Bioaccumulation Of Contaminants Research Articles

Effect of Ultrafiltration–Reverse-Osmosis-Treated Shale Gas Wastewater on Seed Germination and Plant Growth

The safe disposal or reclaim of shale gas flowback and produced water (SGFPW) is a significant challenge given the large amounts and typically heavy contamination. The high levels of total dissolved solids, particulate matter, and organics combined with naturally occurring radioactive material (NORM) and heavy metals reflect the composition of SGFPW, bearing potential environmental hazards of bioaccumulation of contaminants in localized areas of shale gas wastewater disposal. This study investigated the effects of ultrafiltration–reverse-osmosis-treated shale gas wastewater on vegetable seed germination, plant growth performance, and ion concentration in plants, which offered a momentous exploration of the feasibility study on agricultural use for SGFPW reuse. The resulting uptake of heavy metals by vegetables is relatively low, and the radioactive elements are reduced to a safe level as a result of treating water used for irrigation, selecting appropriate crops, and greenhouse cultivation. Through reduction of the bioaccumulation and metal concentrations from SGFPW to plants, this approach decreases health risks associated with NORM intake from edible vegetable biomass.

From forests to fish: Mercury in mountain lake food webs influenced by factors at multiple scales

AbstractMountain lakes, while seemingly pristine, have been subjected to historical fish stocking practices and exposure to atmospherically deposited contaminants like mercury. Mercury bioaccumulation in these ecosystems varies widely due to strong environmental gradients, and there are complex, hierarchical factors that affect mercury transport and loading, methylmercury production, and food web biomagnification. We sought to assess how representative variables associated with watershed, lake, and food web‐scale processes—specifically, catchment tree cover, lake benthic primary production, and fish diet, respectively—are associated with mercury concentrations in mountain lake fish. Mean fish mercury concentrations varied threefold between lakes, with nearshore tree cover and fish diet accounting for the most variance in fish mercury. Tree cover was likely positively correlated to fish Hg due to its contributions to local deposition and its effect on lake biogeochemistry. Fish with benthic diets tended to have higher mercury concentrations, illustrating that food web processes are an important consideration when investigating drivers of contaminant bioaccumulation. Our results suggest that both landscape and ecological factors are determinants of fish mercury bioaccumulation, and thus variables at multiple scales should be considered when managing mountain lake food webs for mercury exposure risk.

Avaliação de um biossorvente à base de fibra de ráfia na sorção de hidrocarbonetos

Oil spills and discharges of petroleum products have severely polluted aquatic ecosystems, oceans, rivers, groundwater and even soil. In August 2019, more than 2,000 km of the northeast and southeast coast of Brazil were struck by a major oil spill in the country’s largest ever environmental disaster. Spill remediation is a significant environmental challenge and the economic and socioenvironmental impacts of these events are diverse. Oil spills in oceans and rivers severely affect the fishing and tourism industries of the areas in question, with damage including severe short and long-term effects on plants and animals, such as respiratory and digestive disorders, reduced growth and reproductive capacity as well as weakened immunity due to the bioaccumulation of toxic contaminants. There are several proposed strategies for removing crude oil and petroleum products from surface water. Contaminated areas can be remediated in-situ or ex-situ, with the former considered the best option in terms of cost and efficiency. In this respect, absorbent materials obtained from biomass have received widespread attention due to their ease of use, buoyancy and low cost. Raffia is a natural fiber abundant in eastern Africa with excellent physical properties, such as low specific weight, good liquid sorption and low conductivity. As such, the present study investigated the application of raffia fiber with different particle sizes ( 300 µm, 300 - 850 µm, 850 - 1000 µm, 1000 - 1400 µm and 1400 - 2000 µm) and fiber/hydrocarbon ratios (1, 2, 3 and 4% w/v) as an absorbent for hydrocarbons, using n-heptane as a model molecule. Microscopic analysis of micronized raffia fiber indicated the presence of honeycomb-shaped cells with well-defined borders and an irregular geometry. These honeycomb structures are preserved, especially in large particle size ranges. Among the granulometries assessed, the highest sorption capacities were obtained for 1000 to 1400 µm raffia fibers, suggesting that honeycomb-shaped structures favor hydrocarbon sorption. Additionally, the fact that smaller particles do not require micronization is economically beneficial and facilitates application of the absorbent material to remediate hydrocarbon-contaminated areas. The results obtained under the conditions studied indicate that sorption capacity increases as the absorbent content rises. Comparison of fiber contents of 1% and 3% w/v for 1000 - 1400 µm particles showed an increase of approximately 43% in sorption capacity when content rose to 3% w/v. The results of the present study demonstrate the potential of natural raffia fiber as an alternative absorbent for hydrocarbons.

