Sulfur Control In Coal Fired Power Plants: A Probabilistic Approach to Policy Analysis

The optimum level of sulfur pollution control for a coal fired power plant is the point where the sum of societal costs, due to pollution, and control costs is minimized. This basic microeconomic concept has been of limited practical value due to considerable uncertainty in estimating both costs. A probabilistic approach is used to characterize these uncertainties quantitatively for a hypothetical 1000 Mw_e plant located near Pittsburgh, Pennsylvania. Only mortality effects within a distance of 80 km of the plant have been included. The results allow explicit consideration of attitude toward risk and appropriate level of investment to prevent deaths. Limitations of the findings are discussed. Implications are described for policy based on alternative sets of values and assumptions.     

Development of a low-cost air sensor package and indoor air quality monitoring in a California middle school: Detection of a distant wildfire

A low-cost air sensor package was used to monitor indoor air quality (IAQ) in a classroom at the Albany Middle School in the San Francisco Bay Area of California. A rapid increase in carbon dioxide (CO₂) was observed in the classroom as soon as it is occupied. When the classroom is unoccupied, the CO₂ levels decay slowly toward the outdoor background level. All high CO₂ concentrations observed inside the classroom, above the outdoor background, was due to exhaling of the occupants. The CO₂ concentrations generally exceed the recommended level of 1000 ppb towards the end of the school day. The exceedances and slow decay may suggest that the ventilation rate in this school is not sufficient. The particulate level in the classroom was low until a distant wildfire advected large amount of particulate matter to the San Francisco Bay Area. Very high (10–15 times compared to the background) particle numbers (per m³ of particles with diameter >0.3 µm) were observed in the classroom during the wildfire. These particles were relatively small (0.3–1.0 µm) and the filters (MERV 8) of the ventilation system were unable to filter them out. Therefore, the measurements made by low-cost particle counters can inform the school administrators of adverse IAQ during future wildfire (or other combustion) events. The particle number was independent of the occupation before and during the wildfire suggesting that all observed particles were infiltrated into the classroom from outside. Consistent with previous studies, no appreciable increase in the local ambient CO₂ background was observed during this distant wildfire event.

Implications: Low-cost air sensors are effective in monitoring indoor air quality in classrooms. The CO₂ levels in classrooms are mainly generated indoors due to exhalation of occupants. Concentration of CO₂ generally exceed the recommended level of 1000 ppb towards the end of the school day. In contrast, the particulate matter mostly comes from outdoors and small particles penetrate though the filters normally used at schools. Distant wildfires do not increase the local CO₂ background appreciably, but significantly increase the particulate matter concentrations both indoors and outdoors. Further investigations are needed to assure that ventilation rates in classrooms are sufficiently health protective.     

Methods to determine response factors for infrared gas imagers used as quantitative measurement devices

Response factors (RF) can be used to characterize relative sensitivity of one compound vs. another compound for the same measurement instrument. Use of RF allows the analysts/operators to calibrate the instrument with one compound and make measurement for a large number of compounds. This method is adopted for Flame Ionization Detector (FID) based survey instruments used in the Leak Detection and Repair (LDAR) practice for control of fugitive emissions of volatile organic compounds. Gas detecting Infrared (IR) cameras have been used for leak detection. However, the RF for IR cameras has not been well established despite some attempt to develop a method for IR camera RF. In addition to a method proposed earlier (Method 1), two new methods for IR camera RF are proposed in this paper: Method 2 based on theoretical approach and Method 3 based on experimental approach. All three methods are examined and compared. Both Methods 2 and 3 have shown the ability to characterize the behavior of RF for various compounds and substantially higher accuracy than Method 1. Method 2 provides a mechanism to generate RF for a large number of compounds without conducting experiments, and is recommended for implementation. The RF derived from this method can be used both in the emerging field of Quantitative Optical Gas Imaging (QOGI) and to answer the most common question that IR camera users ask—whether a particular compound can be imaged by a particular IR camera.Implications: Infrared imager is an efficient tool for detecting gas leaks from process equipment and has been used in leak detection and repair (LDAR) programs for control of fugitive emissions. However, the information regarding which chemical compounds can be imaged and how sensitive a given infrared imager is for various compounds is limited. A theoretical method is presented in this paper that can answer these questions without conducting resource-intensive experiment. The results of this theoretical method has good agreement with experimental data. The method has been used to predict relative sensitivity for 398 compounds.     

