Haitao Wang

The Wutong River, located in northeastern China’s Heilongjiang Province, serves as an important habitat and spawning ground for fish and freshwater shellfish. To investigate the influence of geographic and geomorphic changes on the river basin ecology, the water environment and spatial heterogeneity of freshwater shellfish distribution were monitored in both summer and autumn of 2024. Key water quality indicators were analyzed, including basic parameters (pH and dissolved oxygen), eutrophication indices (nitrogen, phosphorus, and chlorophyll), and pollutant levels (nitrite nitrogen, petroleum, and volatile phenol). Water quality was assessed using the single-factor index method and the Nemerow pollution index method. Results indicated that in 2024, the Wutong River was weakly acidic in summer and weakly alkaline in autumn, with overall high dissolved oxygen levels. The Guanmenzuizi Dam site exhibited the best water quality. According to the single-factor evaluation, water quality in autumn was better than in summer, with iron, manganese, and volatile phenol as the primary pollutants, followed by total nitrogen and permanganate index. Based on the Nemerow index, the river generally met China’s Class III surface water standards. Water quality showed a trend of initial improvement followed by deterioration along the river course. Among 100 sampling points, Unio douglasiae had the highest occurrence rate (76%), followed by Cipangopaludina cahayensis (66%). Other species occurred in ≤50% of samples, with Polypylis hemisphaerula being the rarest (3%). The average species occurrence rate increased from upstream to downstream. This study provides a data baseline for understanding the water environment of the Wutong River and supports research on biodiversity and ecological conservation.

To investigate the influence of factors such as tourism, agriculture, and population density on the presence of microplastic (MP) content in aquatic environments and their associated ecological risks, Jingpo Lake, a remote high-mountain lake situated away from urban areas, was selected as the research subject. This study examined the abundance, types, sizes, colors, and polymer compositions of MPs within the water body, fish, and sediments. By considering variables, including fishing practices, agricultural activities, population dynamics, and vegetation cover, an analysis was conducted to unravel the spatial and temporal distribution of MPs concerning human activities, ultimately leading to an assessment of the ecological risks posed by MP pollution. The findings revealed that the average abundance of MPs in the lake’s surface water was recorded as (304.8 ± 170.5) n/m³, while in the sediments, it averaged (162.0 ± 57.45) n/kg. Inside the digestive tracts of fish, the MP abundance was measured at 11.4 ± 5.4 n/ind. The contamination of MPs within the aquatic environment of Jingpo Lake was found to be relatively minimal. Variations in MP loads across time and space were observed, with MPs predominantly falling within the size range of small planktonic organisms (50–1000 μm). Additionally, the prevalent colors of MPs in the water samples were white or transparent, constituting approximately 55.65% of the entire MP composition. Subsequently, they were black, red, and blue. This colors distribution were consistent across MPs extracted from fish and sediment samples. The chemical compositions of the MPs predominantly comprised PE (31.83%) and PS (25.48%), followed by PP (17.56%), PA (11.84%), PET (6.71%), EVA (4.56%), and PC (2.03%). Regarding the seasonal aspect, MP concentrations were highest during summer (46.68%), followed by spring (36.75%) and autumn (16.56%). The spatial distribution of MPs within Jingpo Lake’s water body, fish, and sediments was notably influenced by human activities, as confirmed by Pearson correlation coefficients. A strong association was observed between MP levels and water quality indicators such as ammonium nitrogen (NH₄-N), total phosphorus (TP), and chlorophyll-a (Chla), suggesting that human-related pollution contributed significantly to MP contamination. The diversity assessment of MP pollutants exhibited the highest variability in chemical composition (1.23 to 1.79) using the Shannon–Wiener Index. Subsequently, the diversity of colors ranged from 0.59 to 1.54, shape diversity from 0.78 to 1.30, seasonal diversity from 0.83 to 1.10, and size diversity from 0.44 to 1.01. The assessment results of ecological risk highlighted that the risk categories for MPs within the surface water, fish, and sediments of Jingpo Lake were categorized as I for the PHI and PLI and as “Minor” for the PERI. These relatively low-risk values were attributed to the predominantly low toxicity of the distributed MPs within the Jingpo Lake basin. Moreover, the results of the risk assessment were found to be interconnected with the distribution of the local population and agricultural activities around the sampling sections. Usage patterns of coastal land and population density were recognized as influential factors affecting MP loads within the water body, sediments, fish, and other components of the lake ecosystem.