Re-assessing the degradation of benthos beneficial use impairment in the Toronto and Region Area of Concern

Sediment quality of the Toronto and Region Area of Concern (AOC) waterfront was assessed using a weight of evidence approach following the Sediment Quality Triad, with the addition of contaminant bioaccumulation data, to determine current status following the 2013 re-designation of the “degradation of benthos” Beneficial Use Impairment as “no longer impaired.” Five stations within the AOC were sampled in 2015 and compared to lower Great Lakes nearshore reference areas (n = 22) selected based on similarity of sediment physicochemical properties. Sediment chemistry was comparable except for a localized instance of elevated perfluorinated compounds at one AOC site. Laboratory sediment toxicity bioassays indicated chronic toxicity associated with point sources to the AOC, corresponding to increased invertebrate body burdens measured in laboratory exposures. Diversity metrics and multivariate analysis showed that benthic invertebrate community composition present at the AOC sites was not significantly different from reference conditions of the lower Great Lakes. The weight of evidence from this study indicates benthic invertebrate communities continue to show effects of degraded sediment conditions at sites impacted by point sources. While the 2013 RAP decision was to re-designate the “degradation of benthos” BUI to “no longer impaired,” our results support the notion that life after AOC delisting must continue to prioritize monitoring efforts.

Mercury exposure in mammalian mesopredators inhabiting a brackish marsh.

Bioaccumulation of environmental contaminants in mammalian predators can serve as an indicator of ecosystem health. We examined mercury concentrations of raccoons (Procyon lotor; n=37 individuals) and striped skunks (Mephitis mephitis; n=87 individuals) in Suisun Marsh, California, a large brackish marsh that is characterized by contiguous tracts of tidal marsh and seasonally impounded wetlands. Mean (standard error; range) total mercury concentrations in adult hair grown from 2015 to 2018 were 28.50μg/g dw (3.05μg/g dw; range: 4.46-81.01μg/g dw) in raccoons and 4.85μg/g dw (0.54μg/g dw; range: 1.53-27.02μg/g dw) in striped skunks. We reviewed mammalian hair mercury concentrations in the literature and raccoon mercury concentrations in Suisun Marsh were among the highest observed for wild mammals. Although striped skunk hair mercury concentrations were 83% lower than raccoons, they were higher than proposed background levels for mercury in mesopredator hair (1-5μg/g). Hair mercury concentrations in skunks and raccoons were not related to animal size, but mercury concentrations were higher in skunks in poorer body condition. Large inter-annual differences in hair mercury concentrations suggest that methylmercury exposure to mammalian predators varied among years. Mercury concentrations of raccoon hair grown in 2017 were 2.7 times greater than hair grown in 2015, 1.7 times greater than hair grown in 2016, and 1.6 times greater than hair grown in 2018. Annual mean raccoon and skunk hair mercury concentrations increased with wetland habitat area. Furthermore, during 2017, raccoon hair mercury concentrations increased with the proportion of raccoon home ranges that was wetted habitat, as quantified using global positioning system (GPS) collars. The elevated mercury concentrations we observed in raccoons and skunks suggest that other wildlife at similar or higher trophic positions may also be exposed to elevated methylmercury bioaccumulation in brackish marshes.

Effects of pollution on marine organisms.

This review covers selected 2019 articles on the biological effects of pollutants, including human physical disturbances, on marine and estuarine plants, animals, ecosystems, and habitats. The review, based largely on journal articles, covers field, and laboratory measurement activities (bioaccumulation of contaminants, field assessment surveys, toxicity testing, and biomarkers) as well as pollution issues of current interest including endocrine disrupters, emerging contaminants, wastewater discharges, marine debris, dredging, and disposal. Special emphasis is placed on effects of oil spills and marine debris due largely to the 2010 Deepwater Horizon oil blowout in the Gulf of Mexico and proliferation of data on the assimilation and effects of marine debris microparticulates. Several topical areas reviewed in the past (e.g., mass mortalities ocean acidification) were dropped this year. The focus of this review is on effects, not on pollutant sources, chemistry, fate, or transport. There is considerable overlap across subject areas (e.g., some bioaccumulation data may be appeared in other topical categories such as effects of wastewater discharges, or biomarker studies appearing in oil toxicity literature). Therefore, we strongly urge readers to use keyword searching of the text and references to locate related but distributed information. Although nearly 400 papers are cited, these now represent a fraction of the literature on these subjects. Use this review mainly as a starting point. And please consult the original papers before citing them.

