Suchergebnisse

AbstractBackgroundThe Xiangjiang River is an important drinking water resource for the Hunan Province of China. It is crucial to ascertain the pollution status, influencing factors, ecological risks, and possible sources of heavy metals in the sediments of the Xiangjiang River. Sediment is both a source and a sink of heavy metals in aquatic ecosystems. In this study, surface sediment was collected from the Zhuzhou Reach of the Xiangjiang River and eight heavy metals were investigated.ResultsIn all sediment samples, all eight heavy metals were detected and their average concentration fell in the order of Zn > Pb > As > Cu > Cr > Ni > Cd > Co. Assessment shows extremely serious Cd pollution and a very high potential ecological risk from Cd. According to correlation analysis and principal component analysis (PCA), As, Cu, Ni, Pb, and Zn originate from industrial wastewater and mineral smelting activities, whereas Co, Cr, and Ni come from natural sources. Redundancy analysis (RDA) reveals that the organic matter content and the particle size of the sediment have a certain influence on the enrichment of heavy metals.ConclusionAmong all eight examined heavy metals in the surveyed area, the content of Zn, Pb, and As is the highest, and that of Cd and Co is the lowest. Despite a low level of absolute content, the Cd in sediment already renders a high ecological risk and thus calls for urgent attention. Anthropogenic activities are the main source of heavy metals in the sediment. The distribution of heavy metals may also be influenced by sediment properties. The results provide guidance for controlling heavy metal pollution and protecting drinking water sources in the Xiangjiang River.

Abstract

Background
Qingcaosha Reservoir is China's largest river impoundment and an important drinking water resource for Shanghai city. Although antibiotics contamination in the reservoir has been reported, little is known about the presence of antibiotic resistance genes (ARGs). In this study, the occurrence and distribution of 12 ARGs and the class 1 integron gene (intI-1) in water and sediments collected from the reservoir were investigated for 1 year.


Results
The 12 ARGs were detected in both water and sediment samples, and no significant temporal or spatial variations were observed. Sulfonamide resistance genes were predominant in the reservoir with a detection frequency of 100%. Statistical analysis indicated a positive correlation in relative abundance between some ARGs such as sul1, sul2, and intI-1. Most ARGs were negatively correlated with total nitrogen and positively correlated with chemical oxygen demand and chlorophyll-a.


Conclusion
In general, ARGs were found to be prevalent in Qingcaosha Reservoir, among which sulfonamide resistance genes were the most dominant and tetB was the least. intI-1 may facilitate the proliferation and propagation of some ARGs, especially sul1 and sul2. The abundance of ARGs was well correlated with aquatic environmental factors in water, providing potential clues for the control of ARG contamination.