Atmospheric Factors Influencing Daily Sulfate Concentrations in Chicago Air

Abstract

Confidence interval construction for central tendency is a problem of practical consequence for those who must analyze air contaminant data. Determination of compliance with relevant ambient air quality criteria and assessment of associated health risks depend upon quantifying the uncertainty of estimated mean pollutant concentrations. The bootstrap is a resampling technique that has been steadily gaining popularity and acceptance during the past several years. A potentially powerful application of the bootstrap is the construction of confidence intervals for any parameter of any underlying distribution. Properties of bootstrap confidence intervals were determined for samples generated from lognormal, gamma, and Weibull distributions. Bootstrap t intervals, while having smaller coverage errors than Student's t or other bootstrap methods, under-cover for small samples from skewed distributions. Therefore, we caution against using the bootstrap to construct confidence intervals for the mean without first considering the effects of sample size and skew. When sample sizes are small, one might consider using the median as an estimate of central tendency. Confidence intervals for the median are easy to construct and do not under-cover. Data collected by the Northeast States for Coordinated Air Use Management (NESCAUM) are used to illustrate application of the methods discussed.     

Reproducibility of regional apportionments of pollution aerosol in the Northeastern United States

Regional apportionments of sulfate and Se in pollution aerosol have been reproduced to within 10% for winter and summer at Narragansett, RI, and for summer at Underhill, VT, over a 3-yr period. Agreement of observed variability of apportionments with earlier estimates of their uncertainties served to empirically confirm both error-propagation methods and original uncertainties assigned to regional signatures. Winter apportionments at Underhill were more variable because of systematic differences in meteorology.     

Air Quality Impacts of Distributed Energy Resources Implemented in the Northeastern United States

Abstract

Emissions from the potential installation of distributed energy resources (DER) in the place of current utility-scale power generators have been introduced into an emissions inventory of the northeastern United States. A methodology for predicting future market penetration of DER that considers economics and emission factors was used to estimate the most likely implementation of DER. The methodology results in spatially and temporally resolved emission profiles of criteria pollutants that are subsequently introduced into a detailed atmospheric chemistry and transport model of the region. The DER technology determined by the methodology includes 62% reciprocating engines, 34% gas turbines, and 4% fuel cells and other emerging technologies. The introduction of DER leads to retirement of 2625 MW of existing power plants for which emissions are removed from the inventory. The air quality model predicts maximum differences in air pollutant concentrations that are located downwind from the central power plants that were removed from the domain. Maximum decreases in hourly peak ozone concentrations due to DER use are 10 ppb and are located over the state of New Jersey. Maximum decreases in 24-hr average fine particulate matter (PM_2.5) concentrations reach 3 μg/m3 and are located off the coast of New Jersey and New York. The main contribution to decreased PM_2.5 is the reduction of sulfate levels due to significant reductions in direct emissions of sulfur oxides (SO_x) from the DER compared with the central power plants removed. The scenario presented here represents an accelerated DER penetration case with aggressive emission reductions due to removal of highly emitting power plants. Such scenario provides an upper bound for air quality benefits of DER implementation scenarios.     

Trends in atmospheric reactive nitrogen for the Eastern United States

Reactive nitrogen can travel far from emission sources and impact sensitive ecosystems. From 2002 to 2006, policy actions have led to decreases in NO(x) emissions from power plants and motor vehicles. In this study, atmospheric chemical transport modeling demonstrates that these emissions reductions have led to a downward trend in ambient measurements of transported reactive nitrogen, especially atmospheric concentrations and wet deposition of nitrate. The trend in reduced nitrogen, namely ammonium, is ambiguous. As reduced nitrogen becomes a larger fraction of the reactive nitrogen budget, wide-spread NH(3) measurements and improved NH(3) emissions assessments are a critical need.     