Bioaccumulation of pesticide contaminants in tissue matrices of dogs suffering from malignant canine mammary tumors in Punjab, India

The unprecedented application of pesticides in Punjab, India during green revolution has lead to an environmental crisis due to the accumulation of persistent organic and pesticide pollutants in the environment and biota of this region. The present study aimed at estimating the abundance of pesticide contaminants in three biological matrices of 36 dogs suffering from malignant canine mammary tumor (mCMT) and 6 tumor free control dogs from Punjab, India. Presence of individual and total pesticides in canine biological samples, age and bodyweight of canine patients was assessed as a potential risk factor for mCMT using logistic regression analysis. Chi-square test was employed to determine tissue-specific accumulations of individual pesticides. Spearman's correlation coefficient was estimated to determine the association between the levels of total pesticides in different tissue matrices and with age and bodyweight of mCMT cases. Gas chromatography-ECD analysis of serum, mammary tissue and adjoining mammary adipose tissue revealed fourteen different pesticides including γ-HCH, α-HCH, dieldrin, aldrin, heptachlor, butachlor, p,p-DDT, o,p-DDT, p,p-DDD, p,p-DDE, L-cyhalothrin, permethrin, fipronil, and fenitrothion. Heptachlor, γ-HCH, aldrin and p,p-DDT were more frequently detected, whereas, p,p-DDE and o,p-DDT were the least common. Differential accumulation of pesticides in tissue matrices, particularly between serum and mammary tissue/adipose tissue was observed. We could not find any association between the total pesticide concentrations among serum, mammary tissue and mammary adipose tissue in mCMT cases. We found that the odds for individual pesticide for serum, mammary tissue and adipose tissue were associated with high uncertainties; however, the total pesticide concentration in mammary tissue was near non-significantly associated with higher risk of mCMT with low uncertainty. Statistically non-significant higher odds of CMT occurrence with increase in age was noticed No association between the concentration of total pesticides in different matrices and age and bodyweight of canine subjects was found.

Contribution of Passive Sampling Devices on the Determination of Hydrophobic Organic Contaminant Bioaccumulation in Marine Organisms

Hydrophobic Organic Contaminants (HOC) are a group of chemicals needed to determine the health of marine ecosystems, and passive sampling devices are promising tools that offer a convenient monitoring opportunity. Traditional biomonitoring studies involved different types of marine organisms, and it appeared that simultaneous deployment of passive samplers with biomonitoring organisms provided the necessary information for the calculation of the aquatic organisms’ bioaccumulation factors (BAF). There was not any other parameter than BAF, that could be used to determine the biomagnification and fate of contaminants in the upper trophic levels, which eventually affect all marine and terrestrial ecosystem health. In the light of the essence of BAF, this study applied a modified version of BAF estimation dependent on the contaminant concentrations both in the passive and active samplers. Thus, BAF parameters could be calculated properly without any need of a contaminant concentration in the surrounding water environment. For this purpose, the HOC concentration detected from the anthropogenic settlements in the coastal regions of Turkey were collocated, evaluated, and represented for different HOC groups. It was concluded that the present method is appropriate and applicable for BAF calculations of different groups of HOCs, where there are simultaneous deployments of both active and passive samplers in the process of biomonitoring studies.

Contaminated aquatic sediments.

The remediation of contaminated aquatic sediments requires a range of expertise from assessment (investigation, risk evaluations, modeling, and remedy selection) to design and construction. Research in 2019 has added to knowledge on optimizing the use of passive samplers for assessing chemical concentrations in sediment porewater. The porewater and black carbon appear to be better predictors of contaminant bioaccumulation than total organic carbon alone. This has led to better characterization of potential risk at sediment sites. Tools to identify and model sources of chemicals have been developed and used particularly for some metals, polynuclear aromatic hydrocarbons and polychlorinated biphenyls. There is great emphasis on beneficially using dredged sediment, treating it as a resource rather than a waste. Amendments used in sediment caps continue to be refined including the use of activated carbon within the caps and by itself. A technique involving 16S rRNA has been established as a means of identifying microbiological composition that naturally degrade contaminants. © 2020 Water Environment Federation PRACTITIONER POINTS: Sediment capping technology continues to advance Sampling and testing methods continue to be refined Natural processes such as biodegradation are being better understood Beneficial use of dredged sediment continue to be emphasized.

