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PubMed2004

Heavy metal and other trace elements in native mussel Diplodon chilensis from Northern Patagonia Lakes, Argentina.

Native mussels, Diplodon chilensis, were sampled from four lakes in Nahuel Huapi National Park, Northern Patagonia, Argentina in order to evaluate heavy-metal distribution in the region and to assess the contribution of this compartment of the trophic web to their circulation in the food chain. The concentration of potential pollutants Ag, As, Cr, Hg, Sb, and Se, and other nine elements of interest (Ba, Br, Ca, Co, Cs, Fe, Na, Sr, and Zn) were determined in Diplodon chilensis pooled samples. Digestive glands were analyzed separately from soft tissues. Geological tracers Sc, Ta, Th, and rare earth elements were also determined in order to discriminate lithophile contributions. Elemental concentrations of Ba, Br, Fe, Sr, Se, and Zn in total soft tissues samples do not show significant differences among sampling sites. Arsenic and Cr contents in total soft tissues and digestive gland pooled samples are higher in sampling points close to zones with human settlements. Silver contents in samples collected in Lake Nahuel Huapi were higher than in the other lakes studied, and up to 50-fold higher than the sample collected in Lake Traful, considered as the reference. Mercury highest concentration values measured in total soft tissues pooled samples from lakes Nahuel Huapi and Moreno were found to be similar to those observed in other reported Hg contamination situations, and they are three to five times higher than those of the reference samples collected in Lake Traful.

Animals↗
PubMed2004

Methylmercury production in High Arctic wetlands.

Mercury is present at elevated levels in the top predators living in High Arctic ecosystems. Because only methylmercury (MeHg) bioaccumulates in food chains, the sources need to be identified. In temperate environments, wetlands are considered to be the principal sources of MeHg, with sulfate-reducing bacteria (SRB) thought to be responsible. The present study investigated whether High Arctic wetlands produced MeHg and whether SRB were involved in MeHg formation. Frozen soil was collected from 18 High Arctic wetlands before ground thaw, and when analyzed for MeHg, values were low, averaging 0.065 ng/g. When soils were incubated for 30 and 60 d at typical summer Arctic soil temperatures (4 degrees C and 8 degrees C), MeHg increased up to 100-fold. These laboratory observations were consistent with field measurements of wetland surface water, where MeHg concentrations increased from near detection limits (0.02 ng/L) at the inflow to an average of 1.21 ng/L at the outflow. Both laboratory and field data showed MeHg production in High Arctic wetlands. The prevalence of SRB in soil was low, however, and DNA analysis of the dissimilatory sulfate-reductase gene specific to SRB was positive at only one site. The present study showed that wetlands in the High Arctic can produce MeHg but that SRB may not the dominant mercury methylators.

Arctic Regions↗
PubMed2001

Preliminary results of biomarker responses in zooplankton of brackish environments.

Zooplankton is an essential component of the food chains of marine and brackish environments. Ecotoxicological risk to zooplankton, evaluated by the biomarker approach, can be used as an early warning signal of risk to the health of marine ecosystems. The aim of this project is to evaluate the application of certain biomarkers in zooplankton. In the present paper, laboratory and field studies were performed with the copepods Acartia margalefi, Acartia latisetosa and the mysid Siriella clausi. Acetylcholinesterase activity (AChE) was determined in homogenates of whole organisms. Mean AChE activity was 10.05 micromol min g(-1) for A. margalefi, 3.30 micromol min g(-1) for A. latisetosa and 79.70 micromol min g(-1) for S. clausi. A. margalefi and S. clausi also showed a linear increase in enzyme activity with increasing concentrations of samples. Preliminary laboratory work was also carried out with specimens of A. latisetosa, which were exposed to an organophosphorus insecticide (parathion). Moderate inhibition of AChE (19%) with respect to controls was observed. AChE activities were two orders of magnitude higher in the zooplankton than in hemolymph samples of the decapod Carcinus aestuarii (Fossi et al., 1996) indicating that these species have a high metabolic rate, which makes them suitable for biomarker studies.

