Elucidate the role of indirect photolytic degradation of alachlor and atrazine in the water column under natural sunlight conditions.
Quantify the effect of photobleaching on NDOM and the role that this process might have on ASOC degradation at the OWC site.
Study the propensity for sunlight, NDOM, and nitrate to degrade other ASOCs e.g., atrazine, metribuzin, and metolachlor under synthetic sunlight.
Identify important daughter products resulting from the photolysis experiments.
Model the degradation kinetics for ASOCs in OWC based upon the parameters derived from the photolysis experiments.

Nonpoint source contamination is difficult to control because it may be distributed across large areas of a watershed. Wetlands, however, may provide a means of management since water from diffuse sources collect in wetland basins before final discharge. Sunlight coupled with natural catalysts such as NDOM and nitrate in wetlands may provide an inexpensive and effective means to treat waters contaminated with herbicides.

Old Woman Creek (OWC) water samples will be spiked with alachlor or atrazine and irradiated with natural sunlight in quartz reaction tubes at different levels in the wetland water column. The loss of the target compounds will be monitored over time and attempts will be made to correlate the rate of degradation to the abundance and properties of the two known photosenstizers, natural dissolved organic matter (NDOM) and nitrate. We will also study the degradation of other herbicides in artificial sunlight and OWC water. Derivatives from the reaction will be quantified by direct aqueous assays using MS-MS coupled to an electrospray interface. Effects of photobleaching on NDOM will also be investigated by irradiating it with artificial sunlight and quantifying changes in its spectroscopic and fluoresecence properties.

We have studied the effect of different dissolved organic matter isolation methods on indirect photolysis. We have used a "probe" molecule (trimethyl phenol) rather than one of the target pesticides because its reaction pathway is better known. The results show that there small, but statistically significant differences in the different isolation methods i.e., between ultrafiltration, C-18 chromatography, and XAD. We have chosen to use ultrafiltration as it provided the least biased resutls. Large volumes of Old Woman Creek water will be processed from a sampling event that will occur in November, and light experiments will be conducted this winter using the target pesticides.