1. Thoughts on a GAW program for Global Long Term Measurements of Volatile Organic Compounds Jan W Bottenheim Science and Technology Branch Environment Canada

2. We all can agree that it is important We all have probably clear ideas how to do it Yet There have been numerous measurement comparison studies The results are mixed There has been a plan to make a GAW WCC, which has had one go since 1995 There is a plan for a demonstration network, written in 1995….

3. A GAW network needs clear objectives What does it desire to measure What are theDOQs, etc, to make it useful What should be the geographic distribution

4. It also needs to be doable Limited list of compounds Technically feasible Canister sampling? One central laboratory, or Strong intercomparison progam between laboratories One common set of standards (see ethyne comparison later on) Buy-in from national programs

5. Example from Canadian efforts Environment Canada has 2 active laboratories: ETC-Ottawa (1) and STB-Toronto (2) (1) sampling at many locations urban and rural (2) does insitu sampling at one research station (CARE), North of Toronto; canisters for (1) are collected at CARE (2) collects canisters at GAW station Alert, that are analyzed by (1); Similarly (2) collects canister samples during the occasional iuntensive field studies, that are then analyzed by (1)

6. How often do (1) and (2) compare? NOMHICE, mid 1990s GAW VOC intercomparison, 2003 Should we compare?

7. Ambient air, during “clean air” episode (most mixing ratios < 0.1 pptv)

8. but Insitu measurements are in danger of being discontinued because of lack of funding (and interest…) The canister measurements are mostly geared towards identifying the presence of compounds (“toxics” such as aromatics and other solvents are a priority) Has problems with mixing ratios large uncertainties Mostly for trends in urban-suburban areas

9. So to repeat A GAW plan has to be simple (alkanes are possible, alkenes probably not, OVOCs probably not (?) Requires buy-in