Acetylcholinesterase↗
PubMed2002

Arsenic and other heavy metals in soils from an arsenic-affected area of West Bengal, India.

Domkal is one of the 19, out of 26 blocks in Murshidabad district where groundwater contains arsenic above 0.05 mg/l. Many millions of cubic meters of groundwater along with arsenic and other heavy metals are coming out from both the hand tubewells, used by the villagers for their daily needs and shallow big diameter tubewells, installed for agricultural irrigation and depositing on soil throughout the year. So there is a possibility of soil contamination which can moreover affect the food chain, cultivated in this area. A somewhat detailed study was carried out, in both micro- and macrolevel, to get an idea about the magnitude of soil contamination in this area. The mean concentrations (mg/kg) of As (5.31), Fe (6740), Cu (18.3), Pb (10.4), Ni (18.8), Mn (342), Zn (44.3), Se (0.53), Mg (534), V (44.6), Cr (33.1), Cd (0.37), Sb (0.29) and Hg (0.54) in fallow land soils are within the normal range. The mean As (10.7), Fe (7860) and Mg (733) concentrations (mg/kg) are only in higher side whereas Hg (0.17 mg/kg) is in lower side in agricultural land soils, compared to the fallow land soils. Arsenic concentrations (11.5 and 28.0 mg/kg respectively) are high in those agricultural land soils where irrigated groundwater contains high arsenic (0.082 and 0.17 mg/l respectively). The total arsenic withdrawn and mean arsenic deposition per land by the 19 shallow tubewells per year are 43.9 kg (mean: 2.31 kg, range: 0.53-5.88 kg) and 8.04 kg ha(-1) (range: 1.66-16.8 kg ha(-1)) respectively. For the macrolevel study, soil arsenic concentration decreases with increase of distance from the source and higher the water arsenic concentration, higher the soil arsenic at any distance. A proper watershed management is urgently required to save the contamination.

Agriculture↗
PubMed2004

Blood concentrations of persistent toxic substances in the indigenous communities of the Russian Arctic.

OBJECTIVES: Investigation was carried out within the framework of the large-scale international project "Persistent Toxic Substances (PTS), Food Security and Indigenous People of the Russian North" under RAIPON/AMAP/GEF aegis. Objectives of the project are to obtain comprehensive information on exposure of indigenous populations to contaminants through food chains (and other sources), and to investigate the possible health effects connected to this exposure. Four regions of Russia are involved in the project: Kola Peninsula (Murmansk oblast), Nenetsk okrug (Pechora river basin), Taimyr Peninsula, Chukotka Peninsula. METHODS: Questionnaire and paired sampling of maternal/cord blood among indigenous women at childbirth (more than 250 persons) as well as among general indigenous population (more than 1,400 persons), additionally breast milk sampling of lactating women (more than 50 persons) in Chukotka was conducted. About 700 blood samples have been analyzed at the Center for Environmental Chemistry, SPA "Typhoon" (Obninsk, Russia), the Regional Center "Monitoring of the Arctic", RCMA (St. Petersburg, Russia), the Norwegian Institute for Air Research, NILU (Tromso, Norway) and at INSPQ (Sainte-Foy, Quebec, Canada). RESULTS AND CONCLUSIONS: On the whole, PTS in human blood of the Russian Arctic natives are similar to those in the coastal areas of Greenland and Canada, and for some POPs such as toxaphenes and mirex, these levels are lower.

Arctic Regions↗
PubMed2006

Tree swallow (Tachycineta bicolor) exposure to polychlorinated biphenyls at the Kalamazoo River superfund site, Michigan, USA.

