Trace Metal Emissions Research Articles

Dry deposition of airborne trace metals on the Los Angeles Basin and adjacent coastal waters

We present an assessment of the deposition rates of airborne trace metals onto the Los Angeles Basin and adjacent coastal waters. For this purpose, the UCLA Surface Meteorology and Ozone Generation (SMOG) air pollution modeling system has been used to simulate the geographical distributions of trace metals and their deposition fluxes. Calculations were performed for average summer and winter conditions, as well as for extreme meteorological events, in particular, for Santa Ana winds. Thus, a series of simulations were carried out that define the range of meteorological conditions contributing to dry deposition in the region. These predictions have been calibrated and validated using measurements collected in the LA area. Significant spatial and temporal variability are found in trace metal concentrations and deposition rates. Large spatial gradients occur near the coast as well as at the mountainous boundaries of the airshed. Considerable diurnal and seasonal variations in trace metal deposition are also noted. For example, the development of a daytime sea breeze, particularly in the warmer months, leads to greater deposition in the northern and eastern basin as well as in the high desert. A nighttime land breeze, especially in the colder months, enhances deposition onto coastal ocean surfaces. Large particles dominate local trace metal deposition in central urban (and adjacent) areas, while fine particles export metals over regional scales through long‐range advection. Since the majority of urban metal deposition occurs on particles larger than 10‐μm diameter, routine measurements of PM10 or PM2.5 concentrations for air quality characterization may not be reliable indicators of local sources. Some 35–45% of all trace metal emissions are deposited locally within the Los Angeles Basin on an annual basis. Santa Monica Bay and its watersheds receive about 6% of this amount, which can have a significant impact on trace metal concentrations in the surface waters of the bay, primarily through land runoff following storms.

Estimation of trace element release and accumulation in the sand bed during bubbling fluidised bed co-combustion of biomass, peat, and refuse-derived fuels ☆

The experimental study and thermodynamic equilibrium calculations were performed to investigate the interactions of fuel-based lead, copper, zinc, and manganese with the bed material of the bubbling fluidised bed boiler (BFB) during the co-combustion of sawdust, peat, and refuse-derived fuel. Flue gas trace element measurements, a chemical analysis of process streams, and mass balance calculations over the boiler reveal that the bed material captures substantial amounts of Pb, Cu, Zn and Mn, but also that these metals are released from the bed when the fuel characteristics or the process parameters are changed. The study shows that the trace metal emissions of a BFB boiler are not necessarily directly related to metal concentrations of the fuel but are rather a result of a complex process combining the release of trace metals from the fuel, the interaction between the fuel and fuel ash particles within the bed material, and the release of trace metals from the bed. The EDS analysis of the bed material particles shows that the original sand particles are covered with a Ca- and K- rich layer. In combustion temperatures, the layer is assumably in a melt form and has an important role in the trace metal accumulation/release process. The thermodynamic multi-phase multi-component equilibrium calculation for zinc suggests that the release of zinc from the bed material is strongly increased with an increasing Cl-concentration of the fuel, due to the conversion of the bed-bound zinc to ZnCl 2.

Estimation of atmospheric trace metal emissions in Vilnius City, Lithuania, using vertical concentration gradient and road tunnel measurement data

A new approach for the estimation of trace metal emissions in Vilnius city was implemented, using vertical concentration profiles in the urban boundary layer and road tunnel measurement data. Heavy metal concentrations were examined in fine and coarse particle fractions using a virtual impactor (cut-off size diameter 2.5 μm). Negative vertical concentration gradients were obtained for all metals (Ba, Pb, V, Sb, Zn) and both fractions. It was estimated that the vertical concentration gradient was formed due to emissions from an area of about 12 km 2. Road tunnel measurements indicated that trace metal concentrations on fine particles were lower than those on coarse particles, which suggested that re-emitted road dust was highly enriched in trace metal due to historic emissions within the tunnel. Emission rates of different pollutants in the road tunnel were calculated using pollutant concentration differences at the tunnel entrance and exit and traffic flow data. Heavy metal emission rates from the area of Vilnius city were estimated using the vertical gradient of heavy metal concentrations and the coefficient of turbulent mixing, as derived from meteorological measurement data. The emission values calculated by the two different methods coincided reasonably well, which indicated that the main source of airborne trace metals in Vilnius city is traffic. The potential of the vertical concentration gradient method for the direct estimation of urban heavy metal emissions was demonstrated.

