The present study was aimed to quantitatively estimate the odor emission of municipal solid waste landfills in the loess area of Northwest China and investigate the technical feasibility of using loess soil as covering material for odor pollution control. For this purpose, the study was conducted in field and chose four types of landfill surface sources representing different periods and different coverage states in this region. The surface odor release rates were determined as follows: 5915µg/(m²·h) for newly formed landfill surface without cover, 122µg/(m²·h) for newly formed landfill surface with loess cover 757µg/(m²·h) for loess-covered surface after 5months, and 14057µg/(m²·h) for re-exposed landfill surface. The results indicated that the loess cover reduced odor emissions by more than 94% at two periods and effectively controlled various odor compounds. The analysis on the loess microbial community structure after 5 months of coverage showed that Actinobacteria had the highest relative abundance, potentially participated in the degradation of volatile organic compounds, and had a stronger effect on the surface. The experimental results demonstrated the effectiveness of loess cover in controlling odor emissions, proving that the application of loess as a landfill cover layer is feasible in the northwest region.

Halogenated organic compounds (HOPs), as important industrial chemicals, are extensively released into the environment during their production, transportation, and usage, ultimately accumulating in waste activated sludge (WAS) from wastewater treatment plants. Anaerobic digestion is a crucial approach for resource recovery from WAS, converting organic matter into valuable products such as volatile fatty acids and methane. However, the effects of HOPs on the anaerobic digestion capacity of WAS and their underlying mechanisms have not been systematically elucidated. Through a comprehensive literature review, this study analyzed the impacts of HOPs on methane production efficiency, key processes, and microbial communities during sludge anaerobic digestion. The results revealed that most HOPs inhibit key stages of anaerobic digestion due to their high toxicity, leading to reduced methane yield, while some low-toxicity HOPs exhibit a "hormesis effect" with promotion at low concentrations and inhibition at high concentrations. HOPs primarily regulate anaerobic digestion efficiency by affecting four critical stages: solubilization, hydrolysis, acidogenesis, and methanogenesis, with the most significant impacts on acidogenesis and methanogenesis. HOPs can influence the function of anaerobic microorganisms by altering microbial community structure, inhibiting key enzyme activities, and interfering with metabolic pathways. This study unveils the mechanisms of HOPs’ effects on sludge anaerobic digestion and proposes future research directions addressing current knowledge gaps, providing a theoretical foundation for resource recovery and safe disposal of WAS.

Based on data from 45 soil cores, 35 lake sediment cores, and 32 sea sediment cores in China, this study found a type of ^239+240Pu peakless distribution cores in soil, lakes, and marine environments, and discussed their causes of ^239+240Pu peakless distribution. The results show that there were two main types of peakless distribution of ^239+240Pu in soil core samples: one that the ^239+240Pu specific activity increased with depth, and the other that the ^239+240Pu specific activity decreased with depth; when using a Convection Dispersion Equation (CDE) model to simulate the migration behavior of ^239+240Pu in soil cores, the apparent convection rate showed a positive correlation with the ^239+240Pu maximum depth (n=45, R²=0.847). There was only one type of peakless distribution of ^239+240Pu in lake and ocean core samples: the ^239+240Pu specific activity decreased with depth. Meanwhile, the sedimentation rate of lake core samples (n=35, R²=0.921) or the maximum apparent convection rate of marine core samples (n=32,R²=0.949) also showed a positive correlation with the ^239+240Pu maximum depth. The maximum apparent convection rate of the exchangeable ^239+240Pu in the peakless distribution core sample was close to the sedimentation rate, and the maximum apparent convection rate didn’t affect the vertical distribution of ^239+240Pu in the core sample.

This study was aimed to rapidly remediate the cracked contaminant containment and carrying structure (3C structure) and carrying structure by composite contaminant containment and carrying structure (4C structure) in operating plant. To assess the effectiveness of the 4C structure, both field and laboratory tests were performed. Field tests included elevation monitoring, rebound modulus testing, and volatile organic compounds (VOCs) concentration detection, while laboratory tests focused on determining the compressive strength and permeability coefficient of the core samples. The results indicated that the injected polymers exert a compressive force on the surface layer of 4C structure, which reduces the elevation variance by 71.4%, thereby markedly enhancing its flatness. Additionally, regarding the 14 filed test points on the surface layer with an average crack width of 7.5mm, the rebound modulus (E) values at 42.9% of these test points achieved over 80% of E value measured within the uncracked control area. The axial compressive strength of core samples from these points increased by 0.38 times, and the penetration resistance of the base soil layer increased by 21.3%. These results suggested a significant improvement in the load-carrying performance of 4C structure compared with the cracked 3C structure. Furthermore, the permeability coefficient of the core samples was reduced by approximately 2orders of magnitude, and the VOCs concentration in the sampling holes decreased by 80%. This demonstrated the contaminant containment performance of 4C structure was also significantly improved. This research provided an innovative method to assess and improve the service performance of cracked contaminant containment and carrying structure in operating plant.

