The Role of a Wildlife Reservoir in the Epidemiology of Bovine Tuberculosis

The objective of this project was to study the epidemiology of bovine tuberculosis in the presence of a wildlife reservoir species. Cross-sectional and longitudinal studies of possum populations with endemic bovine tuberculosis infection were analyzed. The results were used to develop a computer simulation model of the dynamics of bovine tuberculosis infection in possum populations. A case-control study of breakdowns to tuberculosis infection in cattle herds in the Central North Island of New Zealand was conducted to identify risk factors other than exposure to tuberculosis in local possum populations.

Sulfate Mineral Paragenesis in Pennsylvanian Rocks and The Occurrence of Slavikite in Nebraska

The acid weathering of pyrite-bearing Pennsylvanian clastic sedimentary rocks in southeastern Nebraska locally produces the secondary sulfate minerals alunogen, copiapite, epsomite, felsobanyaite/basaluminite, gypsum, halotrichite, jarosite, rozenite, and slavikite. Of these mineral occurrences, four are first-time discoveries in the state or the surrounding region. Slavikite (NaMg2Fe5 (S04)7 (OH) 6• 33H20), which has been reported only once before in North America and from a handful of sites in Europe and South America, was found in abundance at an outcrop at Brownville, NE. The pH values in 1:1 solutions of deionized water of the studied minerals, excluding epsomite, range from 1.94 to 4.82. Therefore, segregations of secondary minerals in themselves are significant microenvironmental reservoirs of acid that can be mobilized during precipitation events. Because of its role in liberating and concentrating ions such as Al3+, Fe2+, Fe3+, Mg3+, and SO42-, acid rock weathering should be considered in local to regional assessments of surface-water and groundwater chemistry. Observations also suggest that rock weathering by the growth of sulfate salts is a potential factor in local hillslope development, one that has not previously been considered in the study area.

A Land-Use and Water-Quality History of White Rock Lake Reservoir, Dallas, Texas, Based on Paleolimnological Analyses

White Rock Lake reservoir in Dallas, Texas contains a 150-cm sediment record of silty clay that documents land-use changes since its construction in 1912. Pollen analysis corroborates historical evidence that between 1912 and 1950 the watershed was primarily agricultural. Land disturbance by plowing coupled with strong and variable spring precipitation caused large amounts of sediment to enter the lake during this period. Diatoms were not preserved at this time probably because of low productivity compared to diatom dissolution by warm, alkaline water prior to burial in the sediments. After 1956, the watershed became progressively urbanized. Erosion decreased, land stabilized, and pollen of riparian trees increased as the lake water became somewhat less turbid. By 1986 the sediment record indicates that diatom productivity had increased beyond rates of diatom destruction. Neither increased nutrients nor reduced pesticides can account for increased diatom productivity, but grain size studies imply that before 1986 diatoms were light limited by high levels of turbidity. This study documents how reservoirs may relate to land-use practices and how watershed management could extend reservoir life and improve water quality.