Microplastics as a Vector for HOC Bioaccumulation in Earthworm Eisenia fetida in Soil: Importance of Chemical Diffusion and Particle Size.

The role of microplastics as a carrier in the bioaccumulation of hydrophobic organic contaminants (HOCs) in soil organisms is poorly understood. Two environmentally relevant scenarios, including earthworm Eisenia fetida exposed to contaminated soil amended with clean microplastics (S1) and clean soil introduced with precontaminated microplastics (S2), were simulated to estimate the importance of microplastics in bioaccumulation. Three polychlorinated biphenyls and polyethylene particles with different sizes were employed. The microplastics under the S1 scenario significantly decreased the polychlorinated biphenyl congener (PCB) bioaccumulation, whereas for the S2 scenario, the PCBs on the microplastics can be assimilated by earthworms. Compared to plastic-free treatments, the freely dissolved concentrations (Cfree) of PCBs were consistently lower in the soils amended with microplastics. Biodynamic model analysis suggested that the contribution of microplastic ingestion to bioaccumulation under the S2 scenario (mean 26.1%) was higher than that under S1 (8.7%), likely because of the slow chemical transfer between plastics and ambient media. These results indicated whether microplastics act as a source or a sink of HOCs depended strongly on the diffusion gradients between microplastics and soils. As ingestion of smallest particles (50-150 μm) showed the greatest contribution to bioaccumulation under S1 and S2 scenarios, the gradual breakdown of microplastics may increase their relative importance in contaminant transfer.

Bio-accumulation of organic contaminants in Indo-Pacific humpback dolphins: Preliminary unique features of the brain and testes

There is little information about the residue levels and congener composition of organic contaminants (OCs) in cetaceans. In the present study, we investigated the polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs) in the blubber, blood, brain and testes of Indo-Pacific humpback dolphins (Sousa chinensis) stranded in the Pearl River Estuary (PRE), China. The lowest blubber/tissue partition coefficients were found for sum hexachlorocyclohexanes (ΣHCHs) and ΣPAHs, while the highest were in ΣPCBs and sum dichlorodiphenyltrichloroethanes (ΣDDTs), likely attributing to the octanol-water partition features. The low levels of OCs in brain and testes theoretically resulted from the blood-brain barrier, blood-testes barrier, contaminant molecule dimensions and unique lipid compositions in the brain and testes. Compared with other contaminants, the higher mean brain/blood and testes/blood partition coefficients found for mirex, heptachlor, dieldrin and endrin would increase the risks associated with exposure-related toxicity and the bioavailability of contaminants within these tissues. Observations also suggest that as lipid mobilizes from blubber, contaminants may redistribute, leading to elevated tissue (such as brain) concentrations. Therefore, dolphins with less blubber may be more susceptible to health risks. The Indo-Pacific humpback dolphins living in PRE are at great risk due to variety of OCs in indirect contact with non-target organisms, affecting the health of animals (toxic effects and accumulation). Our findings contribute to the knowledge of the potential effects of OCs exposure on developmental neurotoxicity and reproductive damage in marine mammals.

Utility of normalizing Tenax extractable concentrations for phase volume in application as an environmental screening tool

Bioaccessibility-based extraction tools, such as single-point Tenax extractions (SPTEs), provide cost-effective and accurate estimates of bioaccumulation and toxicity of hydrophobic organic contaminants during environmental sampling. Use of SPTEs as a screening tool in risk assessment is hindered by the requirement for normalization of extractable concentrations for organic carbon (OC). Normalizing SPTE concentrations for the volume of Tenax used during the extraction could improve the applicability of this methodology by removing the system dependence when applying SPTE concentrations to estimates of bioaccumulation. The objective of this study was to examine the utility of Tenax phase volume normalization in place of OC normalization when using SPTEs to estimate bioaccumulation. No significant differences were observed between the slope of regression lines generated between SPTE concentrations normalized for either Tenax phase volume or OC (p = 0.410), but slight improvement of the regression was noted when using phase volume normalization (R2 = 0.829) compared to OC normalization (R2 = 0.740). Replacing OC normalization with phase volume normalization in use of SPTEs more accurately represents the partition of the chemical to the Tenax during the SPTE, improves estimates of bioaccumulation, and expands the use of SPTEs as a rapid assessment tool for determining bioaccumulation during screening of contaminated environments.

