Arne Semb

Boundary-layer ozone depletion as seen in the Norwegian Arctic in spring

Several years of measurements of ozone, hydrocarbons, sulphate and meteorological parameters from Spitsbergen in the Norwegian Arctic are presented. Most of the measurements were taken on the Zeppelin Mountain at an altitude of 474 m a.s.l. The focus is the episodes of ozone depletion in the lower troposphere in spring, which are studied in a climatological way. Episodes of very low ozone concentrations are a common feature on the Zeppelin Mountain in spring. The low ozone episodes were observed from late March to the beginning of June. When the effect of transport direction was subtracted, the frequenty of the low ozone episodes was found to peak in the beginning of May, possibly reflecting the seasonal cycle in the actual depletion process. Analyses based on trajectory calculations show that most of the episodes occurred when the air masses were transported from W-N. Ozone soundings show that the ozone depletion may extend from the surface and up to 3–4 km altitude. The episodes were associated with a cold boundary layer beneath a thermally stable layer, suppressing mixing with the free troposphere. The concentration of several individual hydrocarbons was much lower during episodes of low ozone than for the average conditions. The change in concentration ratio between the hydrocarbons was in qualitative agreement with oxidation of hydrocarbons by Br and Cl atoms rather than by OH radicals.

Acid deposition and its effects in China: an overview

Acid rain is an increasing environmental problem in China. At present SO2 emission is about 20–22 million tons. However with a growing number of large power plants the long-range transport of air pollutants is expected to increase. The highest acid deposition is near the emission sources. Wind-blown, alkaline soil dust is important in neutralizing the acidity of the emissions, especially in large parts of northern China. In the south, where alkaline soil dust contributes less to acid neutralization, the annual pH in precipitation was below 4.5 at monitoring stations in several provinces and as low as 4.1 in some urban areas. Total sulfur deposition has been estimated to be about 10 g S m−2 year−1 in heavily exposed areas. Negative effects on forests, including die-back, have been reported for relatively small areas near large cities. Since large, regional surveys have not been carried out, there are large uncertainties about effects on a regional level. The high concentrations of gaseous pollutants, especially within and near the cities, are likely to have severe effects on human health as well as on materials and vegetation. Several field and laboratory studies, as well as computer simulations, indicate that acidification of soil and soil water has occurred in the past few decades. This has probably caused elevated concentrations of toxic aluminum in soil water. At present, the toxic effect of Al is likely to be counteracted by high concentrations of calcium at many places. The Chinese authorities have recognized air pollution and acid rain as serious environmental problems, however, there are difficulties in implementing effective measures to reduce the problems. With respect to ecological effects we lack a comprehensive regional overview of the extent of the acid deposition problem in China. Such information is necessary before effective countermeasures can be developed.

Long-range atmospheric transport of trace elements to southern norway

Abstract Results from two investigations of air quality performed in 1978–1979 and 1985–1986 at Birkenes, southern Norway are presentes. The elements Na, Al, Cl, Sc, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Se, Br, Ag, Cd, Sb, La and Pb were determined in daily filter samples and data for SO2 and aerosol sulfate were also collected. The levels in 1985–1986 were lower for most pollution-derived elements than in 1978–1979. This in particular concerned V, Ni, Zn, As, Se, Cd, Sb and Pb, while Br and Sb showed less reduced concentration levels. Sector analysis showed that the main contributing source areas for airborne trace elements in southernmost Norway are southeast to southwest of Birkenes. Comparison of the contributions from different source areas in the two sampling periods indicates that emissions in western Europe had decreased more between the two periods than in eastern Europe. Factor analysis was performed on the two datasets. A five-factor solution revealed the existence of a marine component, a soil component and a general pollution component in the aerosol.

Model Analysis of the Measured Concentration of Organic Gases in the Norwegian Arctic

A 2-D meridional model for the chemistry and transport in the troposphere is used to study the seasonal variation of the concentration of organic gases like C2H2, C2H6, C3H8, C6H6, C7H8. CHCl3 and C2Cl4 at high latitudes. The anthropogenic sources for these species were estimated, and the temporal and latitudinal distribution of OH and O3 was calculated using a complex photochemical reaction system. There is fair agreement between the calculated annual variation and the measured concentrations for C2H2, C2H6, C3H8, C7H8 and C2Cl4 at Spitsbergen during July 1982 and March/April 1983, with a distinct late winter maximum and summer minimum. For CHCl3, the direct anthropogenic source is minor compared to indirect anthropogenic or natural sources. For benzene, emission in car exhaust is important, but other anthropogenic sources are required for the calculations to agree with the measurements. Measured C2H4 and C3H6 concentrations are much higher than the calculated ones based on anthropogenic emissions, and show opposite seasonal trends. This indicates biogenic sources for these compounds.A buildup of PAN (≈300 pptv) is calculated at high latitudes during winter. This makes it the dominant source for NOx as the temperature increases in the spring. NOx is found to be a limiting factor for O3 production at high latitudes during spring.

SULPHUR EMISSIONS IN EUROPE

Abstract Natural and man-made emissions of sulphur to the atmosphere are discussed. Within Europe the man-made emissions, which are closely associated with the consumption of fossil fuels, are over-whelmingly dominant. Emissions from the 11 countries participating in the OECD study were 8.8 M tonnes S in 1973 and have been estimated at about 25 M tonnes for the whole of Europe. Based on information from the participating countries and from various other sources, an emission survey has been worked out. This gives the emissions in 1 2 ° latitude × 1° longitude geographical reference system which has been transferred to a 127 × 127km grid used in dispersion model calculations.

