Evaluation of past and potential phosphorus uptake at the Orlando Easterly Wetland

The Orlando Easterly Wetland (OEW), located near Christmas, Florida, USA, is among the longer-lived treatment wetlands in the United States. It was established in the late 1980s to reduce nitrogen and phosphorus concentrations from tertiary treated wastewater bound for the St. Johns River. A goal of 0.07 mg/l total phosphorus concentration has been set by the regulating agency (St. Johns River Water Management District). In order to understand and define the operating conditions for which this target could be met, a systematic study of historic phosphorus uptake was performed using a traditional first-order model. Phosphorus uptake performance is shown to correlate well with hydraulic performance for two parallel upstream cells. The first-order model is enhanced with predictive capabilities that acknowledge the correlation between the phosphorus uptake rate constant and the hydraulic loading rate observed in the system. Inherent limitations with the first-order modeling approach are addressed and uncertainty in model performance is used to bound predictions.     

The quantitative analysis of endogenous folate catabolites in human urine.

In man folates are catabolized and excreted as inactive cleaved degradation products, a mixture of pteridines and p-aminobenzoylglutamate (pABGlu) or its acetamido derivative (apABGlu). The daily rate of excretion represents the inescapable use of the vitamin in metabolic activity and thus has implications for determining the recommended dietary allowance for the vitamin. Furthermore, the rate of catabolism has been suggested to rise during pregnancy and in certain disease states. A method is described for the quantitative extraction and assay of the folate catabolites pABGlu and apABGlu in human urine. Aliquots of 24-h urine collections are acidified and applied to columns of Dowex 50W cation-exchange resin. The catabolites are selectively batch-eluted with increasing concentrations of HCl. The fraction containing pABGlu is diazotized and then applied to a C18 Sep Pak column for further purification and concentration. The fraction containing apABGlu was deacetylated and reapplied to the Dowex column and then treated identically to the pABGlu fraction. The methanolic concentrates of both extracts were evaporated to dryness and reconstituted with water and pABGlu was regenerated by reductive cleavage of the diazotized material with Zn/HCl. The extracts of the two catabolites were separated by reverse-phase HPLC using a Radial Pak C18 column. Recovery of isolated material was monitored by the addition of high specific activity tritiated labels of both compounds added as internal standards to all urine aliquots prior to purification and analysis.     

Mutagens in the feces of 3 South-African populations at different levels of risk for colon cancer.

The incidence of mutagens in the feces of 3 South-African populations at different risk levels for colon cancer has been determined. Lyophilized fecal samples were extracted with ether and the mutagenicity of the extracts determined using the Salmonella/mammalian microsome mutagenicity test. 19% of the samples from urban white South-Africans, a population at a high risk for colon cancer, were mutagenic using Salmonella typhimurium strain TA100. This incidence was significantly greater (p less than 0.001) than the incidence of mutagen excretion in the low-risk populations of urban blacks (2%) and rural blacks (0%). This pattern was also obtained using Salmonella typhimurium strain TA98. The incidence of mutagen excretion for urban whites was 10%, as compared to 5% and 2% for urban and rural blacks, respectively.