This study was conducted in an agricultural irrigation area of reclaimed water in Suqian City. In the irrigation area, regions with long-term surface water irrigation（S1）, short-term reclaimed water irrigation（S2）, and long-term reclaimed water irrigation（S3）were selected. Undisturbed soil samples were collected from depths of 0~20cm and 20~40cm using plastic and metal rings. CT scanning and image processing technology were used to obtain the connected pores and their structural characteristics under different treatments, while the hydraulic properties of the soils were simultaneously tested. This study aimed to investigate the impact of reclaimed water irrigation on soil pore structure and hydraulic parameters and to analyze the key pore parameters that caused changes in hydraulic properties. The results showed short-term reclaimed water irrigation disrupted the soil pore structure, lending to a simplification of the pore architecture. After long-term reclaimed water irrigation, the soil pore structure improved compared to short-term irrigation, with no significantly difference observed when compared to the soil under long-term surface water irrigation. The use of reclaimed water for irrigation had no significant impact on the pore structure and hydraulic properties of both surface and subsurface soils. Reclaimed water irrigation significantly reduced soil hydraulic conductivity. Compared to the soil under long-term surface water irrigation, the hydraulic conductivity（K_S）for short-term and long-term reclaimed water irrigated soils decreased by 20.81% and 20.18%, respectively. Reclaimed water irrigation had little effect on soil water retention capacity. The changes in pore structure after reclaimed water irrigation significantly affected the soil's hydraulic properties. Redundancy analysis showed that pore parameters explained 83.30% of the variation in hydraulic properties, with surface fractal dimension having the greatest impact on hydraulic properties. Pore shape had no significant relationship with any hydraulic parameters.

Based on the monitoring data of 47 typical fine chemical in-process sites in Shanghai, the pollution of soil and groundwater in this industry was analyzed, the health risk of pollutants was evaluated, and high-priority pollutants were screened. The findings revealed that the industries with the highest pollution risk were those involved in basic chemical raw material manufacturing, pesticide manufacturing, paint and similar product manufacturing, and specialty chemical product manufacturing, collectively representing 70% of the contaminated sites. In comparison, the chemical raw material manufacturing industry exhibited a pollution risk of 54.55%, while the daily chemical products manufacturing industry showed the lowest pollution risk（0%）. The most frequently detected contaminants in the soil and groundwater included arsenic, lead, mercury, nickel, zinc and total petroleum hydrocarbons（TPH）, which were present at relatively low concentrations. In contrast, benzene derivatives（BTEXs）, polycyclic aromatic hydrocarbons（PAHs）, and most chlorinated hydrocarbons（CAHs）were detected in small areas of certain sites, indicating more severe contamination levels. Furthermore, cyanides, antimony, manganese, and tetrachloroethylene were found in larger areas of certain sites, representing the highest contamination levels. The pollution profile of the basic chemical raw material manufacturing industry was the most complex, involving cyanide, antimony, arsenic, manganese, mercury, CAHs, PAHs, and TPH. On the other hand, pesticide manufacturing, paint and similar product manufacturing, and specialty chemical product manufacturing industries were primarily contaminated by CAHs and BTEXs. A notable observation was the evident soil-water compound pollution phenomenon involving chlorinated hydrocarbons and benzenes. Through comprehensive environmental exposure and human health risk assessments, the following were identified as high-priority soil pollutants: arsenic, chloroform, 1,2-dichloroethane, benzo[a]pyrene, antimony, vanadium, trichloroethylene, lead, carbon tetrachloride, and naphthalene. For groundwater, the high-priority pollutants included trichloroethane, tetrachloroethylene, cyanide,1,2-dichloroethane, benzene, methylene chloride, nickel, antimony, manganese and trichloroethylene.