Concentrations of polychlorinated dibenzo-p-dioxins in processed ball clay from the United States

Processed ball clays commonly used by the ceramic art industry in the United States were collected from retail suppliers and analyzed for the presence and concentration of the 2,3,7,8-Cl substituted polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs). The average PCDD toxic equivalent (TEQ) concentrations of these processed ball clays was approximately 800 pg/g (TEQ-WHO) with characteristic congener profiles and isomer distributions similar to patterns of previously analyzed raw and processed ball clays. The PCDF concentrations were below the average limit of detection (LOD) of 0.5 pg/g. Correlation analyses reveal no significant relationship between total organic carbon (TOC) and either individual, homologues, and total tetra-through octa-chlorinated PCDD congeners, or TEQ concentrations of the processed ball clays. The results are consistent with earlier studies on levels of PCDDs in ball clays. Data from earlier studies indicated that dioxins may be released to the environment during the processing of raw clay or the firing process used in commercial ceramic facilities. The presence of dioxin in the clays also raises concerns about potential occupational exposure for individuals involved in the mining/processing of ball clay, ceramics manufacturing and ceramic artwork.     

Air Pollution Emissions from Increased Industrial Coal Use in the Northeastern United States

Evaluating the air pollution impacts of energy use in the industrial sector is difficult because of the diversity and multiplicity of sources and a general lack of systematic, up-to-date data collection mechanisms. Fuel-specific energy consumption for a multi-state region is provided by the U.S. Department of Energy PIES model for a base year (1975), together with scenarios for future years. A computer model developed in this study—the Sub-regional Energy and Emissions Model (SEEM)—is applied to disaggregate the regional industrial figures to the county level according to fuel type and industrial category at the two-digit SIC level. The resulting emissions of total suspended particulates (TSP) and sulfur dioxide (SO₂) for all industrial categories are estimated at the county level by Incorporating county-specific air pollution regulations in SEEM, and are then aggregated to larger geographical regions. The model has been applied to evaluate the increased air pollution impacts of industrial energy use in the northeastern United States for two alternative 1990 scenarios: (1) the midrange/trendlong PIES projections, and (2) a Coal Replacement Scenario, which assumes a higher percentage of fuel burned in new boilers will be coal. The results are discussed in terms of implications for air pollution control policy.     

A Critical Assessment of Atmospheric Visibility and Aerosol Measurements in the Eastern United States

As part of a study examining the technical basis for a secondary national ambient air quality standard for fine particulate matter to protect visibility, we reviewed available data on atmospheric aerosol and visibility in the eastern U.S. This paper presents the results of that visibility and aerosol characterization.

Analysis of airport visibility data indicates that the annual median visual ranges in the East are in the 16-25 km range. In the absence of a "reference method," limited measurements of visibility using various types of instruments provide data generally in agreement with the airport visibility estimates when a contrast threshold of 0.05 is assumed in calculating visual range from the instrumental measurements.

Both long- and short-term aerosol measurements have yielded consistent results; however, because of the differences in instrumentation and laboratory analytical techniques among various studies, data often are not directly comparable. The measured annual average fine particulate matter mass concentration is about 18 μg/m³ in the rural East; during summer it increases to about 23 μg/m³. If all the sulfur in the fine mass is assumed to exist as ammonium sulfate, it would constitute 46 percent of the annual mean and about 60 percent of the summer mean fine mass concentrations. Carbon and volatiles, including water, are believed to constitute significant fractions of the fine mass; however, there are little data quantifying their contributions to fine mass and visibility impairment. Additional long-term measurements of visibility and fine aerosol and its various components are necessary to completely characterize visibility and aerosol in the East.     

Polybrominated diphenyl ethers (PBDEs) in farmed and wild salmon marketed in the Northeastern United States

Recently, we reported on the analysis of polychlorinated biphenyls (PCBs) and chlorinated pesticides in farmed Atlantic salmon (Salmo salar) from Maine, eastern Canada, and Norway, and wild Alaskan Chinook salmon (Oncorhynchus tshawytscha). In this paper, we extend the analysis to polybrominated diphenyl ethers (PBDEs) in these samples. Total PBDE concentrations in the farmed salmon (0.4-1.4ng/g, wet weight, ww) were not significantly different from those in the wild Alaskan Chinook samples (0.4-1.2ng/g, ww), nor were significant differences found among regions. However, significant intra-regional variations in concentrations of total PBDEs and tetra-BDE 47 were observed in the salmon from the Canadian farms (p<0.01). Congener profiles were dominated by BDE-47, followed by the penta-BDEs 99 and 100. PBDE concentrations in the Canadian samples were lower than those reported two years earlier. Removal of skin resulted in no overall reduction in PBDE concentrations in our farmed salmon, and in some cases, PBDE concentrations were higher in skin-off samples. PBDEs were correlated with lipids only in the skinned samples, suggesting that there is greater accumulation and retention of PBDEs in muscle lipids than in skin-associated fat. In skin-on samples, modest correlations were observed between concentrations of PBDEs and PCBs (R(2)=0.47) and mono-ortho PCBs (R(2)=0.50), whereas PBDEs were not correlated with non-ortho PCBs.     

