Seasonal dynamics of polycyclic aromatic hydrocarbons between water and sediment in a tide-dominated estuary and ecological risks for estuary management
Introduction
More than 100 types of polycyclic aromatic hydrocarbons (PAHs) have been found in aquatic environments via several paths including riverine input, atmospheric deposition, or stream inflows (Lang et al., 2008; Gu et al., 2016). These PAHs tend to be adsorbed onto the particles because of their hydrophobicity. They tend to accumulate into sediments, and they may enter marine organisms including fishes (Wang et al., 2010). The PAHs in an aquatic environment (sediment, pore-water, and water) have attracted attention worldwide because of their characteristics of carcinogenicity, persistence, toxicity, and mutagenicity (Harrison et al., 1996; Timoney and Lee, 2011; Deng et al., 2013; Niu et al., 2020). Some of them are on the United States Environmental Protection Agency list of priority pollutants, and have significantly affected the quality of the environment and created threats to human health (Qiu et al., 2009; Moeckel et al., 2014). The PAHs are generally derived from anthropogenic activities, with pyrogenic processes and petrogenic sources acting as the two major sources (Yunker et al., 2002; Chen et al., 2004; Zhang et al., 2016). Understanding the dynamic mechanisms of PAHs is therefore important for predicting their environmental fate and managing the PAH input into marine estuaries.
A water-sediment system forms the boundary interface between water and sediment (Santschi et al., 1990). The diffusion of PAHs between water and sediment is associated with the influence of physical and biological processes. These processes include particle re-suspension into the water body caused by strong hydrodynamic forcing, and particle mixing within the sediment caused by marine currents. The importance of water-sediment exchange processes for determining the spatiotemporal variations of the characteristics of PAHs has rarely been documented (Kirso et al., 1990; Xia and Wang, 2008).
A tide-dominated estuary is characterized by strong interactions between river discharges and tidal currents. Sediment is an important pool that stores organic pollutants and is a potential secondary pollution source when the river discharge and tide strongly interact (Liu et al., 2012; Zhang et al., 2012). Previous studies have reported on the distribution of PAHs in water and sediment in tide-dominated estuaries (Maskaoui et al., 2002; Liu et al., 2017, Liu et al., 2018), but knowledge on the dynamic mechanisms of PAHs across the water-sediment interface still remains poor. The mixing at the interface in an estuary is one of the most important dynamic processes occurring with estuaries (Liu et al., 2018). The estuarine processes not only influence the gradients of physicochemical factors that affect the properties of PAHs in water and sediment, but they also affect the transportation of PAHs between water and sediment in an estuary.
In the present study, the tide-dominated region of the Humen river mouth in the Pearl River estuary (PRE; Fig. 1), as the main river mouth of the cities of Gugangzhou and Dongguan (an economically important region in China), was selected to examine the behavior of PAHs between water and sediment. The PRE system consists of complicated tributaries and river networks having approximately 322 branches and constitutes a major pathway of PAHs being transported to the South China Sea. The variations in hydrological conditions between the wet (April–September) and dry (January–March and October–December) seasons in the PRE are substantial (Lu et al., 2009; Liu et al., 2017). The Pearl River discharges pollutants through eight river outlets at Humen, Jiaomen, Hongqili, Hengmen, Hutiaomen, Jitimen, Yamen, and Modaomen. The Humen river mouth is a typical tide-dominated estuary with seasonal changes in estuarine dynamics; it is the main passage that transports organic pollutants from the large urban areas of Guangzhou and Dongguan. Previous studies have reported on the characteristics of PAHs in the PRE (Mai et al., 2003; Wang et al., 2010; Yuan et al., 2015), and our previous studies have investigated the estuarine behaviors of PAHs in the water column (Liu et al., 2017, Liu et al., 2018; Niu et al., 2018) and surface sediments (Niu et al., 2020) at the Humen estuary. However, documentation of the dynamic mechanisms of PAHs in the water-sediment system of the Humen estuary and the related ecological risks has not completed. Despite the above situation, the objectives of this investigation are to: (1) explore the seasonal changes in the concentration and composition of PAHs and the factors influencing PAH content in water and sediment, (2) document the diffusion of PAHs between water and sediment, (3) assess the related ecological risks, and (4) apportion the anthropogenic contamination sources of PAHs in this tide-dominated Humen river mouth of the PRE. Furthermore, the influences of seasons on river-marine dynamics and on the geochemical behaviors of PAHs between water and sediment have ecologically important implications for managing the input of PAHs in this estuary.
Section snippets
Sample collection
The eight river mouths of the Pearl River estuary system can be divided into two functional groups regarding to their estuarine processes: tide- and river-dominated. Among the four eastern river mouths, the sampling site of the Humen estuary analyzed here has only one gate functioning as seaward. In 2011, bottom water samples (0.5 m over the riverbed) and surface sediment samples (<5 cm) were continuously collected each month in the Humen estuary, using the traditional active sampling method
PAH concentrations
The seasonal dynamics of PAHs were detected in the Humen estuary. For the surface sediment samples (Fig. 2a), the dry weight of ∑2-, ∑3-, ∑4-, ∑5-, and ∑6-ring PAHs varied from 42.00 to 447.10 ng/g (mean 184.50 ng/g), 46.39 to 195.60 ng/g (91.18 ng/g), 108.70 to 299.20 ng/g (178.70 ng/g), 58.78 to 182.10 ng/g (98.79 ng/g), and 21.00 to 76.00 ng/g (35.40 ng/g), respectively. The ∑PAHs varied from 325.47 to 1098.50 ng/g (mean 588.64 ng/g). Heavily contaminated sediments (>500 ng/g, Maioli et al.,
Conclusions
The present study explored the seasonal dynamics and diffusion of PAHs between water and sediment of this tide-dominated Humen estuary, thereby helping to fill the knowledge gap of this complex region. The estuarine behaviors of PAHs varied widely throughout the sampling year and were greatly determined by the co-influencing factors of organic carbon content, sediment properties, and riverine input. Highly contaminated sediments (>1000 ng/g, dry weight) were mainly detected in the dry season
CRediT authorship contribution statement
Lixia Niu: Writing - original draft, Conceptualization, Formal analysis. Xiangxin Luo: Data curation, Software. Huayang Cai: Writing - review & editing. Feng Liu: Data curation. Tao Zhang: Software. Qingshu Yang: Supervision, Project administration, Investigation.