In 1990, a portion of the Kalamazoo River in Michigan, USA, was designated a Superfund site because of the presence of polychlorinated biphenyls (PCBs) in the sediment and floodplain soils. During a four-year period from 2000 to 2003, several avian species were monitored for reproductive effects and concentrations of PCBs in tissues attributed to food chain transfer from contaminated sediments. The tree swallow (Tachycineta bicolor) was chosen as a model receptor for contamination of passerine species. A top-down methodology was used to evaluate the bioaccumulation of PCBs, including non-ortho and mono-ortho congeners, in tree swallow eggs, nestlings, and adults at the Kalamazoo River area of concern (KRAOC) and at an upstream reference site. Generally, a sixfold difference in tissue concentrations of total PCBs was observed between the two sites with concentrations in eggs and nestlings at the KRAOC ranging from 0.95 to 15 microg PCB/g wet weight. Concentrations of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQsWHO Avian) for PCBs, based on bird-specific World Health Organization toxic equivalence factors, were 10- to 30-fold greater in the KRAOC than at the reference location. Egg and nestling TEQsWHO-Avian ranged from 0.21 to 2.4 ng TEQ/g wet weight at the KRAOC. Hazard quotients calculated from literature-derived toxicity reference values were below 1.0 at both the target and the reference site based on the no-observed-adverse-effect level and the lowest-observed-adverse-effect level.

Animals↗
PubMed2005

Transport and fate of dieldrin in poplar and willow trees analyzed by SPME.

Dieldrin is a hydrophobic organochlorine insecticide that is persistent in the environment. The fate and transport of dieldrin in trees is important both in the context of potential remediation, as well as food chain impacts through dieldrin transport to shoots and leaves. Experiments were conducted to measure the degree of dieldrin partitioning to plant tissue and the potential for biodegradation of dieldrin in the microbe rich tree rhizosphere. Dieldrin was analyzed in water and plant tissue using headspace solid-phase microextraction (SPME) coupled with gas chromatography. Poplar and willow saplings planted in soil and watered with 10 microgl(-1) dieldrin for up to 9 months showed no adverse effects due to dieldrin exposure and no dieldrin was observed in plant shoots with a method detection limit (MDL) of 7 ngg(-1). One-week hydroponic tests of poplar saplings exposed to aqueous dieldrin also showed no detection of dieldrin in shoots, with an average of 66% of the dieldrin partitioned to the plant roots and an overall mass balance recovery of 76% in the plant-water system. The root concentration factor (RCF) was found to be 30+/-3 ml water g(-1) root. Biodegradation of dieldrin was not observed in an aqueous batch bioreactor containing 8 microgl(-1) dieldrin, nutrients and bacteria from the root zone of a poplar sapling that had been exposed to dieldrin for 9 months. These results show that planting trees is likely to be safe and potentially useful at sites containing low-levels of dieldrin in groundwater.

Biodegradation, Environmental↗
PubMed2004

Snowmelt sources of methylmercury to high arctic ecosystems.

Mercury in humans and other top predators living in the Arctic is present at elevated levels. Since only methylmercury (MeHg) bioaccumulates in food chains, sources of MeHg need to be identified. Recently, wetlands in the High Arctic were found to produce MeHg, and this was confirmed in laboratory soil incubations. In the present study both wetlands and snowmelt water were evaluated as sources of MeHg to Arctic ecosystems in Nunavut. Three substudies took place on Cornwallis Island, and one took place on Ellesmere Island. First, the effect of wetland presence in lake watersheds was evaluated by comparing four lakes with wetlands present to four lakes without wetlands present. Next, two individual wetlands were spatially and temporally investigated. Finally, three basin tributaries were evaluated for snowmelt MeHg sources. Catchments on Cornwallis Island with wetlands did not have an observable effect on MeHg levels in downstream lake water, but the wetland on Ellesmere Island contributed significant MeHg. In contrast, calculated yields of MeHg in tributaries draining snowmelt on Cornwallis Island were higher (ca. 1.5 mg km(-2) day(-1)) than those measured in temperate catchments characterized by wetlands. Methylmercury and total Hg concentrations in lakes, wetlands, and basin tributaries showed a strong temporal trend that corresponded to inputs from snowmelt water in late spring. This study revealed that wetland export of MeHg to downstream Arctic lakes is site dependent, and snowmelt water was the most significant source of MeHg to Arctic ecosystems located on Cornwallis Island.

Animals↗
PubMed2005

Behavior of lead in a model microbial predator-prey system.