Electroplating is one of the most significant sources of perfluorinated and polyfluoroalkyl substances (PFASs) in the environment. In this study, the occurrence of PFASs in soil of a relocated electroplating plant was analyzed. The probabilistic health risk was evaluated using Monte Carlo simulation, and the soil screening levels of PFASs were suggested. The soil samples were detected with 8PFASs, and perfluorooctane sulfonate (PFOS) was detected with the highest detection frequency of 89% and concentration of 388ng/g among the targeted PFASs. The distribution of PFASs in soil was impacted by the locations of production units. The total concentration and concentrations of single PFAS such as PFOS, perfluorohexane sulfonate (PFHxS) were significantly higher in soil at chromium plating department (P<0.05). Intake through human oral exposure of soil PFASs accounted for 75.2%~77.6%. Carcinogenic risk of perfluorooctanoic acid (PFOA) was 6.22×10^-11, showing no carcinogenic risk in soil. Non carcinogenic risk quotient of PFOS was larger than 1based on the deterministic values of the exposure factors, while other PFASs showed no non carcinogenic risk. Monte Carlo simulation showed that the risk quotient of PFOS ranged from 0.731 to 5.38, with 95% quantile being 3.85. The 95% quantile values of risk quotient of other PFASs were between 8.77×10^-6 and 0.0137. The soil screening levels of targeted PFASs ranged from 78 to 38826ng/g, and PFOS was found to have the most strict level of 78ng/g.

To deeply understand the nitrogen cycling process in alpine forest small watersheds in the northeast of the Tibetan Plateau, the throughfall, soil water and surface runoff at two alpine forest sites in Datong and Huangyuan in the Hehuang Valley in the Tibetan Plateau were studied from April to September 2022. The concentration and flux of dissolved inorganic nitrogen (DIN) were monitored, and the distribution characteristics of nitrogen and oxygen (N and O) isotopes of nitrate (NO₃⁻) along the hydrological path (from throughfall to soil water and then to surface runoff) was analyzed via stable isotope technology. The results showed that the average nitrogen deposition in Datong and Huangyuan (3.60kg/(hm²·a)) was higher than that in the Tibetan Plateau (2.94kg/(hm²·a)), and the nitrogen deposition in Huangyuan (4.17kg/(hm²·a)) was higher than that in Datong (3.02kg/(hm²·a)). The average concentration of NO₃⁻ in soil water at the two alpine forest small watersheds was 5.78mg/L. The average δ¹⁸O-NO₃⁻ ((−1.54±9.77)‰) in soil water was lower than that in throughfall ((74.2±0.01)‰), indicating that nitrification occurred in alpine forest soil. Over 90% of the NO₃⁻ in soil water was from soil nitrification using the end member model analysis, and the remaining approximately 10% might be came from atmospheric deposition. The average concentration of NO₃⁻ in surface runoff at the two alpine forest small watersheds was 5.73mg/L. The δ¹⁸O-NO₃⁻ and δ¹⁵N-NO₃⁻ in surface runoff were enriched along the growth trend of 1:2, indicating that a denitrification process occurred in surface runoff. The δ¹⁵N-NO₃⁻ and δ¹⁸O-NO₃⁻ in the Tibetan Plateau alpine forests decreased from throughfall to soil water, and then increased from soil water to surface runoff.

This study focuses on the East Qinling molybdenum mine area, where the pollution of heavy metals in the surrounding aquatic environment and the mineralogical characteristics of the associated sediment were analyzed. Furthermore, the study examined the migration behavior of molybdenum (Mo) during the leaching process from mine tailings to its mineralization in sediment. The findings revealed that the Mo concentration in the aquatic environment significantly surpassed the environmental background levels. Specifically, the maximum exceedance of Mo in the water samples was recorded at 21600 times above the baseline. Additionally, the geoaccumulation index (Igeo) values in both sediments and tailings exceeded 5. The sediments collected from aquatic environments impacted by AMD in the East Qinling molybdenum mining area predominantly comprised schwertmannite minerals, characterized by distinctive "poly spheroid" and "hedgehog" morphologies, and a substantial amount of Mo was immobilized within the mineral structure. In mine tailings, molybdenum (Mo) predominantly exists in the oxidation state of Mo(VI), whereas in schwertmannite, both Mo(VI) and Mo(IV) are present. This indicates a significant change in the valence state of Mo during its migration from tailings to sediments. Moreover, leaching experiments demonstrated that Mo associated with schwertmannite can be re-released into the environment, the processes were significantly influenced by the mineralogical characteristics of schwertmannite. Specifically, schwertmannite with higher crystallinity was found to be more effective in immobilizing Mo.

