Spatial and environmental characteristics of colloidal trace Cu in the surface water of the Yellow River Estuary, China
Introduction
Trace metals play a vital role in the biogeochemical cycles of estuarine, offshore, and open waters (Bruland and Lohan, 2003; Waeles et al., 2008; Lu et al., 2020). As an important connection between freshwater and seawater, estuaries have a strong hydrodynamic force and numerous physical and chemical parameter gradients that greatly affect the distribution and flux of metals (Wang et al., 2018; Lu et al., 2020). Many trace metals are nutrients that contribute to the primary productivity of aquatic systems, and when the concentration is too low, they become an important limiting factor for primary productivity (Maldonado et al., 2006; Han et al., 2021). On the other hand, if the concentration of these metals exceeds a certain level, they will become toxic metals that accumulate along the food chain and affect human health (Li et al., 2015; Lu et al., 2019). For example, copper (Cu) is characteristic of both a nutrient and toxic metal and its potential toxicity in coastal waters requires further research (Martin et al., 1994; Morel et al., 2003; Rivera-Duarte et al., 2005). Furthermore, Cu plays an important role in marine ecosystems (Peers and Price, 2006): most phytoplankton requires Cu to perform key redox reactions (Illuminati et al., 2017; González-Álvarez et al., 2020).
Most research on dissolved metals in aquatic environments filters water samples through a 0.2 μm or 0.45 μm pore filter membrane, and divides it into the dissolved state and particulate state for further analysis (Li et al., 2015; Wang et al., 2018). However, this technique may underestimate the behavior of dissolved metals, that is, colloidal metals (Guo and Santschi, 2007; Lu et al., 2019). Due to their large specific surface area and diverse species content, aquatic colloids play an important role in the biogeochemical cycle of elements and are receiving increasing attention (Waeles et al., 2008; Liu et al., 2013). In recent years, with the rapid development of various colloid separation technologies, research is no longer limited to the detection of concentration and distribution, but is rapidly extending in the direction of toxicology and environmental behavior (Xu et al., 2018a, Xu et al., 2018b, Xu et al., 2018c; Lu et al., 2020). The study of colloidal behavior in estuarine areas is an important research direction (Waeles et al., 2008; Savenkoa and Pokrovsky, 2019) because the dynamic behavior of estuary colloids is different from that of open water. Estuary colloids are also sensitive to environment variation, which makes this research important for understanding the biogeochemical behaviors of trace elements in estuaries (Gueguen et al., 2002; Lasareva et al., 2017; Xie et al., 2018).
The Yellow River is the largest river in Northern China. It has a large drainage area and contains a large amount of sediment and nutrients from the upper and lower reaches of the Bohai Sea. Therefore, it has the highest sediment content in the world and is the main creator of the world's youngest wetland (Zhang and Huang, 1993; Tang et al., 2010; Wang et al., 2011; Wang et al., 2016; Chen et al., 2020). In addition, the Yellow River Estuary (YRE) is a fast-growing aquaculture area and an important part of the Shandong Peninsula Blue Economic Zone in the national development strategy of China, making research on this area particularly important (Huang et al., 2013; Yuan et al., 2016).
Previous studies on the YRE focus on the concentration, distribution, and potential pollution of traditional dissolved metals (i.e. Zn, Cd, and Pb) (Qiao et al., 2007; Lin et al., 2016; Wang et al., 2018). However, biogeochemical studies on colloidal trace metals in this region, especially colloidal Cu, are limited. As an important biologically active metal, Cu can be easily adsorbed on inorganic/organic ligands in the aquatic environment, thereby increasing its bioavailability. This maybe an important environmental factor in red tides, green tides, and algal blooms in the nearshore area (Hirose, 2006). Therefore, dissolved Cu in the surface water of the YRE was investigated. The main objectives of this study were: (1) to investigate the spatial concentration variations of Cu in five molecular weight fractions of the dissolved pool in surface water of the YRE; (2) to assess the status of Cu as a toxic metal and the resulting ecological risks; (3) to explore the relationship between dissolved Cu behavior and environmental factors in the five molecular weight fractions in the dissolved phase; and (4) to investigate the partition coefficient of Cu between colloidal and total dissolved (TD) phases. These five dissolved state classifications cover the truly dissolved phase (<1 kDa), the low-molecular-weight (LMW) colloidal phase and the high -molecular-weight (HMW) colloidal phase, to facilitate the detailed evaluation of Cu migration between each fraction. The new insights brought about by the application of clean sampling and pretreatment technologies are of great significance for in-depth evaluations of colloid heterogeneity and dynamic behaviors in the river-sea mixing area. In addition, the results obtained from this study would provide a better insight into the physicochemical properties of aquatic colloids and their contributions in metal transportation.
