Wen-Xiong Wang
Hong Kong University of Science and Technology
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Featured researches published by Wen-Xiong Wang.
Science of The Total Environment | 2012
Ke Pan; Wen-Xiong Wang
Rapid growth of the economy in China has been coupled with increasing environmental pollution. The coastal and estuarine ecosystems in China are now facing increasing metal pollution pressures because of the elevated metal discharges from various sources. Industrial and domestic sewage discharges, mining, smelting, e-wastes recycling are important sources contributing to coastal pollution in China. In this review, status of metal contamination along Chinas coasts is assessed by a comprehensive review of metal concentrations recorded in sediments and marine organisms over the past ten years. Studies show that metal contamination in the coastal environments is closely associated with accelerated economic growth in the past decades. High metal contents can be detected in the sediments collected across the coasts in China. Alarmingly high metal concentrations are observed in the sediments, water and organisms collected from the heavily industrialized areas. Metal levels observed in marine bivalves also consistently reflect the elevated metal contamination. Elevated levels of metal contamination along Chinas coastal environment can increase the risk of metal exposure to humans by seafood consumption, raising the alarm for more stringent control of discharge of metals into environment.
Science of The Total Environment | 1998
John R. Reinfelder; Nicholas S. Fisher; Samuel N. Luoma; John W. Nichols; Wen-Xiong Wang
The bioaccumulation of trace elements in aquatic organisms can be described with a kinetic model that includes linear expressions for uptake and elimination from dissolved and dietary sources. Within this model, trace element trophic transfer is described by four parameters: the weight-specific ingestion rate (IR); the assimilation efficiency (AE); the physiological loss rate constant (ke); and the weight-specific growth rate (g). These four parameters define the trace element trophic transfer potential (TTP = IR.AE/[ke + g]) which is equal to the ratio of the steady-state trace element concentration in a consumer due to trophic accumulation to that in its prey. Recent work devoted to the quantification of AE and ke for a variety of trace elements in aquatic invertebrates has provided the data needed for comparative studies of trace element trophic transfer among different species and trophic levels and, in at least one group of aquatic consumers (marine bivalves), sensitivity analyses and field tests of kinetic bioaccumulation models. Analysis of the trophic transfer potentials of trace elements for which data are available in zooplankton, bivalves, and fish, suggests that slight variations in assimilation efficiency or elimination rate constant may determine whether or not some trace elements (Cd, Se, and Zn) are biomagnified. A linear, single-compartment model may not be appropriate for fish which, unlike many aquatic invertebrates, have a large mass of tissue in which the concentrations of most trace elements are subject to feedback regulation.
Science of The Total Environment | 1999
Wen-Xiong Wang; Nicholas S. Fisher
Delineating the routes of metal uptake in marine invertebrates is important for understanding metal bioaccumulation and toxicity and for setting appropriate water and sediment quality criteria. Trace element biogeochemical cycling can also be affected if the rates of metal uptake and regeneration by marine animals are dependent on the routes of metal accumulation. In this paper we review recent studies on the pathways of metal accumulation in marine invertebrates. Both food and water can dominate metal accumulation, depending on the species, metal and food sources. Trace elements which exist in seawater primarily in anionic forms (e.g. As and Se) are mainly accumulated from food. For metals that tend to associate with protein, uptake from water can be an important source. Kinetic modeling has recently been used to quantitatively separate the pathways of metal uptake in a few marine invertebrates. This approach requires measurements of several physiological parameters, including metal assimilation efficiencies (AE) from ingested food, metal uptake rates from the dissolved phase, and metal efflux rates (physiological turnover rates) in animals. For suspension feeders such as mussels and copepods, uptake from the dissolved phase and food ingestion can be equally important to metal accumulation. Metal AE and partition coefficients for suspended particles, which are dependent on many environmental conditions, can critically affect the exposure pathways of metals. For marine surface deposit feeding polychaetes such as Nereis succinea, nearly all metals are obtained from ingestion of sediments, largely because of their high ingestion rates and low uptake from solution. The bioavailability of metals from food and the trophic transfer of metals must be considered in establishing water and sediment quality.
