Concentrations, Possible Sources and Health Risk of Heavy Metals in Multi-Media Environment of the Songhua River, China

Kunyang Li,Shang Gao,Rupert Hough,Qiang Fu,Lihui An,Zulin Zhang,Song Cui,Fuxiang Zhang

doi:10.3390/ijerph17051766

Abstract

Heavy metal pollution in the river environment has been a source of widespread interest due to potential threats to human health and ecosystem security. Many studies have looked at heavy metal pollution in the context of single source-pathway-receptor relationships, however few have sought to understand pollution from a more wholistic multi-media perspective. To investigate potential risks in a more wholistic way, concentrations of six heavy metals (Cd, Cr, Ni, Cu, Zn and Pb) were detected in multi-media (water, sediment and riparian soil) collected from 14 sampling sites in the main stream of the Songhua River. Chemical analyses indicated that the average concentration of heavy metals in water followed: Zn > Cr > Cu > Pb > Ni > Cd, with a different trend observed in sediments and riparian soil: Zn > Cr > Ni > Pb > Cu > Cd. The potential risk was evaluated using the heavy metal pollution index (HPI), Nemerow pollution index (PN), hazard index (HI) and carcinogenic risk (CR) metrics. Results showed that all HPI values were lower than the critical level of 100 indicating that the levels of these targeted heavy metals were within drinking water safety limits. The PN indicated that both sediment (2.64) and soil (2.95) could be considered “moderately polluted”, with Cd and Zn providing the most significant contributions. A human health risk assessment suggested that the non-carcinogenic risks were within acceptable levels (HI < 1), as was the cancer risk associated with dermal adsorption (CR <10−6). However, the CR associated with ingestion exposure (4.58 × 10−6) exceeded the cancer risk threshold (10−6) indicative of elevated cancer incidence in exposed populations. Health-risk estimates were primarily associated with Cd in the Songhua River. Source apportionment was informed by Pearson correlation analysis coupled with principal component analysis (PCA) which indicated that Cu was mainly derived from natural (geogenic) sources; Cr and Ni were associated with industrial emissions; Pb might be derived from agricultural and transportation sources; Zn might be from industrial, agricultural activities and transportation; while Cd is likely from industrial and agricultural emissions. The source apportionment information could provide the basis for a risk-management strategy focused on reducing Cd and Zn emissions to the riverine environment. Results from this study will provide the scientific knowledge that is needed for measuring and controlling heavy metals sources and pollution characteristics, and identifying the potential cancer risk with different exposure pathways, as well as making effective environmental management policies at catchment or regional scales.

Highlights

Heavy metals are ubiquitous pollutants in the environment, derived from both geogenic and anthropogenic sources [1,2,3]
Sediments are generally considered as both “source” and “sink” for most heavy metals and other pollutants in the water environment, measurements made in sediments can be a useful indicator of potential ecological risk to the aquatic environment [10,11,12,13]
The average concentrations in water followed: Zn > Cr > Cu > Pb > Ni > Cd, and these levels were significantly higher than the background concentrations found in the Songhua River (p < 0.01) [37]

Summary

Introduction

Heavy metals are ubiquitous pollutants in the environment, derived from both geogenic and anthropogenic sources [1,2,3]. Excessive emissions and accumulation of heavy metals can cause serious pollution to environmental media such as air, soil, water and sediments, with potential implications for ecological safety and human health [4,5,6]. Rapid development of industry, agriculture and urbanization often results in polluting discharges (e.g., wastewater, agricultural run-off) to watercourses that impact water quality, with knock-on implications for ecosystem and human health [3,8,9]. Sediments are generally considered as both “source” and “sink” for most heavy metals and other pollutants in the water environment, measurements made in sediments can be a useful indicator of potential ecological risk to the aquatic environment [10,11,12,13].

Objectives

Methods

Results