Marginal PM25: Nonlinear Aerosol Mass Response to Sulfate Reductions in the Eastern United States

ABSTRACT

Reductions in airborne sulfate concentration may cause inorganic fine particulate matter (PM₂₅) to respond nonlinearly, as nitric acid gas may transfer to the aerosol phase. Where this occurs, reductions in sulfur dioxide (SO₂) emissions will be much less effective than expected at reducing PM_2.5. As a measure of the efficacy of reductions in sulfate concentration on PM , we define marginal PM_2.5 as the local change in PM_2.5 resulting from a small change in sulfate concentration. Using seasonal-average conditions and assuming thermodynamic equilibrium, we find that the conditions for PM_2.5 to respond nonlinearly to sulfate reductions are common in the eastern United States in winter, occurring at half of the sites considered, and uncommon in summer, due primarily to the influence of temperature. Accounting for diurnal and intraseasonal variability, we find that seasonal-average conditions provide a reasonable indicator of the time-averaged PM_2.5 response. These results indicate that reductions in sulfate concentration may be up to 50% less effective at reducing the annual-average PM_2.5 than if the role of nitric acid is neglected. Further, large reductions in sulfate will also cause an increase in aerosol nitrate in many regions that are the most acidic.     

Trends in speciated fine particulate matter and visibility across monitoring networks in the Southeastern United States

Trends in fine particulate matter <2.5 microm in diameter (PM2.5) and visibility in the Southeastern United States were evaluated for sites in the Interagency Monitoring of Protected Visual Environments, Speciated Trends Network, and Southeastern Aerosol Research and Characterization Study networks. These analyses are part of the technical assessment by Visibility Improvement-State and Tribal Association of the Southeast (VISTAS), the regional planning organization for the southeastern states, in support of State Implementation Plans for the regional haze rule. At all of the VISTAS IMPROVE sites, ammonium sulfate and organic carbon (OC) are the largest and second largest contributors, respectively, to light extinction on both the 20% haziest and 20% clearest days. Ammonium nitrate, elemental carbon (EC), soils, and coarse particles make comparatively small contributions to PM2.5 mass and light extinction on most days at the Class I areas. At Southern Appalachian sites, the 20% haziest days occur primarily in the late spring to fall, whereas at coastal sites, the 20% haziest days can occur through out the year. Levels of ammonium sulfate in Class I areas are similar to those in nearby urban areas and are generally higher at the interior sites than the coastal sites. Concentrations of OC, ammonium nitrate, and, sometimes, EC, tend to be higher in the urban areas than in nearby Class I areas, although differences in measurement methods complicate comparisons between networks. Results support regional controls of sulfur dioxide for both regional haze and PM2.5 implementation and suggest that controls of local sources of OC, EC, or nitrogen oxides might also be considered for urban areas that are not attaining the annual National Ambient Air Quality Standard for PM2.5.     

A Comparison of Measured and Simulated Ozone Concentrations in the Rural Areas of the Eastern United States during Summer 1995

ABSTRACT

The recent regulatory actions toward a longer-term (i.e., 8-hr) average ozone standard have brought forth the potential for many rural areas in the eastern United States to be in noncompliance. However, since a majority of these rural areas have generally few sources of anthropogenic emissions, the measured ozone levels primarily reflect the effects of the transport of ozone and its precursor pollutants and natural emissions. While photochemical grid models have been applied to urban areas to develop ozone mitigation measures, these efforts have been limited to high ozone episode events only and do not adequately cover rural regions. In this study, we applied a photochemical modeling system, RAMS/UAM-V, to the eastern United States from June 1-August 31, 1995. The purpose of the study is to examine the predictive ability of the modeling system at rural monitoring stations that are part of the Clean Air Status Trends Network (CASTNet) and the Gaseous Pollutant Monitoring Program (GPMP).

