Maris A. Lusis

Ten-year trends in sulphate, nitrate and hydrogen deposition in central Ontario

Abstract The decrease in emissions of SO2 in eastern North America in the past decade was strongly correlated with a decrease in bulk deposition rates and concentrations of SO42− and H+ in precipitation in central Ontario. Nitrate emissions, deposition and concentration have not changed significantly over the same period.

Concentration and deposition of trace metals in Ontario-1982

Results of trace metal concentrations in air and precipitation and the corresponding wet and dry deposition in Ontario in 1982 arc reported. In terms of the spatial patterns, in general, there was a decreasing gradient from south-to-north in both concentration and deposition. Patterns differed with each parameter although certain groups of metals (e.g., Fe and Al; Pb, Zn, and Mn) displayed similar patterns. In general, wet deposition was greater than dry deposition at all sites. Geographically, the variability in the wet to dry deposition ratio for coarse particles (MMD > 2.5 μm) was small. However, it increased from the south to the north for fine particles (MMD < 2.5 μm), being higher away from the source areas. Scavenging ratios (W) have been derived from the precipitation and air concentrations of trace metals. The scatter in W is quite large for all trace metals, up to 2 orders of magnitude. There was little seasonal variability in W for fine particles (Pb, Mn, Zn, and Cd). However, coarse particles (Fe, Al, and Cu) were more efficiently scavenged by snow than by rain.

Impact of INCO smelter emissions on wet and dry deposition in the Sudbury area

Abstract The results presented here are based on approximately 2 years (mid-1978 to mid-1980) of ambient air and precipitation concentration monitoring of selected pollutants, including S compounds and trace metals, in the Sudbury area. Together with supporting measurements of particle size distributions, the air concentration data were used to estimate dry deposition rates. A detailed meteorological analysis of the data allowed the smelter impact on the wet and dry deposition of S and trace metals to be determined. With the exception of Cu and Ni, most of the wet deposition in the Sudbury area (within a radius of 40 km) can be attributed to sources other than the INCO smelter. Nevertheless, a definite influence of the smelter on the local downwind precipitation quality can be detected for almost all the substances known to be emitted. For example, average downwind precipitation Cu and Ni concentrations were found to be an order of magnitude higher than background values. In many cases, the INCO smelter influence can be detected at distances of more than 40 km from the source. Most particulate constituents (acids, sulfates, trace metals) are scavenged quite efficiently from the smelter plume during both rain (and snow) storms, with almost total removal occurring within the Sudbury area ( R = 40 km) for some trace metals (e.g. copper). On the other hand, the percentage of total emitted S scavenged by precipitation locally is quite small, mainly because this S is largely in the form of SO 2 , which is subject to a low precipitation scavenging efficiency. During precipitation events, the INCO smelter contributes, on average, 70% of the total Cu and Ni wet deposition within 40 km of the smelter, and less than 20% of the total for other trace metals and S. Dry deposition is estimated to be a relatively inefficient removal mechanism for plume SO 2 and other substances present predominantly in the sub-μm particle size range (i.e. SO 4 2− , Pb, Zn, Cd), less than 20% of the emissions being deposited within 40 km of the smelter sources. On the other hand, it is estimated that a higher proportion of the particles in the coarse size range (containing most of the airborne Fe, Al and Ni) (up to about 15%) is deposited within this same distance. During the study period, the smelter contribution to the total dry deposition within 40 km was greatest for S (primarily due to SO 2 ) and nickel, making up 25 and 64% of the total. The contribution of the other metals examined (Fe, Pb, Zn, Cd and Al) was generally less than 20%. For S and trace metals in large particles (Fe, Ni, Al) wet and dry deposition is similar. Particles in the sub-μm size range (Zn, Pb, Cd) are primarily deposited by precipitation. As far as total deposition is concerned, the major smelter impact is on Cu and Ni. For most of the other substances examined, INCO contributes about 20% or less.

Airborne particulate size distribution measurements in nickel smelter plumes

Abstract This paper reports the results of particle sizing measurements in the plume from two smelters at Sudbury, Ontario (INCO and Falconbridge) which were studied in 1979 and 1980. Andersen impactors, mounted on a Hughes 500C helicopter, were used. Due to bounce-off problems, it was found necessary to use sticky substrates for the coarse particles. In both the INCO and Falconbridge smelters, constituents could be classified as coarse particles having mass median diameter equal to or greater than 2.5 μm (including Fe, Cu, Ni, Al and Mn) and fine particles having mass median diameter less than 2.5 μm (including SO4Pb, Zn, Cd and As). Most of these distributions were not log-normal, but displayed bimodal or multi-modal characteristics.