Predation at the microbial level can affect the fate of toxic trace metals. Metals associated with bacterial prey can be released into the dissolved phase following digestion by a predator, and/or metals can remain in the predator and be transferred potentially to the next level of the food chain. Toxic metal ions in the aqueous phase also are expected to modify the growth and predation rate of a microbial predator. A model predator-prey system was developed to test the effects of Pb on cells and to help elucidate the fate of Pb in this type of interaction. Established methods that have been shown to be suitable for distinguishing dissolved, prey-bound, predator-bound, and ingested Pb were used to establish the pathway of Pb over time. Growth parameters were measured using batch reactors for the protozoan predator Tetrahymena thermophila and the bacterial prey Pseudomonas putida without Pb and at several concentrations of Pb. The effect of prey density on predation and Pb phase distribution also was investigated. Results demonstrate that some kinetic parameters related to prey consumption and growth of T. thermophila are altered by Pb. Upon addition of predator to prey cells in equilibrium with dissolved Pb, dissolved and prey-bound Pb become associated with the predator through ingestion and adsorption. Ingested Pb is excreted later as a bound metal associated with T. thermophila waste matter. A preliminary mathematical model was developed to describe predator-prey dynamics and their influence on the behavior and fate of Pb. Growth data were used to obtain model parameters, and model simulations for Pb fractionation are compared to experimental observations.

Animals↗
PubMed2001

Decline in endangered species as an indication of anthropic pressures: the case of European mink Mustela lutreola Western population.

Populations of threatened species, especially predators at the top of the food chain, may be affected by anthropic pressures. The endangered western population of European mink Mustela lutreola has shown a large decline over 50% of its natural range. M. lutreola disappeared from northwestern France between 1984 and 1997, and the decline was associated with an increase in mustelid trapping, changes in watercourse quality, and habitat modifications due to agricultural practices. The pattern of decline showed a fragmentation restricting the minks into very small areas. Trapping was the first known cause of mortality. Although feral American mink Mustela vison may compete with autochthonous carnivores, M. lutreola had disappeared from streams before the introduction of the American species, suggesting that competitive interactions were not responsible. Furthermore, American mink has never been found or has remained rare in 62.4% of the area from which M. lutreola has disappeared. During the past 25 years, permanent grassland surfaces were reduced by 40%, whereas fodder culture increased by 470%, causing considerable habitat changes. Furthermore, 55.7% of water courses were classified as being of bad quality or polluted. Therefore, our data suggests that a conjunction of intensive trapping, alterations in water quality and habitat modification was critical for the European mink's decline. Although there are difficulties in ascribing specific cause to distribution changes in a top predator, this decline can be regarded as an indication for anthropic pressures on natural habitats.

Agriculture↗
PubMed2000

Polychlorinated biphenyls are selectively neurotoxic in the developing Spisula solidissima embryo.

Polychlorinated biphenyls (PCBs) are ubiquitous environmental pollutants that accumulate to toxic levels in the food chain. Using Spisula solidissima (surf clam) embryos as a developmental model, it was shown that Aroclor 1254 specifically targets two neuronal structures during embryonic development. Embryos were exposed to 1, 10), or 100 ppm Aroclor 1254 or an acetone vehicle control posthatching for 24, 48, and 72 h. Embryos labeled with a serotonin antibody or a neural antigen antibody and a rhodamine-conjugated secondary antibody were viewed by confocal microscopy. The cerebropleural ganglion showed a decrease both in serotonin production and in the size of the serotonin-synthesizing region upon exposure to 10 and 100 ppm Aroclor 1254. These decreases were detectable as early as 48 h postfertilization. When exposed to 100 ppm Aroclor 1254, the primitive neural plexus, which coordinates the movements of the mouth and velum, showed a delay in onset and cessation of expression of a molluscan-specific neural antigen. Exposure to Aroclor 1254 did not affect the overall growth and morphology of the embryos. In addition, analyses of total protein profiles and heat-shock protein 70 levels showed that exposure to Aroclor 1254 did not trigger protein degradation or cause a stress or shock response. These results show that exposure of Spisula embryos to Aroclor 1254 specifically targets neurogenesis while having no effect on the overall growth of the embryo.

