Mercury Cell Chlor-alkali Plant Research Articles

Business Roundup

BUSINESS Business Roundup ShareShare onFacebookTwitterWechatLinked InRedditEmail C&EN, 2018, 96 (21), p 15May 21, 2018Cite this:C&EN 96, 21, 15AbstractIndorama Ventures has agreed to acquire Avgol Industries, an Israeli maker of nonwoven materials for diapers, feminine hygiene products, and adult incontinence products. The deal values Avgol at more than $300 million. Inovyn has shut down its mercury cell chlor-alkali plant in Stenungsund, Sweden, in line with European regulations banning such technology. The firm is converting the site to membrane technology, which doesn’t use mercury. Tronox will acquire a titanium slag smelter in Jizan, Saudi Arabia, from a joint venture between Saudi Arabian chemical maker Tasnee and its titanium dioxide arm Cristal. The transaction for the facility, which makes feedstock for TiO2 pigment, will help advance Tronox’s merger with Cristal. DSM is expanding capacity for Dyneema UD, a unidirectional laminate based on ultra-high-molecular-weight polyethylene and used in antiballistic vests. The company will carry out the 20% boost at its plants in Heerlen, the Netherlands, and Greenville, N.C. It will alsoView: PDF | Full Text HTML

Spanish firm replaces mercury-cell process

To comply with European legislation, the Spanish basic chemicals producer Ercros will close its mercury-cell chlor-alkali plants, which have a combined annual capacity of 213,000 metric tons, by the end of 2017. It will replace the capacity with a 45,000-metric-ton plant based on membrane technology. The firm says the membrane-based plant will cost $60 million and open in 2018. Ercros says it does not plan to replace all of the mercury capacity because its biggest customer, Covestro, plans to close its Spanish isocyanate plant, which consumes chlor-alkali.

Mercury concentrations in marine sediments near a former mercury cell chlor-alkali plant in eastern Canada

Concentrations of total mercury (THg) were measured in coastal marine sediments near a former chlor-alkali plant in Chaleur Bay, New Brunswick. The chlor-alkali plant has been a local point source of THg since operation began in 1963. Historical THg contamination of marine sediments and biota has been widely reported. No baseline assessment has been conducted following plant closure in 2008. Surface (0–2cm) oxidized marine sediments were sampled along a single 5.2km transect radiating from the former plant and analysed for THg. THg concentrations ranged from 0.04–0.28μgg−1. Some localised THg concentrations exceeded Canadian marine sediment quality guidelines (n=4), but all samples (n=14) were significantly lower than previous studies conducted during plant operation. Plant closure (source control) and natural sediment recovery likely responsible for attenuating THg concentrations, but burial in deeper anoxic sediments may increase bioavilability of Hg that could pose ecological risks to marine biota.

Mercury contamination of riverine sediments in the vicinity of a mercury cell chlor-alkali plant in Sagua River, Cuba

Sediment is a great indicator for assessing coastal mercury contamination. The objective of this study was to assess the magnitude of mercury pollution in the sediments of the Sagua River, Cuba, where a mercury-cell chlor-alkali plant has operated since the beginning of the 1980s. Surface sediments and a sediment core were collected in the Sagua River and analyzed for mercury using an Advanced Mercury Analyser (LECO AMA-254). Total mercury concentrations ranged from 0.165 to 97 μg g−1 dry weight surface sediments. Enrichment Factor (EF), Index of Geoaccumulation (Igeo) and Sediment Quality Guidelines were applied to calculate the degrees of sediment contamination. The EF showed the significant role of anthropogenic mercury inputs in sediments of the Sagua River. The result also determined that in all stations downstream from the chlor-alkali plant effluents, the mercury concentrations in the sediments were higher than the Probable Effect Levels value, indicating a high potential for adverse biological effects. The Igeo index indicated that the sediments in the Sagua River are evaluated as heavily polluted to extremely contaminated and should be remediated as a hazardous material. This study could provide the latest benchmark of mercury pollution and prove beneficial to future pollution studies in relation to monitoring works in sediments from tropical rivers and estuaries.