Hydrocarbon fuel gas reformer assembly for fuel cell power plant

Coal as well as fuel oil combustion generates emissions of potentially toxic trace pollutants including organic and inorganic chemical compounds besides major pollutants. A study on As, Cd, Co, Cr, Cu, Hg, Fe, Mn, Ni, Pb, Se, and Zn emissions from a 220 MW coal-fired power plant equipped with a electrostatic precipitators (ESPs) and 6 MW oil fired-power plant was carried out, using stack monitoring kit, Envirotech APM 620, which is similar to EPA Method 29. Simultaneous sampling of coal, fuel oil, oil waste, bottom ash, fly ash, flue gases, and particles associated with the gas phase has been performed. This sampling method was used for trace metal sampling. The content of all these metals in coal, oil, oil waste, bottom ash, fly ash have been determined by XRF, whereas their contents in the flue gases, and particles associated with the gas phase has been analyzed with ICP-AES. The mass balances obtained for trace elements were satisfactory in case of fuel oil based power plant, whereas in case of coal fired power plant, the mass balance for all the trace elements were below 50% except for the As, Se, and Hg. The enrichment factors for all trace metals was <1 in both cases. The above sampling method is moderately adequate method for trace element sampling in coal as well as oil fired power plants except for Hg. The results indicate that trace metals emissions were higher in coal-based power plant than the fuel oil-fired power plant.

An assessment of global and regional emissions of trace metals to the atmosphere from anthropogenic sources worldwide

An accurate and complete emission inventory for atmospheric trace metals on a global scale is needed for both modeler community and policy makers to assess the current level of environmental contamination by these pollutants, major emission sources and source regions, and the contribution of the atmospheric pathway to the contamination of terrestrial and aquatic environments. Major progress has been made in assessing emissions of trace metals in various countries and even regions, e.g., Europe, since the first global emission estimate for these pollutants was made by Nriagu and Pacyna (1988). These improved national and regional emission inventories have been used in this work to assess the global trace metal emissions from anthropogenic sources in the mid-1990s. The results of this work conclude that stationary fossil fuel combustion continues to be the major source of Cr, Hg, Mn, Sb, Se, Sn, and Tl with respect to the coal combustion and the major source of Ni and V with respect to oil combustion. Combustion of leaded, low-leaded, and unleaded gasoline continues to be the major source of atmospheric Pb emissions. The third major source of trace metals is non-ferrous metal production, which is the largest source of atmospheric As, Cd, Cu, In, and Zn. The largest anthropogenic emissions of atmospheric trace metals were estimated in Asia. This can be explained by growing demands for energy in the region and increasing industrial production. As a result, the Asian emissions are not only larger than the emissions on other continents, but also show an increasing trend. Another factor contributing to high emissions in Asia is the efficiency of emission control, which is lower than in Europe and North America. Concerning the two latter continents, emissions of trace metals show a decreasing tendency over the last two decades. Key words: anthropogenic sources, atmospheric emissions, trace metals, global emission inventory

Capture of gas-phase arsenic oxide by lime: kinetic and mechanistic studies.

