APM-3 Recommended Standard Methods for Continuing Air Monitoring for Gaseous Contaminants

The purpose of Manual APM-3 is to provide a guide which will help increase the uniformity between various surveys, and thereby increase the useability of the data by others.     

Recommended metric for tracking visibility progress in the Regional Haze Rule

For many national parks and wilderness areas with special air quality protections (Class I areas) in the western United States (U.S.), wildfire smoke and dust events can have a large impact on visibility. The U.S. Environmental Protection Agency’s (EPA) 1999 Regional Haze Rule used the 20% haziest days to track visibility changes over time even if they are dominated by smoke or dust. Visibility on the 20% haziest days has remained constant or degraded over the last 16 yr at some Class I areas despite widespread emission reductions from anthropogenic sources. To better track visibility changes specifically associated with anthropogenic pollution sources rather than natural sources, the EPA has revised the Regional Haze Rule to track visibility on the 20% most anthropogenically impaired (hereafter, most impaired) days rather than the haziest days. To support the implementation of this revised requirement, the EPA has proposed (but not finalized) a recommended metric for characterizing the anthropogenic and natural portions of the daily extinction budget at each site. This metric selects the 20% most impaired days based on these portions using a “delta deciview” approach to quantify the deciview scale impact of anthropogenic light extinction. Using this metric, sulfate and nitrate make up the majority of the anthropogenic extinction in 2015 on these days, with natural extinction largely made up of organic carbon mass in the eastern U.S. and a combination of organic carbon mass, dust components, and sea salt in the western U.S. For sites in the western U.S., the seasonality of days selected as the 20% most impaired is different than the seasonality of the 20% haziest days, with many more winter and spring days selected. Applying this new metric to the 2000–2015 period across sites representing Class I areas results in substantial changes in the calculated visibility trend for the northern Rockies and southwest U.S., but little change for the eastern U.S.

Implications: Changing the approach for tracking visibility in the Regional Haze Rule allows the EPA, states, and the public to track visibility on days when reductions in anthropogenic emissions have the greatest potential to improve the view. The calculations involved with the recommended metric can be incorporated into the routine IMPROVE (Interagency Monitoring of Protected Visual Environments) data processing, enabling rapid analysis of current and future visibility trends. Natural visibility conditions are important in the calculations for the recommended metric, necessitating the need for additional analysis and potential refinement of their values.     

Advances in the Analysis of Air Contaminants Comments

Abstract

Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organometallic compound used as an octane improver in unleaded gasoline. The combustion of MMT leads to the formation of manganese (Mn) oxides, mainly Mn₃O₄. The objective of this study is to assess the variations over time and space of respirable (Mn_R) and total (Mn_T) Mn in the urban atmosphere and to evaluate human exposure by inhalation. Two sampling sites were selected on the island of Montreal based on their local traffic density (municipal botanical garden, C^-= 10,000–15,000 vehicles d^-1; Montreal Waterworks, C⁺= 100,000–130,000 vehicles d^-1). Air samplings were made during the day at stations located 10 m from the road using portable pumps, some of which were equipped with a cyclone. Mn_R and Mn_T and other metals were measured on Teflon filters by neutron activation. Mn exposure doses by inhalation were calculated using Monte–Carlo simulations. Mn_R and Mn_T average concentrations were significantly higher at site C⁺ (Mn_R = 0.024 µg m^-3; Mn_T = 0.050 µg m^-3) than at site C^- (Mn_R= 0.015 µg m^-3; Mn_T= 0.027 µg m^-3). Temporal profiles at sites C⁺ and site C^-were similar, with a coefficient of correlation of 0.24 for Mn_R and 0.26 for Mn_T. Trend analyses (ARIMA) also showed that the period of the week (work days vs. off days) was significantly related to Mn_R and Mn_T variations at both sites. The average exposure dose by inhalation to Mn_R and Mn_T ranged from 0.001 to 0.030 µg kg^-1 day^-1 and 0.001 to 0.05 µg kg^-1 day^-1. Mn_R and Mn_T concentrations reflected a positive relationship with traffic density. However, it remains difficult to attribute these results directly to the combustion of MMT in unleaded gasoline. On average, the Mn_R and Mn_T inhalation doses were 2 to 15 times lower than the reference dose (RfC) proposed by the U.S. Environmental Protection Agency (EPA) for the general population.     