Animals↗
PubMed2001

Ecological impacts of arable intensification in Europe.

Although arable landscapes have a long history, environmental problems have accelerated in recent decades. The effects of these changes are usually externalized, being greater for society as a whole than for the farms on which they operate, and incentives to correct them are therefore largely lacking. Arable landscapes are valued by society beyond the farming community, but increased mechanization and farm size, simplification of crop rotations, and loss of non-crop features, have led to a reduction in landscape diversity. Low intensity arable systems have evolved a characteristic and diverse fauna and flora, but development of high input, simplified arable systems has been associated with a decline in biodiversity. Arable intensification has resulted in loss of non-crop habitats and simplification of plant and animal communities within crops, with consequent disruption to food chains and declines in many farmland species. Abandonment of arable management has also led to the replacement of such wildlife with more common and widespread species. Soils have deteriorated as a result of erosion, compaction, loss of organic matter and contamination with pesticides, and in some areas, heavy metals. Impacts on water are closely related to those on soils as nutrient and pesticide pollution of water results from surface runoff and subsurface flow, often associated with soil particles, which themselves have economic and ecological impacts. Nitrates and some pesticides also enter groundwater following leaching from arable land. Greatest impacts are associated with simplified, high input arable systems. Intensification of arable farming has been associated with pollution of air by pesticides, NO2 and CO2, while the loss of soil organic matter has reduced the system's capacity for carbon sequestration. International trade contributes to global climate change through long distance transport of arable inputs and products. The EU Rural Development Regulation (1257/99) provides an opportunity to implement measures for alleviating ecological impacts of arable management through a combination of cross-compliance and agri-environment schemes. To alleviate the problems described in this paper, such measures should take account of opportunities for public/private partnerships and should integrate social, cultural, economic and ecological objectives for multifunctional land use.

Agriculture↗
PubMed2003

Sediment-water distribution of organic contaminants in aquatic ecosystems: the role of organic carbon mineralization.

The distribution between sediments and water plays a key role in the food-chain transfer of hydrophobic organic chemicals. Current models and assessment methods of sediment-water distribution predominantly rely on chemical equilibrium partitioning despite several observations reporting an "enrichment" of chemical concentrations in suspended sediments. In this study we propose and derive a fugacity based model of chemical magnification due to organic carbon decomposition throughout the process of sediment diagenesis. We compare the behavior of the model to observations of bottom sediment-water, suspended sediments-water, and plankton-water distribution coefficients of a range of hydrophobic organic chemicals in five Great Lakes. We observe that (i) sediment-water distribution coefficients of organic chemicals between bottom sediments and water and between suspended sediments and water are considerably greaterthan expected from chemical partitioning and that the degree sediment-water disequilibrium appears to follow a relationship with the depth of the lake; (ii) concentrations increase from plankton to suspended sediments to bottom sediments and follow an inverse ratherthan a proportional relationship with the organic carbon content and (iii) the degree of disequilibrium between bottom sediment and water, suspended sediments and water, and plankton and water increases when the octanol-water partition coefficient K(ow) drops. We demonstrate that these observations can be explained by a proposed organic carbon mineralization model. Our findings imply that sediment-water distribution is not solely a chemical partitioning process but is to a large degree controlled by lake specific organic carbon mineralization processes.

Animals↗
PubMed2002

Methyltransferase: an enzyme assay for microbial methylmercury formation in acidic soils and sediments.