Declaration of competing interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
Acknowledgments
This study was financially supported by the National Key R&D Program of China (No. 2016YFC0402601) and National Natural Science Foundation of China (No. 21077139, 51709289, 51909290, and 41476073). The authors would like to thank the editor and anonymous reviewers for their time on this manuscript. The authors also thank LetPub (www.letpub.com) for its linguistic assistance during the preparation of this manuscript.
References (56)
- et al.
Atmospheric concentrations, dry deposition and air-soil exchange of polycyclic aromatic hydrocarbons (PAHs) in an industrial region in Turkey
J. Hazard. Mater.
(2008) - et al.
Distributions of polycyclic aromatic hydrocarbons in surface waters, sediments and soils of Hangzhou City, China
Water Res.
(2004) - et al.
Source apportionment of polycyclic aromatic hydrocarbons in surface sediment of mud areas in the East China Sea using diagnostic ratios and factor analysis
Mar. Pollut. Bull.
(2013) - et al.
Assessing soil-air partitioning of PAHs and PCBs with a new fugacity passive sampler
Sci. Total Environ.
(2017) - et al.
Recognizing different impacts of human and natural sources on the spatial distribution and temporal trends of PAHs and PCBs (including PCB-11) in sediments of the Nador Lagoon (Morocco)
Sci. Total Environ.
(2015) - et al.
Polycyclic aromatic hydrocarbons (PAHs) in sediments of Zhelin Bay, the largest mariculture base on the eastern Guangdong coast, South China: characterization and risk implications
Mar. Pollut. Bull.
(2016) - et al.
Distribution, sources and ecological risk assessment of PAHs in surface sediments from Guan River Estuary, China
Mar. Pollut. Bull.
(2014) - et al.
Naphthalene degradation in seawater by UV irradiation: the effects of fluence rate, salinity, temperature and initial concentration
Mar. Pollut. Bull.
(2014) - et al.
Sorption of hydrophobic pollutants on natural sediments
Water Res.
(1979) - et al.
Polycyclic aromatic hydrocarbons (PAHs) in sediment and sea urchin (Echinometra mathaei) from the intertidal ecosystem of the northern Persian Gulf: distribution, sources, and bioavailability
Mar. Pollut. Bull.
(2017)
Accumulation of carcinogenic hydrocarbons at the sediment-water interface
Mar. Chem.
1,2-Dihydroxynaphthalene as biomarker for a naphthalene exposure in humans
Int. J. Hyg. Environ. Health
Spatial distribution and source apportionment of PAHs in surficial sediments of the Yangtze estuary, China
Mar. Pollut. Bull.
Seasonal changes of polycyclic aromatic hydrocarbons in response to hydrology and anthropogenic activities in the Pearl River estuary, China
Mar. Pollut. Bull.
Impacts of estuarine mixing on vertical dispersion of polycyclic aromatic hydrocarbons (PAHs) in a tide-dominated estuary
Mar. Pollut. Bull.
Occurrence of nutrients in riverine runoff of the Pearl River Delta, South China
J. Hydrol.
Contamination by polycyclic aromatic hydrocarbons in the Jiulong River Estuary and Western Xiamen Sea, China
Environ. Pollut.
Characterization, source identification and risk associated with polyaromatic and chlorinated organic contaminants (PAHs, PCBs, PCBzs and OCPs) in the surface sediments of Hooghly Estuary, India
Chemosphere
Distribution and characteristics of polycyclic aromatic hydrocarbons (PAHs) in sediments of Hadhramout coastal area, Gulf of Aden, Yemen
J. Mar. Syst.
Dynamics of polycyclic aromatic hydrocarbons (PAHs) in water column of Pearl River estuary (China): seasonal pattern, environmental fate and source implication
Appl. Geochem.
Polycyclic aromatic hydrocarbons (PAHs) in the water column and sediment core of Deep Bay, South China
Estuarine Coastal and Shelf Science
Chemical processes at the sediment-water interface
Mar. Chem.
Relationship between polycyclic aromatic hydrocarbons (PAHs) and particle size in dated core sediments in Lake Lianhuan, Northeast China
Sci. Total Environ.
PAH diagnostic ratios for the identification of pollution emission sources
Environ. Pollut.
Occurrence and phase distribution of polycyclic aromatic hydrocarbons in riverine runoff of the Pearl River Delta, China
Mar. Pollut. Bull.
Characterization of PAHs in surface sediments of aquaculture farms around the Pearl River Delta
Ecotoxicol. Environ. Saf.
Diffusion of polycyclic aromatic hydrocarbons between water and sediment and their ecological risks in Wuhu city, Yangtze River Delta urban agglomerations, China
Appl. Geochem.
Spatial and temporal distribution of polycyclic aromatic hydrocarbons (PAHs) in sediments from Daya Bay, South China
Environ. Pollut.
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