Trace metal emission from coal combustion is a major concern for coal-burning utilities. Toxic compounds such as arsenic species are difficult to control because of their high volatility. Mineral sorbents such as lime and hydrated lime have been shown to be effective in capturing arsenic from the gas phase over a wide temperature range. In this study, the mechanism of interaction between arsenic oxide (As2O3) and lime (CaO) is studied over the range of 300-1000 degrees C. The interaction between these two components is found to depend on the temperature; tricalcium orthoarsenate (Ca3As2O8) is found to be the product of the reaction below 600 degrees C, whereas dicalcium pyroarsenate (Ca2As2O7) is found to be the reaction product in the range of 700-900 degrees C. Maximum capture of arsenic oxide is found to occur in the range of 500-600 degrees C. At 500 degrees C, a high reactivity calcium carbonate is found to capture arsenic oxide by a combination of physical and chemical adsorption. Intrinsic kinetics of the reaction between calcium oxide and arsenic oxide in the medium-temperature range of 300-500 degrees C is studied in a differential bed flow-through reactor. Using the shrinking core model, the order of reaction with respect to arsenic oxide concentration is found to be about 1, and the activation energy is calculated to be 5.1 kcal/mol. The effect of initial surface area of CaO sorbent is studied over a range of 2.7-45 m2/g using the grain model. The effect of other major acidic flue gas species (SO2 and HCl) on arsenic capture is found to be minimal under the conditions of the experiment.

An assessment of global and regional emissions of trace metals to the atmosphere from anthropogenic sources worldwide

An assessment of global and regional emissions of trace metals to the atmosphere from anthropogenic sources worldwide

Pilot scale study of trace element vaporization and condensation during combustion of a pulverized sub-bituminous coal

Trace metal emissions from coal-fired power plants are largely associated with the fly ash. The work reported here is part of a larger effort to develop a fundamental model for transformation of trace metals in coal to air toxic emissions from coal-fired power plants. Because the time-temperature history of the combustion gases determines the condensation behavior of gaseous species, experimental study of these phenomena require a realistic post-combustion environment. Pilot-scale combustion of a Powder River Basin coal was conducted using realistic post-combustion conditions. Trace element distributions were measured in the submicron fly ash at the inlet to an electrostatic precipitator. Flame temperature had a dramatic impact on the amount of certain trace elements such as As and Se in the submicron ash, indicating that these elements vaporize during the combustion process. The amount of vaporization was not sensitive to coal grind. There is evidence for the reaction of As and Se vapors with the large (supermicron) ash in the post-combustion flue gas via a surface reaction. The correlation between arsenic and calcium in the ash suggests the formation of calcium arsenate. No such correlation was observed between selenium and calcium.

A Simple Two-Reactor Method for Predicting Distribution of Trace Elements in Combustion Systems

Utilization of fossil fuels in energy production results in emissions of pollutants. Development in combustion technology has, however, during recent years focused on decreasing emissions of particulates, sulfur, and nitrogen oxides. In addition, combustion also includes a potential risk for emission of trace metals. Due to the fact that many trace elements have been identified as having a negative effect on human health and the natural environment, they have received special attention from a regulatory point of view. This paper describes a simple method for predicting the fate of eight trace elements (As, Cd, Hg, Ni, Pb, Se, V, and Zn) in combustion processes. Using the fuel composition and power plant operating conditions, the trace element concentrations in various ashes and the flue gas are determined. The method, which is based on a global equilibrium approach, describes the overall behavior of the eight trace elements successfully. Distribution/partitioning of the trace elements between the bottom ash, fly ash, and the flue gases is described and compared to measured data from a full-scale coal-fired power plant burning bituminous coal. The outcome from the prediction is actual concentrations of trace elements in main power plant streams.

99/02074 Trace metal emissions from the Estonian oil shale-fired power plant: Aunela-Tapola, L. A. et al. Fuel Process. Technol., 1998, 57, (1), 1–23

99/02074 Trace metal emissions from the Estonian oil shale-fired power plant: Aunela-Tapola, L. A. et al. Fuel Process. Technol., 1998, 57, (1), 1–23

99/02220 Airborne trace metal emissions from electric utility generating facilities in the Philadelphia region: public health risk and environmental policy: Miller, W. C. Diss. Abstr. Int., B, 1998, 59, (4), 1567, 276 pp. Avail. UMI, Order No. DA9829952