Methylmercury (MeHg) is a highly toxic form of mercury that bioaccumulates in aquatic food chains. However, methods to reliably identify sites of MeHg formation or to quantify MeHg production require the use of isotopic tracers, which limits their use. In this paper, a method is presented to quantify the methylation of mercury by a methyltransferase pathway. This methyltransferase pathway is one of the biochemical pathways responsible for biological mercury methylation. Protein is extracted from environmental samples, and mercury methyltransferase (HgMT) activity of soil extracts is calculated by assessing increases in methyltransferase activity induced by Hg addition. In enzyme extracts from pure cultures or soil samples, HgMT activity correlated with net MeHg production and Hg consumption, suggesting that HgMT activity can be used to estimate MeHg production in field samples. Over the course of a three-month period in a freshwater wetland, HgMT activity correlated with net MeHg concentrations (r2 = 0.55; p < 0.057). Furthermore, HgMT activity predicted (r2 = 0.80; p < 0.01) gross MeHg formation in freshwater wetlands as well as in laboratory microcosms calculated using previously published rate constants. Our results show that a methyltransferase assay, in combination with demethylation estimates, accurately predicts MeHg formation under field and laboratory conditions. This assay does not require the use of mercury added to field samples to estimate activity but rather estimates the biological activity present in the soil by quantifying the amount of enzyme present in the soil. Such an assay is well suited for use in field surveillance programs assessing MeHg formation in a variety of environments.

Animals↗
PubMed2004

Gas-phase HO-initiated reactions of elemental mercury: kinetics, product studies, and atmospheric implications.

Mercury is an environmentally volatile toxic fluid metal that is assumed to have a long atmospheric residence time and hence is subject to long-range transport. The speciation and chemical transformation of mercury in the atmosphere strongly influences its bioaccumulation potential in the human food chain as well as its global cycling. To investigate the oxidation of Hg0 by HO, the dominantdaytime atmospheric oxidant, we performed kinetic and product studies over the temperature range 283-353 K under near atmospheric pressure (100+/-0.13 kPa) in air and N2 diluents. Experiments were carried out by the relative rate method using five reference molecules and monitored by gas chromatography with mass spectroscopic detection (GC-MS). The HO were generated using UV photolysis of isopropyl nitrite at 300 < or = lambda < or = 400 nm in the presence of NO. The room-temperature rate constant was found to be (9.0+/-1.3) x 10(-14) cm3 molecule(-1) s(-1). The temperature dependence of the reaction can be expressed as a simple Arrhenius expression (in unit of 10(-14) cm3 molecule(-1) s(-1)) using ethane as the reference molecule: kHg + HO = 3.55 x 10(-14) exp((294+/-16)/T). The major reaction product, HgO, was identified in the gaseous form, as aerosols and as deposits on the container walls, using chemical ionization mass spectrometry (CI-MS), electron impact mass spectrometry (EI-MS), GC-MS, and cold vapor atomic fluorescence spectrometry (CVAFS). Experimental results reveal that ca. 6% of the reaction products were collected on a 0.2 microm filter as suspended aerosol, ca. 10% were in the gaseous form, and about 80% were deposited on the reaction vessel wall. The potential implications of our results in the understanding of tropospheric mercury transformation are herein discussed.

Air Pollutants↗
PubMed2005

MODELKEY. Models for assessing and forecasting the impact of environmental key pollutants on freshwater and marine ecosystems and biodiversity.

BACKGROUND: Triggered by the requirement of Water Framework Directive for a good ecological status for European river systems till 2015 and by still existing lacks in tools for cause identification of insufficient ecological status MODELKEY (http:// www.modelkey.org), an Integrated Project with 26 partners from 14 European countries, was started in 2005. MODELKEY is the acronym for 'Models for assessing and forecasting the impact of environmental key pollutants on freshwater and marine ecosystems and biodiversity'. The project is funded by the European Commission within the Sixth Framework Programme. OBJECTIVES: MODELKEY comprises a multidisciplinary approach aiming at developing interlinked tools for an enhanced understanding of cause-effect-relationships between insufficient ecological status and environmental pollution as causative factor and for the assessment and forecasting of the risks of key pollutants on fresh water and marine ecosystems at a river basin and adjacent marine environment scale. New modelling tools for risk assessment including generic exposure assessment models, mechanistic models of toxic effects in simplified food chains, integrated diagnostic effect models based on community patterns, predictive component effect models applying artificial neural networks and GIS-based analysis of integrated risk indexes will be developed and linked to a user-friendly decision support system for the prioritisation of risks, contamination sources and contaminated sites. APPROACH: Modelling will be closely interlinked with extensive laboratory and field investigations. Early warning strategies on the basis of sub-lethal effects in vitro and in vivo are provided and combined with fractionation and analytical tools for effect-directed analysis of key toxicants. Integrated assessment of exposure and effects on biofilms, invertebrate and fish communities linking chemical analysis in water, sediment and biota with in vitro, in vivo and community level effect analysis is designed to provide data and conceptual understanding for risk arising from key toxicants in aquatic ecosystems and will be used for verification of various modelling approaches. CONCLUSION AND PERSPECTIVE: The developed tools will be verified in case studies representing European key areas including Mediterranean, Western and Central European river basins. An end-user-directed decision support system will be provided for cost-effective tool selection and appropriate risk and site prioritisation.

