Mark S. Coyne

Hydrologic Properties of Pervious Concrete

Pervious concrete is concrete made by eliminating most or all of the fine aggregate (sand) in the concrete mix, which allows interconnected void spaces to be formed in the hardened product. These interconnected void spaces allow the concrete to transmit water at relatively high rates. The main objective of this project was to conduct research on the potential application of pervious concrete in agricultural settings, specifically for use in animal feed lots, manure storage pads, animal manure and bedding compost facilities, or floor systems in animal buildings. Laboratory tests were conducted on replicated samples of pervious concrete formed from two rock sources (river gravel and limestone) for coarse aggregates and different size fractions to determine hydrologic relationships. Linear relationships were found between density and porosity, density and permeability, porosity and permeability, and porosity and specific yield. The results suggest that properties such as permeability, porosity, and specific yield are not significantly affected by different aggregate types. However, density and porosity can be effective methods for predicting porosity, specific yield, and permeability. In addition, t-tests were conducted to determine the effect of aggregate types on the solid/liquid separation properties of the pervious concrete after adding composted beef cattle manure and bedding to the surface of the specimens. The amount of composted beef cattle manure and bedding retained within the specimens was significantly less (p = 0.012) when samples constructed of #8 river gravel were used rather than the other aggregates. The #8 river gravel also had significantly less reduction in permeability compared to other aggregates. Although the #8 river gravel had a different effect on the compost retained and the reduction in permeability for the specimens, all four aggregates exhibited a significant reduction in the permeability after the compost was applied.

Distinguishing between human and animal sources of fecal pollution in waters: a review.

This review paper discusses some of the earlier and current methods used to identify the human and non-human sources of fecal pollution in water. It is mainly focused on chemical approaches, i.e., fecal sterol and bile acid biomarkers, to identify the sources of fecal pollution. Findings of our study are in agreement with earlier investigations, that it is unlikely for any single determinant to be useful in all situations but a multiple biomarker approach or statistical analysis of microbial and chemical determinants offer the possibility of identifying and apportioning human and animal fecal inputs to natural waters.

Nitrite reduction by Fe(II) associated with kaolinite

Interactions of iron (Fe) with the nitrogen (N) cycle have emerged and contain elements of abiotic and biological reactions. One such abiotic reaction which has received little study is the reactivity of NO2− and Fe(II) associated with a major clay mineral, kaolinite. The main objective of this study was to evaluate the reactivity of NO2− with Fe(II) added to kaolinite under anoxic conditions. Stirred batch reactivity experiments were carried out with 10xa0gxa0L−1 kaolinite spiked with 25 and 100xa0µM Fe(II) at pH 6.45 in an anaerobic chamber. Approximately 500xa0µM NO2− was added to initiate the reaction with Fe(II)-loaded kaolinite. The rate of nitrite removal from solution was 2.4-fold slower in the high Fe(II) treatment when compared with the low Fe(II) treatment. A large portion of the NO2− removed from solution was confirmed to be reduced to N2O(g) in the Fe(II)-kaolinite slurries. However, NO2− reduction was also noticed in the presence of kaolinite-alone and to somewhat lesser extent in the presence of dithionite-citrate-bicarbonate (DCB)-treated kaolinite. Chemical extractions coupled with infrared spectroscopy suggest that Fe(III) oxide mineral impurities and structural Fe(III) in kaolinite may participate in NO2− removal from solution. Furthermore, a magnetite mineral was identified based on X-ray diffraction analysis of untreated kaolinite and DCB-treated kaolinite. Our findings reveal a novel pathway of NO2− transformation in the environment in the presence of Fe(II) associated (sorbed and impurity) with kaolinite.