Rudolf F. Pueschel

Solar Radiation: Absence of Air Pollution Trends at Mauna Loa

Measurements of solar radiation made at Mauna Loa, Hawaii, over a period of 13 years give no evidence that human activities affect atmospheric turbidity on a global scale. Short-term fluctuations in insolation appear to be associated with naturally produced tropospheric aerosols. The intrusion of volcanic dust into the stratosphere results in prolonged increases in atmospheric opacity due to the extended residence times of aerosols in the stratosphere.

A method for the detection of individual nitrate particles

Abstract A method of detection, quantitative for pure nitrate aerosols and applicable to individual submicrometer and micrometer size atmospheric nitrate particles, has been developed. It is based on the reaction of the nitrate ion with nitron and can be applied to soluble nitrates. Nitrites, sulfates, chlorides, iodides and carbonates can be distinguished from nitrates. The size of the reaction spot depends on the size of the particle, the thickness of the nitron film and the relative humidity at which the reaction takes place. By fixing the values of the last two parameters, a single correlation can be established between the reaction spot and the particle diameter. For pure nitrate particles of 0.5, 0.75, and 1.0 μm dia. the ratio of the reaction spot to the particle diameter was 2.5, 3.3 and 3.8, respectively. By knowing this ratio one can obtain the size distribution of the nitrate panicles in the sample. The method permits a distinction to be made between sodium titrate and ammonium nitrate particles. The method requires sampling time in the order of minutes for clean air to seconds for very polluted areas. Examples of the application of the method to atmospheric aerosol from power plants, urban and rural areas show that nitrates are predominantly found in aerosols of diameters 1 μm.

Contribution of gulf area natural sulfur to the North American sulfur budget

To evaluate the contribution of natural sulfur compounds from the Gulf of Mexico to the overall North American sulfur budget two series of air sampling flights were performed over the gulf area. Total aerosol mass load and sulfate concentration data indicate, in agreement with our previous findings on gas-phase products, that these observations can be divided into two categories. One group of measurements was taken under offshore airflow and the other under onshore flow conditions. From the measurements performed under clean (onshore) flow, average inside boundary layer SO/sub 4//sup 2 -/ concentrations were evaluated. Using these data, together with our previously reported dimethyl sulfide levels, a simple model was developed to estimate the sulfur flux transported northward from the gulf area. Upper and lower limits of this contribution are estimated at 0.25 and 0.04 Tg (S) year/sup -1/, respectively. Although this quantity is relatively low compared with the national US anthropogenic emission, it has significance for the global sulfur cycle, and it can cause a significant acidification of cloud water. 24 references, 5 figures, 3 tables.

Cloud nucleus formation in a power plant plume

Abstract A rate of production of ca 10 16 particles s −1 of H 2 SO 4 aerosol that acts as cloud condensation nuclei at 1% supersaturation has been estimated to take place in the emission plume from the Four Comers power plant near Farmington, N.M. This generating plant produces about 2175MW at full capacity and emits about 3.7kgs −1 of SO 2 , 2.2 kgs −1 of NO x , and 0.9 kgs −1 of particulates. The site area is desert; annual precipitation averages around 15cm, daytime relative humidity is typically 10–20% and annual sunshine is 75% of possible. An instrumented aircraft was utilized during five investigative periods over a 2-year span to measure plume parameters and to collect plume aerosol samples. The estimated production rate of 10 16 particles s −1 in the plume is equivalent to a gas phase oxidation of SO 2 and homogeneous nucleation-condensation of about 5 μg m −3 h −1 of H 2 SO 4 and is consistent with this mechanism being the primary route for removal of SO 2 .

Sulfur dioxide flux measurements over the western atlantic ocean

Aircraft measurements of SO2 were made along the U.S. East Coast and in the vicinity of the Bermuda Islands during the period 2 March–11 April, 1985. SO2 was detected in all samples taken inside the boundary layer 100 km off shore. The maximum 1.0-min average concentration observed was 9.9 ppb (on the East Coast), and the average for the duration of the study was 2.1 ppb. The SO2 concentration in the free troposphere at the same location ranged from < 0.1 ppb to a maximum of 4.2 ppb. The air parcel sampled during the maximum event was back-tracked across the Ohio Valley region. Sulfur dioxide concentrations in the vicinity of the Bermuda Islands, inside and above the boundary layer, were less than the detection limit (0.1 ppb) during most of the time. On one event elevated SO2 levels were recorded, however they could not be traced to a source in N America. On the basis of the concentration and wind speed data, an altitude profile of SO2 flux was constructed for a portion of the U.S. East Coast. Integration of the analytical function describing the profile provided an estimate of SO2 flux eastbound of ~ 1 Tg (S)a−1.