This study focuses on the karst depression in Fenghuang Village, Zhongliang Mountain, Chongqing, using the composite fingerprinting technique. An optimal combination of fingerprint properties was selected to quantify the contributions of potential sources to the depression deposits by using multivariate linear mixed model (IsoSource) and Bayesian mixed models (MixSIAR, SIMMR, and SIAR). In addition, the applicability of these models was further assessed by using their root mean square error (RMSE) and in combination with previous reports. Results indicated that the cumulative identification accuracy of the five fingerprint properties, i.e., the total carbon (TC) content, sand content, grain size at 70% frequency (D70), soil organic carbon (SOC) content, and sulfur (S) content, reached 89.5%, and therefore these properties constituted an optimal combination. The RMSE values for the four models were: MixSIAR (2.05), SIMMR (2.05), SIAR (2.07), IsoSource (2.34). Since the RMSEs of the three Bayesian mixed models were lower than that of the IsoSource model, the applicability of the Bayesian mixed models for quantifying the contributions of sediment sources to the depression deposits was higher than that of the multivariate linear mixed model. Among the three Bayesian mixed models, the MixSIAR and SIMMR models had the highest accuracy. Results from the MixSIAR and SIMMR models indicated that arable land was the primary source of the depression deposits, followed by ditch walls, with forest and grassland contributing the least. The composite fingerprinting technique could effectively quantify the sediment sources in the small watersheds in the depression. In this study, the composite fingerprinting technique was employed to unveil the sediment source of depression deposits in a typical karst trough valley in Southwest China, aiming to provide a reference for model selection in similar studies.

The InVEST-PLUS model was coupled to calculate and analyze the spatiotemporal dynamics of four types of ecosystem services in Guizhou Province from 2000 to 2030 under different scenarios. Based on Spearman’s correlation analysis, the trade-offs/synergies between various service functions were examined, and self-organizing feature mapping networks were utilized to reveal the ecosystem service bundles. The results showed that from 2000 to 2020, the changes in land structure were mainly characterized by the continuous decrease of arable land and the fluctuating changes of forest and grassland, with a significant expansion of construction land. The natural development scenario showed the most significant increase in construction land among the three scenarios, with an increase of 25.39%, while in the ecological protection scenario, the main ecological land such as forest and grassland were protected. The water yield and soil conservation showed a fluctuating trend of first decreasing and then increasing from 2000 to 2020, while habitat quality and carbon storage showed a declining trend. The average value of carbon storage decreased from 234.05t/hm² to 231.70t/hm², and the average value of habitat quality decreased from 0.64 to 0.60. Relatively, in the ecological protection scenario, except for a slight decrease in water yield, other ecological function indicators improved, especially carbon storage and habitat quality, which reached the highest values. The trade-offs (3pairs) and synergies (3pairs) between ecosystem service functions in the study area showed a relatively balanced state. Under the ecological protection scenario, the correlation coefficients between different ecosystem services gradually increased, indicating an overall trend of environmental improvement in the region. Based on the clustering results, four types of ecosystem service bundles (ESB) were identified in Guizhou Province. From 2000 to 2030, the spatial pattern of various ecosystem service clusters in the study area remained basically stable, but there was spatial and temporal heterogeneity among different ESBs.

To understand nitrogen pollution and sources of Laizhou Bay, nitrogen sources and transformation processes in the coastal rivers entering the sea of Laizhou Bay were studied. Water quality parameters, nitrogen content, and stable isotopes were used to clarify the sources and key processes in river estuary. The results indicate strong temporal and spatial consistency between δD and δ¹⁸O of water, EC, and salinity, suggesting significant seawater mixing effects in the estuary, which was significantly weakened upstream of the river. NO₃^--N was found to be the dominant form to inorganic nitrogen in most reaches of the river during high flow and low flow seasons, ranging from 37.2% to 81.7% and 29.5% to 95.9%, respectively, except for a few sites. Furthermore, extreme values of ρ(TN) and ρ(NH₄⁺-N) values were observed at some sample sites during low flow season, which were significantly higher than those during the high flow season. Some water samples had ρ(NH₄⁺-N) values exceeding 2mg/L, resulting in an inferior Category V water quality. The long-term variation of ρ(NO₃^--N) from 2005 to 2023 showed an initial increase followed by a decrease in rivers entering Laizhou Bay. The δ¹⁵N-NO₃^- varied from +5.7‰ to +18.6‰ and from +4.5‰ to +20.0‰ during the high flow and low flow seasons, respectively, while the δ¹⁸O-NO₃^- varied from +4.2‰ to +13.8‰ and from -0.5‰ to +20.1‰, with no obvious seasonal variations. The nitrate isotope results showed that nitrification was major process affecting riverine nitrogen entering Lanzhou Bay, and that some river samples were also influenced by denitrification. During low flow season, NO₃^--N at the low salinity sampling sites was mainly sourced from manure and sewage, while most estuary sites during the high flow season were affected by the salty tide backflow, and agricultural fertilization impacted most river sections. This study provides insights into the emission characteristics of nitrogen pollution sources and spatial and temporal variability in Laizhou Bay’s coastal zone estuaries, offering valuable research demonstrations and data references for future prevention, control, and management efforts for nitrogen pollution in rivers entering the sea around the Bohai Sea.