哈尔滨何家沟内源污染治理中试试验

To promote the ecological restoration of small watersheds in Harbin, a pilot-scale study was conducted to remediate endogenous pollution in Hejia Ditch using sediment elution technology. The comprehensive impacts of elution on sediment and overlying water quality were systematically evaluated, and the mechanisms underlying the observed improvements were elucidated. Following sediment elution, the concentrations of organic matter, total nitrogen (TN), and total phosphorus (TP) in the sediment were decreased by 5.11%, 10.19%, and 8.71%, respectively. Meanwhile, the transparency, dissolved oxygen (DO), and oxidation-reduction potential (ORP) of the water body increased by 102.46%, 11.07%, and 15.66%, respectively. The average removal efficiencies of chemical oxygen demand (COD) and ammonium nitrogen (NH₄⁺-N) reached 35.67% and 22.65%, respectively. Sediment elution effectively reduced the suspended fine particles in the surface sediment layer while facilitating in-situ coverage by larger inorganic particles, resulting in the formation of a clearer and more stable sediment–water interface. Following the pilot trial, the average clay content in the sediment decreased by 8.87%, while the sand content increased by 12.37%, with D₅₀ and D₉₀ particle sizes rising by 32.39% and 159.97%, respectively. The mechanical disturbance and sediment particle size redistribution induced by the elution process enhanced oxygen mass transfer across the sediment-water interface, leading to a significant enrichment of facultative anaerobic phyla such as Chloroflexi and Spirochaetota. This microbial shift likely suppressed the generation of malodorous gases, including hydrogen sulfide and ammonia, thereby mitigating sediment resuspension events. Furthermore, the observed increase in microbial diversity and richness contributed to enhanced ecosystem stability and self-purification capacity. Overall, these results indicate that sediment elution is an effective technology for the in-situ remediation of internal pollution in black and odorous urban river and provide a scientific basis for the long-term ecological restoration and management of small watersheds.