Accumulation patterns and species-specific characteristics of yttrium and rare earth elements (YREEs) in biological matrices from Maluan Bay, China: Implications for biomonitoring.

The critical usage of rare earth elements (REEs) in a variety of industrial applications has increased their release to the environment as emerging contaminants, while little is known about the fate and transport of REEs in coastal aquatic biota. In the present study, seven common species were collected and the concentrations of 15 naturally occurring REEs (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) were determined. Significant differences in total REEs concentrations were found among species even in the same taxa or phylum, suggesting that REEs bioaccumulation patterns appeared to be species- and element-dependent even in the same taxa or phylum, but with limited potential for bio-magnification based on the nitrogen isotope signatures (δ15N). Except for occasional anomalies for redox-sensitive elements of Ce and Eu, the abundance patterns of REEs normalized to chondrite revealed similar REE distribution trends, indicating a common source of REEs in all samples. Additionally, the abundances of light REEs (from La to Eu) were much higher than those of heavy REEs (from Gd to Lu and Y), demonstrating the fractionation between the light and heavy REEs. Furthermore, REEs concentrations in molluscs were notably higher than other species, implying their potential as bio-indicators of REEs due to the habitat and specific feeding behavior. Overall, this is not only the first study to focus on distribution levels, accumulation characteristics, geochemical and fractionation patterns of REEs in coastal species from identical area, but quantifying and tracing REE behavior will contribute to better evaluating the possible environmental impacts of REEs enrichment for future biomonitoring research.

Concentration-dependent effects of lithium on Daphnia magna: Life-history profiles and integrated biomarker response implementation.

The growing use of lithium (Li) in industrial and energy applications and increasing demand worldwide has inevitably resulted in its wide dispersal, representing a significant threat to aquatic systems. Unfortunately, as a ubiquitous emerging contaminant, the comprehensive toxicological information regarding Li at multifarious levels is limited. To diminish this gap, this work was focused to explore Li-induced cascading effects on Daphnia magna as a key species in freshwater ecosystems. Specifically, the organisms were chronically exposed to gradient Li concentrations with emphasis on characterizing life-history traits from individual to population scale, primarily as observed by a markedly concentration-dependent decrease along exposure gradients. In parallel, a robust set of biomarkers relating to energy reserves, antioxidant and biotransformation enzymes, cellular damage, ionoregulation and neurotoxicity were assayed for further understanding potential underlying mechanisms. As a result, biomarker alterations were characterized by significant decreases in energy storage and enzymatic profiles of antioxidant and biotransformation systems, not only triggering an imbalance between reactive oxygen species (ROS) generation and elimination under Li exposure, but compromising the fecundity fitness of phenotypical costs. In contrast, malondialdehyde (MDA) levels were remarkably enhanced as a consequence of inefficient antioxidant and biotransformation capacity leading to lipid peroxidation (LPO). Additionally, Li exerted a dose-dependent biphasic effect on the activities of superoxide dismutase (SOD), Na+,K+-ATPase and acetylcholinesterase (AChE) by interfering with inherent balance. In terms of responsive patterns and dose-effect trends, the integrated biomarker response indices (IBRv2) and star plots were consistent with the differences in biomarker profiles, not only presenting comprehensively biological effects in a visualized form, but signaling the importance of progressive induced changes in an integrative way. Overall, these findings highlighted the need for elucidating Li-produced impacts from a comprehensive perspective, providing valuable insights into better understanding the toxicity of Li in relation to aquatic ecosystem functioning and ecological relevance.

Two-phase effects of environmentally relevant lanthanum on life-history traits of Daphnia magna and transgenerational bioenergetic profiles: Implications for nutritional and environmental consequences.