99/02220 Airborne trace metal emissions from electric utility generating facilities in the Philadelphia region: public health risk and environmental policy: Miller, W. C. Diss. Abstr. Int., B, 1998, 59, (4), 1567, 276 pp. Avail. UMI, Order No. DA9829952

Trace metal emissions from the Estonian oil shale fired power plant

Emission levels of selected trace metals from the Estonian oil shale fired power plant were studied. The plant is the largest single power plant in Estonia with an electricity production capacity of 1170 MW e (1995). Trace metals were sampled from the flue gases by a manual method incorporating a two-fraction particle sampling and subsequent absorption of the gaseous fraction. The analyses were principally performed with ICP-MS techniques. The trace metal contents of Estonian oil shale were found to be in the same order of magnitude as of coal on average. The high total particle concentrations in the flue gases of the studied oil shale plant contribute, however, to clearly higher total trace metal emission levels compared to modern coal fired power plants. Although the old electrostatic precipitators in the plant have been partly replaced by state-of-the-art electrostatic precipitators, the majority of the boilers are currently equipped with the old precipitators. The results of the study show remarkably high concentrations of toxic heavy metals in the flue gases (e.g., Pb, Zn, Mn and As: >200 μg/m 3 each) and clear accumulation of Pb, Cd, Zn, Tl and As on the fly ash. Additionally, significant portions of some heavy metals (e.g., Hg, Cd, As and Pb) were found in the absorption liquids of the sampling line, indicating the presence of either vaporous metal species or metals condensed on very small particles in the flue gases. The experimental results were interpreted by theoretical modeling using Global Equilibrium Analysis. The modeling could reasonably well explain the experimental results, especially the enrichment of certain trace metals in the fly ash as a result of volatilization/condensation phenomenon.

Groundwater composition near the nickel—copper smelting industry on the Kola Peninsula, central Barents Region (NW Russia and NE Norway)

The chemical composition of 185 groundwater samples collected from two catchments in the extreme NE Norway and NW Russia over the period April 1994 to November 1995 is reported in terms of Ag, Al, As, B, Ba, Be, Bi, Br, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, K, Li, Mg, Mn, Mo, Na, Ni, NO 3, P, Pb, PO 4,Rb, S, Sb, Se, Si, SO 4, Sr, Th, Ti, Tl, U, V and Zn concentrations (as determined by ICP-MS, ICP-AES and IC), pH and electrical conductance. One catchment (C2) is located in Russia 5 km downwind of the nickel—copper ore smelting industry in Monchegorsk, which is a major SO 2 and trace metal emission source, the other (C5) is located in Norway 30 km off-wind from the nickel-copper ore smelter in Nikel and 52 km off-wind from the nickel—copper ore roasting plant of Zapoljarniy, which are also significant emitters of inorganic atmospheric pollutants. Groundwater chemistry mostly reflects the mineralogical composition of the gabbro aquifer in C2 and the Quaternary deposits in C5, although groundwater in C2 also shows signs of incipient contamination from surface waters (heavy metals, sulphate, chloride). Groundwater in C2 appears to have been acidified by S-compounds emitted from Monchegorsk, but the groundwater's capacity to neutralise incoming acidity has not been exhausted. In C5, groundwater has not been acidified to any extent and has a high acid neutralising capacity. This study demonstrates that the geological substrate of a catchment is a fundamental control on how groundwater responds to atmospheric pollution, even if the latter is severe.