Mathematical Model for Photocatalytic Destruction of Organic Contaminants in Air

Abstract

Photocatalytic oxidation (PCO) was investigated in a bench-scale reactor for the abatement of two airborne organic contaminants: toluene and ethanol. A mathematical model that includes the impacts of light intensity, initial contaminant concentration, catalyst thickness, and relative humidity (RH) on the degradation of organic contaminants in a photocatalytic reactor was developed to describe this process. The commercially available catalyst Degussa-PtTiO₂ was selected to compare with the MTU-PtTiO₂-350 catalyst, which was synthesized by the sol-gel process, platinized, and calcined at 350 °C. For toluene removal using the MTU-PtTiO₂-350 catalyst, the degradation rate increased with increases in light intensity from 0.2 to 2.2 mW/cm² and in catalyst thickness from 0.00037 to 0.00361 cm. However, further increases in light intensity and catalyst thickness had only slight effect on the toluene degradation rate. Increasing the initial concentration from 6.29 to 127.9 μg/L and the RH from 10 to 85% resulted in decreases in the toluene degradation rate. For ethanol removal using the MTU-PtTiO₂- 350 catalyst, the degradation rate increased more rapidly with an increase in RH from 17 to 56%; the RH had little effect on the ethanol degradation rate while it further increased from 56% to 82%. We discuss applicability of the model to estimate the influence of process variables and to evaluate photocatalyst performance.     

Potential Impact on Standards for Toxic Air Contaminants

Since the Bhopal incident, the public has placed pressure on regulatory agencies to set community exposure limits for the dozens of chemicals that may be released by manufacturing facilities. More or less objective limits can be established for the vast majority of these chemicals through the use of risk assessment. However, each step of the risk assessment process (i.e., hazard identification, dose-response assessment, exposure assessment, and risk characterization) contains a number of pitfalls that scientists need to avoid to ensure that valid limits are established. For example, in the hazard identification step there has been little discrimination among animal carcinogens with respect to mechanism of action or the epidemiology experience. In the dose-response portion, rarely is the range of “plausible” estimated risks presented. Physiologically based pharmacokinetic (PB-PK) models should be used to understand the difference between the tissue doses and the administered dose, as well as the difference in target tissue concentrations of the toxicant between rodents and humans. Biologically-based models like the Moolgavkar-Knudson-Venzon (MKV) should be developed and used, when appropriate. The exposure assessment step can be significantly improved by using more sensitive and specific sampling and analytical methods, more accurate exposure parameters, and computer models that can account for complex environmental factors. Whenever possible, model predictions of exposure and uptake should be validated by biological monitoring of exposed persons (urine, blood, adipose) or by field measurements of plants, soil, fish, air, or water. In each portion of an assessment, the weight of evidence approach should be used to identify the most defensible value. In the risk characterization, the best estimate of the potential risk as well as the highest plausible risk should be presented. Future assessments would be much improved if quantitative uncertainty analyses were conducted. Procedures are currently available for making future assessments. By correcting some of these shortcomings in how health risk assessments have been conducted, scientists and risk managers should be better able to identify scientifically appropriate ambient air standards and emission limits.     

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.     

Odorous volatile organic sulfides in wastewater treatment plants in Guangzhou, China

Odorous volatile organic sulfides (VOSs) in headspace atmosphere and wastewaters were identified and quantified synchronously in two municipal wastewater treatment plants (WWTPs) in Guangzhou, China. Dimethyl sulfide (DMS), with concentrations ranging from 0.66 to 5.41 mg/m3, was the major VOS in air samples. Carbonyl sulfide (COS), carbon disulfide (CS2), and dimethyl disulfide (DMDS) ranged from 0.01 to 0.21, 0.03 to 0.44, and 0.06 to 1.61 mg/m3, respectively. Methanethiol was not found in any gas samples. The concentrations of DMS in wastewaters ranged from 23.68 to 308.17 mg/m3 and were also the highest values compared with other VOSs, for all of the treatment processes. Methanethiol was detected in all wastewater samples, except that from the aeration tank, which ranged from 113.08 to 216.82 mg/m3. The COS, carbon disulfide, and DMDS in wastewaters ranged from 0.11 to 2.21, 1.37 to 23.29, and 0.24 to 106.75 mg/m3, respectively. Odors from pollution related to VOS were different in the two plants, and they were strongly associated with the characteristics of incoming wastewater and treatment processes. The VOSs in ambient air samples from nearby residential areas downwind of the plant border were also measured, and the results strongly suggested that control measures are needed for odor pollution in the WWTPs to mitigate malodor in the surrounding neighborhoods.     

Data Analysis Procedures for the Ozone NAAQS Statistical Format

The Clear Air Act of 1970 established the authority to control hazardous air pollutants. Section 112 of the legislation requires the Administrator to publish, and from time to time revise, a list of hazardous air pollutants for which he intends to establish emission standards, and to establish emission standards for those pollutants. These national emission standards for hazardous air pollutants are commonly referred to as “NESHAP” standards. All of the NESHAP that have been promulgated as of April 1984 are summarized in the table which accompanies this article. Two types of references are included in the table. The first reference identifies the issue of the Federal Register in which the NESHAP is explained in detail. The second reference identifies the background information document (BID) which contains the technical and economic information developed to support the NESHAP.     

