[Sediment Characteristics of Sewer in Different Functional Areas of Kunming]

Distribution characteristics and ecological risk assessment of heavy metals in sediments of Shahe reservoir

Shahe Reservoir of Northern Canal Basin was selected as the study area. Nineteen surface (0~20 cm) sediment samples and three sediment core samples were collected to analyze the spatial distribution characteristics of As, Cd, Cu, Mn, Pb and Zn in the sediments. The geo-accumulation index, potential ecological risk index and risk assessment code were used to evaluate heavy metal pollution, as well as its potential risk was analyzed according to the speciation of heavy metals. Results showed that the average enrichment factors of heavy metals compared to the background value in soil of Beijing were ranked at the order as the point source pollution area > the central area of the reservoir > the downstream area of the reservoir > the Nansha River > the upstream area of the reservoir > the Beisha River, namely, 2.57 times, 2.06 times, 1.97 times, 1.95 times, 1.87 times and 1.85 times, respectively. The sediment core samples in the central area of the reservoir and the inlet of the Beisha River showed a trend of increasing firstly and then decreasing with the change of depth. Pollution assessment results showed that sediment was moderately contaminated or moderately to strongly contaminated by As, but the other heavy metals were not polluted or lightly polluted. The potential ecological risk index of all sampling sites was less than 150, showing a low ecological risk. As Cr and Cu were mainly in the speciation of residues, with low bioavailability. Although the content of Mn and Zn were low, they showed high bioavailability. Based on correlation analysis and principal component analysis, it was speculated that the sources of various heavy metal pollution in the sediment were similar, which were possibly input from the external wastewater. The heavy metals in sediment were positively related to nutrients and organic matter, indicating that all of them were mostly from the same point polluted sources.

Current status, existent problems, and coping strategy of urban drainage pipeline network in China

Urban drainage pipeline systems collect and transport domestic sewage, industrial wastewater, and rainwater. They are important components of urban infrastructure. The quality of drainage facilities directly determines the level of urban development and affects the urban landscape and sanitary environment. In recent years, however, the phenomenon of "attaching importance to construction, despising management and maintenance" has prevailed in China's urban drainage pipeline network. The problems such as structural damage, corrosion, and blockage of the sewage pipelines are becoming increasingly prominent in China, causing a lot of operational challenges such as direct discharge of sewage, backward irrigation of river and lake water, infiltration of external water, and overflow pollution. To comprehensively acquire these information about China's urban drainage pipeline network, this paper reviews current status of construction, operation, management and maintenance, existent problems, and coping strategy of the sewage pipelines. Finally, future directions are also discussed in detail for rational construction and maintenance of sewage pipelines.