The impacts of dry-rewetting and freeze-thaw cycles on DTPA-extractable Pb（II）content and Pb speciation in soils and material structure of weathered coal-based immobilized microbial materials were investigated through a controlled simulated experiment. This study aimed to explore the mechanisms through which these two factors affect the effectiveness of lead-contaminated soil remediation using selected microbes. The results showed that after 35 dry-rewetting cycles, the DTPA-extractable Pb（II）content in low-concentration lead-contaminated soil（LS）and high-concentration lead-contaminated soil（HS）decreased by 46.41% and 29.42%, respectively, compared to the initial levels. After 35 freeze-thaw cycles, the content in LS and HS decreased by 40.06% and 32.77%, respectively. Additionally, the residual fraction of Pb in LS increased under both dry-rewetting and freeze-thaw treatments. Structural analysis revealed that the surface of weathered coal-became rougher, with increases in specific surface area, oxygen-containing functional groups, and Pb adsorption sites increased after dry-wet and freeze-thaw cycles. These changes enhanced complexation with functional groups thereby improving the stability of the passivation effect on lead contamination.

To comprehensively evaluate the reduction potential of diffuse nitrogen pollution under the field-ditch-pond system optimization, a watershed hydrological model was used to simulate the multi-scenario optimization of field ponding water level, ditch, and pond in a typical paddy field watershed. Results showed that different optimizations had different interception effects on diffuse nitrogen pollution, and that interception effects were different over distinct hydrological years. Under the optimization of field ponding water level, the total nitrogen loss from paddy fields after optimizing the drainage water level was reduced by 7.9% to 93.9% compared to conventional water level management, with the nitrogen interception effect being better in dry years than in wet years. Under ditch optimization, the reduction rate of nitrogen loss in the watershed increased from 0.8% to 26.7% after increasing the grass planting density of ditches, with the nitrogen interception effect being better in wet years than in dry years. Under pond optimization, the reduction rate of nitrogen loss in the watershed increased from 10.5% to 18.1% after increasing the catchment area of the pond, with the nitrogen interception effect being better in dry years than in wet years. Under the multi-optimization of the field-ditch-pond system, the interception effect of field ponding water level optimization on watershed nitrogen loss was better than that of pond optimization and ditch optimization. In summary, the multi-optimization of the field-ditch-pond system can effectively control the diffuse nitrogen pollution in paddy field watersheds and could promote the sustainable development of rice production.

To predict the long-term response of soil and surface water chemistry after the reduction in acid deposition, a dynamic MAGIC model combined with long-term monitoring data was conducted on a subtropical forest in Tieshanping, Chongqing, Southwest China. Under the “actual emission reduction” scenario based on China's “14th Five-Year Plan”（where the sulfur dioxide（SO₂）emissions remained at the 2020 level, and the nitrogen oxides（NO_x）and ammonia（NH₃）emissions were reduced by over 10%and 8%, respectively, by 2025）, the simulation results indicated that sulfate（SO₄²⁻）concentrations in soil water（S1and S2）and surface water（SW）initially increased, and stabilized after 2028 until 2050. The average SO₄²⁻ concentrations in S1, S2 and SW water from 2021 to 2050 were 1426, 1414, and 938µeq/L, respectively, which were still above the 1980levels. The decline of SO₄²⁻ concentrations in surface water was delayed by approximately 23 years. Soil water nitrate（NO₃⁻）concentrations showed a declining trend by 2050, but it remained above the threshold（443µeq/L）, whereas surface water NO₃⁻ concentrations had decreased below its threshold（411µeq/L）. The decline of NO₃⁻ concentrations in surface water was lagged approximately 13 years, compared to it in throughfall. Additionally, the concentrations of base cation（calcium, Ca²⁺）in both soil and surface water increased. The pH and Acid Neutralizing Capacity（ANC）in soil and surface water remained below their acidification thresholds. The acidification recovery showed a lag effect. The strong acidic anions in soil and surface water will decrease below their thresholds, pH will increase, and ANC will increase above 0µeq/L, when the stricter emission control policies were implemented, for example the SO₂ emissions decrease to 80% of 2021l evels by 2030 and 70% of 2021 levels by 2050, and the NH₃ emissions, NO_x emissions, and Ca²⁺ deposition decrease to 60% of 2021 levels by 2030 and 40% of 2021 levels by 2050. Moreover, further global temperature increases showed insignificant impact on the major strong acidic anions and acidification indicators in the highly acidic soils and surface waters of the subtropical forest.