The versatile applicability of rare earth elements (REEs) especially lanthanum (La) in diverse fields, has led to large-scale mineral exploitation globally, inevitably resulting in substantial release of La into environment. As emerging anthropogenic environmental contaminant, La-induced toxicological effects and potential ecotoxicological implications in relation to realistic levels of La in aquatic ecosystems are becoming major concerns. To address these issues, Daphnia magna was selected as a prototype, and toxicity tests were conducted to explore the effects of La exposure on life-history characteristics and fecundity fitness, as showcased by quantitative variations from the individual level to population scale. In parallel, to further denote transgenerational caloric impacts of parental La exposure, bioenergetic profiles on newborn neonates were concurrently determined by measuring macromolecule forms in terms of proteins, glycogens and lipids to quantify nutritional alterations at progeny level. The results revealed that low-dose La exposure slightly stimulated the demographic potential and nutritional responses, exhibiting dose-dependent hormesis-like effects and promising non-toxicological potential to Daphnia, whereas high-dose La exposure of greater than 59.2 µg La L - 1, conspicuously imposed detrimental effects on quantity and quality of offspring, i.e. not only reducing body size, lifespan expectancy and reproductive output in a concentration-dependent way and resulting in lower population fitness by a dynamic life-table analysis, but eventually leading to the decrease of nutritional qualities and caloric contents on neonates. Taken together, these two-phase findings regarding the dose-related shift from hormesis to inhibition not only provided valuable insights into the complicated biological outcomes of La effects on environmentally-relevant organisms, but experimentally highlighted the significant implications of considering environmental and nutritional consequences in ecologically assessing the La-triggered risk at environmentally realistic occurrences, particularly on gradient scenarios crossing upstream and downstream of highly complex mining watersheds.

Integrated assessment of biomarker responses in caged shrimps (Litopenaeus vannamei) exposed to complex contaminants from the Maluan Bay of China.

The marine shrimp Litopenaeus vannamei were used as an active biomonitoring organism to assess the bioavailability and impact of metal contaminants in seven study sites along the Maluan Bay of China. Metal concentrations in the hepatopancreas of shrimps were determined in conjunction with four biomarkers responses after a 7 day in situ cage exposures. The results showed that contaminant tissue burdens at the deployment sites were greater than those of the reference site, and antioxidant enzyme activities were strongly inhibited compared to those of reference organisms. Variations in these biomarker responses were correlated significantly (p < 0.05 or p < 0.01) with the specific metal pollutants at the study sites, but no significant correlations existed between catalase activity responses and the metal contaminants. This suggests the presence of undetermined contaminants or other exposure routes that may be responsible for the decreased catalase activity. Multivariate analysis revealed a causal relationship between contaminants at each deployment site and the biochemical "response" of the caged shrimps at these sites and demonstrated the presence of two contaminant "hot" spots. This investigation suggested that the incorporation of chemical data on trace metal concentrations with the analysis of antioxidant enzymatic activities in caged shrimps can be a useful tool for the identification of causal toxic contaminants in complex mixtures.

Geochemical behavior and fractionation characteristics of rare earth elements (REEs) in riverine water profiles and sentinel Clam (Corbicula fluminea) across watershed scales: Insights for REEs monitoring.

The increasing global demand for rare earth elements (REEs) has led to their recognition as emerging contaminants; however, the effect that biota have on the cycling of these elements at the watershed scale is not currently well understood. In this study, water samples and field freshwater clams Corbicula fluminea were concurrently collected along watershed gradients, and concentration profiles of 14 naturally occurring REEs were measured in operationally defined water fractions and soft tissues of the freshwater clams. Moreover, Post Archean Australian Shale (PAAS) normalized REE patterns, fractionation indices, and anomalous values were determined to further extract characteristic features. As a result, both the water and biological samples had variable REE compositions, with higher concentrations of light REEs (LREEs) than middle REEs (MREEs) and heavy REEs (HREEs), while decreasing concentrations were generally observed as filter pore size decreased, implying that large colloidal and particulate fractions were important carriers of REEs. The spatial distribution patterns of REEs revealed a clear site effect among profiles, with variability more pronounced among watersheds and with peaks in sites from a small watershed near the hotspots of the mining area, and then exhibited a decreasing trend with distance from there. Meanwhile, significant bioaccumulation of REEs was observed potentially reflecting different degrees of contamination gradients among the watersheds. The PAAS-normalized distribution patterns tended to be slightly enriched in MREEs, producing a peculiar "roof-shaped" feature and characteristic fractionation. Remarkably, bio-concentration factors (BCFs) highlighted the importance of large colloidal and particulate phases in assessing biologically available REEs for filter-feeding species. Collectively, our study strongly favored that accumulation patterns and fractionation characteristics of REEs in C. fluminea can serve as a reliable indicator of geochemical behavior, providing a promising biomonitoring tool to quantitatively denote different degrees of REE contamination and assess possible impacts in mining watersheds.