97/02326 Demonstration of COHPAC II for control of fine particulate emissions and air toxics from coal-fired power plants

The Clean Air Act Amendments of 1990 require utilities to reduce sulfur dioxide (SO{sub x}) emissions and study the potential effect of trace emissions, such as mercury, from power plants. Certain approaches for SO{sub x} control that could be cost-effective for specific sites, such as fuel switching and sorbent injection, can severely affect the particulate collection performance of existing electrostatic precipitators (ESPs). For many existing ESPs, especially those with small collection areas, costly solutions might be required, such as construction of new fabric filter (baghouse) systems, a significant increase in the size of an existing ESP, or the use of high efficiency scrubbers. The COmpact Hybrid PArticulate Collector (COHPAC) is an EPRI-patented concept which can potentially provide up to 60% savings in capital cost requirements compared to more traditional systems. The approach is to retrofit either a stand-alone pulse-jet baghouse downstream of the existing particulate control device, usually an under-performing ESP (COHPAC I), or retrofit a pulse-jet baghouse (PJB) into the last field of an existing ESP (COHPAC II). The combination of low ash loading and charged ash entering the baghouse will allow the PJB to operate with fewer bags, a higher than normal filtering air-to-cloth ratio and moderate pressuremore » drop. In this Southern Company/Electric Power Research institute sponsored demonstration an existing three-field, pilot-scale ESP has been refurbished and fitted with a pulse-jet baghouse compartment in place of the last of its three precipitator fields (COHPAC II). Tests are being performed to evaluate ESP and baghouse performance and measure trace metal emission control capabilities downstream of the unit. Performance to date is discussed.« less

Source strength assessment of volcanic trace elements emitted from the Indonesian arc

We have for the first time estimated volcanic emission of volatile metals for a large regional volcanic source showing permanent activity, namely the Indonesian Arc. We have done this by normalizing concentrations of metals ratios in volcanic plumes to SO 2 emission rates. Metal/SO 2 ratios measured in magmatic gases are used to estimate emissions from eruptive activity, whereas those measured in fumarolic gases are used to estimate emissions from non-eruptive activity. The SO 2 emission rate obtained is 3.5 × 10 6 tons per year, which represents about 20% of the annual worldwide volcanic flux of SO 2. The obtained trace metal ( 210Po, Pb, Bi, Cd, Zn and Cu) fluxes account for only about 5 to 30% of their global volcanic flux. These relatively low values for trace metal emissions (relative to the volcanic activity and the number of active volcanoes of the region) appear to reflect the andesitic magma composition of the volcanoes of the arc.

Trace metal emissions from co-combustion of refuse derived and packaging derived fuels in a circulating fluidized bed boiler

Energy recovery from refuse derived fuels (RDF) and packaging derived fuels (PDF) is one option in integrated waste management. Nine RDF and PDF co-combustion tests with peat and coal in a circulating fluidized bed boiler were carried out in this work. Heavy metal emissions in flue gas and fly ash were measured. Multivariate data analyses were used to find out the most important parameters affecting metal emissions in the flue gas. The results showed that total heavy metal emissions were low. Although RDF and PDF had more heavy metals than peat and coal, the multivariate data analysis showed that an increase of the RDF or PDF share in the fuel mixture up to 20% did not correlate directly with the metal emissions in the flue gas. Distribution of Cd, Cu, Zn and Sn between flue gas and fly ash correlated with each other. Injection of limestone to bind sulphur and chlorine did not have a significant effect on heavy metal emissions in the flue gas. Heavy metals concentrated on the fly ash, but all fly ashes passed the EPA-TCLP tests.

Coal fuel cycle externalities estimates (Part of the U.S. Initiative of the U.S. DOE/CEC Study)

Electricity is of considerable benefit to the consumer and society. However, the price paid by the consumer does not necessarily reflect the full cost. There are two components to the full cost. One component is the private costs that are paid by the consumer, such as labor, capital, fuel, insurance, etc. The other component includes the cost or benefit accrued to third parties, such as: effects of global warming potential; effects on health from the emissions of SO 2, NO x, and particulates; and other considerations. These costs or benefits are termed externalities, and usually are not included in the price paid by the consumer. Externalities estimates are presented for site-specific Pulverized Fuel electric generation stations located in the southwestern and southeastern part of the U.S.A. The results are referenced to the specific location and may not be applicable to other sites or technologies. The externalities are discussed for a wide range of effects, from global warming potential through trace metal emissions to energy security.