Animals↗
PubMed2002

Tubifex: a sensitive model for UV-B-induced phototoxicity.

The natural increase of UV-B radiation levels due to depletion of the ozone layer in the atmosphere may impose additional stress for the survival of zooplanktons which serve as a major constituent of the aquatic food chain. To study the adverse effects of UV-B radiation on the aquatic biomass, studies were conducted using the aquatic organism Tubifex as a model, as UV-B radiation is known to penetrate into the natural waters. UV-B radiation induced mortality in tubifex and the production of activated oxygen species by these organisms. Alterations in DNA, RNA, protein, glutathione (GSH), hydrogen peroxide H(2)O(2), thiobarbituric acid-reactive substance (TBA-RS), ATPase, AChE, GST, and LDH activities in Tubifex at various doses (0-2.0 J) of UV-B radiation were found. LC(50) value for UV-B-induced mortality of Tubifex was 0.80+/-0.15 J and the threshold dose was 0.35+/-0.05 J; mortality began within 3h postirradiation. UV-B dose-dependent production of singlet oxygen, superoxide anion, and hydroxyl radicals by Tubifex was observed. DNA, RNA, protein, and GSH contents were found to decrease significantly (P<0.001) while H(2)O(2) and TBA-RS increased (P<0.01) under the influence of UV-B radiation. The activities of ATpase, AChE, and GST enzymes were inhibited (P<0.01) and LDH activity was significantly increased (P<0.001) in Tubifex exposed to UV-B radiation. The results suggest that an increase in UV-B radiation alters several biochemical processes, leading to the mortality of the organism. Tubifex could be useful as a sensitive alternate model for studying UV-B-induced phototoxicity and possible mechanisms of action.

Animals↗
PubMed2002

Investigation into the importance of the stomatal pathway in the exchange of PCBs between air and plants.

The transfer of persistent organic pollutants (POPs) from air to vegetation is an important air-surface exchange process that affects global cycling and can result in human and wildlife exposure via the terrestrial food chain. To improve understanding of this process, the role of stomata in uptake of gas-phase polychlorinated biphenyls (PCBs) was investigated using Hemerocallis x hybrida "Black Eyed Stella", a plant with a high stomatal density. Uptake of PCBs was monitored over a 72-h period in the presence and absence of light. Uptake rates were significantly greater in illuminated (stomata open) plants than unilluminated (stomata closed) plants for 18 of the 28 measured PCB congeners (p < 0.05). Depuration of PCBs was monitored in a subsequent experiment over a period of 3 weeks. Levels after 3 weeks of depuration time were still much higher than the concentration prior to contamination. Tri- and tetrachlorinated PCBs showed the greatest depuration, with less than 20% and 50% of accumulated PCBs respectively remaining, while approximately 70% of higher chlorinated PCB congeners remained in the plants at the end of the experiment. Treatments with/without light (to control stomatal opening during uptake) and with/without abscisic acid (ABA) application (to control stomatal opening during depuration) were compared. After contamination indoors for 3 days, there was a significantly higher concentration of PCBs (p < 0.05) in the light contaminated plants than the dark-contaminated plants for 13 of the 28 measured PCB congeners. The ABA treatment affected depuration of PCB-18 only. "Light/ABA-treated" plants had a significantly slower depuration rate for PCB-18 than "light/untreated", "dark/ABA-treated", and "dark/untreated" plants (p < 0.05). The results of the study indicate that there is a stomatal effect on the rate of exchange of PCBs between Hemerocallis leaves and air.

Environmental Monitoring↗