Concentrations of some heavy metals in water, suspended solids, and biota species from Maluan Bay, China and their environmental significance.

Concentrations of heavy metals (Cu, Zn, Cd, and Pb) in surface water (including total recoverable, dissolved, suspended solids) and in aufwuchs encrusted on Moerella iridescens Benson from seven selected sites and two reference sites in Maluan Bay were investigated in order to understand current metal contamination due to industrialization and urbanization in Xiamen, China. The muscle tissues of the study species (Penceus penicillatus, Scylla serrata Forskal, Harengula zunasi Bleeker, Tillapia nilotica) from a trawling area within Maluan Bay were also analyzed in order to evaluate its safety as seafood. Based on the obtained data, metal concentrations in surface water were compared with Marine Seawater Quality Standards of China and the US EPA acute and chronic criteria, which showed that Maluan Bay may be subjected to different levels of contamination by the metals. Metal concentrations under study in the edible parts (muscle) of the investigated biota species were within the safety permissible levels for human consumption. Through Pearson's correlation analysis, the relationships between metal concentrations in surface water and in M. iridescens were evaluated. Copper concentrations in M. iridescens were more strongly positively correlated with particulate copper in suspended solids and total recoverable copper in water rather than with dissolved copper at the sampling sites. The data suggested that copper-rich suspended solids contributed substantially to copper accumulation by M. iridescens and played a critical role in the pathway of copper into the food chain. The conclusions of this investigation are likely to be applicable to other relevant scenarios.

Effects of dietary cadmium exposure on reproduction of saltwater cladoceran Moina monogolica Daday: Implications in water quality criteria.

The chronic toxicity of dietary cadmium to the saltwater cladoceran Moina monogolica Daday and its relative toxicity compared with aquatic exposure were investigated in the present study. The microalgae Chlorella pyrenoidosa, exposed to cadmium in growth inhibition tests, had a 96-h median effective concentration (EC50) of 81.2 microg Cd/L (95% confidence intervals [CIs] = 71.9-95.1). C. pyrenoidosa exposed for 96 h to sublethal dissolved cadmium concentrations in the range 4.10 +/- 0.30 to 70.29 +/- 0.31 microg/L resulted in algal cadmium burdens up to 73.86 x 10(-16) g Cd/cell. Cellular cadmium burdens accumulated in a dose-dependent manner, whereas cell densities inversely declined from 670 x 10(4) to 38 x 10(4) cells/ml with exposure to the increasing aqueous cadmium concentrations. C. pyrenoidosa preexposed to cadmium and used as food in a chronic 21-d toxicity test with the cladoceran M. monogolica, containing no added dissolved cadmium, inhibited reproduction. Significant reductions of the net reproduction rate (R(0)) per brood were observed in all broods, and the decline in the number of neonates produced increased with each subsequent brood. The cadmium concentration (4.10 +/- 0.30 microg/L) in the algal culture water that produced the lowest algal cadmium burden (2.85 +/- 0.76 x 10(-16) g Cd/cell) was shown to inhibit M. monogolica reproduction and was compared with the water quality criteria (WQC) of China. This comparison indicated that dietary exposure to cadmium may cause sublethal responses at concentrations below the current cadmium WQC of China for aquaculture.

