The Southern Ontario Oxidant Study (SONTOS)
December 1, 1997
Introduction
The Southern Ontario Oxidant Study (SONTOS) was initiated in 1992. It grew out of, and built upon, existing atmospheric chemistry research supported by the Ontario Ministry of the Environment. The objectives for SONTOS were stated at the outset as follows:
- To understand the contributions of local sources of NOx and VOC's in the formation of ground level ozone in the Windsor-Quebec corridor, relative to the contributions from the long range transport of ozone and its precursors from sources in the mid-western U.S.
- To understand the impact of large urban sources, such as Toronto, on ozone chemistry at downwind locations.
- To understand the relative roles of NOx, anthropogenic hydrocarbons and biogenic hydrocarbons on the ground level ozone chemistry in the Windsor-Quebec corridor.
SONTOS was approved as a CIRAC (Canadian Institute for Research in Atmospheric Chemistry) project, and has received wide support from members of CIRAC.
History
Major field measurement campaigns took place under SONTOS in the summers of 1992 and 1993. Intensive chemical and meteorological measurements were made at a site near Hastings, Ontario (near the eastern end of Rice Lake). These were supported by measurements on board an aircraft, and by additional measurements at other ground level locations. The 1993 campaign was coordinated closely with a similar measurement campaign carried out in southeastern Michiga n (the Southeastern Michigan Oxidant study - SEMOS).
During 1994 and 1995 measurements were carried out for a limited set of chemical species (mainly hydrocarbons), while analysis and interpretation of the existing data base continued. Further intensive measurements were made in the summer of 1996, in coordination with NARSTO-CE and the Montreal Area Oxidant Study. The primary focus in this SONTOS campaign was on aircraft-borne measurements, with support by a ground station at Binbrook, and long-path measurements made at Oshawa (eas t of Toronto), backed up by routine measurements made in the Provincial Air Quality monitoring network.
Participants
SONTOS has been supported financially by the Provincial and Federal governments as well as by the private sector. Specifically, the contributions received from Ontario Hydro, Consumers Gas, Gas Technology Canada, Dow Can ada, Imperial Oil and Ford Canada have added significantly to the success of the study.
Scientific participation has been equally wide ranging, with active involvement by scientists from the Ontario Ministry of the Environment, Environment Canada, York University, Ontario Hydro, Unisearch Associates, and Ortech Internation al. Further details of participation and the measurements made in the two field campaigns are given in the attached table. The figure shows the geography of the study area, and the locations of the monitoring sites.
Major Findings and Accomplishments
It has been very clearly demonstrated that high levels of ozone can be stored, and preferentially transported over the Great Lakes. High doses of ozone can then be delivered to sensitive recept ors (humans, crops and/or materials) on land under the influence of the lake breeze.
Meteorological measurements made in SONTOS have shown that the lake breeze front penetrates as far as 30 to 40 km inland, which is further than was previously believed. This means that high levels of ozone from Lakes Erie, Hur on and Ontario can be delivered to most of southern Ontario, and particularly to those regions which contain almost all of the population of the province.
The implication of these findings is that any model which is used to develop and evaluate ozone abatement and control strategies must be able to simulate the lake breeze phenomenon. In particular this requires that the spatial resolution of the model or models must be of the order of 5 km, rather than the 20 to 40 km which is provided by most of the models currently being used.
The atmospheric chemistry taking place at the Hastings monitoring site is similar to what has been observed at a number of other rural sites in North America. In particular, local production of ozone is significantly less impo rtant than importation.
Isoprene, which is a hydrocarbon emitted by a number of varieties of trees, is usually the major contributor to reactivity (leading to ozone production) at rural and many urban sites during the summer. This is important, becau se these natural emissions are not controllable.
However, it has also been established that isoprene is a component of motor vehicle emissions, although the relative contribution from this source is small (less than 10%) in summer.
Inspection of a number of ratios of chemical constituents measured in SONTOS has confirmed that ozone production in rural Ontario is NOx limited.
SONTOS results have been described in at least 12 peer-reviewed journal articles and 18 presentations at international scientific conferences. At least __ students have been trained in the atmospheric sciences as a direct resu lt of their participation in SONTOS.
Measurements carried out during the summer 1992 field study
|
Parameter |
Technique |
Investigator |
|
Hastings |
|
|
|
NO, NO2, NOx, NOy |
Chemiluminescence |
Several |
|
Ozone |
UV absorption |
Several |
|
PAN |
Automated GC |
P. Shepson, York U. |
|
Carbonyls |
DNPH/LC |
P. Shepson, York U. |
|
Organic nitrates |
Charcoal tube/GC |
P. Shepson, York U. |
|
Peroxy radicals |
Radical amplifier |
D. Hastie, York U. |
|
Hydrogen peroxide |
Tunable diode laser |
D. Hastie, York U. |
|
Formaldehyde |
Tunable diode laser |
D. Hastie, York U. |
|
Hydrocarbons (C2 to C10) |
Canister, GC/FID |
H. Niki, York U. |
|
SO2, SO42-, NO3-, HNO3 |
Filter pack |
Ontario Min. of Env. |
|
VOC |
Automated GC |
L. Poissant, AES |
|
Meteorology (wind speed, direction, temperature, RH) |
Met. tower (x2) |
P. Roussel, Ontario Hydro |
|
Vertical profiles |
Acoustic sounder |
P. Roussel, Ontario Hydro |
|
Binbrook |
|
|
|
NO, NO2, NOx |
Chemiluminescence |
P. Roussel, Ontario Hydro |
|
Ozone |
UV absorption |
P. Roussel, Ontario Hydro |
|
Hydrocarbons (C2 to C10) |
Canister, GC/FID |
H. Niki, York U. |
|
Aircraft |
|
|
|
NO, NO2, NOx, O3 |
Luminox |
G. Mackay/H. Schiff, Unisearch |
|
Hydrocarbons (C2 to C10) |
Canister, GC/FID |
H. Niki, York U. |