The occurrence of steroidal estrogens in south-eastern Ontario wastewater treatment plants.

We measured steroidal estrogens in wastewater in Ottawa and Cornwall (Ontario, Canada) to determine removal efficiency of these steroids during the treatment process, and whether removal varies during a seasonal cycle. Estrone (E1), 17β-estradiol (E2) and 17α-ethinylestradiol (EE2) were found at maximum concentrations in raw sewage (RS), at 104, 66.9 and 5.

Estimating mercury concentrations and fluxes in the water column and sediment of Lake Ontario with HERMES model.

The HERMES model-predicted Hg concentrations and fluxes in Lake Ontario were based on twelve lake and drainage basin variables (i.e., water temperature, precipitation rate, air Hg, surface area, mean depth, water volume, water inflow rate, inflow water Hg, inflow and lake suspended particulate matter, air-water and water-air mass transfer coefficients, and sedimentation rate).

Fate and developmental effects of dietary uptake of methylmercury in Silurana tropicalis tadpoles.

Adverse effects of methylmercury (MeHg) exposure during amphibian metamorphosis remain to be fully characterized. Most previous investigations determined effects of short-term exposure to elevated dose rates, without information on mercury (Hg) depuration and degradation pathways. Since metamorphosis is primarily controlled by thyroid hormones (TH), alterations in this process suggest a disruption of the TH endocrine axis.

Lumiestrone is Photochemically Derived from Estrone and may be Released to the Environment without Detection.

Endocrine disrupting chemicals are adversely affecting the reproductive health and metabolic status of aquatic vertebrates. Estrone is often the dominant natural estrogen in urban sewage, yet little is known about its environmental fate and biological effects. Increased use of UV-B radiation for effluent treatments, and exposure of effluents to sunlight in holding ponds led us to examine the effects of environmentally relevant levels of UV-B radiation on the photodegradation potential of estrone.

Biogeochemical factors influencing net mercury methylation in contaminated freshwater sediments from the St. Lawrence River in Cornwall, Ontario, Canada.

The activity of various anaerobic microbes, including sulfate reducers (SRB), iron reducers (FeRP) and methanogens (MPA) has been linked to mercury methylation in aquatic systems, although the relative importance of each microbial group in the overall process is poorly understood in natural sediments. The present study focused on the biogeochemical factors (i.e.

Preexposure to ultraviolet B radiation and 4-tert-octylphenol affects the response of Rana pipiens tadpoles to 3,5,3'-triiodothyronine.

Exposure to multiple environmental stressors is negatively impacting the health of amphibians worldwide. Increased exposure to ultraviolet B radiation (UVBR) and chemical pollutants may affect amphibian populations by disrupting metamorphosis; however, the actual mechanisms by which these stressors affect development remain unknown. Because amphibian metamorphosis is controlled by thyroid hormones (TH), changes in developmental rates by environmental stress suggest a disruption of the thyroid system.

Predicting mercury concentrations and fluxes in the water column and sediment of lakes with a limited dataset.

The purpose of the present study was to evaluate the mercury (Hg) Environmental Ratios Multimedia Ecosystem Sources (HERMES) model on two Ontario, Canada lakes (Harp and Dickie) and to include modifications to enable the model to estimate the major model input variables that tend to be missing for lakes with limited datasets. No significant differences were found for either sediment solid or bulk water total mercury (THg) when the HERMES model was applied to the two Ontario lakes, regardless of whether all available data were altered during application or only the 10 variables that tend to cause the most variation in model output (i.e.

Simplified sample preparation procedure for measuring isotope-enriched methylmercury by gas chromatography and inductively coupled plasma mass spectrometry.

Many procedures have been developed to measure the concentration of monomethylmercury (MeHg) from different sample matrices, and the use of stable isotopes of mercury now provides opportunities to determine its formation and degradation rates. Here, a modified procedure for measuring mercury isotopes in sediment samples that uses acid leaching-ion exchange-thiosulfate extraction (TSE) to isolate and purify the methylated mercury from the matrix is proposed. The latter is followed by aqueous-phase ethylation, purge and trap on Tenax, gas chromatography separation of ethylated mercury compounds, and inductively coupled plasma mass spectrometry detection.