Analysis of heavy metal emission data from municipal waste combustion

Heavy metals contained in municipal solid waste (MSW), after combustion in modern waste-to-energy facilities, are collected in bottom and fly ash, only a small quantity being discharged from the stack as particulate or vapor. These metals are found to be broadly distributed throughout the constituents, limiting the potential for reducing them by targeting specific components. The many factors which determine metals partitioning to bottom ash, boiler hopper and emission control flyash, and stack emissions, shows that the complex relationship between feed composition and emissions makes it difficult if not impossible to assign cause and effect on their quantities and concentrations in these discharges. Data showing the relationship between particulate matter, emission controls, and emission factors for the heavy metals is examined. A finding that substantial spiking of lead and cadmium in the feed resulted in only marginal changes in stack emissions indicates that efforts to remove these metals from the waste would not produce a significant change in stack emissions. The range of trace metal emissions from a single waste-to-energy (WTE) facility over a period of three to four years is compared with the range reported from individual tests of about twenty facilities also having acid gas controls and fabric filters, indicating that the waste composition and the combustion and emission control technology employed all contribute to the variability of metals and particulate emissions. The relationship between annual averages and probable maximum values which may be anticipated from periodic testing is examined. Special attention is given to mercury, its various species, chemical reactions, and the effectiveness of various carbon-based reagents used for emission control. Emissions from WTE facilities are compared with those from oil and coal-fired utility boilers on a mass per kWh generated.

96/03356 - Trace emissions from coal combustion: Measurement and control

Scanning electron microscopy with wavelength-dispersive spectrometry has been used to measure trace metals in coal and ash. Hg, As. Ni, and Se have been detected in individual pyrite grains in Illinois #6 coal at levels up to 2680 ppm, 410 ppm, 320 ppm, and 880 ppm, respectively. These elements were present in fewer than half the grains analyzed. Cr has been detected at up to 950 ppm in half of clay mineral grains analyzed in Illinois #6 coal. The same trace metals were detected in pyrite and clay grains from Pittsburgh #8 coal. Ash samples show a similarly heterogeneous distribution of trace metals. Hg has been detected at up to 700 ppm in 24% of aluminosilicate. particles analyzed in ash from Absaloka coal, a subbituminous Montana fuel. These data confrm that coal cleaning processes which remove pyrite are likely to be suitable for trace metal emissions control. In addition, back-end control devices which target specific types of ash particles may be helpful for control of air toxics emissions.

Comparison of metal concentrations in the fore and hindguts of the crayfish Cambarus bartoni and Orconectes virilis and implications regarding metal absorption efficiencies

The anthropogenic perturbation of trace metal cycle has resulted in increased emission of trace metals into the atmosphere. This has resulted in the elevation of trace metals in recently deposited sediments of lakes far removed from the original source. Benthic invertebrates, such as crayfish, live and feed directly on recently deposited sediments and are in direct contact with metals both of natural and anthropogenic origin. Crayfish may be good indicators of sediment-metal levels as they appear to retain tissue-metal concentrations that are correlated to environmental levels (e.g., for Cu, Zn and Fe). However, it is suggested that as crayfish homeostatically control tissue elemental concentrations they, in fact, cannot be used as indicators of environmental metal level. One aspect often missing is a comparison of how efficiently crayfish can absorb the element from its food under different environmental conditions. Differences in the ability of the crayfish to absorb elements from food will in turn influence ultimate tissue concentrations. One possible way to assess the importance of food as a source of elemental contamination is through gut content analysis. For essential elements not in excess (i.e., uncontaminated sites), foregut concentrations should either be equal to or greater than hindgut concentrations. Alternatively, essentialmore » elements in excess (i.e., from contaminated sites) or non-essential elements such as Cd, foregut elemental concentrations should be less than hindgut. This study aims at determining the importance of food as a source of essential (Zn, Cu, Mn, Fe, Mg and Ca) and non-essential elements (Al, Cd) in crayfish sampled from two metal and acid stressed-sites versus two non-contaminated reference sites. 22 refs., 1 fig., 2 tabs.« less