Evaluating Polymeric Sampling as a Tool for Predicting the Bioaccumulation of Polychlorinated Biphenyls by Fish and Shellfish.

Recent research has shown that polymeric sampling data generally can predict the bioaccumulation of hydrophobic organic contaminants by benthic and sessile invertebrates. Based on literature data, this review evaluated polymeric sampling as a tool for predicting the bioaccumulation of polychlorinated biphenyls (PCBs) by pelagic and mobile fish and shellfish. Lipid-normalized concentrations (CL) were linked to corresponding equilibrium polymer concentrations (CP) to evaluate the (1) correlation between CL and CP, (2) accuracy when using CP as surrogates for CL, (3) effects of experimental variables on these results, and (4) implications associated with this approach. Generally, strong positive log-log linear correlations existed between CL and CP, meaning that increasing bioaccumulation was well-reflected by increasing polymer accumulation. Further, the majority of the regression lines, as well as individual CL to CP ratios, were within a factor of 10 from the hypothetical 1:1 relationship, suggesting that polymers accumulated concentrations comparable to body residues in fish and shellfish. Interestingly, overall stronger correlations and lower CL to CP ratios resulted when CP were based on sediment compared to water column-deployed samplers. These findings provide a tool for environmental managers when assessing and managing risk associated with PCB-contaminated sediments and waters in protecting vulnerable fish and shellfish species.

Contaminant Biotransport by Pacific Salmon in the Great Lakes

In the Laurentian Great Lakes, introduced Pacific salmon (Oncorhynchus spp.) deposit resources and contaminants as carcass and gametic tissue during spawning migrations to tributaries. Such ecosystem linkages can increase growth and contaminant bioaccumulation in stream-resident fish but mechanisms driving this process remain unclear. In this mini-review, we synthesize findings from observational, experimental, and modeling studies related to Pacific salmon contaminant biotransport in the Great Lakes. First, contaminant biotransport varies among Great Lakes basins suggesting that basin-level characteristics including salmon abundance and historic contamination are important factors controlling the movement of contaminants from the lakes to tributaries. Second, stream-resident fish exposed to salmon have 24-fold higher PCB but moderately lower Hg concentrations when compared to locations without salmon. This finding is explained by differential bioaccumulation of PCB and Hg into different tissue types; analysis of salmon tissue indicates that eggs have elevated PCB and lower Hg than carcasses. Third, stream-resident fish exhibit a dietary shift and increased ration reflecting salmon egg consumption. Last, models suggest that salmon egg consumption can drive a trade-off between PCB and Hg bioaccumulation. This review identifies mechanisms controlling the transfer of salmon-derived energy potential strategies for management. Future research should be directed at identifying other biovectors and determining a list of emerging contaminants that could be subject to biotransport.

Data on hydrocarbons in sediment samples, and its body burden levels in tissues of Anomalocardia flexuosa from toxicity testing.

The analysis of hydrocarbons in terms of individual compounds is relevant to understand the origin and source of these substances, as well as its distribution in environmental compartments, including sediments and biota. Hydrocarbons concentrations were determined in sediments and in whole-body soft tissues of the tropical clam Anomalocardia flexuosa in sediment toxicity testing using samples of Mucuripe bay (Ceará State, NE Brazil) collected in 2011 during dredging events [1]. Data of target compounds included aliphatic (AHs) and aromatic hydrocarbons (PAHs), and linear alkylbenzenes (LABs). AHs compounds were determined on gas chromatography with flame ionization detector (GC-FID), while PAHs and LABs were determined on gas chromatography coupled to a mass spectrometer (GC/MS) in a selected ion mode (SIM). The potential of this dataset is baseline information on hydrocarbons contamination in sediments from a semi-arid region and the bioaccumulation of organic contaminants in marine organisms that can be used as models in ecotoxicological studies.