In situ bioavailability of DDT and Hg in sediments of the Toce River (Lake Maggiore basin, Northern Italy): accumulation in benthic invertebrates and passive samplers.

DDT and mercury (Hg) contamination in the Toce River (Northern Italy) was caused by a factory producing technical DDT and using a mercury-cell chlor-alkali plant. In this study, DDT and Hg contamination and bioavailability were assessed by using different approaches: (1) direct evaluation of sediment contamination, (2) assessment of bioaccumulation in native benthic invertebrates belonging to different taxonomic/functional groups, and (3) evaluation of the in situ bioavailability of DDT and Hg using passive samplers. Sampling sites were selected upstream and downstream the industrial plant along the river axis. Benthic invertebrates (Gammaridae, Heptageniidae, and Diptera) and sediments were collected in three seasons and analyzed for DDT and Hg content and the results were used to calculate the biota sediment accumulation factor (BSAF). Polyethylene passive samplers (PEs) for DDT and diffusive gradients in thin films (DGTs) for Hg were deployed in sediments to estimate the concentration of the toxicants in pore water. Analysis for (DDx) were performed using GC-MS. Accuracy was within ±30% of the certified values and precision was >20% relative standard deviation (RSD). Total mercury concentrations were determined using an automated Hg mercury analyzer. Precision was >5% and accuracy was within ±10% of certified values. The results of all the approaches (analysis of sediment, biota, and passive samplers) showed an increasing contamination from upstream to downstream sites. BSAF values revealed the bioavailability of both contaminants in the study sites, with values up to 49 for DDx and up to 3.1 for Hg. No correlation was found between values in sediments and the organisms. Concentrations calculated using passive samplers were correlated with values in benthic invertebrates, while no correlation was found with concentrations in sediments. Thus, direct analysis of toxicant in sediments does not provide a measurement of bioavailability. On the contrary, analysis of bioaccumulation in benthic organisms provides the most realistic picture of the site-specific bioavailability of DDx and Hg, but this approach is time-consuming and not always feasible. On the other hand, the in situ deployment of passive samplers proved to be a powerful tool, providing a good surrogate measure of bioaccumulation.

Environmental Assessment of Remediation Technologies for Mercury Containing Wastes Using Lca Approach

Mercury cell chlor-alkali plants are not anymore considered a good industrial practice and the Integrated Pollution Prevention and Control of the European Union has indicated that chlor-alkali installations require obtaining licenses based on the Best Available Techniques. The purpose of this paper is to present the findings on the environmental impact study of current and future technologies to remediate mercury contaminated wastes from a chlor-alkali Cuban plant using Life Cycle Assessment (LCA) approach. The future remediation alternative consists on the proposal of thermal treatment to remove Hg while the current option includes the waste stabilization and disposal. The environmental impact assessments for both technological alternatives have been compared regarding their impact and damage categories using LCA. From an environmental point of view, a significant reduction on the human health impact (95.4 %), ecosystem quality impact (83 %) and impact on resources (78.5 %) would be achieved in comparison with the existing treatment applied by the chlor-alkali Cuban plant. The proposed thermal treatment technology is a significant costs project, but represents considerable benefits for the environment and human health.

Atmospheric mercury pollution around a chlor-alkali plant in Flix (NE Spain): an integrated analysis.

An integrated analysis approach has been applied to a mercury (Hg) case study on a chlor-alkali plant located in the Ebro River basin, close to the town of Flix (NE Spain). The study focused on atmospheric Hg and its incorporation in soils and lichens close to a mercury cell chlor-alkali plant (CAP), which has been operating since the end of the 19th century. Atmospheric Hg present in the area was characterized by means of seven total gaseous mercury (TGM) surveys carried out from 2007 to 2012. Surveys were carried out by car, walking, and at fixed locations, and covered an area of some 12km(2) (including the CAP area, the village in which workers live, Flix town, and the Sebes Wildlife Reserve). Finally, an atmospheric Hg dispersion model was developed with ISC-AERMOD software validated by a lichen survey of the area. The results for the atmospheric compartment seem to indicate that the Flix area currently has the highest levels of Hg pollution in Spain on the basis of the extremely high average concentrations in the vicinity of the CAP (229ngm(-3)). Moreover, the Hg(0) plume affects Flix town center to some extent, with values well above the international thresholds for residential areas. Wet and dry Hg deposition reached its highest values on the banks of the Ebro River, and this contributes to increased soil contamination (range 44-12,900ngg(-1), average 775ngg(-1)). A good fit was obtained between anomalous areas indicated by lichens and the dispersion model for 1year.