The results show that the measured daily 1-hr ozone maxima and the seasonal average of the daily 1-hr ozone maxima are in better agreement with the predictions of the modeling system than those for the daily 8-hr ozone maxima. Also, the response of the modeling system in reproducing the measured range of ozone levels over the diurnal cycle is poor, suggesting the need for improvement in the treatment of the physical and chemical processes of the modeling system during the nighttime and morning hours if it is to be used to address the 8-hr ozone standard.     

Direct Effects of Atmospheric Sulfate Deposition on Vegetation

Acid sulfate aerosol (500 μg/m³) had no effect on soybean or pinto bean after a single 4-h exposure. However, visible Injury and chlorophyll loss occurred when plants were sequentially exposed to acid aerosol and ozone (380 μg/m³) for 4 h. In yellow poplar seedlings exposed to ozone (200 μg/m³), sulfur dioxide (210 μg/m³) and simulated rain solutions (pH 5.6, 4.3 and 3.0) for 6 weeks, root dry weight, leaf area increase, mean relative growth rate and unit leaf rate decreased linearly with pH in ozone-treated plants. However, unit leaf rate and mean relative growth rate increased linearly in response to sulfur dioxide as solution acidity increased. Ambient wet and dry sulfate concentrations appear insufficient to directly impact vegetation.     

An Analysis of the Yearly Changes in Sulfur Concentrations at Various National Parks in the United States, 1980-1996

ABSTRACT

An apparent increasing trend in the summer concentrations of particulate sulfur at Shenandoah (for the time period 1982-1995) and at Great Smoky Mountains (for the time period 1984-1995) has been pointed out by some researchers. Others have suggested that these increasing trends may be an analytical artifact resulting from the switch from the Stacked Filter Units (SFU) measurement system to the IMPROVE (Interagency Monitoring of Protected Visual Environments) measurement system that occurred during the winter of 1987. To obtain a better understanding of the effect of the protocol change, we investigate the changes in the seasonal averages of sulfur concentrations for successive pairs of years for the period 1980-1996 for about 20 national park sites in the United States. For the period 1980-1987, we use sulfur data from the old (SFU) database and for the period 1988-1996, we use the IMPROVE database. Changes from one year to the next similar to that between 1987 and 1988 occurred during other years and seasons suggesting that chance causes alone could perhaps explain it, the degree to which chance could have caused the changes was measured using the permutation test for matched. At the very least, additional information such as side by side readings using SFU and IMPROVE measurement methods, may be needed to better understand any systematic effect in the sulfur measurements that may be ascribable to the protocol change.     

Determination of Microgram Quantities of Inorganic Sulfate in Atmospheric Particulates

Abstract

Before a community-wide woodstove changeout program, a chemical mass balance (CMB) source apportionment study was conducted in Libby, MT, during the winter of 2003–2004 to identify the sources of fine particulate matter (PM_2.5) within the valley. Results from this study showed that residential woodstoves were the major source, contributing approximately 80% of the ambient PM_2.5 throughout the winter months. In an effort to lower the ambient PM_2.5, a large woodstove changeout program was conducted in Libby from 2005 to 2007 in which nearly 1200 old woodstoves were changed out with cleaner burning models. During the winter of 2007–2008, a follow-up CMB source apportionment study was conducted to evaluate the effectiveness of the changeout. Results from this study showed that average winter PM_2.5 mass was reduced by 20%, and woodsmoke-related PM_2.5 (as identified by the CMB model) was reduced by 28% when compared with the pre-changeout winter of 2003– 2004. These results suggest that a woodstove changeout can be an effective tool in reducing ambient levels of PM_2.5 in woodstove-impacted communities.     

Manual Procedures for the Estimation of Atmospheric Fluorides

Manual methods for the determination of air-borne fluorides, including the discrimination of gaseous and particulate forms, have been reviewed. Published methods have been re-examined and comparative sampling data presented, to point out advantages of some newer techniques in sampling, separation, and quantitation.     

