Chemoheterotrophic denitrification technologies using biopolymers as a solid carbon source and biofilm carriers have been widely trialed to remove nitrate from groundwater. Here, we use a polyhydroxyalkanoates (PHA) and cellulose blend as a slowly released carbon material, the performance of which was detected through static and dynamic experiments. In the static experiment, the carbon released from the straw, cob and bagasse was 66.95, 40.12 and 40.65 mg L⁻¹, respectively. Results show that the straw possessed higher carbon content than the others. In the dynamic experiments, the PHA/cellulose blend exhibited excellent nitrate removal efficiency and less adverse effects in nitrite accumulation during stable operation. The nitrate nitrogen removal rate reduced from 99.80% to 73.13% as nitrate loading increased from 40 to 60 mg L⁻¹. The microbial structure of a permeable reactive barrier (PRB) system was revealed by high-throughput sequencing analysis. Azospira, Rhizomicrobium and Acidovorax were found to be the predominant species in the PHA system after the system had stabilized. Our results highlight that the PHA/cellulose blend is an economically attractive carbon source with good denitrification performance.

The concentrations of heavy metals (As, Cd, Cr, Cu, Hg, Ni, Pb and Zn) in 17 surface sediment samples from the Hailar River, the upper source of the Ergun River, which is the boundary river between China and Russia, were analyzed. Traceability and cause analysis of heavy metals in sediment were carried out by correlation analysis and principal component analysis. The results showed that the concentrations of Hg and Cd in sediments exceeded the soil background values. Due to the high biological toxicity factor of Hg, Hg is the highest potential ecological risk factor in the Hailar River and its tributary the Yimin River. The sources of Hg and As were likely to come from human activities including mining, coal burning and animal husbandry; other HMs, especially Zn and Cr, mainly come from mining and natural factors. Due to the high level of urbanization and more agricultural activities, the pollution potential of Cd, Hg and Pb in the Yimin River and the lower reaches of the Hailar River was greater. The results of this study will help to understand the distribution and pollution of heavy metals in river sediments in the basin and provide management support for China’s local environmental management departments and relevant national departments of China.

The Erguna River, a Sino-Russian transboundary river, is vital for regional ecology, but land use impacts on its water quality remain unclear. This study aimed to reveal their response relationship. Using ArcGIS/ENVI, it classified land use in 2010 and 2016 into six types, and applied Pearson correlation to 10 monitoring sections’ water quality data. Results showed land use–water quality correlations were temporally and spatially variable: correlations weakened with increasing buffer distance, with the strongest associations within 1000 m. From 2010 to 2016, grassland shifted from a positive (water-purifying) to negative (pollutant-source) impact on water quality (BOD₅ and arsenic), which was driven by area reduction and overuse; forestland transitioned from no significant effect to a positive (pollutant-intercepting) role, attributed to area expansion. Arable and construction land showed no significant correlations with water quality, due to low proportions of construction land in cross-border areas, and arable land is mostly distributed in areas far from the riverbank. This study provides critical scientific support for transboundary water resource cooperation and targeted ecological management of the Erguna River Basin.

Through sampling and analysis of 20 groundwater monitoring wells from nine oil storage enterprises in the Jiangbei New District of Nanjing, the pollution characteristics and chemical spatial distribution of total petroleum hydrocarbons (TPH) in the groundwater of the study area were revealed. TPH was detected in all 20 groundwater samples, with concentrations ranging from 0.26 to 90.24 mg/L. A factor analysis identified two principal factors, F1 and F2, representing the biodegradation processes of iron–manganese reduction and sulfate reduction, respectively. A correlation analysis showed that TPH was significantly positively correlated with total dissolved solids (TDS), total hardness, Fe, Mn²⁺, and oxygen consumption, but its correlation with sulfides and SO₄²⁻ was not significant. A further multiple regression analysis indicated that the relative contribution rates of electron acceptors followed the order of iron reduction (90.62%) > manganese reduction (9.35%) > sulfate reduction (0.032%), suggesting that TPH biodegradation is primarily dominated by iron–manganese reduction. Additionally, the study found that microbial growth was more robust in freshwater environments, facilitating TPH degradation, whereas saline environments inhibited microbial activity, thereby hindering TPH degradation.