Vertical distribution and inventories of 239+240Pu and mercury in Sagua la Grande estuary, Cuba

The vertical activity distribution and inventories of 239+240Pu profile and Hg were determined in Sagua la Grande estuary, Cuba. The shape of the 239+240Pu profile in the core column resembled very closely the history of atmospheric nuclear weapons' testing, and the maximum deposition in 1963 was recorded in the sediment core history. The 239+240Pu activity concentrations in the surface layer sediments varied from 0.163 to 0.611 mBq g−1. The inventory of 239+240Pu was 42 ± 5.6 Bq m−2, a value close to that expected from direct global fallout. Using the 239+240Pu as a chronomarker the mass sedimentation rate in the area for the last 60 years was calculated, reaching values of 0.173 g cm−2 y−1. The mercury profile reflects the history of anthropogenic pollution in the estuary and perfectly describes the operation of the mercury-cell chlor-alkali plant, for production of NaOH, which began operations in 1980. The inventory of Hg was 2.42 ± 0.19 μg cm−2. These results contribute to the scarce regional database for pollutants and anthropogenic radionuclides in the Caribbean marine environment, particularly in relation to 239+240Pu.

Lichen and soil as indicators of an atmospheric mercury contamination in the vicinity of a chlor-alkali plant (Grenoble, France)

Atmospheric mercury (Hg) deposition around a mercury cell chlor-alkali plant located near Grenoble, south-east France, was assessed using Hg concentrations in lichens and soils. Hg content in the epiphytic Xanthoria parietina lichen ranged from ∼0.07 to ∼2.51 μg g −1, and concentrations decreased with increasing distance to the plant, with a contamination radius of ∼2 km. Soil Hg concentration profiles were consistent with an atmospheric origin, with higher concentrations in the upper part of the profiles. Concentration of Hg in lichens and top soils (0–10 cm depth) as a function of the distance to the chlor-alkali plant exhibited highly similar variations. Using a simple first-order deposition model, mean Hg fallouts for the whole history of chlor-alkali plant are estimated to ∼36 g Hg day −1 in this area, compatible with values reported for reactive gaseous mercury (RGM) emissions of similar industrial plants. Using literature data on RGM to total Hg emission ratio, we estimate that the plant emitted ∼650 kg Hg year −1. Two kilometres away from the plant, Hg content in top soils falls to values of (0.13 ± 0.07) μg g −1 Hg, which is the local anthropogenic geochemical background level, but higher than unperturbed geochemical background found at the bottom of soil profiles (below 40 cm depth) estimated to (0.04 ± 0.01) μg g −1 Hg. The present study evidences that lichens are a pertinent proxy for soil Hg contamination around chlor-alkali plants. They are attractive biomonitoring tools since sampling and preparations protocols for lichens are less time consuming than those used for soils.

Mercury contamination in the vicinity of a chlor-alkali plant and potential risks to local population

