Levels and characteristics of polychlorinated biphenyls in surface sediments of the Chaobai river, a source of drinking water for Beijing, China

Highlights

• PCB levels in sediments from drinking water source in Beijing were investigated.

• Dioxin-like PCBs were corresponded with constituents of commercial PCBs.

• Atmospheric deposition and source pollution from factories were dominant sources.

• Slight PCB pollution was found and can hardly induce adverse biological effects.

Abstract

We collected surface sediments from the Chaobai river, the dominant source of drinking water for Beijing, China, to assess the status of contamination by polychlorinated biphenyls and evaluate their sources. Total concentrations of polychlorinated biphenyls in the sediments ranged from 0.125 to 70.6 ng/g dry weight and correlated with the locations relating to painting operation such as printing factories and construction material markets. Dioxin-like polychlorinated biphenyls were present and corresponded with constituents of commercial polychlorinated biphenyl mixtures. Principal component analysis indicated two dominant sources of polychlorinated biphenyls in the sediments—deposition from airborne emissions and point-source pollution from factories. An ecological risk assessment concluded that there was only slight polychlorinated biphenyl pollution in the sediments of the Chaobai river, which was not likely to induce adverse biological effects. Our findings provide information for polychlorinated biphenyl risk assessment and recognition of the dominant sources of these compounds in drinking water in China.

Introduction

Persistent organic pollutants in the environment are of particular concern because of their carcinogenicity. Airborne organic pollutants can enter water, soil, and sediment matrices and bioaccumulate through the food chain, resulting in adverse effects on human and ecosystem health (Volschenk et al., 2019). Polychlorinated biphenyls (PCBs) are manmade pollutants banned by the Stockholm Convention (Liu et al., 2016). PCBs (chemical formula C₁₂H_(10-n)Cl_n) are biphenyls substituted by 1–10 chlorine atoms, therefore containing a total of 209 congeners and 10 homologue groups. Among PCBs, the 12 dioxin-like PCB (dl-PCB) congeners have been studied extensively because they elicit toxic effects that are similar to those of dioxins, including immunotoxicity and developmental toxicity (Brankovic et al., 2019). Although the commercial production and application of PCBs were prohibited globally in the late 1970s, they are still present in the environment at notable concentrations (Gao et al., 2013; Zhang et al., 2011). The phenomenon can be explained by the unintentional production by industrial thermal processes, as PCBs were listed both in the Annex A and C of the convention. POPs listed in Annex A were the ones previously produced and need to be eliminated, while being listed in Annex C indicated that PCBs can be unintentionally emitted by industrial thermal processes. Our previous studies reported that thermal industries including waste incineration, steelmaking, iron ore sintering, coking and cement kiln can unintentionally produce and emit PCBs to the environment (Ba et al., 2009; Li et al., 2014; Liu et al., 2009; Lv et al., 2011; Nie et al., 2012).The commercial PCBs and unintentionally produced PCBs can enter into the environment, some of which may be emitted to the air, and the other parts may leak into the ground or enter the rivers and coastal areas. (Ba et al., 2009; Li et al., 2014; Liu et al., 2009; Lv et al., 2011; Nie et al., 2012).

Considerable levels of PCBs have been detected in environmental and biological media, including sediments (De Souza et al., 2018; Ehsani and Hayes, 2018; Hanh et al., 2018; Hilton et al., 2018; Walters et al., 2018), water (Howell et al., 2008; Zhang et al., 2003), air (Audy et al., 2018; Cetin et al., 2018), and aquatic organisms (Bocio et al., 2007; Cui et al., 2018; Romanic et al., 2018). Rivers and sediments serve as a sink for PCBs, and sediment resuspension can release PCBs and make them bioavailable (Ehsani and Hayes, 2018). As sediment is one of the most important environmental media and source of PCBs, the presence of PCBs in sediments can be representative of the current PCB pollution level in the environment. Studies on PCBs in sediments have been conducted extensively in salt water because of intensive human activities around river estuaries and offshore (Hanh et al., 2018). PCBs in the environment mainly from the PCB-containing products and the unintentional emission from industrial processes. Disassembling PCB-containing equipment is considered a significant source of environmental release of PCBs in China, especially in the southeastern coastal areas, where intensive dismantling of electronic waste has been conducted. (Cui et al., 2013; Wang et al., 2011; Zhao et al., 2019). Unintentional emission from thermal industrial processes is also considered a dominant contributor, and some thermal related industries are located in Beijing and Tianjin areas. However, few studies have been conducted on freshwater river sediments, especially in rivers that supply drinking water to Beijing, which can directly influence the health of residents in Beijing. The sources and current pollution levels of PCBs in source river of drinking water are unclear and require investigation, and the knowledge of PCBs in source of drinking water can provide important information for human health risk assessment.

In the present study, we quantified the concentrations of PCBs in sediments collected from 18 sites along the Chaobai river, a source of drinking water to Beijing and Tianjin, with a focus on the 12 dl-PCB congeners. The possible sources of PCBs in the river were evaluated by the distribution pattern of dl-PCBs using principal component analysis. Our findings provide important information for the cognition on PCB levels and their dominant sources in the representative drinking water source in China.