Trophic structure and mercury distribution in a Gulf of St. Lawrence (Canada) food web using stable isotope analysis.

Even at low concentrations in the environment, mercury has the potential to biomagnify in food chains and reaches levels of concern in apex predators. The aim of this study was to relate the transfer of total mercury (THg) and methylmercury (MeHg) in a Gulf of St. Lawrence food web to the trophic structure, from primary consumers to seabirds, using stable nitrogen (δ(15)N) and carbon (δ(13)C) isotope analysis and physical environmental parameters.

Environmental factors affecting ultraviolet photodegradation rates and estrogenicity of estrone and ethinylestradiol in natural waters.

The environmental fate and persistence of steroidal estrogens is influenced by their photodegradation. This can potentially occur both in the presence of the ultraviolet (UV) portion of solar radiation and in tertiary wastewater treatment plants that use UV radiation for disinfection purposes. To determine patterns of UV photodegradation for estrone (E1) and 17α-ethinylestradiol (EE2), water samples containing these compounds were exposed to levels of UVB radiation that would simulate exposure to ambient sunlight.

Organochlorines, brominated flame retardants and mercury levels in six seabird species from the Gulf of St. Lawrence (Canada): relationships with feeding ecology, migration and molt.

Concentrations of organochlorines (OCs), brominated flame retardants (BFRs) and mercury (Hg) were measured in eggs of six seabird species breeding in the Gulf of St. Lawrence, Canada. Stable nitrogen (delta15N) and carbon (delta13C) isotopes were used as ecological tracers to measure trophic level and connectivity with benthos, respectively.

Mercury transport between sediments and the overlying water of the St. Lawrence River area of concern near Cornwall, Ontario.

Contaminated sediments in the St. Lawrence River remain a difficult problem despite decreases in emissions. Here, sediment and pore water phases were analyzed for total mercury (THg) and methyl mercury (MeHg) and diffusion from the sediment to the overlying water was 17.

Size distribution of methylmercury associated with particulate and dissolved organic matter in freshwaters.

Water samples were collected from 20 wetland, river and lake sites across Eastern Ontario and Western Quebec to investigate the distribution of methylmercury (MeHg) associated with various size fractions of dissolved organic matter (DOM). Tangential Flow UltraFiltration (TUF) was used to fractionate DOM by nominal molecular size (<0.2 microm, <300 kDa, <30 kDa, <5 kDa and <1 kDa).

Dissecting the spatial scales of mercury accumulation in Ontario lake sediment.

Total mercury concentration was analyzed in 171 lakes from pre-industrial (>30 cm depth; Hg(pre-industrial)) and present-day sediments (0.5-1 cm; Hg(present-day)). Numerous hot or cold spots of sediment mercury enrichment (Hg EF; Hg(pre-industrial)/Hg(present-day)) were evident as determined by local tests of autocorrelation, although in most cases, the maximum correlation among sites was not the nearest neighbor, indicating a strong influence of watershed characteristics.

Temporal analysis of net fluvial methylmercury loading in a dystrophic and a clear water lake.

The concentration of methylmercury (MeHg) in aquatic ecosystems is the net result of the highly dynamic abiotic and biotic processes of mercury methylation and demethylation. In this study, we conduct an examination of the net fluvial loading of methylmercury (MeHg(Net)=MeHg(Watershed)-MeHg(Lake outflow)) across a 3 year time frame in both a dystrophic lake and an oligotrophic lake. A significant portion of MeHg(Net) variance in both lakes could be attributed to a seasonal pattern (11.

Sediment mercury dynamics and historical trends of mercury deposition in the St. Lawrence River area of concern near Cornwall, Ontario, Canada.

The St. Lawrence River near Cornwall, Ontario was designated an Area of Concern by the International Joint Commission in 1985. Sediments from this area have historically been contaminated with mercury (Hg), and although concentrations have decreased since the 1970s, they still remain high.

Identification of sulfate-reducing bacteria in methylmercury-contaminated mine tailings by analysis of SSU rRNA genes.

Sulfate-reducing bacteria (SRB) are often used in bioremediation of acid mine drainage because microbial sulfate reduction increases pH and produces sulfide that binds with metals. Mercury methylation has also been linked with sulfate reduction. Previous geochemical analysis indicated the occurrence of sulfate reduction in mine tailings, but no molecular characterization of the mine tailings-associated microbial community has determined which SRB are present.