A mercury-cell chlor-alkali plant operated in Estarreja (North-western Portugal) for 50 years causing widespread environmental contamination. Although production by this process ceased in 2002, mercury contamination from the plant remains significant. The main objective of this study was to investigate mercury impact on the nearby environment and potential risks to local population. To assess the level of contamination soil samples were collected from agricultural fields in the vicinity of the plant, extending the study by taking samples of the predominant vegetation suitable for animal and human consumption, water samples, and fish species from a nearby coastal lagoon, to gain a preliminary insight into the potential for contamination of the terrestrial and aquatic food web. To determine population exposure to mercury, hair samples were collected from local residents. Total mercury concentration in the 0–15 cm layer of soil was found to be highly variable, ranging between 0.010 and 91 mg kg − 1 , although mercury contamination of soils was found to be restricted to a confined area. Lolium perenne roots contained between 0.0070 and 2.0 mg kg − 1 , and there is evidence that root systems uptake mercury from the soil. Levels of mercury in the aerial parts of plants ranged between 0.018 and 0.98 mg kg − 1 . It appears that plants with higher mercury concentration in soils and roots also display higher mercury concentration in leaves. Total mercury concentration in water samples ranged between 12 and 846 ng L − 1 , all samples presenting concentrations below the maximum level allowable for drinking water defined in the Portuguese law (1.0 μg L − 1 ). Mercury levels in fish samples were below the maximum limit defined in the Portuguese law (0.5 mg kg − 1 ), ranging from 0.0040 to 0.24 mg kg − 1 . Vegetables collected presented maximum mercury concentration of 0.17 mg kg − 1 . In general, food is not contaminated and should not be responsible for major human exposure to the metal. Mercury determined in human hair samples (0.090–4.2 mg kg − 1 ; mean 1.5 mg kg − 1 ) can be considered within normal limits, according to WHO guidelines suggesting that it is not affecting the local population. Despite being subject to decades of mercury emissions, nowadays this pollutant is only found in limited small areas and must not constitute a risk for human health, should these areas be restricted and monitored. Considering the present data, it appears that the population from Estarreja is currently not being affected by mercury levels that still remain in the environment.

Mercury pollution in Ria de Aveiro (Portugal): a review of the system assessment

The Ria de Aveiro (Portugal) is a coast al lagoon adjacent to the Atlantic Ocean and it has an inner bay (Laranjo bay) that received a highly contaminated effluent discharged by a mercury cell chlor-alkali plant from the 1950s until 1994. The aim of this study is to review in a holistic way several research studies that have been carried out in the Ria de Aveiro, in order to evaluate the remobilization of the mercury accumulated within the system and the recovery of the lagoon. The spatial distribution of the total mercury in the surrounding terrestrial environment has also been considered. Results indicate that the main mercury contamination problems in the Ria de Aveiro are confined to the Laranjo bay. Mercury export to the coastal waters and its impact on the nearshore compartments (water column, sediment and biota) are low. No direct effects of the mercury from nearby industrial activities were detected in Aveiro's urban soils, although historical mercury contamination is still affecting soil quality in the immediate vicinity of the chlor-alkali plant, located in Estarreja. Moreover, macrophyte harvesting for human direct or indirect use and the consumption of mussels, crabs and the sea bass from the Laranjo bay may constitute a health risk. Further studies focusing on developing skills for the restoration of the ecosystem are presently underway.

Mercury contamination in the vicinity of a derelict chlor-alkali plant. Part I: Sediment and water contamination of Lake Balkyldak and the River Irtysh

A mercury-cell chlor-alkali plant operated in Pavlodar, Northern Kazakhstan, for 18 years and caused widespread contamination of the surrounding environment. Untreated wastewater from the plant was discharged to Lake Balkyldak, a shallow impounded lake without an outlet. The nearby River Irtysh was also suspected to be impacted by mercury (Hg) via the transport of contaminated groundwater. We took sediment and water samples from both aquatic systems, and also sampled soils along the shoreline of the lake and in the Irtysh flood plain. Sediments from Lake Balkyldak were found to be very heavily contaminated, with Hg concentrations in the surface layer reaching up to approximately 1500 mg kg(-1) near the wastewater outfall pipe. The contaminated lake sediments are prone to wind-driven resuspension and are acting as a strong source of Hg to the water column. Unfiltered lake water samples taken in shallow areas within 10-15 m from the shoreline contained from 0.11 microg Hg L(-1) in the less contaminated northern part of the lake to 1.39 microg L(-1) near the pollutant outfall in the south (up to 7.3 microg L(-1) on windy days). Sediments from the River Irtysh were only slightly impacted, with maximum Hg concentrations of 0.046 mg kg(-1) in the old river channel and 0.36 mg kg(-1) in floodplain oxbow lakes. In water samples from the River Irtysh, Hg was generally not detected, although trace concentrations (3 to 9 ng L(-1)) were found in some samples taken from oxbow lakes. We conclude that the river is not significantly impacted by Hg, but the highly contaminated Lake Balkyldak poses a threat and is in need of remediation. Potential remediation options for the lake are reviewed and are discussed in the context of experiences made at other Hg-contaminated sites.

