Concentration, distribution, and assessment of dissolved heavy metals in rivers of Lake Chaohu Basin, China

Highlights

• Dissolved metals distribution patterns were established at whole Lake Chaohu Basin.

• Dissolved metals concentrations were generally low.

• The mean hazard index was 1.51, rating as “slightly affected” state generally.

• The potential risk for human health still existed in rivers in Lake Chaohu Basin.

• A high risk was observed for chromium, arsenic, and nickel.

Abstract

This study aimed at establishing the spatial and seasonal distribution patterns of dissolved metals, and assessing the water quality and potential human health risk, in rivers of Lake Chaohu Basin (LCB, China). Four seasonal samplings were conducted at 83 sites from April to December in 2018. The water quality was assessed using heavy metal evaluation index (HEI), while hazard index (HI) and carcinogenic risks indicated potential human risk, according to 12 metals (Cr, Mn, Fe, Ni, Cu, Zn, As, Mo, Cd, Sb, Ba, and Pb). Spatially, sites were effectively classified into Group I and II using cluster analysis. Generally, dissolved metals were low in rivers of LCB at whole basin scale. Total metals concentrations, as well as HEI and HI, were significantly higher in Group II compared with Group I. The mean total concentration was 496.38 μg L⁻¹, with the highest mean of Zn (233.39 μg L⁻¹), followed by Ba (170.66 μg L⁻¹). The pollution status was generally classified as “slightly affected” by HEI, with a mean of 1.51. According to HI, there were 6.02% and 10.84% of all the 83 sites (main in Nanfei River) with greater chances of harmful health risks for adults and children, respectively. Furthermore, a high risk was observed of Cr, As, and Ni, which was listed in the decreasing order. Although the dissolved metals were relatively low, the potential risk for human health still existed in rivers of LCB, which the local manager should pay more attention to in future.

Introduction

Nowadays, surface water contamination in various ecosystems has raised great concern worldwide due to increased pollution and climate change (Michalak, 2016; Scanlon et al., 2007). As an important water resource for multiple purposes, water quality in rivers has been already illustrated by numerous researchers (Eccles et al., 2020; Zhang and Li, 2021). Water pollution affects the use of water resources, especially drinking water supply. Based on the data of World Health Organization (WHO, 2017a), there were about 2 billion people worldwide without a reliable source of drinking water. Water with poor quality probably results in public health problems. Therefore, it is vital to estimate water quality condition firstly and then implement some protection and improvement measures if needed, which is common in numerous countries and areas (Astel et al., 2006; Nazeer et al., 2014; Wu et al., 2018a). For example, it is essential to rate water quality in Europe, primarily when the Water Framework Directive was fully implemented.

Among various contaminations, heavy metals and the associated effects are crucial issues in relevant studies (Bing et al., 2019; Chowdhury et al., 2016; Hu et al., 2019). As their toxicity, bioaccumulation and persistence level in environment, heavy metals with an excess amount can threaten aquatic organisms and human health, resulting in irreversible damage (USEPA, 2015). For example, heavy metals may result in permanent intellectual disabilities, and learning and attention problems with long term exposure (Sarkar, 2009). Furthermore, there are cancer (such as the connection of skin cancer and inorganic arsenic [As]) and/or non-cancer risk in humans even with chronic exposure (Jaishankar et al., 2014; USEPA, 2015). Heavy metals are released from multiple sources, including natural process (e.g., mineral weathering and atmospheric deposition), and anthropogenic activities (e.g., industrial processes) (Szefer et al., 1999; Wong et al., 2003). Although heavy metals are mainly stored in sediments, they can be released in water column in aquatic environments, which are also crucial in determining their bioavailability to organisms and affect water quality to a great extent (Qu et al., 2018). Consequently, much more attention should be paid to the distribution of dissolved heavy metal and their risks to human health (Githaiga et al., 2021).

Lake Chaohu Basin (LCB) is vital for local economic development. Meanwhile, LCB received considerable attention because of its severe pollution since the 1980s, especially the ecological problems (such as cyanobacteria bloom) in Lake Chaohu (Huang et al., 2018; Shang and Shang, 2007; Yin and Zhang, 2003). As a result, relatively more attention has been focused on Lake Chaohu rather than the rivers connecting to the lake (Xie, 2009; Zhang and Kong, 2015). For example, some studies have illustrated heavy metals in Lake Chaohu, concerning their distribution, source identification, bioavailability, risk evaluation, and so on (Fang et al., 2019; Liu et al., 2016), while relevant work was relatively limited in rivers of this basin. There are more than 30 rivers distributed across the basin, which are all inflows except Yuxi River. The environmental condition in inflows affect the water quality of connecting the lake to a great extent (Lin et al., 2021). In addition, for such a complex and huge basin, there is still a lack of information on the distribution pattern and potential risks of heavy metals in the rivers, especially at the whole basin scale.

In the present study, heavy metals in the main rivers of LCB were investigated seasonally. The main objective was to establish the distribution patterns of dissolved heavy metals at spatial and seasonal scales in the whole LCB basin. We also evaluated the water quality and potential risk of heavy metals on human health, considering dermal pathway and ingestion for both adults and children. This study will be an essential supplement to the water quality condition and potential human health risk assessment in LCB, which is beneficial to local managers.