An evaluation of the precision, and various sources of error, in daily and cumulative precipitation chemistry sampling

Experiments have been carried out to assess the precision and various potential sources of error in precipitation chemistry and deposition measurements made by the Acidic Precipitation in Ontario Study (APIOS). It was found that reproducibility of daily precipitation concentration measurements of S04− and NO3− using colocated Aerochem Metrics samplers is 96% or better for 50% of the time, and 73% or better for 95 % of the time. For these parameters, MIC Type A 28-d samplers give reproducibilities of 94% or better 50% of the time, and 79% or better 95 % of the time. The reproducibility for the concentration of the other major ions, and loading (concentration times sample depth) is somewhat poorer. Concentration changes due to sample degradation or evaporative losses under field conditions are negligible or small on average, even for 28-d samples. For 28-d concentration measurements using MIC Type A collectors, errors due to evaporation amount to about 3% as an annual average, and 5% during the summer period. For S04− and NO3−, overall long-term errors due to exposure under field conditions (including dry contamination and degradation due to chemical reactions), and sample handling, are less than 10%, at least for the techniques used in APIOS. A major potential source of error still to be quantified is unrepresentative sampling by automatic wet-only collectros (i.e., missing of initial portions of precipitation events due to sluggish sensor response, or less than 100% collection efficiencies of precipitation amounts).

A precipitation sampler intercomparison

A three month experimental study to evaluate the relative performance of three different designs of ‘event’ precipitation chemistry samplers was carried out at Woodbridge, Ontario beginning in August 1979. The samplers evaluated were an automatic Aerochem Metrics, ‘wet-only’ type (A), a funnel-and-bottle type (F), and a large-mouth plastic bucket with a specially-fabricated polyethylene bag insert (S). Each sampler was run in duplicate, with a sampling period of 24 hr.The results show that at sites where dry deposition is important, bulk samplers (‘F’ and ‘S’ types) yield significantly different results from the wet-only collector including rainfall amount, H+ , SO4−, NO3−, Na+, K+, Ca++, and Mg++. However, the bulk samplers, especially the ‘S’ type, are found to be satisfactory under certain conditions. For conditions which correspond to daily rainfall less than 2.8 mm and windier and drier sampling, there is even evidence of dry contamination of the wet-only type sampler.

Impact of the inco nickel smelter emissions on precipitation quality in the sudbury area

Abstract An analysis was carried out on precipitation chemical data from 31 events in August and September 1978 and from June to October 1979, collected largely within a 50 km radius of the INCO Nickel Smelter at Sudbury. Ontario. During these periods INCOs daily SO 2 emissions ranged from 658 to 2320td −1 . and averaged approx. 1700td −1 . With these emissions, it was found that the relative contribution of INCO emissions to the total wet-deposition of acids, sulfur and a number of trace metals in the Sudbury area (i.e. within about 50km of the smelter) is small (with the exception of copper and nickel), in the order of 10–20%, and depends on the weather system passing through the area. Warm fronts generally bring with them polluted air masses from Southern Ontario and the Eastern United States, and for acids, sulfur, and a number of trace metals, the INCO contribution to wet deposition in the Sudbury area appears to be about 10% of the total. For cold fronts, the percentage contribution from INCO is roughly twice as great. For copper and nickel, the smelter contribution appears to be roughly 40% of the total wet-deposition, regardless of the type of weather system. Nevertheless a definite influence of the smelter plume on the local downwind quality of precipitation can be detected, especially for sulfates and trace metals. The smelter impact on precipitation acidity is less pronounced. It was also found that during rainstorms, most particulate constituents (acids, sulfates, trace metals) are removed quite efficiently from the smelter emissions. Typically, almost 100% of these constituents may be removed within 50km during the rainy period. The percentage of the emitted sulfur that is removed by precipitation is much lower, mainly because this sulfur is largely in the form of sulfur dioxide which is subject to a low precipitation scavenging efficiency.

Airborne sulfur dioxide to sulfate oxidation studies of the INCO 381m chimney plume.

Abstract Investigations of the rate of oxidation of SO2 in the plume of the INCO 381 m chimney at Sudbury, Ontario, Canada were carried out using an instrumented helicopter. Over a wide range of experimental conditions, the SO2 → SO2−4 conversion rate was found to be relatively low — typically less than 0.5% h−1. The paniculate sulfur found in the plume appeared to be mainly in the form of sulfuric acid and was less than 4% of the total plume sulfur. All results apply to distances within roughly 100 km from the chimney. No quantitative conclusion can be drawn regarding the reaction mechanism. There is evidence in the data for both homogeneous and heterogeneous processes.

The application of a passive permeation device for the measurement of ambient sulfur dioxide

Abstract The development and application of a simple permeation device used to help define long-term atmospheric SO2 concentrations are described. Performance of the device was evaluated in laboratory and field situations. Permeation constants calculated are quite reproducible, with an accuracy of roughly ± 50%. There appears to be a concentration dependence of the permeation constant, when SO2 concentrations are less than about 2 μg m−3. Based upon field observations, a permeation constant of 1.3 × 10 −5 m 3 s −1 may be assumed for this device when monitoring for SO2.

A North American Field Study to Evaluate Eulerian Models

The largest environmental measurement program in North American history is underway. It is geared toward providing a two-year data set of air quality, emissions, precipitation composition, and meteorological variables with which the performance of Eulerian acid deposition models can be evaluated. It is sponsored by or includes the participation of over a dozen organizations in governmental and private sectors from Canada, the United States, and West Germany (Table 1). What has led up to this massive undertaking?