Mercury levels and liver pathology in feral fish living in the vicinity of a mercury cell chlor-alkali factory

Twenty-three barbels ( Barbus graellsii), 30 bleaks ( Alburnus alburnus) and 4 sediment samples were collected from four areas of the Cinca River (NE Spain), upstream and downstream of a mercury cell chlor-alkali plant. Mercury concentration in sediments downstream of the plant was about 25 times higher than the concentration upstream. Mercury levels in the muscle and liver of barbels downstream of the chlor-alkali plant were 10 and 30 times higher than those upstream. The average mercury concentration in the muscle and liver of barbels downstream of the factory was 1.48 and 1.78 mg/kg w.w., with maximal concentrations of 2.43 and 3.64 mg/kg w.w, respectively. Liver/muscle ratio of mercury was significantly higher in barbels sampled downstream of the factory. Bleak showed a similar pattern, with a significantly higher whole-body mercury concentration downstream of the chlor-alkali plant. Nevertheless, a progressive decrease in mercury concentration downstream of the impact area was found in bleak, but not in barbel. Histopathological analysis showed that fish downstream of the factory had significantly higher prevalence of liver pathologies ( p < 0.05). Although there are no specific histopathological markers of mercury exposure, barbels with the highest Hg levels in the liver also showed the most severe pathologies, and the processes found in these barbels were consistent with the pro-oxidant effect of heavy metals.

Urinary mercury in adults in Poland living near a chloralkali plant

We conducted a study within the framework of the interdisciplinary European Mercury Emission from Chloralkali Plants (EMECAP) project to assess exposure to mercury (Hg) and the contribution of Hg emissions from a mercury cell chloralkali plant to urinary mercury (U-Hg) in adults living near the plant. We collected data from questionnaires and first morning urine samples from 75 subjects living near the Tarnow plant in Poland and 100 subjects living in a reference area. Median U-Hg was 0.32 μg/g creatinine (μg/gC) and 0.20 μg/gC, respectively. The median U-Hg was also higher in the amalgam-free subjects living near the plant (0.26 μg/gC) than in the reference group (0.18 μg/gC), but no such association was found in a multivariate analysis. There was a statistically significant positive association between U-Hg and number of teeth with amalgams, a negative association with age and a tendency towards higher U-Hg in female subjects. In the amalgam-free subjects there were statistically significant effects of female sex and fish consumption, and a negative association with age. The additional long-term average air Hg concentration from the plant, based on EMECAP environmental measurements and modelling, was estimated to be 1−3.5 ng/m 3 for the residential study area and should have a very small effect on U-Hg. The other Hg emission sources such as coal combustion facilities located nearby should be taken into account in assessing the overall impact of air Hg on U-Hg in this area.

Emissions, dispersion and human exposure of mercury from a Swedish chlor-alkali plant

Mercury in air near a mercury cell chlor-alkali plant in Sweden has been measured within the EU-project EMECAP. Based on the measurements and modelling the annual distributions of GEM and RGM have been calculated for the local area around the plant. The average concentration of GEM in residential areas near the plant was found to be 1–3.5 ng m −3 higher in comparison to the background concentration in this part of Sweden. The emission of RGM (0.55 kg year –1) results in elevated RGM concentrations close to the plant. The greatest impact on the local area is due to wet deposition of RGM. However, only a small fraction (0.4%) of all mercury being emitted was found to be deposited in the local area. No impact on urinary mercury could be demonstrated in the population living close to the plant.

Elemental mercury emissions from chlor-alkali plants measured by lidar techniques

Differential absorption lidar (DIAL) techniques have been utilized to measure elemental gaseous mercury fluxes from mercury cell chlor-alkali (MCCA) plants as a part of the European Union funded European mercury emissions from chlor-alkali plants (EMECAP) project. Three plants have been selected as study objects and a total of six measurement campaigns have been performed, one intercalibration campaign and five flux evaluation campaigns, in both winter and summer. The measurements were carried out using the Swedish optical parametric oscillator- (OPO) based mobile lidar system developed at Lund Institute of Technology. The study shows large differences in the mercury emissions measured in winter or summer and at the different plants. The average values for the campaigns ranged from 6 g h −1 in the winter campaign at the Swedish plant to 54 g h −1 in the summer campaign at the Italian plant.