The combination of ground remote sensing and UAV remote sensing was used to estimate the nitrogen content of typical grassland vegetation in Inner Mongolia. This experiment was carried out in the grassland ecology research base of Inner Mongolia University from August to September 2023, and the ground ASD spectral data and UAV Resonon data were collected. Based on ASD data, four spectral parameters of vegetation index, hyperspectral characteristic variable, continuum removal variable and wavelet coefficient were constructed, and LASSO was used to screen sensitive parameters. Five models of multiple linear, XGBoost, SVM, ANN and KNN were constructed to estimate the nitrogen content of vegetation. The results showed that the SVM method based on wavelet coefficients was the optimal model（validation set R²=0.72, RMSE and MAE were 0.26 and 0.18, respectively）. Finally, the model was used to estimate and map the UAV Resonon data（validation set R²=0.41, RMSE and MAE were 0.42 and 0.32, respectively）. The research showed that the combination of ASD and UAV images with machine learning algorithms could be used to realize the estimation of grassland vegetation nitrogen content, and was provided basic data and technical support for optimizing fertilization and improving forage quality.

To investigate the influence of microbial communities on arsenic speciation in lake sediments of the Hetao Basin in Inner Mongolia during the ice-bound period, the sediments from Wuliangsuhai（WLSH）were taken as the research object. Using 16SrRNA high-throughput sequencing technology, the structural characteristics of microbial communities in WLSH sediments during the ice-bound period were studied. Additionally, methods such as redundancy analysis（RDA）, correlation analysis, and co-occurrence network analysis were employed to explore the response relationship between sediment microbial communities and arsenic speciation during the ice-bound period. The results indicated that, apart from the residual arsenic, strongly adsorbed arsenic and arsenic co-precipitated with AVS（Acid-extractable sulfides in sediment）, carbonates, manganese oxides, and poorly crystalline Fe hydroxides accounted for a relatively high proportion in the sediments of WLSH during the ice-bound period. When the sedimentary environment was unstable during the ice-bound period, there was a risk of secondary release of arsenic in the sediments of WLSH. The microbial community in the WLSH sediments during the ice-bound period exhibited abundant diversity, and the richness and diversity of microbial community species showed obvious spatial distribution characteristics. There was a significant collinear relationship between microbial communities and arsenic speciation during the ice-bound period, with Thiobacillus, Bacillus, Steroidobacter, Desulfosarcinaceae, and Anaerolinea exhibiting the most pronounced effects on arsenic speciation. Furthermore, adsorbed As, As co-precipitated with AVS, carbonates, manganese oxides, and poorly crystalline Fe hydroxides, as well as As in pyrite, could mutually transform during the ice-bound period, and Thiobacillus and Steroidobacter played crucial roles in this transformation process. This study aims to explore the impact of microbial communities on arsenic speciation in sediments of WLSH during the ice-bound period, providing a microbial theoretical basis and scientific evidence for lake arsenic pollution control. It provides significant implications for the rational development and utilization of water resources, as well as the protection and restoration of aquatic ecological environments.

Based on core sampling, sequential extraction procedure in the laboratory, correlation analysis between sediments and groundwater, and mineral saturation index（SI）of groundwater, this paper explored the distribution, form and influencing factors of RIS in Quaternary sediments in the middle and lower reaches of Chaobai alluvial-proluvial fan, in Beijing. Results showed that the content of RIS in the study area followed a descending order of: Pyrite-S（CRS）>essential sulfur（ES）>acid volatile sulfide（AVS）, among which CRS accounting for 80.1%, ES and AVS accounting for 13.4% and 5.56% respectively. 67% of samples had CRS/AVS value higher than 3. The RIS content in sediments in the upper reaches was lower than that in the lower reaches, and RIS contents in the four aquifers from shallow to deep were 84.3, 37.4, 39.1 and 10.5mg/kg respectively, showing an overall decreasing trend. The results of RDA and correlation analysis indicated that the TOC content, CRS/AVS value and water content in sediments were crucial factors affecting the content and form of RIS in the study area. Specifically, the content of RIS was also affected by the groundwater pH value, iron/sulfur ratio and hydrogeological conditions, and the form of RIS was affected by the COD_Mn and ORP of groundwater. The SI value of FeS in groundwater fluctuated around 0, and the SI value of FeS₂>0. In summary, RIS in the sediments of the study area is basically unaffected by human disturbance, and the activity and bioavailability of sulfide are low. The sediments may affect the concentrations of sulfate, sulfide, iron and arsenic in groundwater mainly through AVS precipitation/dissolution and ES disproportionation reaction.