Quantitative identification of nitrate sources in a coastal peri-urban watershed using hydrogeochemical indicators and dual isotopes together with the statistical approaches.

Surplus nutrient load and complex migration and transformation processes are the challenges for water quality management in the peri-urban coastal watershed, leading to increasing concerns worldwide. We investigated the spatio-temporal variation of hydrogeochemical parameters in surface water of Jimei Lake watershed, and distinguished the sources and transformation of nitrate-N (NO3--N) using dual isotopes of nitrate (δ15N and δ18O in NO3-) with hydrogeochemical indicators. Principal component analysis (PCA) on hydrogeochemical parameters demonstrated that surface water was seriously polluted by nutrients, especially in the southeast of the downstream. There were signs of seawater intrusion and increased wastewater discharge in the mid-lower reaches with high ammonium concentrations. Nitrification occurred throughout the monitoring period with lower δ15N and δ18O values and NO3- derived from mixed pollution sources. Results of Bayesian model showed that dominant NO3- input originated from manure and sewage (M&S, 71% and 76% in the wet and dry season, respectively) and atmospheric deposition (22% and 16%, respectively). This result implied that the controls and treatment of M&S discharges are essential to alleviate of NO3- pollution. The proposed method is helpful to understand the origins of NO3- and may be suitable to develop measures for the reducing of nitrogen loadings in the peri-urban watershed.

Effects of microplastics and their adsorption of cadmium as vectors on the cladoceran Moina monogolica Daday: Implications for plastic-ingesting organisms.

As pervasive and resilient contaminants, microplastics (MPs) have potential to interact with the toxicity of metals through adsorption on the surface. In this study, we focused on 7-day adsorption of cadmium (5, 10 µg/L) to aged polyethylene-MPs particles (300 µg/L), and further examined 21-day chronic effects of MPs and MPs-Cd on cladoceran Moina monogolica Daday. The effects criteria selected were physiological changes (e.g., parental survival time, somatic growth and reproductive parameters) and nutritional profiles in offspring. Exposure of M. monogolica to both MPs and MPs-Cd can impair the development, reproductive output and fecundity across treatment groups, ultimately leading to parental mortality and poor nutritional status in progeny. Importantly, MPs with adsorbed Cd showed greater adverse dose-dependent effects than bare MPs, likely due to the mechanisms of physico-chemical interactions related to the Cd release from MPs-Cd inside organisms. MPs can pose not only a direct harm to the organisms but also an indirect hazard via adsorption as "transport vector", having implications for the function and resilience of aquatic ecosystems. Our findings experimentally highlight the importance of characterizing chemical profiling of contaminants adsorbed to field plastics in order to better assess environmentally relevant risks associated with MPs and metals in coastal areas.

Acute and chronic cadmium toxicity to a saltwater cladoceran Moina monogolica Daday and its relative importance.

Acute and chronic toxicity tests of a saltwater cladoceran Moina monogolica Daday exposed to cadmium were conducted according to the American Society for Testing and Materials (ASTM) guidelines. The 24- and 48-h LC50s and their 95% confidence intervals (CIs) were calculated as 9.59 (8.91-10.26) and 1.87 (1.46-2.32) mg Cd/l, respectively, based on measured cadmium concentrations. When compared with different phyla or classes of saltwater animals, M. monogolica had moderate sensitivity and was suitable to be used as an indicator organism. Eight end points used to evaluate chronic effects were affected at chronic cadmium concentrations. Test organisms ceased to reproduce when exposed to equal to or greater than 308.10 microg Cd/l. Comparisons of chronic effects showed that mechanisms of metal accumulation patterns M. monogolica exposed to cadmium are different from those of dissolved copper exposure. The point estimates using linear regression equations of net reproductive rate generated the maximum-acceptable-toxicant concentration of 1.78 microg Cd/l, the lowest-observed-effect concentration of 3.01 microg Cd/l and the no-observed-effect concentration of 1.11 microg Cd/l. Comparisons among thresholds, cadmium concentrations in natural aquatic systems and water quality criteria showed that aquatic organisms were possibly negatively affected at some sites of higher cadmium concentrations. Further research is needed to focus on risk assessment of cadmium on saltwater aquatic organisms and water quality criteria development of China.

