TOTAL PHOSPHOROUS IN GEOLOGICAL AND AGRICULTURAL SAMPLES FROM EKU’S MEADOWBROOK FARM

Phosphorous from agricultural activities and farmland runoff is associated with widespread contamination and expanding eutrophication of freshwaters. Therefore, a highly desirable goal from the standpoint of environmental protection is to limit entry of nutrients into watersheds. A first step in mediating phosphorus contamination is characterizing its distribution and concentration in waters and in other samples from farmlands. Phosphorous in nature is partitioned into five forms: (1) dissolved in water; (2) sorbed onto surfaces of clay minerals, or Fe and Al oxides; (3) within primary phosphate minerals; (4) as organic detritus; and (5) within living organisms.

In this project, we measured total phosphorous in geological and agricultural samples from EKU’s Meadowbrook Farm using EPA method 365.2. The method releases phosphorus from solids, and converts resultant and other phosphorous compounds to dissolved phosphate or orthophosphate (PO₄^3-). Polyphosphates, and some organic phosphorus compounds, are converted to orthophosphate by sulfuric acid hydrolysis. Organic phosphorus compounds are converted to orthophosphate by persulfate digestion. Orthophosphate, then reacts with ammonium molybdate and antimony potassium tartrate in an acidic medium to form an antimony-phospho-molybdate complex. This complex is reduced to a blue-colored compound by ascorbic acid, where color intensity is proportional to phosphorus concentration. We describe the results of our adaptation of the EPA method to measure total phosphorous of samples of water from farm runoff from EKU’s Meadowbrook Farm. The accuracy and precision of our technique was evaluated using quality control samples.