Estrogenic exposure affects metamorphosis and alters sex ratios in the northern leopard frog (Rana pipiens): identifying critically vulnerable periods of development.

During the transformation from larval tadpole to juvenile frog, there are critical periods of metamorphic development and sex differentiation that may be particularly sensitive to endocrine disruption. The aim of the present study was to identify sensitive developmental periods for estrogenic endocrine disruption in the northern leopard frog (Rana pipiens) using short, targeted exposures to the synthetic estrogen, ethinylestradiol (EE2). Post-hatch tadpoles (Gosner stage 27) were exposed over five distinct periods of metamorphosis: early (stage 27-30), mid (stage 30-36), early and mid (stage 27-36), late (stage 36-42), and the entire metamorphic period (chronic; stage 27-42).

Chronic exposure of Rana pipiens tadpoles to UVB radiation and the estrogenic chemical 4-tert-octylphenol.

While adverse effects of exposure to ultraviolet B radiation (UVBR) and environmental pollutants on amphibians have been documented, few studies examined the effects of interactions between environmental stressors on amphibian health. Here the impacts of chronic exposure to UVBR and the estrogenic chemical 4-tert-octylphenol (OP), alone and in combination, on the survival, development, growth, and metamorphosis of Rana pipiens (northern leopard frog) tadpoles are evaluated. Tadpoles were exposed to environmentally relevant levels of OP (0.

Hormone cross-regulation in the tadpole brain: developmental expression profiles and effect of T3 exposure on thyroid hormone- and estrogen-responsive genes in Rana pipiens.

During metamorphosis, the tadpole neuroendocrine brain is a major target for the organisational effects of hormones acting via both endocrine feedback mechanisms and local hormone production. While the receptor-mediated actions of thyroid hormones in brain development have been well described, there is evidence that thyroid hormones could also be an important modulator of estrogen action during metamorphosis. To better understand hormone action and potential cross-regulation between thyroid hormone and estrogen, we examined changes in thyroid hormone receptors (TRalpha and TRbeta) and the estrogen receptor (ERalpha) in the brain of Rana pipiens throughout metamorphosis and in response to 48 h waterborne triiodothyronine (T3) exposure (0.

Seasonal and inter-annual variations in methyl mercury concentrations in zooplankton from boreal lakes impacted by deforestation or natural forest fires.

We compared the effects of natural and anthropogenic watershed disturbances on methyl mercury (MeHg) concentration in bulk zooplankton from boreal Shield lakes. MeHg in zooplankton was monitored for three years in nine lakes impacted by deforestation, in nine lakes impacted by wildfire, and in twenty lakes with undisturbed catchments. Lakes were sampled during spring, mid- and late summer.

Exposures to estradiol, ethinylestradiol and octylphenol affect survival and growth of Rana pipiens and Rana sylvatica tadpoles.

Endocrine disrupting compounds (EDCs) are often detected in the aquatic environment and can negatively affect the health of wildlife populations. However, little is known about the sensitivity of native amphibians to EDCs. Wood frogs (Rana sylvatica) and Northern leopard frogs (Rana pipiens) were exposed to three estrogenic EDCs: estradiol (E2), ethinylestradiol (EE2), and 4-tert-octylphenol (OP).

Photochemical reduction and reoxidation of aqueous mercuric chloride in the presence of ferrioxalate and air.

In this study, ferric oxalate is used to represent the photosensitive Fe(III) complexes as well as the diacid compounds which are at significant concentrations in cloud and rain droplets. Because of the common carboxylate functional group; ferric oxalate is also used as a model to represent humic substances found in natural water. UVA irradiation of aqueous acidic mercuric chloride (pH 1-4) in the presence of an excess of ferrioxalate results in partial reduction of the mercuric ion to elemental mercury.

Abiotic methylation of mercury in the aquatic environment.

Methylation of inorganic mercury in the aquatic environment has been considered to be largely the result of biological processes, primarily involving sulfate-reducing bacteria. However, these processes cannot account for all of the methylmercury that is formed naturally. A growing body of evidence suggests that chemical reactions represent another possible pathway for mercury methylation in the aquatic environment.