Integrated assessment of sediment quality in a coastal lagoon (Maluan Bay, China) based on AVS-SEM and multivariate statistical analysis.

Total metal concentrations and acid-volatile sulfide (AVS) measurements coupled with simultaneously extracted metals (SEM) were determined in heterogeneous sediments from Maluan Bay, China. Zn was the predominant component of SEM, while Cd was the least. In sediment cores, AVS increased with sediment depth, followed by a decrease with large variation, while SEM fluctuated. Multiple empirical sediment quality guidelines (SQGs) and equilibrium partitioning (EqP) approaches were applied to assess the contamination degree, sediment quality and potential risks associated with bioavailable metals, indicating that not all sediments with [SEM]-[AVS] > 0 were capable of causing toxicity because TOC is also an important metal-binding phase. In order to screen out the physicochemical variability and the complexity and large variance of datasets, multivariate statistical techniques were utilized to comprehensively reveal pollution status by visualized factor scores. Collectively, this study favors the integrative utilization of multifarious methods to scientifically diagnose the pollution characterization for sustainable coastal management.

Complex role of titanium dioxide nanoparticles in the trophic transfer of arsenic from Nannochloropsis maritima to Artemia salina nauplii.

Increasing concern has been focused on the potential risks associated with the trophic transfer to aquatic organisms of ambient contaminants in the presence of titanium dioxide nanoparticles (nano-TiO2). This study investigated the influence of nano-TiO2 on the trophic transfer of arsenic (As) from the microalgae Nannochloropsis maritima to the brine shrimp Artemia salina nauplii. We found that nano-TiO2 could significantly facilitate As sorption on N. maritima within an exposure period of 24 h, and this sorption subsequently led to higher As trophic transfer from the algae to A. salina according to trophic transfer factors (TTFAs+nano-TiO2 > TTFAs). However, after 48 h of depuration, the retention of As in A. salina fed As-nano-TiO2-contaminated algae was even lower than that in A. salina fed As-contaminated algae at the same exposure concentrations. This result indicates that the increased food chain transfer of As in the presence of nano-TiO2 can be explained by adsorption of As onto nano-TiO2 in contaminated food (algae), but the bioavailability of As in A. salina is reduced after the introduction of nanoparticles. Although the stress enzyme activities of superoxide dismutase (SOD) and acetylcholinesterase (AChE) in A. salina at a lower As concentration treatment in the presence of nano-TiO2 were not significantly changed, they increased with higher exposure concentrations of As with or without nano-TiO2. Our study highlighted the complex role of nanomaterials in the transfer of ambient contaminants via trophic chains and the potential of nano-TiO2 to reduce the bioavailability of As via trophic transfer to saltwater zooplankton.

Reproductive toxicity of dietary copper to a saltwater cladoceran, Moina monogolica Daday.