Design and Performance Characterization Strategy Using Modeling for Biofiltration Control of Odorous Hydrogen Sulfide

Abstract

Biofilter, dynamic modeling software characterizing contaminant removal via biofiltration, was used in the preliminary design of a biofilter to treat odorous hydrogen sulfide (H₂S). Steady-state model simulations were run to generate performance plots for various influent concentrations, loadings, residence times, media sizes, and temperatures. Although elimination capacity and removal efficiency frequently are used to characterize biofilter performance, effluent concentration can be used to characterize performance when treating to a target effluent concentration. Model simulations illustrate that, at a given temperature, a biofilter cannot reduce H₂S emissions below a minimum value, no matter how large the biofilter or how long the residence time. However, a higher biofilter temperature results in lower effluent H₂S concentrations. Because dynamic model simulations show that shock loading can significantly increase the effluent concentration above values predicted by the steady-state model simulations, it is recommended that, to consistently meet treatment objectives, dynamic feed conditions should be considered. This study illustrates that modeling can serve as a valuable tool in the design and performance optimization of biofilters.     

Contaminants in waste foundry sand and its leachate

The environmental characteristics of Waste Foundry Sands (WFS), including chemicals in WFS and its leachate, are essential in understanding the environmental impact, rational disposal and potential development of beneficial applications of this solid industrial waste. This paper presents an assessment of broad-spectrum chemicals (metallic, non-metallic and organic chemicals) in aspects of their statistics (mean, median and the 95th percentile) in dry-weight WFS and WFS leachates based on laboratory measurements of 594 WFS samples from 123 foundry facilities in the USA. Results indicate that WFS is basically not hazardous except a risk associated with WFS from copper-based foundry facilities. Leachability of metallic chemicals varies among investigated WFS. A clear delineation between different leaching protocols is implicated.     

Day-of-Week Patterns in Toxic Air Contaminants in Southern California

Abstract

Day-of-week mean ambient concentrations were computed for six high-cancer-risk toxic air contaminants (TACs): 1,3-butadiene, benzene, acetaldehyde, formalde-hyde, carbon tetrachloride (CCl₄), and perchloroethylene. Data from six urban sites in southern California, from 1989 through 2001, were analyzed. Graphical displays were used to search for repeated patterns. Benzene and 1,3-butadiene, emitted mainly by mobile sources, exhibit distinctly lower concentrations on Sundays and slightly lower concentrations on Saturdays and Wednesdays. Acetaldehyde and formaldehyde show some trace of a weekly pattern similar to that of benzene and 1,3-butadiene, but the pattern is not strongly marked. Perchloroethylene, used primarily as a dry-cleaning solvent, is also distinctly lower on Sundays. CCl₄ does not show a dayof-week pattern.     

微生物降解土壤中石油污染物的研究进展

石油的开采、加工、输送及使用过程中，对大气、土壤、水体带来了严重污染，目前在利用微生物降解石油污染物的研究已有很多，并筛选出许多可降解石油污染物的细菌和真菌，这些菌株在降解过程中，主要受营养元素和表面活性的影响，特别是在多环芳烃的微生物降解方面，因此，针对国内外在石油污染物生物降解方面的研究成果进行了综述及展望。     

Techniques and Procedures for the Measurement of Aircraft Gas Turbine Engine Emissions

In 1968 the Society of Automotive Engineers formed the Committee on Aircraft Exhaust Emissions Measurement (E-31) whose charge was the development of acceptable standards of measurement for the characterization of aircraft engine exhaust. This committee’s efforts have resulted in the issuance of two Aerospace Recommended Practices, ARP 1179 “Aircraft Gas Turbine Exhaust Smoke Measurement” and ARP 1256 “Procedure for the Continuous Sampling and Measurement of Gaseous Emissions from Aircraft Turbine Engines.” These Recommended Practices have in large part been adopted by the Environmental Protection Agency and promulgated in Federal Register Volume 38, Number 136, Tuesday, July 17, 1973.

For the past three years Pratt & Whitney Aircraft has been measuring emissions from aircraft gas turbine engines using on-line instrumentation systems designed both in accordance with these Aerospace Recommended Practices and in response to the operational needs of a large experimental engineering test facility. In addition to a discussion of these systems this paper describes the experience derived from continuous testing programs in support of this test facility with consideration being given to the specific problems of sampling, sample handling, system accuracy, and data recording and reduction. Comment is made as to the practical limitations of the recommended methods and procedures as applied to emission control technology programs and suggestions are presented for improving the measurement technology.     

New and Improved Procedures for Gas Sampling and Analysis in the National Air Sampling Network

The NASN sampler for the collection of gaseous pollutants has been modified to increase its versatility and efficiency. Oxides of nitrogen are collected in bubblers employing a 70-100 μ frit with a collection efficiency of approximately 50% depending upon the frit porosity. Included in the sampler is a bubbler for the collection of aldehydes in which the aldehyde-MBTH complex is stable at least two weeks. This inert bubbler, which is constructed of polypropylene and Teflon, makes it possible for samples to be collected over the network and analyzed at a central laboratory. In addition, gaseous ammonia is collected in 0.1N H₂SO₄. This collecting system has an efficiency of greater than 85%. Low-level samples are analyzed automatically employing Nesslerization, whereas high-level samples from source emissions may be collected in indicating boric acid and titrated with 0.02N H₂SO₄. The sampler will accommodate either 50 or 100 ml polypropylene collecting tubes.