Environmental Toxicology and Chemistry | 2011
Chun-Mei Zhao; Wen-Xiong Wang
Silver nanoparticles (AgNP) are now widely used as antibacterial products, and their potential toxicities in aquatic organisms are a matter of increasing concern. In the present study, we conducted experiments to reveal the acute and chronic toxicities of AgNP and its bioaccumulation from both aqueous and dietary sources in a model freshwater cladoceran, Daphnia magna. No mortality was observed in 48-h acute toxicity testing when the daphnids were exposed up to 500 µg Ag/L as AgNP. The AgNP accumulation reached as high as 22.9 mg Ag/g dry weight at the highest AgNP concentration tested (500 µg/L). In contrast, D. magna was extremely sensitive to free Ag ion (Ag(+) , added as AgNO(3) ), with a measured 48-h 50% lethal concentration of 2.51 µg/L. Thus, any AgNP potential acute toxicity may be caused by the release of Ag(+) into the solution. During the 21-d chronic exposure, dietborne AgNO(3) had the most significant influence on reproduction, whereas waterborne AgNP had the most significant inhibition on growth. Significant delay and decrease of reproduction in daphnids exposed to dietborne AgNO(3) occurred at a dissolved Ag concentration of 0.1 µg/L added to the algae. Significant inhibitions of growth and reproduction were also found for the AgNP exposure, with the lowest observed effective concentration of 5 µg/L and 50 µg/L, respectively. Chronic effects of AgNP were probably caused by the low food quality of algae associated with AgNP and the low depuration of ingested AgNP. Environmental risk assessments of AgNP should therefore include tests on the chronic toxicity to aquatic organisms as well as the direct and indirect effects of AgNP resulting from the release of Ag(+) into the environment.
Comparative Biochemistry and Physiology C-toxicology & Pharmacology | 2008
Wen-Xiong Wang; Philip S. Rainbow
Over the past decades, comparative physiology and biochemistry approaches have played a significant role in understanding the complexity of metal bioaccumulation in aquatic animals. Such a comparative approach is now further aided by the biokinetic modeling approach which can be used to predict the rates and routes of metal bioaccumulation and assist in the interpretation of accumulated body metal concentrations in aquatic animals. In this review, we illustrate a few examples of using the combined comparative and biokinetic modeling approaches to further our understanding of metal accumulation in aquatic animals. We highlight recent studies on the different accumulation patterns of metals in different species of invertebrates and fish, and between various aquatic systems (freshwater and marine). Comparative metal biokinetics can explain the differences in metal bioaccumulation among bivalves, although it is still difficult to explain the evolutionary basis for the different accumulated metal body concentrations (e.g., why some species have high metal concentrations). Both physiological/biochemical responses and metal geochemistry are responsible for the differences in metal concentrations observed in different populations of aquatic species, or between freshwater and marine species. A comparative approach is especially important for metal biology research, due to the very complicated and potentially variable physiological handling of metals during their accumulation, sequestration, distribution and elimination in different aquatic species or between different aquatic systems.
Environmental Science & Technology | 2010
Chun-Mei Zhao; Wen-Xiong Wang
Silver nanoparticles (AgNP) are widely used as antibacterial products, and there are increasing concerns for their potential environmental risks in aquatic ecosystems. The biokinetics of AgNP in aquatic organisms has not yet been determined. In the present study, we employed a radiotracer methodology to quantify the biokinetics of AgNP in a freshwater cladoceran Daphnia magna, including the uptake from water, dietary assimilation, and elimination of AgNP. We found that the uptake of AgNP was concentration dependent and governed by two phases. The uptake rate constant (k(u)) was 0.060 L/g/h at low AgNP concentrations (2, 10, and 40 μg/L), which was 4.3 times lower than that of the Ag free ion. At a higher AgNP concentration (160 and 500 μg/L), the uptake rate increased disproportionately, likely as a result of direct ingestion of these nanoparticles by the daphnids. When the AgNP were associated with the algal food, their dietary assimilation efficiency (AE) was in the range of 22-45%, which was much higher than the dietary assimilation of Ag quantified under the same food conditions. The efflux rate constants of AgNP in daphnids were also much lower than those of the Ag, again suggesting the difficulty of eliminating AgNP by the daphnids. Water excretion was the main elimination route for both AgNP and Ag, but a higher percentage of AgNP was lost through fecal production. Finally, we used a kinetic equation to compare the importance of aqueous and dietary uptake of AgNP using the quantified kinetic parameters. The biokinetic model showed that more than 70% of AgNP accumulated in the daphnids was through ingestion of algae, highlighting the importance of AgNP transport along the food chain. Our present study showed the unique characteristic of AgNP biokinetics and suggested that more attention should be paid to the dietborne AgNP toxicity in aquatic ecosystems.
