Spatio-temporal Characteristics of CODMn in Surface Waters of Middle and Downstream of the Pearl River and Water Environment Evaluations
In order to understand the spatio-temporal pattern of CODMn and impacting factors in the surface water of the middle and downstream of the Pearl River, seasonal investigations were carried out in 2015. During the investigation, the mass concentration of CODMn was in the range of 1.14~15.8 mg·L-1, with an average of 3.93 mg·L-1. For seasonal characteristics, CODMn of the dry season (March and December) was significantly higher than that of the flood period (June and September). Runoff is the main factor affecting the seasonal variation. As for the spatial distribution pattern, the content of CODMn in the studied area could be divided into three levels, represented by three clusters. Among them, cluster 1 represents the sites along the West River, cluster 2 represents the adjacent sites of Guangzhou city, and cluster 3 represents the central Pearl River Delta. The highest content of CODMn was found in cluster 2, followed by that in cluster 3 and the lowest in cluster 1. Correlation analysis with other physical and chemical factors showed that CODMn had a significant negative correlation with salinity, conductivity and DO, and was significantly positively correlated with total nitrogen, total phosphorus, silicate and chlorophyll a. Pollution conditions and water quality levels based on CODM nwas also analyzed. The seasonal results showed that water quality during flood periods was between class Ⅰ and Ⅱ, while 37.6% sites showed worse than class Ⅲ. It was obviously water quality in flood periods was better than that in dry sesons. There is a big difference in water quality in different regions. Among them, mean value of Pi along the West River was 0.47, less polluted, and the annual water quality maintained between class Ⅰ and class Ⅲ. The mean value of Pi nearing Guangzhou city was 1.21, heavily polluted, and 42.7% sites did not meet the class Ⅲ water quality standards. The mean value of Pi in central Pearl River Delta was 0.6, only 12.5% sites were worse than class Ⅳ water quality, most were better than class Ⅲ. Above all, runoff is the main factor affecting the seasonal variation of CODMn in the surface water of the middle and downstream of the Pearl River; production and living pollution caused by human activities is an important factor affecting the spatial distribution of CODMn content in the studied regions. Our results are helpful for understanding pollution conditions and environmental protection in the studied area.
Pearl Riversurface waterCODMncontentspatio-temporal patternwater quality evaluation
国家科技期刊平台
NSTL
万方数据
维普
