One of the most important parts of formulating a National Ambient Air Quality Standard is specifying the measurement methods for determining and attaining compliance. The samples taken for compliance are often pushed beyond their original purpose to identify sources, to evaluate the effectiveness of controls, and to determine relationships between pollution levels and public health. A full understanding of available sampling and analysis methods is needed, as well as an analysis of their costs, before acceptable monitoring approached can be specified. This review identifies issues related to measurement methods used to determine compliance with standards, describes current and future measurement methods and their limitations, and determines the extent to which existing technology can meet short-term and long-term needs for measuring compliance.

Measurement Methods to Determine Compliance with Ambient Air Quality Standards for Suspended Particles

During a cruise from Hamburg to Montevideo, aerosol samples representing air masses from Europe, the Sahara, tropical Africa, South America, and open oceanic regions were collected. They showed significant amounts of soot carbon over large areas of the remote Atlantic, often similar to concentrations in rural continental areas. Back-trajectories and the ratios of soot carbon to total fine (less than 1.7 micrometers in diameter) carbon and of excess fine potassium (the portion not attributable to soil dust or sea salt) to soot carbon indicate that biomass burning in tropical regions is an important source of soot carbon to the world atmosphere. The ratio of excess potassium to soot carbon in the fine fraction of aerosols is proposed as an indicator of the relative contributions of biomass and fossil-fuel burning to soot carbon aerosols. The ratio of soot carbon to fine carbon suggests that most of the particulate organic carbon over the Atlantic is of continental origin.

https://science.sciencemag.org/content/sci/220/4602/1148.full.pdf

Soot Carbon and Excess Fine Potassium: Long-Range Transport of Combustion-Derived Aerosols

The growth of membrane technology

A catalytic reduction technique for the measurement of total reactive odd-nitrogen NO
 y
 in the atmosphere was evaluated in laboratory and field tests. NO
 y
 component species include NO, NO2, NO3, HNO3, N2O5, CH3COO2NO2(PAN), and particulate nitrate. The technique utilizes the reduction of the higher oxides to NO in reaction with CO on a metal catalyst and the subsequent detection of NO by chemiluminescence produced in reaction with O3. The efficiency and linearity of the conversion of the principal NO
 y
 species were examined for mixing ratios in the range of 0.1 to 100 parts per billion by volume (ppbv). Results of tests with Au, Ni, and stainless steel as the catalyst in the temperature range of 25–500°C showed Au to be the preferred catalyst. NH3, HCN, N2O, CH4, and various chlorine and sulfur compounds were checked as possible sources of NO
 y
 interference with the Au catalyst. The effects of pressure, O3, and H2O on NO
 y
 conversion were also examined. The results of the checks and tests in the laboratory showed the technique to be suitable for initial NO
 y
 measurements in the atmosphere. The technique was subsequently tested in ambient air at a remote ground-based field site located near Niwot Ridge, Colorado. The results of conversion and inlet tests made in the field and a summary of the NO
 y
 data are included in the discussion.

Evaluation of a catalytic reduction technique for the measurement of total reactive odd-nitrogen NOy in the atmosphere

In April and May of 1988 along 170{degree}W from 53{degree}N to 14{degree}S, simultaneous concentration measurements were made of the major components of the sulfur and reduced nitrogen cycles. The species measured included seawater dimethylsulfide, DMS(s), and total ammonia, NH{sub 3} (s,tot) = NH{sub 3} (s) + NH{sub 4}{sup +} (s); atmospheric gas phase DMS (g), NH{sub 3} (g), and SO{sub 2} (g); and atmospheric particulate phase NH{sub 4}{sup +} (p), non-seasalt sulfate, nss SO{sub 4}{sup =} (p), and methanesulfonate, MSA (p). Based on isentropic calculated back trajectories at 1,000, 950, 850, and 700 mbar arrival heights, three apparent air mass regimes were encountered; one from 50{degree}N to 30{degree}N which recently had been in contact with Asia, one from 29{degree}N to 15{degree}N which had passed over Hawaii during a volcanic eruption several days earlier, and one from 14{degree}N to 11{degree}S which was the most representative of remote marine air. Changes in the relative concentrations of the atmospheric S and NH{sub 3} species reflected the origin of the air masses sampled. The NH{sub 3} (g) concentrations were low over the entire region studied, indicating that the lifetime of NH{sub 3} in the marine boundary layer is on the order of hours. Thesemore » low NH{sub 3} concentrations led to only partially neutralized sulfate aerosol particles. The mean NH{sub 4}{sup +} (p) to nss SO{sub 4}{sup =} (p) molar ratio was 1.3 {plus minus} 0.71. The highest ratios were found in continentally influenced air masses where the NH{sub 4}{sup +} (p) was most likely of continental origin and in remote marine air masses with an absence of continentally derived nss SO{sub 4}{sup =} (p). The lowest ratios found were a result of high nss SO{sub 4}{sup =} (p) concentrations in air masses influenced by the Hawaiian volcanic plume.« less

Benjamin Y. H. Liu

Papers

Efficiency of membrane and nuclepore filters for submicrometer aerosols