Great Lakes Resource at Risk

For centuries the Great Lakes have been treated callously These five magnificent lakes—Superior, Michigan, Huron, Erie, and Ontario—located along the eastern half of the Canadian–U.S. border have served as a virtual sewer catching waste from industry, agriculture, commercial shipping, and households. Their natural barriers to other water systems have been breached, exposing indigenous ecosystems to aggressive invaders. They’ve been used as a highway for colossal ships that require deepened and broadened channels to crisscross the lakes, and that import exotic species along with their intended cargo. At times it could seem that this long-suffering water system will see no end of indignities. But recent renewed focus on the unique and tremendous value of this resource by governments and communities surrounding the lakes may turn the tide of neglect and abuse. According to the U.S. Environmental Protection Agency (EPA), the Great Lakes contain 21% of the Earth’s and about 84% of United States’ surface freshwater. That’s about 22,000 cubic kilometers of water spread over 94,250 square miles. Each year the lakes provide more than 6.7 million cubic meters of water to municipalities and quadruple that to industry. They support a commercial fishery worth about $13 million as of 2002, according to the U.S. Geological Survey (USGS), and a sport-fishing industry of nearly $1.3 billion as of 2001, according to the U.S. Fish and Wildlife Service. Today about 25% of Canadians and 10% of Americans—a total of more than 33 million people—live in the Great Lakes watershed. “The whole industrial expansion that took place during the ‘robber baron’ era [of the late nineteenth century] expanded along the shores of the Great Lakes,” says Deborah Swackhamer, a University of Minnesota professor of environmental chemistry. Soon ships were carrying iron ore, coal, and limestone from mines and quarries to steel mills and later steel to factories and products to markets. In addition to serving as a transportation system, the lakes provided a place to discharge manufacturing by-products. Unlike a sewer, however, whatever enters this lake system stays awhile. On average, less than 1% of the five lakes’ water turns over each year, which means that many pollutants stay in place. They settle in sediments, adhere to other surfaces, become suspended in water, and bioaccumulate in organisms. Similarly, with the exception of migratory birds, most wildlife in the basin spend their entire life cycle in or near the lakes. As a result of all these stressors, the lakes now house fish that are dangerous to eat, water that can be unsafe to drink, anoxic “dead zones”—areas in which virtually no plants or animals can survive—that appear each summer like clockwork, and an ever-growing population of unwanted species from other parts of the world.

Mercury Contamination of Marine Sediments and Blue Mussels (Mytilus edulis) in the Vicinity of a Mercury Cell Chlor-Alkali Plant in Dalhousie, New Brunswick, Canada

Abstract This report examines mercury concentrations in the marine environment of the Restigouche River, near a mercury cell chloralkali plant operated by Pioneer Chemicals Canada Inc. (PCI) in Dalhousie, New Brunswick. The PCI plant is a known point source of mercury in the area, but the extent of marine contamination in the Baie des Chaleurs as a result of those discharges has not been recently evaluated. Marine sediments (five transects), mussel tissue (six locations) and effluent samples (four locations) were obtained in the vicinity of the PCI plant and analyzed for total mercury. Mussel tissues were also analyzed for condition index, metallothioneins and zinc in the digestive gland and gonad as well as gonad vitellin-like proteins and digestive gland lipid peroxidation. Results indicated that the area of the Restigouche River around the PCI plant had elevated concentrations of mercury in sediment and mussel tissue compared with local background concentrations. Mercury concentrations in sediments decreased with distance from the chlor-alkali plant. Concentrations in sediments ranged from 0.03 mg/kg at a distance of 4.6 km to 1.96 mg/kg at a distance of 20 m from the shoreline at the plant. Nine sites had mercury concentrations exceeding the CCME Interim Sediment Quality Guideline (0.13 mg/kg), the furthest of which was 1090 m from PCI. Mercury concentrations in water discharges from four of the five observed outfalls ranged from 0.84 to 4.32 µg/L. Mercury concentrations in mussel tissue ranged from 0.02 mg/kg at a distance 4.6 km from the plant to 1.40 mg/kg directly in front of the plant. Condition index and zinc concentrations in mussels close to the plant were correlated with mercury levels; however, some abnormal biomarker results were found at locations far from the plant as well, indicating other sources of contaminants. Further studies are recommended to define the area of contamination near the PCI plant, as well as to determine the potential impact of other sources of mercury in the area. The environmental risk of the mercury contamination should also be more clearly established.