In the present study, the chronic toxicity of dietary copper to Moina monogolica Daday was investigated. Microalgal growth inhibition tests were conducted for 96 h with the green algae Chlorella pyrenoidosa exposed to copper. The 96-h median effective concentration (95% confidence interval) was 509.12 (388.68-629.56) microg/L. Then, C. pyrenoidosa was exposed for 96 h to a control and to seven dissolved copper concentrations. Cellular copper concentration accumulated in a dose-dependent manner and was plotted against cell density. These algae were used as food in a 21-d bioassay with M. monogolica in seawater to which no dissolved copper was added. Brood size was not reduced in the first brood, but significant reductions at all algal-exposure copper concentrations (44.78-817.17 microg/L) were observed in all subsequent broods, with increasing magnitude in each brood. Neither longevity nor number of broods per female was significantly affected, even at the highest copper exposure, though both endpoints did show a consistent downward trend with increasing copper exposure. Total reproduction, brood size, and net reproductive rate were decreased significantly in all dietary copper exposures (algae exposed to 44.78-817.17 microg/L). In contrast, the intrinsic rate of natural increase was reduced significantly only with algae exposed to greater than 619.27 microg/L, most likely because of the heavy influence of early reproduction on this metric. Because cell density in algal cultures decreased with increasing copper concentrations, it is possible that changes in the nutritional content of the algal diet could have played a role in causing the observed changes in reproduction of M. monogolica.

Estrogenic compound profiles in an urbanized industry-impacted coastal bay and potential risk assessment by pollution indices and multivariative statistical methods.

The occurrence and distribution of target estrogenic compounds in a highly urbanized industry-impacted coastal bay were investigated, and contamination profiles were evaluated by estimating total estradiol equivalents (∑EEQs) and risk quotients (RQs). Phenolic compounds were the most abundant xenoestrogens, but seldom showed contribution to the ∑EEQs. The diethylstilbestrol (DES) and 17α-ethinylestradiol (EE2) were the major contributors followed by 17ß-estradiol (E2) in comparison with a slight contribution from estrone (E1) and estriol (E3). Both ∑EEQs and RQs indicated likely adverse effects posed on resident organisms. Further, multivariate statistical method comprehensively revealed pollution status by visualized factor scores and identified multiple "hotspots" of estrogenic sources, demonstrating the presence of complex pollution risk gradients inside and particularly outside of bay area. Overall, this study favors the integrative utilization of pollution indices and factor analysis as powerful tool to scientifically diagnose the pollution characterization of human-derived chemicals for better management decisions in aquatic environments.

Removal of phosphate from aqueous solution by zeolite synthesized from fly ash.

Fifteen Chinese fly ashes were converted hydrothermally into zeolites, and phosphate immobilization capacity (PIC) of the synthesized zeolites and the corresponding raw fly ashes were determined using an initial phosphate concentration of 1000 mg/L. Results showed that there was a remarkable increase in PIC (from 1.2 to 7.6 times) following the synthesis process. Fractionation of immobilized phosphorus indicated that Fe+Al-P increased most significantly and consistently among all the phosphorus fractions following the conversion of fly ash to zeolite. The PIC and Ca+Mg-P were closely related to Ca content (with r values of 0.9683 and 0.9651, respectively) rather than Mg content (with r values of 0.3920 and 0.3212, respectively). The r values of PIC and Fe+Al-P with Fe content (with r values of 0.4686 and 0.6385, respectively) were higher than those with Al content (with r values of -0.7857 and -0.3770, respectively). Although calcium and iron components were mainly involved in phosphate immobilization, there was no significant change of Ca and Fe content following the conversion of fly ash to zeolite. Increase in dissociated Fe(2)O(3) and specific surface area probably accounted for the enhancement in PIC of synthesized zeolites compared with corresponding fly ashes. The PIC value of zeolites showed a significant correlation with dissociated Fe(2)O(3) (r=0.6186). The specific surface area increased 26.0-89.4 times as a result of the conversion of fly ash to zeolite. The maximum removal of phosphate occurred within different pH ranges for zeolites which were synthesized from high, medium and low calcium fly ashes and this behavior was explained by the reaction of phosphate with calcium and iron components.

Simulating ocean acidification and CO2 leakages from carbon capture and storage to assess the effects of pH reduction on cladoceran Moina mongolica Daday and its progeny.