Section snippets
Sampling and pre-filtration
A survey of the YRE was carried out in July 2020: 10 stations in the river-sea mixing zone were selected (Fig. 1; bright yellow area). All vessels were pre-cleaned before sampling, modified from the cleaning process in Li et al. (2015) and Lu et al. (2020). Briefly, all utensils were rinsed three times with 10% Decon 90™ detergent (v/v) and ultra-pure water (R = 18.2 MΩ-cm), soaked in 10% nitric acid (HNO3) and 10% hydrochloric acid (HCl) for 48 h, then placed in a clean bench to dry, and
Dissolved Cu concentrations and CF values
The mean concentrations and CF value distribution of the TD Cu in the YRE are presented in Fig. 2. The CF values of the sampling sites and seawater standard are summarized in Table 2. The TD Cu range from 41.96–73.29 nmol L−1, with an average of 59.03 nmol L−1. The highest concentration of TD Cu was found at site 2 (73.29 nmol L−1), followed by sites 5 (72.24 nmol L−1) and 9 (63.81 nmol L−1). The lowest TD concentration was found at site 7 (41.96 nmol L−1), followed by sites 3 (48.77 nmol L−1)
Conclusions
In this study, the spatial distribution, sources and character of <1 kDa truly dissolved phase, colloidal phase (1–3 kDa, 3–10 kDa, 10–100 kDa and 100 kDa −0.45 μm), and TD phase (<0.45 μm) Cu in the YRE, China, was investigated using the modified CFU method and clean sampling technique. The water quality of TD Cu was examined, and the dynamic changes in size distribution and the relationship between mixing behavior and environmental parameters were evaluated. Grade-one seawater quality
CRediT authorship contribution statement
Yuxi Lu: Investigation, Formal analysis, Conceptualization, Methodology, Validation, Writing – original draft. Dawei Pan: Funding acquisition, Resources, Conceptualization, Methodology, Validation, Supervision, Writing – review & editing. Tingting Yang: Formal analysis. Chenchen Wang: 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.
Acknowledgements
We gratefully thank anonymous reviewers for their constructive comments and suggestions. This work was financially supported by the Original Innovation Project (ZDBS-LY-DQC009) and the Strategic Priority Research Program (XDB42000000) of Chinese Academy of Sciences, and the National Key R&D Program of China (2019YFD0901103).
References (58)
- et al.
Correlation patterns between magnetic parameters and heavy metals of core sediments in the Yellow River estuary and their environmental implications
Mar. Pollut. Bull.
(2020) - et al.
Distribution of selenium and its relationship to the eco-environment in Bohai Bay seawater
Mar. Chem.
(2010) - et al.
A handling-free methodology for rapid determination of Cu species in seawater based on direct solid micro-samplers analysis by high-resolution continuum source graphite furnace atomic absorption spectrometry
Talanta
(2020) - et al.
Organic colloid separation in contrasting aquatic environments with tangential flow filtration
Water Res.
(2002) - et al.
On trace metal geochemistry in the Danube River and western Black Sea
Estuar. Coast. Shelf Sci.
(1998) An ecological risk index for aquatic pollution control. A sedimentological approach
Water Res.
(1980)- et al.
A functional micro-needle sensor for voltammetric determination of iron in coastal waters
Sensors Actuators B Chem.
(2021) - et al.
Dissolved trace metal distributions in port Jackson estuary (Sydney Harbour)
Aust. Mar. Pollut. Bull.
(2003) - et al.
Heavy metal pollution status in surface sediments of Swan Lake lagoon and Rongcheng Bay in the northern Yellow Sea
Chemosphere
(2013) - et al.
Distribution of Cd, Pb and Cu between dissolved fraction, inorganic particulate and phytoplankton in seawater of Terra Nova Bay (Ross Sea, Antarctica) during austral summer 2011-12
Chemosphere
(2017)
Dissolved trace metal distributions and cu speciation in the southern Bohai Sea, China
Mar. Chem.
Heavy metal spatial variation, bioaccumulation, and risk assessment of Zostera japonica habitat in the YRE, China
Sci. Total Environ.
Combining cross flow ultrafiltration and diffusion gradients in thin-films approaches to determine trace metal speciation in freshwaters
Geochim. Cosmochim. Acta
Separation and determination of colloidal trace metals in seawater by cross-flow ultrafiltration, liquid-liquid extraction and ICP-MS
Mar. Chem.
Colloidal toxic trace metals in urban riverine and estuarine waters of Yantai City, southern coast of North Yellow Sea
Sci. Total Environ.
Marine bioinorganic chemistry: the role of trace metals in the oceanic cycles of major nutrients
Metals in suspended sediments from the Changjiang (Yangtze River) and Huanghe (Yellow River) to the sea, and their comparison
Estuar. Coast. Shelf Sci.
Dissolved copper speciation behavior during estuarine mixing in the San Simon Inlet (wet season, Galicia). Influence of perticulate matter
Estuar. Coast. Shelf Sci.
Distribution characteristics and controlling factors of soluble heavy metals in the YRE and adjacent sea
Procedia Environ. Sci.
Behavior of colloidal trace metals (Cu, Pb and Cd) in estuarine waters: an approach using frontal ultrafiltration (UF) and stripping chronopotentiometric methods (SCP)
Estuar. Coast. Shelf Sci.
Sources and distribution of aliphatic and polycyclic aromatic hydrocarbons in Yellow River Delta nature reserve, China
Appl. Geochem.
Spatial and seasonal characteristics of dissolved heavy metals in the surface seawater of the YRE, China
Mar. Pollut. Bull.
An ultraclean cross-flow ultrafiltration technique for the study of trace metal phase speciation in seawater
Mar. Chem.
Spatial and temporal variations of bulk and colloidal dissolved organic matter in a large anthropogenically perturbed estuary
Environ. Pollut.
Molecular size-dependent abundance and composition of dissolved organic matter in river, lake and sea waters
Water Res.
Variations in size and composition of colloidal organic matter in a negative freshwater estuary
Sci. Total Environ.
Dynamic molecular size transformation of aquatic colloidal organic matter as a function of pH and cations
Water Res.
Characterization, origin and aggregation behavior of colloids in eutrophic shallow lake
Water Res.
Chromophoric dissolved organic matter in summer in a coastal mariculture region of northern Shandong Peninsula, North Yellow Sea
Cont. Shelf Res.
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