Nonvolatile,semivolatile, or volatile: Redefining volatile for volatile organic compounds

Although widely used in air quality regulatory frameworks, the term “volatile organic compound” (VOC) is poorly defined. Numerous standardized tests are currently used in regulations to determine VOC content (and thus volatility), but in many cases the tests do not agree with each other, nor do they always accurately represent actual evaporation rates under ambient conditions. The parameters (time, temperature, reference material, column polarity, etc.) used in the definitions and the associated test methods were created without a significant evaluation of volatilization characteristics in real world settings. Not only do these differences lead to varying VOC content results, but occasionally they conflict with one another. An ambient evaporation study of selected compounds and a few formulated products was conducted and the results were compared to several current VOC test methodologies: SCAQMD Method 313 (M313), ASTM Standard Test Method E 1868-10 (E1868), and U.S. EPA Reference Method 24 (M24). The ambient evaporation study showed a definite distinction between nonvolatile, semivolatile, and volatile compounds. Some low vapor pressure (LVP) solvents, currently considered exempt as VOCs by some methods, volatilize at ambient conditions nearly as rapidly as the traditional high-volatility solvents they are meant to replace. Conversely, bio-based and heavy hydrocarbons did not readily volatilize, though they often are calculated as VOCs in some traditional test methods. The study suggests that regulatory standards should be reevaluated to more accurately reflect real-world emission from the use of VOC containing products.

Implications:The definition of VOC in current test methods may lead to regulations that exclude otherwise viable alternatives or allow substitutions of chemicals that may limit the environmental benefits sought in the regulation. A study was conducted to examine volatility of several compounds and a few formulated products under several current VOC test methodologies and ambient evaporation. This paper provides ample evidence to warrant a reevaluation of regulatory standards and provides a framework for progressive developments based on reasonable and scientifically justifiable definitions of VOCs.     

An evaluation of the interaction of morning residual layer and afternoon mixed layer ozone in Houston using ozonesonde data

The Tropospheric Ozone Pollution Project (TOPP) launched >220 ozonesondes in Houston (July 2004–June 2008) providing examples of pollution transported into, re-circulated within, and exported from the Houston area. Fifty-one launches occurred during the Texas Air Quality Study (TexAQS) II and the summer portion of IONS-06 (INTEX [Intercontinental Transport Experiment] Ozonesonde Network Study). On 11 days during TexAQS II and on 8 other occasions, ozonesondes were launched both at dawn and in the afternoon. Analysis of these “intensive” launch sequences shows that morning residual layer (RL) ozone concentrations ([O₃]) explained 60–70% of the variability found in the afternoon mixed layer (ML). Furthermore, maximum RL [O₃] is nearly identical to the mean ML [O₃] from the previous afternoon (morning minus afternoon = ?1.6 ± 8.4 ppbv). During TexAQS II, mean [O₃] below 1.3 km (the mean ML height from ozonesonde data) increased from 37 ± 22 ppbv in the morning to 74 ± 18 ppbv in the afternoon, suggesting an average net local daily O₃ production of ～500–900 tons over the metropolitan Houston area.     

Decabromodiphenylether and hexabromocyclododecane in wild birds from the United Kingdom, Sweden and The Netherlands: Screening and time trends

The brominated flame retardant decabromodiphenylether (DBDE) was analysed in wild birds to identify the most suitable species for monitoring time trends in DBDE contamination. This information was later used for the design of a 10-year trend study on DBDE in the European Union. DBDE was measured in muscle tissue, liver, and eggs from 10 terrestrial and four aquatic bird species. DBDE was detected in 47% of the terrestrial bird samples (nine species) and in 9% of the aquatic bird samples (six species). Peregrine falcon and sparrowhawk specimens were selected as most suitable species to determine temporal trends of DBDE. For sparrowhawks, no significant change in DBDE concentrations between 1973 and 2001 was found, although in later years more DBDE concentrations were above the detection limit. Peak DBDE levels measured in peregrines in 1995, were followed by a decline in concentrations until 2001. The same species were used for a trend study on hexabromocylcododecane (HBCD). Twenty-four percent of peregrine falcon eggs and 12% of sparrowhawk muscle samples demonstrated measurable HBCD residues. Three diastereomers of HBCD were analysed and the α-diastereomer was the predominant one in most samples. No clear time trends were observed for HBCD in either species. This study demonstrated that these DBDE and HBCD are bioavailable to birds of Northern Europe, although bioaccumulation seems to occur to a limited extent.     

