Abstract
Assessing spatiotemporal variation in water quality and heavy metals concentrations in wetlands and identifying metal contamination source are crucial steps for the protection and sustainable utilization of water resources. Using the water quality identification index (Iwq), heavy metal pollution index (HPI), hierarchical cluster analysis (HCA) and redundancy analysis (RDA), we evaluated spatiotemporal variation in water quality and heavy metals concentrations, and their interrelation in wetlands along the middle and lower Yellow River. The average Iwq was highest during flood season but the average HPI was lowest in the same season. Meanwhile, the trend in mean HPI across three hydrological seasons was the opposite to that of mean Iwq. There was significant variation in wetlands water pollution status across seasons. During the flood season, the wetlands in the affected area with hanging river were seriously polluted. In other seasons, pollution in the artificial wetlands was even more severe. Moreover, serious pollution of wetlands in belt transect #03 (Yuanyang-Zhongmu) was more frequent. Dissolved oxygen and chemical oxygen demand strongly influenced heavy metal concentrations, while other water quality parameters had different influences on heavy metal concentrations in different hydrological seasons. The causes of water pollution were divided into natural factors and human disturbance (with potential relationships between them). The polluted wetlands were greatly affected by the Yellow River during the flood season while they were more impacted by agricultural and domestic sewage discharge in other seasons. However, heavy metal deposition and leaching into riparian wetlands were still affected by diverse channel conditions. If this trend is allowed to continue unabated, wetlands along the middle and lower Yellow River are likely to lose their vital ecological and social functions.
Highlights
Wetlands are among the most productive and vulnerable ecosystems in the world, have fundamental ecological functions, and play an irreplaceable role in the maintenance of biodiversity and human development [1,2,3]
According to the Pearson correlation analysis (Table 6), only As and Zn were significantly correlated with water quality, as was negatively correlated with total nitrogen (TN) in standard deviation (SD)
The spatiotemporal difference of water quality parameters may be mainly caused by the discharge of agricultural and domestic sewage around the sample sites
Summary
Wetlands are among the most productive and vulnerable ecosystems in the world, have fundamental ecological functions, and play an irreplaceable role in the maintenance of biodiversity and human development [1,2,3]. Riparian wetlands are buffer zones for the water and nutrient budget of the landscape which play an important ecological role. Because they tend to be quite narrow in width, their importance for landscape ecology, biogeochemistry, and biodiversity is often overlooked [6]. Riparian wetlands are often threatened by water resources and hydropower projects that primarily consider human demand, causing changes in the hydrological regimes, eutrophication, nutrient enrichment, salinization, and pollution with organic compounds, pesticides and heavy metals [7,8,9,10,11]. It is important to study trace element concentrations, distributions, sources, and health risks to protect water resources and control water pollution
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