Spatial Variation in Acidic Sulfate and Ammonia Concentrations within Metropolitan Philadelphia

Abstract

Acidic sulfate concentrations were measured in metropolitan Philadelphia during the summers of 1992 and 1993, as part of a continuing effort to characterize particle concentrations in urban environments. Sampling was performed simultaneously at eight sites located within and around metropolitan Philadelphia. Sites were selected based on their population density and on their distance and direction from the city center. Air pollution sampling was conducted every other day during the summer of 1992 and every day during the summer of 1993. All samples were collected for 24-h periods beginning at 9 a.m. (EDT). All acidic sulfate and ammonia samples were collected using modified Harvard-EPA Annular Denuder Systems (HEADS).

In this paper, we examine the spatial variation in acidic sulfate and ammonia concentrations within the metropolitan Philadelphia area. We also identify factors that may influence their variation and develop models to predict their concentrations. Outdoor sulfate (SO₄ ^2?) concentrations were uniform within metropolitan Philadelphia; however, aerosol strong acidity (H⁺) concentrations varied spatially. This variation generally was independent of wind direction, but was related to local factors, such as the NH₃ concentration, population density, and distance from the center of the city. Physico-chemical models, which were developed using data collected during the summer of 1992, were excellent predictors of 24-h and mean summertime H⁺ concentrations measured during the summer of 1993. Models accounted for 78% of the variation in 24-h H⁺ levels. Results suggest that a single stationary ambient (SAM) monitor would be sufficient to estimate SO₄ ^2? exposures for populations living in Philadelphia. For H⁺, however, multiple monitoring sites or models should be used to determine the outdoor H+ exposures of populations living in urban environments, although a single SAM site may provide an excellent index of H⁺ variation over time.     

The Gas Supply Situation in the United States

The body of information presented in this paper is directed to those individuals who require information on the present natural gas supply and demand relationship and the prospects for future changes, including individuals concerned with air quality control and the use of natural gas for combating air pollution.

If natural gas could continue to capture large shares of the energy market, as in the past when supply was not a growth inhibiting factor, annual demand for gas is projected to increase to 34.5 and 46.4 trillion cubic feet in 1980 and 1990, respectively. Annual production levels which could be supported by presently proven reserves and anticipated future reserve additions are estimated to peak in the mid-1970’s and decline to about 18 trillion cubic feet in 1990.

When viewed from the perspective of anticipated indigenous supply deficiencies, the acquisition of supplemental sources of gas becomes of paramount importance. Pipeline imports, the only substantive supplemental source presently available, could almost double by 1980 and be about 2 trillion cubic feet annually in 1990.

Available volumes of gas from Alaska could be 0.7 trillion cubic feet in 1980 and could increase to 2.3 trillion cubic feet annually by 1990. Actual initial deliveries of gas are inextricably related to construction of an oil pipeline from Prudhoe Bay. Construction delays postpone initial delivery dates for gas as well as oil.

Advancements in cryogenic transportation and storage technologies have made the heretofore largely untapped supplies of gas from several countries with limited internal markets available to the United States as LNG. Annual LNG imports could be about 0.3 trillion cubic feet in 1975 and perhaps 2 and 4 trillion cubic feet by 1980 and 1990, respectively.

Pipeline quality gas from coal presents the prospect for a supplemental source of gaseous fuel independent of foreign sources and free from balance of payments problems. The first pipeline quality gas from coal may be expected by 1976, and by 1980 perhaps 0.3 trillion cubic feet could be provided annually from this source; in 1990, 3.3 trillion cubic feet might be available. An additional, but presently unqualified, source of synthetic gas will be the conversion of liquid hydrocarbons.

In the aggregate, supplemental gas supplies are anticipated to total about 4.6 and 11.5 trillion cubic feet annually by 1980 and 1990, respectively. While demand for gas is anticipated to increase, domestic conventional gas production is projected to peak in the mid-1970’s and decrease somewhat thereafter. As a consequence, a continuing gas supply-demand imbalance is anticipated.