Assessment of mercury emissions inventories for the Great Lakes states

Anthropogenic mercury (Hg) air emissions for the eight Great Lakes states in 1999–2000 were evaluated by analyzing three inventories. The US Environmental Protection Agency (EPA) National Emissions Inventory (NEI) had the most complete coverage for all states, and total Hg emissions ranged from 4226 lb in Minnesota to 15,828 lb in Pennsylvania. Coal-fired electric utilities accounted for 52.7% of the region's Hg emissions, varying from 20.2% of the total in New York to 67.5% in Ohio. Other important contributors to regional emissions included municipal waste combustion (5.6%), mercury-cell chlor-alkali plants and hazardous-waste incinerators (4% each), stationary internal combustion engines (ICEs) (3.5%), industrial, commercial, and institutional (ICI) boilers (3.3%), and lime manufacturing (3.0%). Although medical waste incineration accounted for just over 1% of regional emissions using the original classifications, the inclusion of health care facilities that may have been inappropriately identified with other sectors would increase the sector to 4.5% of regional emissions (and decrease the stationary ICE sector to 1.4% of the regional total). There were substantial differences for some sectors between the NEI and the Great Lakes Regional Air Toxics Emissions Inventory (GLEI), as well as unexplained differences within inventories between states (particularly for the cement, lime, and asphalt industries, and for lamp breakage). Toxics Release Inventory data for 2000 mainly covered electric utilities, and differences from the NEI were significant for several states. An independent assessment indicates the possibility of underestimated Hg emissions by about twofold for ICI boilers, although data for the sector (in particular concerning fuel oil emissions) are highly uncertain. Limited data indicate the likelihood of significant underestimates of electric arc furnace mercury emissions in the NEI and GLEI inventories. Several measures are here identified for improving the reliability of the inventories, both for modeling of atmospheric transport and deposition modeling and for tracking progress in Hg reduction initiatives.

A comparison of the speciation and fate of mercury in two contaminated coastal marine ecosystems: The Venice Lagoon (Italy) and Lavaca Bay (Texas)

We compared the speciation of Hg in two estuaries, Lavaca Bay (Texas) and the Venice Lagoon (Italy). Both are large, shallow embayments that are contaminated by direct discharges from mercury‐cell chlor‐alkali plants and dominated by rapid tidal flushing. Although contaminated by discharges into Lavaca Bay from 1966 to 1979 and into the Venice Lagoon from 1951 to 1989, Hg concentrations have dwindled to similar moderate levels in sediments (200‐2,000 ng g‐1) and water (1‐3 ng L‐1 dissolved) since the advent of pollution abatement. The Venice Lagoon contains lower levels of CH3Hg than Lavaca Bay, which is surprising, given the much larger degree of wetlands coverage in the lagoon. A narrow temporal peak in methylation was seen in early spring at both sites, although it was much stronger in Lavaca Bay. Data indicated that sediment CH3Hg is more strongly correlated with variables such as habitat and seasonality than with total Hg. In Lavaca Bay, because of high sedimentation rates and low remixing, the highest levels of Hg are buried 10‐30 cm below the surface. Combined with previous observations of strong Hg methylation after dredging activities, this argues for leaving Hg‐contaminated sediment in place, to be buried by the deposition of cleaner sediments. In Venice Lagoon, decisions may be complicated by continuous remixing of the upper sediment layers, moving the highest levels of Hg toward the surface and distributing it over a far larger area than has been seen in Lavaca Bay.