Poyang Lake is characterized by significant water level fluctuations, leading to complex transformation processes among precipitation, soil water, and groundwater. Due to the limitations of intricate wetland conditions and traditional monitoring methods, it is challenging to conduct quantitative studies on soil water movement and its interaction with groundwater. In this study, three vegetation communities at different elevations in Poyang Lake were investigated to analyze the isotopic composition of precipitation, lake water, groundwater, and soil water（0~80cm）. The characteristics of wetland soil water movement were examined across various hydrological periods. The results showed that the slope of the soil evaporation line（SEL）in the Artemisia capillaris community（5.91）was significantly lower than that of the local meteoric water line（LMWL, 7.60）. The lc-excess values of soil water in 0~60cm layer were negative, indicating strong evaporation, with a maximum impact depth of 60 cm. The slopes of the SEL in the Phragmites australis and Carex cinerascens communities（6.70 and 6.75, respectively）were slightly lower than the LMWL, and the lc-excess values of soil water were close to 0, indicating minimal evaporation. Regarding soil water movement, the δ¹⁸O values of soil water in the A. capillaris community increased with depth during spring（May）and summer（June to August）, indicating piston-flow dominated transport. During autumn（September and October）, soil water δ¹⁸O values became enriched and decreased with depth, indicating the dominant influence of evaporation. Furthermore, the soil water δ¹⁸O values in the A. capillaria community were significantly enriched compared to groundwater isotopes. No depleted isotope signals or evidence of groundwater supply were detected in the soil water, even when the groundwater table was at its shallowest（1.92m）. These results suggest that vertical hydrological connectivity between root-zone soil water and groundwater was blocked. In contrast, soil water movement in the P. australis and C. cinerascens communities was significantly influenced by groundwater level fluctuations. During the groundwater level rise period（April and May）, shallow soil water（0~40cm）in these two communities primarily originated from atmospheric precipitation, while deep soil water（40~80cm）was replenished by capillary rise of groundwater. Groundwater contributed more than 50% to the replenishment of root-zone soil water. During the shallow groundwater table period（June and August）, frequent exchanges occurred between soil water and groundwater in the P. australis community. In the groundwater table decline period（September and October）, the P. australis and C. cinerascens communities exhibited non-uniform soil water flow processes, characterized by noticeable preferential flow.

The Dongjiang River Basin was chosen as the study area to compare the nitrogen concentrations and isotopes in the river with different land uses, so as to provide a better understanding and evidence for impacts of urbanization on active nitrogen turnover. In this study, the distinct characteristics of nitrogen concentrations and isotopes were found in urbanized rivers compared to rivers with other land uses. Firstly, the nitrogen concentrations in urbanized rivers were gradually increased due to urbanization and nitrate has become a main nitrogen speciation. Secondly, based on the isotope Rayleigh fractionation model, it was found that the nitrification potential in urbanized river channels was enhanced and about 25.8% of nitrate nitrogen came from nitrification in situ. In addition, a positive correlation between ln（NO₃^--N）and δ¹⁵N-NO₃^- was recorded in urbanized rivers. Moreover, Δδ¹⁵N/Δδ¹⁸O in the dry and wet seasons were –2 and -6, respectively, indicating that the denitrification potential was weakened to provide evidence for nitrate accumulation in urbanized river channels. Likewise, a weak correlation between δ¹⁵N-PN and δ¹⁵N-NH₄⁺ was also recorded in urbanized rivers, and the ¹⁵N enrichment factor of nitrate assimilation also differed from the theoretical value, indicating a weak assimilation of ammonia and nitrate nitrogen. Finally, more input pathways and less sink processes of nitrogen in urbanized rivers have become a key mechanism for elevated riverine nitrogen concentrations in the lower reaches of Dongjiang river.