European survey for NOx emissions with emphasis on Eastern Europe

Abstract Emission estimates are presented for NO x from stationary and mobile sources in Europe with particular eempasis on Eastern Europe. Total emissions of NO x in Europe were estimated to 23.9 × 10 6 as NO 2 in 1985 with a ca 50 per cent contribution from Eastern Europe. The calculated emissions were based on the emission factors proposed in this work, and on statistical data. The proposed emission factors were country specific for stationary sources in Eastern Europe. For mobile sources, uniform emission factors for each vehicle type and driving mode were used for all countries. For stationary sources in Western Europe, the emission figures from OECD were used. The NO x emissions from stationary sources in Europe were calculated to be equal to the NO x emissions from mobile sources in Europe. The contribution of NO x emissions from stationary sources in Eastern Europe was, however, 60 per cent, and for Western Europe, 40 per cent. The spatial distribution of NO x emissions in Europe is also shown in the EMEP grid system of 150 km × 150 km . The NO x emission factors and the NO x emissions in Eastern Europe were then compared with estimates from the EMEP programme and with data from national authorities in Eastern Europe. Good agreement was obtained for the G.D.R., Hungary and, to some extent, Poland. The largest differences were found for the U.S.S.R., Albania, Bulgaria, Romania and Yugoslavia. Natural emissions of NO x in Europe were also estimated and it was suggested that they are not significant (below 3 per cent) compared to anthropogenic emissions. The following can be recommended: (1) a unified methodology to calculate NO x emission factors; (2) a handbook of NO x emission factors; (3) an atlas of major point sources in Europe, and (4) a methodology to calculate accuracy of NO x emission estimates.

Measurements of particulate matter within the framework of the European Monitoring and Evaluation Programme (EMEP): I. First results

Particulate matter (PM) monitoring presents a new challenge to the transboundary air pollution strategies in Europe. Evidence for the role of long-range transport of particulate matter and its significant association with a wide range of adverse health effects has urged for the inclusion of particulate matter within the European Monitoring and Evaluation Programme (EMEP) framework. Here we review available data on PM physico-chemical characteristics within the EMEP framework. In addition we identify future research needs for the characterisation of the background PM in Europe that include detailed harmonised measurements of mass, size and chemical composition (mass closure) of the ambient aerosol.

Sulphur and nitrogen deposition in Norway, status and trends

The total deposition of sulphur (S) and nitrogen (N) components in Norway during the period 1988–1992 has been estimated on the basis of measurement data of air- and precipitation chemistry from the national monitoring network. There are large regional variations in depositions with highest values in the southwestern part of Norway. Time series analysis of annual mean concentrations of sulphur dioxide (SO2) and sulphate (SO4−−) in air, non marine SO4−−, nitrate (NO3−) and ammonium (NH4+) in precipitation, shows a significant reduction in the S concentrations both in air and precipitation. In precipitation the concentrations are reduced by 30–45 percent in Southern Norway and 45–55 percent in Central and Northern Norway. Even larger reductions are observed in air concentrations with 50–65 percent reduction in Southern Norway and 65–88 percent reduction further north. For N components there are generally no significant trends in concentration levels nor in precipitation or air. The observed trends are comparable with reported trends in emission.

Amounts and sources of fluoride in precipitation over southern Norway

Abstract Fluoride is a ligand which forms complexes with Al3+ in natural waters with relatively low pH. It is not well established the extent to which fluoride in precipitation is primarily recycled from sea water, derived from dust or volcanic emissions or has an anthropogenic origin. The average concentration of F− as determined by ion chromatography assuming no interference with simple organic acids in over five hundred samples of precipitation collected at four sampling stations in southern Norway in 1983, is 20 μg l −1. A comparison of the concentrations and amounts of fluoride measured in the precipitation samples with internally consistent measurements of other components such as Cl−, Br−, and SO42− on the same samples using correlation analysis, indicates that a major portion of the fluoride, i.e. more than 90%, have a non-marine origin.

Experimental acidification of alpine catchments at Sogndal, Norway : results after 8 years

Manipulations with whole catchments were initiated in Norway in 1983 (RAIN project Reversing Acidification In Norway) to obtain direct experimental evidence relating to the reversibility of soil and water acidification, rate of change, and the relative roles of sulfur and nitrogen. We present here results for soil and runoff chemistry during 8 years of acid addition at Sogndal, a pristine acid-sensitive site in central Norway characterized by gneissic bedrock, thin and patchy soils, and alpine vegetation. Catchment SOG2 receives 100 meq m−2 yr−1 H2SO4, catchment SOG4 receives a 1∶1 mixture of H2SO4 and HNO3, while catchments SOG1 and SOG3 serve as untreated controls. Acid is applied to the snowpack in April and in 5 portions of 11 mm of pH 3.2 acidified lakewater during the snowfree period.The 8-years of acid addition have caused major changes in runoff chemistry. Concentrations of sulfate and base cations have increased while acid neutralizing capacity (ANC) has decreased. Henriksens F-factor (change in concentration of non-marine Ca+Mg divided by change in concentration of non-marine SO4) is about 0.35, but is expected to decrease as soil acidification proceeds. Runoff is acidic, aluminum-rich, and toxic to fish and other aquatic organisms. Repeated soil sampling indicates no dramatic trends related to treatment. Year-to-year variations are large, and mask changes expected. The input-output budgets indicate that over the 8-yr period Ca has been depleted by about 5% of the total soil pool of exchangeable Ca. The observed trends are consistent with response predicted by MAGIC, a process-oriented model of soil and water acidification. The gradual increase in nitrate flux from catchment SOG4 may be the first indication of ‘nitrogen saturation’ induced simply by increasing nitrogen deposition.