Occurrence and distribution of OCPs and PAHs in water, soil and sediment of Daye lake

Highlights

• Distribution, sources and risk assessment of PAHs and OCPs were reported.

• Σ₂₄OCPs and Σ₁₆PAHs were more frequently detected in three media of Daye lake.

• Possible sources for PAHs and OCPs were investigated individually.

• Carcinogenic PAHs and DDTs showed severe impact on ecology of the lake.

• ILCRs for sediment and soil showed potential human risk.

Abstract

To elucidate the concentrations, spatial distribution, sources, and risk of sixteen polycyclic aromatic hydrocarbons (PAHs) and twenty-four organochlorine pesticides (OCPs), thirteen sites were chosen for collecting water, sediment, and soil samples from Daye lake in April 2019. All pollutants were frequently observed in three media of Daye lake. Higher concentrations of OCPs were determined in the soil whereas PAHs were dominant among sediment samples. However, the water of Daye lake is contaminated with both of the pollutants. In water, ΣDRINs, ΣDDTs, ΣHCHs and LMW PAHs accounted for 22.1%, 19.6%, 17.9% and 85.5%, respectively. Among sediments, OCPs and PAHs were ranged from 1.53–51.38 ng·g⁻¹ and 14.38–4659.66 ng·g⁻¹, respectively. While soil accounted for a larger percentage of heptachlorepoxide i.e. 96.5% and HMW PAHs i.e. 82.7%. Furthermore, the low α-to γ-HCH ratio suggested fresh input of HCH and the higher ratio of (DDE + DDD)/DDT determined the historical use of DDT. Additionally, diagnostic molecular ratio along with principal component analysis evaluated that PAHs mainly came from fossil fuel, biomass, and coal combustion. Moreover, ecological risk assessment of Daye lake indicated that the carcinogenic PAHs in water and soil can pose 10% risk to the environment also OCPs in sediments has a visible effect on ecology. According to incremental lifetime cancer risks (ILCRs) evaluation, OCPs have negligible to low cancer risk among all sites for water, soil, and sediments while PAHs value fluctuate in the midst of 10⁻⁶ to 10⁻² which shows the potential risk of cancer on children as well as adults. Therefore, measures should be taken to control them in time.

Introduction

Semi volatile persistent organic pollutants i.e. organochlorine pesticides (OCPs) and polycyclic aromatic hydrocarbons (PAHs) are of great concern around the world for their persistence, impact on non-target organisms, and bioaccumulation in the tissues. Due to their ubiquitous nature, these compounds have been found in all environmental matrices (Qu et al., 2019a, Qu et al., 2019b; Mahmood et al., 2015; Oros et al., 2005). The presence of semi-volatile persistent organic pollutants (POPs) in multiple compartments is driven by their application in history and long-range transport (Aichner et al., 2007; Wang et al., 2015). Through several processes, these pollutants found their way to water systems including urban, industrial, and agricultural runoff as well as atmospheric deposition (Hosono et al., 2011; Yılmaz et al., 2016; Zheng, 2008). Primarily, PAHs are originated from incomplete combustion of organic materials (coal combustion, vehicle emissions, domestic heating, biomass burning, industrial activities, oil spillage, etc.), while OCPs have been used widely as pesticides for agriculture, as insecticide, rodenticides, and antifouling agent in history (Oliveira et al., 2016; Qi et al., 2020; Thiombane et al., 2018; Xing et al., 2016; Yılmaz et al., 2016). After the prohibition in the 1980s, OCPs can still be found in different matrices of the environment because of their low degradation/long half-life (Li et al., 2016, Li et al., 2018; Xing et al., 2020; Zhao et al., 2017a). Moreover, OCPs, such as DDTs¹ and HCHs², and Σ_7Carc³ PAHs may induce several adverse impacts, such as immunotoxicity, genotoxicity, carcinogenicity, reproductive toxicity, and endocrine disruption (Li et al., 2016; Qu et al., 2019a; Sun et al., 2015; Zhonghua et al., 2016).

As the largest and developed agricultural country, China once was a major consumer and producer of OCPs. The production quantity of DDTs and HCHs from 1950s to 1980s in China were 4.9 and 0.4 million metric tons, corresponding to 20% and 33% of the total worldwide productions, respectively. (Liu et al., 2013). Apart from OCPs, PAHs are also ubiquitous in China's environment due to change in energy structure in the region. In 2003, the annual consumption of coal, petroleum, and biomass were 1660, 287 and 537 million metric tons, respectively (Xu et al., 2006; Zhonghua et al., 2016). In recent years, OCPs and PAHs were often determined in different matrices of various lakes in China. OCPs and PAHs are two serious environmental problems of the region owing to their characteristics. However, China has settled the regulations for OCP_S and PAHs levels in water and soil but there are no sediment quality guidelines established yet.

Daye, an industrial city, is not only characterized by urbanization and industrialization, including chemical plants and smelter, but also a center of mining and metallurgy with almost 65 mineral mines with copper and iron are prominent minerals (Li and Zhang, 2010). Daye lake is the 7th largest freshwater lake in Hubei province and serves as the main water source of domestic, agriculture, and industrial utilization for the population of Daye city (Zhang et al., 2014). The effluent, solid wastes, and emissions from surrounding areas serve as pollution sources of Daye lake. Moreover, agricultural activities and combustion processes in the area contributed to OCPs and PAHs pollution whereas mining activities and wastewater discharged from the nearby industries contributed to heavy metal pollution (Gis, 2015). Over past two decades, pollution was very serious in this region. The lotus root, shrimp, and crab gradually disappeared and annual output of fish gradually decreased to 10% of the original. Furthermore, exploitation of mineral resources caused land subsidence, soil erosion, destruction of biodiversity, frequent geological disasters, and decline of ecological quality (Du et al., 2015).

According to water quality monitoring, Daye lake basin was affected by eutrophication from 2009 to 2012 due to rural living resources and aquaculture around the lake. Besides this, among three main inflowing streams, Sanliqi lake was observed serious destruction with mineral influx/enrichment during the past six decades due to the advancement of industrial and agricultural activities between 1945 and 1993 (Zeng et al., 2015). However, Daye lake was at high ecological risk as well as a variety of health risks to the local population because of heavy metal pollution (Liu and Li, 2011; Zhang et al., 2015). Whereas researchs related to organic pollution, including OCPs and PAHs, are scarce. According to Zhang, the pollution-related to PAHs in Daye lake was moderate while none of the studies has been done on OCPs (Zhang et al., 2017). So, quality of water body, sources of anthropogenic pollution and their impacts on environment are significant characteristics to ensure the sustainable development of Daye lake ecosystem. For that, this study will (1) determine the concentrations of pollutants in different matrices of Daye lake basin; (2) illustrate and understand the spatial distribution of semi-volatile organic compounds OCPs and PAHs in the area; (3) figure out the mechanisms and sources of the pollutants in Daye lake (4) and evaluate the ecological and health risk of OCPs and PAHs.