Ground level nitrogen dioxide concentrations in the rural Waikato Valley, New Zealand

Ground level nitrogen dioxide (NO2) concentrations have been measured for one year over an area of 400 square kilometres in rural New Zealand using an array of 21 sites. Three passive samplers were exposed at each site for intervals of two weeks from August 1989 to August 1990. The exposure sites were centred around the Waikato Valley township of Huntly (population 6900). Important features of the survey area include a 1000 MW thermal power station situated on the outskirts of the town, the Waikato River and State Highway 1, a major north-south traffic route along the valley. The NO2 concentrations in the survey area ranged from below 0.1 to 10.1 ppb, with an annual average of 1.2 ppb. Seasonal variations indicate summer values about three times lower than those found in the winter. The spatial distribution of NO2 appears to be related to contributions from State Highway 1.