), reactive aromatic hydrocarbons (AHs) have typically been classified as anthropogenic air pollutants. However, biogenic emission can also be a potential source of atmospheric AHs. Herein, field observations in a eutrophic lake were combined with laboratory incubation experiments to investigate the biogenic AH emission. Field work showed that the water-air fluxes of AHs measured at sites with high cyanobacteria abundance could reach an order of magnitude greater than those at sites with low cyanobacteria abundance, suggesting that cyanobacteria could be the important contributor to measured AHs. Laboratory incubation experiments further confirmed the AH emission of cyanobacteria and revealed that the emission could change significantly over the lifespan of cyanobacteria and varied to their growing conditions. By combining field observations and laboratory incubation experiments, it has been suggested that the emission of different AH species from cyanobacteria could be modulated by variable biogeochemical mechanisms and that the biochemical process of toluene could be different from that of other AHs. This study investigates AH emissions from inland aquatic ecosystem and suggests that biogenic emission could be a potential source of atmospheric AHs.

During the initial impoundment period of a canyon-shaped reservoir, the water body fluctuated violently regarding water level, hydrological condition, and thermal stratification. These variations may alter the structure of phytoplankton community, resulting in algal blooms and seriously threatening the ecological security of the reservoir. It is of great significance to understand the continuous changes of phytoplankton in the initial impoundment period for the protection of reservoir water quality. Therefore, a two-year in-situ monitoring study was conducted on water quality and phytoplankton in a representative canyon-shaped reservoir named Sanhekou and the interannual changes of phytoplankton community and its response to environmental changes during the initial impoundment period were discussed at taxonomic versus functional classification levels. The results showed that the total nitrogen and permanganate index levels were relatively high in the first year due to rapid water storage and heavy rainfall input, and the more stable hydrological conditions in the second year promoted the increase of algae density and the transformation of community, and the proportion of cyanobacteria increased significantly. The succession order of phytoplankton in the first year of the initial impoundment period was Chlorophyta-Bacillariophyta-Chlorophyta, or J/F/X1-P/MP/W1-A/X1/MP, respectively. And the succession order in the second year was Cyanobacteria/Chlorophyta-Bacillariophyta-Chlorophyta, or L_M/G/P-P/A/X1-X1/J/G. Water temperature, relative water column stability, mixing depth, and pH were crucial factors affecting phytoplankton community succession. This study revealed the interannual succession law and driving factors of phytoplankton in the initial impoundment period and provided an important reference for the operation management and ecological protection of canyon-shaped reservoirs.

In the context of the prevalent winter air quality issues in China marked by declining PM_2.5 and rising O₃, this study employed a modified WRF-Chem model to examine the aerosol radiation interaction (ARI), heterogeneous chemistry (AHC), and their combined impact (ALL) on the variations in O₃ and PM_2.5 during the 2014–2020 in eastern China. Our analysis confirmed that ARI curtailed O₃ while elevating PM_2.5. AHC reduced O₃ through heterogeneous absorption of NO_x and hydroxides while notably fostering fine-grained sulfate, resulting in a PM_2.5 increase. Emission reductions mitigated the inhibitory impact of ARI on meteorological fields and photolysis rates. Emission reduction individually without aerosol feedback led to a 5.43 ppb O₃ increase and a 22.89 µg/m³ PM_2.5 decrease. ARI and AHC amplified the emission-reduction-induced (ERI) O₃ rise by 1.83 and 0.31 ppb, respectively. The response of ARI to emission diminution brought about a modest PM_2.5 increase of 0.31 µg/m³. Conversely, AHC, acting as the primary contributor, caused a noteworthy PM_2.5 decrease of 4.60 µg/m³. As efforts concentrate on reducing PM_2.5, the promotion of ARI on PM_2.5 counterbalanced the efficacy of emission reduction and the AHC-induced strengthening of PM_2.5 decrease. The ALL magnified the ERI O₃ increase by 38.9% and PM_2.5 decrease by 18.7%. Sensitivity experiments with different degrees of emission reduction demonstrated a consistent linear relationship between the ALL-induced enhancement of O₃ increase and PM_2.5 decrease to the ERI PM_2.5 decline. Our investigation revealed the complex connection between emissions and aerosol feedback in influencing air quality.

By encapsulating nanoscale particles of goethite (α-FeO(OH)), hydrous ceric oxide (CeO₂·H₂O, HCO) and silver nanoparticles (AgNPs) in the pores of polystyrene anion exchanger D201, a novel nanocomposite FeO(OH)-HCO-Ag-D201 was prepared for the effective removal of arsenic from water. The isotherm study shows that FeO(OH)-HCO-Ag-D201 has excellent adsorption performance for As(III) and As(V), with an increased adsorption capacity of As(III) to 40.12 mg/g compared to that of 22.03 mg/g by the composite adsorbent without AgNPs (FeO(OH)-HCO-D201). The adsorption kinetics data showed that the sorption rate of FeO(OH)-HCO-Ag-D201 for As(III) is less than that for As(V), and the adsorption of As(III) and As(V) were consistent with the pseudo-second-order model and the pseudo-first-order model, respectively. Neutral or basic conditions are favored for the adsorption of As(III/V) by FeO(OH)-HCO-Ag-D201. Compared with nitrate/chloride/bicarbonate, sulfate/silicate/phosphate showed more remarkable inhibition of arsenic removal by FeO(OH)-HCO-Ag-D201, whereas natural organic matter showed no interference to the arsenic removal. The As(V) adsorption involved different interactions such as electrostatic attraction and surface complexation, while the adsorption of As(III) involved the part oxidization of As(III) to As(V) and the simultaneous adsorption of As(III) and As(V). In addition to the Ce(IV) in CeO₂·H₂O acted as an oxidant, the synergistic effect of α-FeO(OH) and AgNPs also contributed to the oxidization of As(III) to As(V). Moreover, the reusable property suggested that this FeO(OH)-HCO-Ag-D201 nanocomposite has great potential for arsenic-contaminated water purification.