Second year - Goal is the quantification of the extent to which photochemical processes actually occur in the water bodies of the Calumet watershed, thru in situ experiments. In addition to the task-oriented goals above, a third goal is the development of a general protocol for carrying out such studies. Since our graduate student arrived in early September, we have mapped and adjusted the intensity of the simulated solar source and used the resulting irradiation field in tests of candidate hydroxyl radical probe compounds, as described in the narrative below. This is judged to be sufficient for the anticipated number of replicates and controls samples. Recent tests have shown that two of the OH-radical probes reported in the literature are unsuitable for our purposes, due to volatility losses that are significant compared to the photolysis time scale.
Tests are now underway using other possible probe compounds.
Project activity to date has been on items 1 and 2. The requirements for the source were dictated by the data objectives. It is important to be able to simultaneously irradiate several reaction vessels, so that in addition to replicate sample irradiations, irradiation of control experiments, additional samples with additives, etc, can be carried out under identical conditions. In order to accommodate an adequate number of these vessels, a 2'x3' wooden box was constructed to house the lamps, providing eye protection for staff and projecting the irradiation down onto a grided irradiation field beneath the box. The BL lamps were chosen, rather than the more common BLB because the spectrum of the BL lamps extends on into the visible region.