Nitrogen and sulphur over the Western Atlantic Ocean

This paper reports new surface and aircraft measurements of sulphur and nitrogen species made during WATOX-85 at Lewes, Delaware and Bermuda. Concentrations of most species measured in this portion of the western Atlantic Ocean atmosphere were higher than those found in remote marine environments, showing clearly the influence of anthropogenic emissions from North America. The experiment was designed such that measurements were made following cold frontal passages in conditions of strong, dry westerly flow, to ensure that measurements at Bermuda were in air masses that had earlier crossed the east coast in the region of Lewes. Boundary-layer SO2 concentrations decreased by a factor of 20 between the east coast and Bermuda, while sulphate was the same at both locations. First-order decay distances for SO2 and total S were 340 and 620 km, respectively, under these conditions. The decay distance for total S is substantially shorter than previously determined, indicating that SO2 in particular is removed in near-coastal environments more quickly than previously supposed. Boundary-layer NOx and HNO3 concentrations decreased by close to an order of magnitude between the east coast and Bermuda, whereas for NO3− the decrease was a factor of two. Corresponding first-order decay distances of NO'x and total N were 500 and 550km, respectively

Description and Intercomparison of Techniques to measure N and S compounds in the Western Atlantic Ocean Experiment

The data set of N and S compound measurements from WATOX-85 has been examined in detail to assess that data quality and suitability for use in addressing the goals of the Western Atlantic Ocean Experiment. Accuracy estimates for particulate SO42− and NO3−, SO2 and HNO3 have been made on the basis of the investigators' estimates and the results of intercomparisons. Intercomparisons of ground-based particulate SO42− and all filter SO2 and HNO3 measurements show them to be consistent with the 20% accuracies quoted by the investigators. Ground-based particulate NO3− and aircraft particulate SO42− show inconsistencies such that the accuracies can be no better than 28% and the aircraft particulate NO3 has an accuracy of no better than 60%

Assessment of wet deposition monitoring in Atlantic Canada

The precipitation chemistry stations operating in the Atlantic Provinces during the period 1980–1982 were assessed by comparing their siting characteristics and sampling procedures with the criteria recommended by the Canadian Federal‐Provincial Research and Monitoring Coordinating Committee (RMCC). The data collected at these stations were also evaluated according to standards recommended by the Unified Deposition Data Base Committee. Only one quarter of the 32 stations satisfied all of these criteria. In addition, there is evidence to suggest that some of the laboratories experienced problems analysing for nitrate or pH. Therefore, producing a coherent region‐wide data set for the major ions in precipitation was not feasible. However, the qualifying measurements were adequate to indicate an excess sulphate deposition of slightly less than 20 kg ha−1 a−1 to most of the region, with less than 10 kg ha−1 a−1 to Labrador. Although this analysis was restricted to the monitoring in Atlantic Canada, the results are of broader relevance in illustrating the potential problems inherent in merging data from several networks

The early detection of sulphur emissions reductions using Wet Deposition Measurements

This paper is the outgrowth of a workshop on the Detection of Trends in Wet Deposition Data, attended by atmospheric modellers, atmospheric chemists and statisticians in Toronto, November 1983. Methods for detecting changes or trends in network data which are described and evaluated include statistical and meteorological analyses of ‘before’ and ‘after’ time series at single stations, the analysis of changes in frequency distributions, and the analysis of entire network data sets. Relative advantages of using precipitation concentration vs deposition data sets are examined, and the added information on trends available from air concentration measurements (SO2 and particle-SO42−) is shown. The paper concludes with recommendations for data requirements and preferred approaches to trend or change detection using available statistical and modelling techniques

Inorganic nitrogen over the Western North Atlantic Ocean

The concentrations of the reactive nitrogen species NO2, NOx(= NO + NO2), NOy (the sum of all compounds of nitrogen and oxygen with the exception of N2O), particulate NO3 −, and volatile NO3 − were measured from ship and aircraft platforms over the western North Atlantic Ocean as part of the GCE/CASE/WATOX experiment. Air masses sampled were divided into continentally influenced and typical marine on the basis of trajectories, and radon and black carbon measurements. From the NO3 − measurements on size separated aerosol and the altitude variations of volatile NO3 − and particulate NO3 −, a significant interaction between volatile NO3 − and sea salt aerosol was indicated. The average marine concentrations measured were: 18 nmol m−3 for NO2, 29 nmol m−3 for NOx, 46 nmol m−3 for NOy, and 10 nmol m−3 for total inorganic NO3 −. The reactive nitrogen species were present at concentrations some 40 times those encountered in the remote Pacific Ocean, whereas the inorganic NO3 − was only 3 times higher

A risk assessment of sulphur deficiency in cereals using soil and atmospheric deposition data

A qualitative model was used to assess the risk of S deficiency in cereals in Britain. A risk index was generated for each of 6301 soil data points by considering the inputs of S from atmospheric deposition, the content of soil organic matter, and factors influencing the potential leaching of sulphate, i.e. soil type, texture, pH and annual rainfall. The results show that currently 11% of the British land area is at high risk of S deficiency, and a further 22% at medium risk. The high risk areas are in south-east Scotland, the Scottish Borders, East Anglia, the Welsh Borders and south-west England. These agree well with the distribution of reported incidences of S deficiency in cereals. If the UK target for reduction in SO2 emissions by the year 2003 is met, the model predicts that the high and medium risk areas will increase to 23 and 27%, respectively. Thus, agricultural use of S-containing fertilizers is likely to increase in importance in the near future