Food and Chemical Toxicology | 2008
Jean-Claude Amiard; Claude Amiard-Triquet; Laetitia Charbonnier; Aurélie Mesnil; Philip S. Rainbow; Wen-Xiong Wang
Maximum acceptable concentrations of metals in food - based on total concentrations - have been established in many countries. To improve risk assessment, it would be better to take into account bioaccessible concentrations. A total of seven species of molluscs from France, UK and Hong Kong was examined in this study including clams, mussels, oysters, scallops and gastropods. The species which have total metal concentrations higher than the most severe food security limits are mainly oysters (all of the three studied species), the gastropod Buccinum undatum for cadmium and zinc, and scallops for cadmium. The lowest bioaccessibility (in % extractability with gut juices) was observed for silver (median for all of the species: 14%), it was moderate for lead (median: 33%) and higher for cadmium, zinc and copper (medians were respectively 54%, 65%, and 70%). In most cases, bioaccessible concentrations remained higher than the safety limits, except for cadmium in scallops and zinc in B. undatum. The influence of feeding habit (masticated or swallowed, addition of vinegar or lemon) on metal bioaccessibility in oysters is limited. On the contrary, cooking the gastropods decreased the bioaccessibility of metals, except silver.
Environmental Pollution | 2001
Wen-Xiong Wang; Robert C.H Dei
We examined the influences of major nutrients (N, P, Si) on the accumulation of three trace metals [Cd, Se(IV), and Zn] in four species of marine phytoplankton (diatom, green alga, dinoflagellate, prasinophyte). Relative metal uptake was quantified by the kinetic measurements of metal concentration factor over a short exposure period. Our study demonstrated that nutrient addition significantly influenced the metal uptake rate and the cell growth rate in all four phytoplankton species. An increase in ambient N concentration considerably enhanced metal uptake by the cells. The dry weight concentration factor increased by 2.4-14.9 times for Cd, 1.1-4.0 times for Se, and 1.1-5.4 times for Zn in all four phytoplankton species with an addition of 176.4 microM N. The effects of P or Si addition on metal uptake and cell growth were less pronounced than the effects of N addition. Under most circumstances the rate of metal uptake increased exponentially with increasing cell growth rate constant. Only Se(IV) uptake in the diatom Phaeodactylum tricornutum was not correlated with cell growth rate. Se(IV) was not accumulated by the green algae Chlorella autotrophica at a high P concentration (7.2 microM), but appreciable accumulation was documented in cells inoculated without P addition. Our study therefore demonstrated that nutrient enrichments in many coastal waters can considerably affect trace metal uptake in phytoplankton and presumably metal trophic transfer in marine food chains.
Environmental Chemistry | 2013
Wen-Xiong Wang; Philip S. Rainbow
Environmental Context. There is a considerable interest in predicting cadmium (Cd) toxicity to aquatic organisms, largely stemming from environmental Cd pollution and the need to establish water quality criteria to protect aquatic ecosystems. Chemistry-orientated models have been developed over the past decades to predict Cd toxicity, focusing on identifying which Cd forms are present in the aquatic environment, and investigating their interaction with the biological site of action. Understanding the cellular fates of Cd may provide an alternative method to predict Cd toxicity, as the complex cellular interactions of Cd within the organisms can, in this way, be addressed. Abstract. The internal metal sequestration strategies of different aquatic organisms are complex and variable; thus it is a formidable task to predict metal toxicity. Metals accumulated by aquatic organisms are associated with different subcellular compartments (i.e. heat-sensitive proteins, heat-stable proteins (metallothioneins), granules, cellular debris, and organelles). Such subcellular partitioning is dynamic in response to metal exposure and other environmental conditions, and is metal- and organism-specific. Previous models predicting metal toxicity have relied on the free ion metal activity (i.e. the free ion activity model) or more recently on the metal binding with the proposed toxicological site of action (i.e. the biotic ligand model). Neither of these models considers the complexity of internal metal subcellular fractionation, which may significantly affect metal toxicity in aquatic organisms and subsequent trophic transfer of metals to consumers. Recent studies in small aquatic organisms have revealed that the subcellular partitioning model (SPM) may provide an improved method to predict Cd toxicity, but more studies are needed in the future.
Marine Pollution Bulletin | 2010
Xiujuan Yu; Yan Yan; Wen-Xiong Wang
Surface sediments collected from the Pearl River Estuary (PRE) and the Daya Bay (DYB) were analyzed for total metal concentrations and chemical phase partitioning. The total concentrations of Cr, Cu, Ni, Pb, and Zn in the PRE were obviously higher than those in DYB. The maximum concentrations of trace metals in DYB occurred in the four sub-basins, especially in Dapeng Cove, while the concentrations of these metals in the western side of the PRE were higher than those in the east side. Such distribution pattern was primarily due to the different hydraulic conditions and inputs of anthropogenic trace metals. The chemical partitioning of metals analyzed by the BCR sequential extraction method showed that Cr, Ni, and Zn of both areas were present dominantly in the residual fraction, while Pb was found mostly in the non-residual fractions. The partitioning of Cu showed a significant difference between the two areas.