Acid clouds and precipitation in eastern Colorado

Abstract Rain and snow samples were collected at the eastern foothills of the Rocky Mountains and analyzed for chemical composition. Many precipitation samples had pH values considerably more acidic than the 5.6 value of pure water containing only an equilibrium amount of atmospheric CO2. Clear and considerable dependencies of the acidity on seasonal synoptic scale weather patterns are demonstrated. Cloud water samples, collected by aircraft over eastern Colorado, also showed low pH values. The acidity of clouds was greatest near the city of Denver.

Chemical characteristics of oil refinery plumes in Los Angeles

Abstract Airborne in situ measurements of gases (NO, NO2, SO2, O3) and aerosol size distributions have been made in the vicinity of oil refineries in southern Los Angeles. Filter and impactor samples have been collected for post-flight chemical particle analyses using the BaCl2 and Nitron reaction spot techniques, and X-ray energy spectrometry. It was found that the refinery operations increase the number concentration of aerosols in the size range between 0.05 μm and 23.5 μm particle radius. Sulfate and nitrate particles have been identified as oxidation productions of SO2 and NOx, respectively. Sulfate particles have been found with a mode of less than 0.1 μm diameter, whereas inorganic nitrates dominate the mode between 1 and 10 μm. The strong affinity for water of the nitrates strongly affects visibility, cloud formation and the cloud drop size spectrum.

Aerosol Backscatter Coefficient Profiles Measured at 10.6 μm

Abstract Using an airborne lidar, we have measured atmospheric aerosol backscatter coefficients (differential backscatter cross section per unit volume) for 10.6 μm wavelength laser radiation as a function of height to 5200 m for a number of meteorological conditions over the United States high plains. Airborne in situ samplers measured the particle size distribution at the same time and altitude as the lidar measured backscatter. One backscatter coefficient profile at 10.6 μm was compared with a 0.694 μm lidar backscatter profile as well as with the particle size distribution profile. The average infrared backscatter coefficient ranged from ∼8 × 10−9 m−1 sr−1 at the surface to 1 × 10−10 sr−1 at 5200 m altitude.

Impact of particle characterization in confounding reported particle deposition velocities

Abstract Chemical and physical particulate matter data were collected at the site of previously reported particle dry deposition velocity (vd) measurements. These data suggest the reported vd of 0.38 ±0.29cms−1 for particles of diameter 0.15–0.3μm may be less than the true value for anthropogenic particles at this Boulder Atmospheric Observatory site. A small biological particle surface-derived upflux may have reduced particle profile gradients resulting in understated vd. In addition, the present data suggest these vd values are rather site specific and that measured particle vd at other air/land interface sites may also be site specific.

Formation of Sulfate Particles in the Plume of the Four Corners Power Plant

Abstract On 6 June 1978, the Four Corners coal-fired power plant plume near Farmington, New Mexico, was sampled with an instrumented twin-engine Aero-commander 680E, up to 90 km downwind from the source. Measurements consisted of aerosol size distribution, condensation nuclei, various gases, individual particle chemistry using electron microscopy techniques and meteorological parameters. A substantial formation of condensation nuclei took place downwind of the plant at a rate of 1.3 × 1016 s−1 in the first 0.3 h, 3.3 × 1017 s−1 up to 2.5 h, and 8 × 1017 s−1 in the 2.5–12.5 h plume travel time. The corresponding conversion rates were 0.15, 0.5 and 0.3% h−1, respectively. The conversion rate due to oxidation of SO2 on surfaces of fly ash particles was negligible. Dry removal of particles was very high and reached an estimated maximum of 36% during the first 2.5 h probably due to partial impingements of the plume to the ground. Analysis of individual particles collected on nuclepore filters using a scanning ...