Aerial Detection of Vegetation Damage Utilizing a Simple 35-mm Camera System

The body of information presented in this paper is directed to environmental scientists interested in the detection of vegetation damage from air pollution. A dual 35-mm camera bank, manually operated from a small aircraft, was tested as a sensor system for detecting vegetation damage caused by air pollution. The cameras were filled with color and color infrared film and attached to a frame so that simultaneous exposure was possible. This gave a matched pair of photographs for each scene.

A test site was selected that contained three very large coal-fired power plants and a complex of beehive coke ovens. The power plants burn medium-sulfur coal (2 to 3%) which, after coal preparation, results in stack emissions of between 1500 and 2000 ppm sulfur dioxide (S0₂). The coke ovens are relatively old and have effectively no pollution controls. The ovens emit hydrogen sulfide, sulfur dioxide, a variety of benzene-based organics, and heavily dust-laden smoke. The areas near the power plants and coke ovens were monitored by photographic overflights on a regular basis. A variety of aerial photographs were made to test for optimum light conditions, exposure times, and altitudes. Field trips were carried out to examine photographed areas at the ground level.

Two areas were found to have vegetation damage on a scale that made aerial photographs useful. One area was damaged from effluent from the coke ovens; another area exhibited symptoms characteristic of oxidant-type damage where low sulfur dioxide concentrations may have been a contributing factor. In each case the 35-mm camera system was a success in terms of detecting and recording the stress. The chief advantages of such a technique are ease of operation, flexibility, and economy. Compared with conventional aerial photography, the savings are considerable. The disadvantages are small area coverage per photograph and difficulty in obtaining vertical photographs that would have a uniform scale. However, for this particular project, these were not serious drawbacks.