Evaluation of pollution status of groundwater resources of parts of Owerri metropolis and environs, Southeastern Nigeria, using health risk and contamination models

Some groundwater resources within Owerri Metropolis and environs, Southeastern Nigeria were evaluated to ascertain the level of groundwater contamination as well as the intrinsic health risk that may result from the oral ingestion of the groundwater from the study area. Groundwater samples from 27 boreholes were taken and analysed using standard procedures. The results revealed pH levels (6.04 ± 0.09 to 6.47 ± 0.06) which were lower than the World Health Organisation (WHO) permissible limit. Elevated levels of lead (0.01 ± 0.01 to 0.08 ± 0.02 mg/L) concentration above the WHO standard for safe drinking water were observed in some samples. Though the pollution load index for the area was low, however, the contamination factor revealed lead (Pb) contamination of the samples with positive correlations existing between the metallic pollutants. Electrical conductivity and dissolved solids showed a very strong correlation with r = 1. However, the result of the water quality index revealed that the groundwater samples were within good to excellent water quality. The principal component analysis of the samples grouped the metallic pollutants into three different components, suggesting similarity in the source of occurrence with only one coherent cluster established by the hierarchical component analysis indicating their association in terms of occurrence. The individual hazard quotient and hazard index of the metallic pollutants for adults and children were < 1, which implies slight or no negative health hazard from the intake of the water samples, though the presence of Pb in some samples may pose some health risk. Similarly, low chronic daily intake values were recorded. Though low PLI and CDI were recorded across the area in addition to HQ and HI values < 1, appropriate treatment is recommended for the studied groundwater samples before consumption to prevent an impending health challenge due to possible bioaccumulation of metallic contaminants which may take place over time.

Halogenated organic contaminants of concern in urban-influenced waters of Lake Ontario, Canada: Passive sampling with targeted and non-targeted screening

Passive samplers are useful tools for monitoring hydrophobic, persistent, and potentially bioaccumulative contaminants in the environment. In this study, low density polyethylene passive samplers were deployed in urban-influenced and background nearshore freshwaters of northwestern Lake Ontario and analyzed for a broad range of both legacy halogenated organic contaminants (HOCs) and halogenated flame retardants (HFRs). Non-targeted analysis was conducted for screening additional halogenated substances. For most compounds, concentrations were greatest in the industrialized Hamilton Harbour and more generally at sites that have stronger influences of wastewater effluent discharges and stormwater run-off through rivers and creeks. Polychlorinated biphenyls (PCBs) remain the dominant class of HOCs in water, with dissolved-phase concentrations ranging from 10 to 4100 pg/L (ΣPCBs), followed by polybrominated diphenylethers (ΣPBDEs; 14–960 pg/L) and the organochlorine pesticides (OCPs; 22–290 pg/L). Several non-PBDE brominated flame retardants (nBFRs) and chlorinated Dechlorane-related compounds were detected, with hexabromocyclododecanes (ΣHBCDD; sum of 3 diastereoisomers) the most abundant (1.0–21 pg/L). Non-targeted screening of samples by high resolution mass spectrometry using Kendrick mass defect plots for data analysis indicated that several other halogenated compounds were present in waters at relatively high abundances compared to the flame retardants, based on semi-quantitative estimates. These included methyl-triclosan, four halogenated anisoles (2,4,6-tribromoanisole, dimethyl-trichloroanisole, pentachloroanisole, and pentachlorothioanisole), and pentachloro-aniline. Dissolved-phase methyl-triclosan was estimated to contribute up to approximately 40% of the summed target HOC concentrations. Polyethylene passive samplers provided an excellent medium for both non-targeted screening of HOCs not currently included in monitoring programs and tracking brominated and chlorinated chemicals slated for reductions in uses and emissions through international (Stockholm Convention) and binational (Great Lakes) agreements.

Assessing Impacts of Metallic Contamination along the Tidal Gradient of a Riverine Mangrove: Multi-metal Bioaccumulation and Biomagnification of Filter-Feeding Bivalves