Contaminant Retention Potential of Forested Filter Strips Established as SMZs in the Piedmont of Georgia1

Abstract: It is common practice in the United States and elsewhere to maintain vegetated filter strips adjacent to streams to retain contaminants in surface runoff. Most research has evaluated contaminant retention in managed agricultural field strips, while relatively few studies have quantified retention in forested filter strips, particularly for dissolved contaminants. Plot‐scale overland flow experiments were conducted to evaluate the efficiency of natural forested filter strips established as streamside management zones (SMZs) for retaining phosphorus (P), atrazine, and picloram transported in runoff. Retention was evaluated for five different slope classes: 1‐2, 5‐7, 10‐12, 15‐17, and 20‐22%; two cover conditions: undisturbed forest floor (O horizon intact) and forest floor removed by raking; and two periods with contrasting soil moisture conditions: summer‐dry and winter‐wet season. Surface flow was collected at 0, 2, 4, 6, and 10 m within the filter strip to evaluate changes in solution concentration as it moved through the O horizon and the surface soil horizon mixing zone. On average, a 10 m length of forested SMZ with an undisturbed forest floor reduced initial solution concentration of total dissolved P by 51%, orthophosphate P by 49%, atrazine by 28%, and picloram by 5%. Percentages of mass retention through infiltration of water plus concentration reductions in runoff were 64% for total dissolved P, 62% for orthophosphate P, 47% for atrazine, and 28% for picloram for undisturbed forest floor conditions. Lower retention occurred following forest floor removal, particularly for P. Average dissolved P retention was 16% lower following forest floor removal. For undisturbed sites, differences in retention were more closely related to forest floor depth than to slope or antecedent soil moisture. These results indicate that forested SMZ filter strips provide a significant measure of surface water protection from dissolved P and herbicide delivery to surface water.     

Flame lonization Hydrocarbon Analyzer

Outbreaks of bronchial asthma, defined by sharp peaks above the average number of emergency room visits at Charity Hospital in New Orleans, have been noted in this city since the early 1950’s. These outbreaks have occurred during the summer and fall, with the months of October and November containing the most frequent and severest episodes. Early work on this problem associated emissions from spontaneous underground burning in abandoned city dumps with the high incidence and extracts for skin testing prepared from the emissions produced a significant number of positive skin tests in persons involved in the asthma outbreaks. Recent investigation showed that other sources of allergenic air pollution in the city were related to the epidemics of asthma. Attention has been focused on a large public grain elevator at the Mississippi River in the southwestern portion of the city. Grain extracts have produced high percentages of positive responses in susceptible patients with low response rate found in control subjects. Persons known to have participated in these outbreaks have been characterized as being allergic; a low incidence of patients with chronic bronchitis and emphysema has been found in this group. New meteorological data regarding the outbreak periods has been collected.     

Validation of a new method for measuring and continuously monitoring the efficiency of industrial flares

A new method has been developed for a direct and remote measurement of industrial flare combustion efficiency (CE). The method is based on a unique hyper-spectral or multi-spectral Infrared (IR) imager which provides a high frame rate, high spectral selectivity and high spatial resolution. The method can be deployed for short-term flare studies or for permanent installation providing real-time continuous flare CE monitoring.

In addition to the measurement of CE, the method also provides a measurement for level of smoke in the flare flame regardless of day or night. The measurements of both CE and smoke level provide the flare operator with a real-time tool to achieve “incipient smoke point” and optimize flare performance.

The feasibility of this method was first demonstrated in a bench scale test. The method was recently tested on full scale flares along with extractive sampling methods to validate the method. The full scale test included three types of flares – steam assisted, air assisted, and pressure assisted. Thirty-nine test runs were performed covering a CE range of approximately 60-100%. The results from the new method showed a strong agreement with the extractive methods (r²=0.9856 and average difference in CE measurement=0.5%).

Implications: Because industrial flares are operated in the open atmosphere, direct measurement of flare combustion efficiency (CE) has been a long-standing technological challenge. Currently flare operators do not have feedback in terms of flare CE and smoke level, and it is extremely difficult for them to optimize flare performance and reduce emissions. The new method reported in this paper could provide flare operators with real-time data for CE and smoke level so that flare operations can be optimized. In light of EPA’s focus on flare emissions and its new rules to reduce emissions from flares, this policy-relevant development in flare CE monitoring is brought to the attention of both the regulating and regulated communities.