Spatial-temporal variations and pollution risks of mercury in water and sediments of urban lakes in Guangzhou City, South China.

This study aims to investigate the spatial and temporal characteristics, pollution degrees, and potential ecological risks of mercury (Hg) in urban lake waters and sediments in Guangzhou, where is a typical area of Hg emission and population-economic-industrial concentration in South China. In different districts of this city, the water from 15 lakes were collected continuously from June 2020 to May 2021, and the sediments from 9 lakes were collected in 2015 and 2021. The seasonal changes of Hg concentration (Hg-C) in the water were found to be high in winter and low in summer. The spatial distribution of Hg-C in sediments showed that it was high in urban central areas and low in suburbs. The Nemero index and geological accumulation index showed that there were uncontaminated of Hg in the collected lake water, and above moderately contaminated in the lake sediments in urban center, respectively. The Hg pollution potential ecological risk index showed that there was low risk in the collected water, high and extremely high risk in the lake sediments in urban center, respectively. The principal component analysis (PCA) and correlation analysis (CA) of Hg and meteorological factors showed that precipitation, temperature, and vapor pressure had negative effects on the seasonal changes of Hg-C in water, and air pressure and wind direction had positive effects. The PCA and CA of Hg and other geochemical elements showed that anthropogenic emissions may be the main sources of Hg in sediments, which was also supported by the data of population density, road density, and motor vehicles per 1000 people. This study provided a reference for urban lake pollution treatment, resident health, and ecological environment protection.

Distribution of Potential Harmful Trace Elements and Potential Ecological Risk in the Jiulongchi Wetland of Fanjing Mountain, Southwest China.

In order to understand the distribution and ecological risk of potential harmful trace elements (PHTEs) in the high altitude areas of the Fanjing Mountain World Natural Heritage Property, 30 surface samples including soil and plants were collected in April, 2019 in the Jiulongchi wetland which lies in the saddle between the New Jinding Peak of Fanjing Mountain and Fenghuang Peak. The contents of 23 major and trace elements were determined, and the pollution characteristics and potential ecological risk of 11 PHTEs (Mn, V, Zn, Cr, Co, Ni, Cu, As, Cd, Sb and Pb) were discussed. The element contents showed significant differences in plant and soil samples. Enrichment factor and single-factor pollution index demonstrated that Mn, Zn, Co, As and Cd in the soil were in a clean state. The potential ecological risk index and pollution load index indicated an overall good ecological condition of Jiulongchi wetland, with a weak pollution degree. Comparisons of relevant studies showed the anthropogenic activities have considerable impacts on the pollution status of PHTEs with significant spatial differences in Fanjing Mountain. Multivariate statistical analysis proved that Pb and Sb were main pollutants of the soil in the Jiulongchi wetland, and the mining and smelting of minerals such as mercury, manganese and lead-zinc ore in the adjacent areas could be the main pollution sources through atmospheric deposition. This study could provide targeted strategies for the environmental protection and management of the Property and give scientific evidence for the pollution prevention in southwest China.