Most riverine mangroves (characterized by salinity fluctuations and tidal inundations), are seriously threatened by metallic pollution. Whether differences in salinity and tidal effects along the river continuum can affect metallic bioaccumulation and the biomagnification of species is still unknown. Bivalves are representative sessile inhabitants in mangrove ecosystems, with a high capacity to bioaccumulate metallic contaminants. The present study used two bivalves, Meretrix lusoria and Mytilopsis sallei, to monitor inter-site changes in metallic contamination and assess the associated ecological impacts along the tidal gradients of riverine mangroves. The concentrations of a total of six metals (Cr, Ni, Cu, Zn, Cd and Pb) in M. lusoria and M. sallei, collected at three different sites along Danshuei Riverine Mangrove, were investigated. The metallic concentrations of the whole soft body of the studied bivalves, and the associated surface sediment from each site, were analyzed using inductively coupled plasma mass spectrometry (ICP-MS) to determine the inter-site effects on the bioaccumulation and biomagnification of metallic contaminants in bivalves. There are increasing concentrations of four metallic contaminants, Zn, Cr, Cd and Cu, in the seaward direction of the bivalves. The increasing mean metallic concentrations along the seaward direction may be the effect of salinity, further decreasing the rate of the elimination of these metals, thus resulting in a net increase in metallic contaminants. Our results clearly show prominent inter-site changes in the metallic burdens of bivalves in our study on riverine mangrove ecosystems associated with different levels of bioaccumulation and biomagnification of metallic contaminants. Thus, it is important to monitor multiple sites along the dynamic environment of riverine mangroves in order to gain a good understanding of the ecological impact of metallic pollution risks. The present findings provide important evidence of the use of simple indices to assess the ecological impacts of metallic pollution in riverine mangroves.

Biomarkers responses of the clam Anomalocardia flexuosa in sediment toxicity bioassays using dredged materials from a semi-arid coastal system

Few test organisms are employed for sediment toxicity assessments in Tropical regions, including Brazil. We assessed the ability of the clam Anomalocardia flexuosa to respond to contamination in sediment bioassays using dredging materials of a semi-arid region (Ceará State, NE Brazil), with attention to sublethal responses. Sediments were collected during and after dredging (survey 1 and 2, respectively) and animals exposed in laboratory over 28 days, with responses measured at 7 days. Bioaccumulation of contaminants was determined in whole-body soft tissues as a metric of bioavailability, and biomarkers' changes were monitored in terms of enzymes of phase I and II metabolism, acetylcholinesterase (AChE), and antioxidant responses, lipid peroxidation (LPO) and DNA damage (strand breaks). Clams accumulated aliphatic (AHs) and aromatic hydrocarbons (PAHs), and linear alkylbenzenes (LABs) compared to control conditions (day 0), with increased amounts of As, Cd, Cu, and Zn observed in some samples. The enzyme glutathione S-transferase was enhanced in animals exposed to samples, indicating activation of phase II metabolism. Changes observed in glutathione peroxidase (GPx), glutathione reductase (GR), LPO and strand breaks were related to oxidative stress. AChE enzymatic activity also changed, as an indicator of neurotoxicity caused by sediment exposure. The computed integrated biomarker response index (IBR) ranked sites according to the contamination status and proximity to its sources. Correlations found for biomarkers and bioaccumulation of hydrocarbons indicated the influence of harbor activities, effluent discharges, and urban runoff on the sediment pollution of Mucuripe Bay. Data also showed that SQGs are unable to predict bioaccumulation and subchronic effects. Based on our results we consider that biomarkers responses in A. flexuosa are important endpoints to be applied in sediment toxicity bioassays in tropical regions.

Evaluation of dredged sediment for aquatic placement: interpreting contaminant bioaccumulation.

The potential bioaccumulation of sediment-associated contaminants is one of the primary concerns associated with the aquatic placement of dredged sediment. Laboratory bioaccumulation tests with representative infaunal organisms exposed to dredged sediment and reference sediment are used to assess the potential for contaminant-related bioaccumulation impacts. Dredged sediment testing and evaluation guidance provides statistical inferences and numerous assessment factors (e.g., the magnitude of difference (MOD)) to interpret results; however, detailed information for applying these factors is lacking. Therefore, the focus of this work was to provide context for the application of the MOD as a line of evidence for evaluating bioaccumulation risk associated with dredged material placement in aquatic environments by considering variance (as coefficient of variation (CV)), MOD, and statistical differences associated with bioaccumulation bioassay tissue concentrations in three case studies. Based on peer-reviewed data and dredged material monitoring data, relatively low within-sample variability (CVs < 50%) of tissue concentrations can be achieved for commonly assessed constituents (e.g., polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), metals, and butyl tins). Thus, statistical comparisons were generally able to detect significant differences (p < 0.05; α = 0.05) across tissue concentrations with relatively low MODs (< 2-fold difference). Based on the observed variance, MOD, and statistical differences associated with bioaccumulation bioassay tissue concentrations, a 2-fold MOD can provide an additional line of evidence to evaluate bioaccumulative risk when statistical significance is observed. These results indicated that a judicious consideration of the sample variance and MOD is a useful factor when discerning meaningful differences among contaminant tissue concentrations.