The Southern Ontario Oxidant Study (SONTOS)
Summer 1993 Field Campaign
Abstract
Another successful field campaign was undertaken during the summer of 1993. Additional industrial sponsorship of the study made it possible to carry out extra measurements. In addition, close cooperation was achieved with a similar field measurement campaign in southeast Michigan.
The summer of 1993 saw a successful follow up to the first SONTOS field campaign, which took place in 1992 (Right Atmosphere _____). Once again, a very detailed set of chemical measurements was made at the Hastings site (Figure 1), supported by aircraft-borne measurements, and data collected at sites to the south and west of Toronto. These measurements were made in support of the SONTOS objective of elucidating further the factors which give rise to high ambient oxidant concentrations in the Windsor-Quebec City corridor.
Essentially all of the participants in the 1992 field campaign returned to the field in 1993. Participating groups were from York University, Ontario Hydro, Unisearch Associates and the Ontario Ministry of Environment and Energy. The suite of measurements included:
- NO, NO2, NOy, NOx
- O3
- PAN
- Carbonyls
- Organic nitrates
- Peroxy radicals
- Hydrogen peroxide
- Formaldehyde
- C2 to C10 hydrocarbon
- SO2
- Particulate matter (number and size)
- Meteorology (including acoustic sounder)
As was done in 1992, measurements were made at Binbrook, and also on board an aircraft. Industrial sponsors from 1992, Consumers Gas and Ontario Hydro, renewed their sponsorship for 1993, and additional sponsorship was received from Imperial Oil and Dow Chemical. This additional funding permitted expansion of the campaign in two ways. Three extra aircraft flights were made, over and above those originally planned, and extra measurements (NOx, O3 and hydrocarbons) were made at a site in the Longwoods Conservation Area, near London, Ontario.
An important additional feature of the 1993 field campaign was that it was undertaken in cooperation with a similar study in Southeast Michigan. Coordination between the two studies was arranged by way of twice-daily conference calls. Where appropriate, aircraft flights for the two studies were arranged to sample the same air mass. On occasion this meant that the SONTOS flight took place the day after the flight for the SE Michigan Oxidant Study (SEMOS). It is anticipated that this cooperation will strengthen both studies. In particular, it will allow SONTOS scientists to form a much clearer picture of the evolution of concentrations in the air parcels travelling from the southwest to Hastings.
Quality assurance and quality control of the data are currently in progress, and a detailed discussion of the data, with planning of the analyses to be carried out, will take place at a Data Evaluation Workshop planned for January 1994. Although ozone levels in 1993 were again not particularly high, several interesting cases have already emerged from the preliminary examination of the data. These include:
The highest ground-level O3 observed during the summer was 147 ppb at Sarnia (and Port Huron on US side) on 10 August 1993. This may have resulted from northward transport through Flint, Michigan, on 9 August, with overnight storage over Lake Huron.
The concentration of ozone measured on board the aircraft reached 190 ppb off Toronto on August 12, with high levels also observed near the top of CN Tower. Ground level concentrations at this time were much lower (about 50 ppb).
Southwesterly flow was established at end of field campaign (26/27 August). The ozone concentration at Hastings on this day reached 110 ppb.
SONTOS continues as an example of an extremely fruitful cooperation between government, industry and academia. We look forward to the continuation of this partnership.