In order to evaluate the effects of pH reduction in seawater as a result of increasing levels of atmospheric CO2, laboratory-scale experiments simulating the scenarios of ocean acidification (OA) and CO2 leakages of carbon capture and storage (CCS) were performed using the model organism Moina mongolica Daday. The LpH50s calculated in cladoceran toxicity tests showed that M. mongolica exhibited intermediate sensitivity to OA, which varied among species and with ontogeny, when compared with different phyla or classes of marine biota. Survival, reproduction and fecundity of parthenogenetic females were evaluated after 21-day exposures. Results showed that increased acidity significantly reduced the rate of reproduction of M. mongolica resulting in a decreased intrinsic rate of natural increase (rm) across the gradients of pH reduction. The analysis of macromolecule contents in neonates suggested that nutritional status in progeny from all broods were significantly reduced as seawater pH decreased, with increasing magnitude in latter broods, except the contents of protein from two former broods and lipids from the first brood. Our findings clearly showed that for this ecologically and economically important fish species, the negative effects of pH reduction on both "quantity" and "quality" of progeny may have far-reaching implications, providing direct evidence that OA could influence the energetic transfer of marine food web and ecosystem functions in acidified oceans in the future.

[Distributions of Arsenic Species in Different Eutrophic Waters of Lake Taihu and Their Relations to Environmental Factors].

A detailed field survey of arsenic species and water quality parameters was conducted in different eutrophicated regions of Lake Taihu (Zhushan Bay, Meiliang Bay, Gonghu Bay and Southern Taihu) in summer and winter. Furthermore, spatial and seasonal distributions of arsenic species and their relations to water quality parameters were investigated with multivariate analysis techniques. Higher average contents of total arsenic (TAs), arsenate[As(Ⅴ)], arsenite[ As(Ⅲ)] and methylarsenicals [sum of monomethylarsenic acid (MMA) and dimethylarsenic acid (DMA)] were observed in northern regions (including Zhushan Bay, Meiliang Bay, and Gonghu Bay) (TAs:2.58-3.34 µg·L-1, As(Ⅴ):1.37-2.34 µg·L-1, As(Ⅲ):0.53-0.64 µg·L-1, methylarsenicals:0.16-0.36 µg·L-1), compared to those in Southern Taihu (1.73, 1.10, 0.31, 0.10 µg·L-1). The results exhibited obvious spatial characteristics of arsenic species in the surface water of Lake Taihu. Besides, average values of TAs, As(Ⅴ), As(Ⅲ) and methylarsenicals in summer were 3.40, 2.06, 0.73 and 0.25 µg·L-1, respectively, higher than those in winter (1.78, 1.10, 0.30, 0.17 µg·L-1), reflecting significant seasonal characteristics of arsenic distribution. Factor analysis revealed the significant relationships of TAs and As(Ⅴ) with several water quality parameters, which suggested that spatial and seasonal distributions of TAs and As(Ⅴ) in Lake Taihu were affected by external pollution and internal arsenic release from sediments. Redundancy analysis further indicated significant effects of total phosphorus (TP) and total iron (TFe) on the distributions of TAs and As(Ⅴ). At the mean time, the above statistical analyses exhibited that As(Ⅲ) and methylarsenicals were positively correlated with chlorophyll-a (Chl-a). A large amount of microalgae could accumulate As(Ⅴ) and transform it more strongly to As(Ⅲ) and methylarsenicals in eutrophic regions when compared to mesotrophic region,especially in summer, reflecting the regulation of microalgae on arsenic biotransformation.

Subcellular partitioning profiles and metallothionein levels in indigenous clams Moerella iridescens from a metal-impacted coastal bay.

In this study, the effect of environmental metal exposure on the accumulation and subcellular distribution of metals in the digestive gland of clams with special emphasis on metallothioneins (MTs) was investigated. Specimens of indigenous Moerella iridescens were collected from different natural habitats in Maluan Bay (China), characterized by varying levels of metal contamination. The digestive glands were excised, homogenized and six subcellular fractions were separated by differential centrifugation procedures and analyzed for their Cu, Zn, Cd and Pb contents. MTs were quantified independently by spectrophotometric measurements of thiols. Site-specific differences were observed in total metal concentrations in the tissues, correlating well with variable environmental metal concentrations and reflecting the gradient trends in metal contamination. Concentrations of the non-essential Cd and Pb were more responsive to environmental exposure gradients than were tissue concentrations of the essential metals, Cu and Zn. Subcellular partitioning profiles for Cu, Zn and Cd were relatively similar, with the heat-stable protein (HSP) fraction as the dominant metal-binding compartment, whereas for Pb this fraction was much less important. The variations in proportions and concentrations of metals in this fraction along with the metal bioaccumulation gradients suggested that the induced MTs play an important role in metal homeostasis and detoxification for M. iridescens in the metal-contaminated bay. Nevertheless, progressive accumulation of non-essential metals (Cd, and especially Pb) resulting from "spillover" was observed in putative metal- sensitive (e.g., mitochondria and heat-denaturable protein (HDP)) or lysosome/microsome fractions, demonstrating that metal detoxification was incomplete and increased the toxicological risk to M. iridescens inhabiting the metal-impacted environments. Through multiple stepwise regression analysis, the induction of MTs was statistically correlated with the HSP concentrations of Cu, and to a lesser extent with Zn, and ultimately to the Cd concentrations, exhibiting significant dose-dependent relationships. Overall, these findings not only revealed the fates of accumulated metals, but scientifically favored an improved understanding of the detoxification at the subcellular level in response to metal accumulation, supporting the focus of metabolic availability assessment on the intracellular processes or events occurring within organisms.

Spatial and seasonal changes of arsenic species in Lake Taihu in relation to eutrophication.

Spatial and seasonal variations of arsenic species in Lake Taihu (including Zhushan Bay, Meiliang Bay, Gonghu Bay, and Southern Taihu) were investigated. Relatively high levels of total arsenic (TAs) and arsenate (As(V)) were observed in hyper-eutrophic regions during summer and autumn, which is attributed to exogenous contamination and seasonal endogenous release from sediments. The distributions of TAs and As(V) were significantly affected by total phosphorus, iron, manganese, and dissolved organic carbon. Arsenite (As(III)) and methylarsenicals (the sum of monomethylarsenic acid (MMA(V)) and dimethylarsenic acid (DMA(V))), mainly from biotransformation of As(V), were affected by temperature-controlled microalgae activities and local water quality parameters, exhibiting significantly higher concentrations and proportions in hyper-eutrophic and middle eutrophic regions during summer compared to mesotrophic region. The eutrophic environment, which induces changes in the main water quality parameters such as phosphorus, chlorophyll-a, iron, manganese, and dissolved organic carbon, can favor the biogeochemical cycling of arsenic in the aquatic systems.

Metal release from contaminated coastal sediments under changing pH conditions: Implications for metal mobilization in acidified oceans.

To investigate the impacts and processes of CO2-induced acidification on metal mobilization, laboratory-scale experiments were performed, simulating the scenarios where carbon dioxide was injected into sediment-seawater layers inside non-pressurized chambers. Coastal sediments were sampled from two sites with different contamination levels and subjected to pre-determined pH conditions. Sediment samples and overlying water were collected for metal analysis after 10-days. The results indicated that CO2-induced ocean acidification would provoke increased metal mobilization causing adverse side-effects on water quality. The mobility of metals from sediment to the overlying seawater was correlated with the reduction in pH. Results of sequential extractions of sediments illustrated that exchangeable metal forms were the dominant source of mobile metals. Collectively, our data revealed that high metal concentrations in overlying seawater released from contaminated sediments under acidic conditions may strengthen the existing contamination gradients in Maluan Bay and represent a potential risk to ecosystem health in coastal environments.