Ecotoxicological risks associated with land treatment of petrochemical wastes in Oklahoma

Scope and method of study. This study investigated the effects of residual contamination in a terrestrial mammal system. The study sites consisted of five paired sites, each pair being an abandoned petrochemical landfarm and an uncontaminated reference site. Populations of cotton rats (Sigmodon hispidus) and rodent assemblages were monitored summer and winter on each site for 2 years. At the end of each season, a sample of 12 cotton rats from each site were returned to the laboratory for immunological, hematological, and reproductive assays and measurements. Treatment differences in physiological and morphological parameters were tested using a randomized block design with site as a blocking variable. Individual site comparisons were made using t-tests adjusted for multiple comparisons. Population parameters were estimated using the robust design data type in program MARK.; Findings and conclusions. Overall analysis indicated that rats inhabiting landfarms exhibited decreased relative spleen size compared to rats collected from reference sites. Cotton rats collected from landfarms also had increased hemoglobin, hematocrit and platelet levels, and decreased blood leukocytes during summer. During winter, an increase in the number of popliteal node white blood cells was observed from rats collected on landfarms. No difference was detected for lymphocyte proliferation in response to concanavalin A, pokeweed, or interleukin-2. Comparisons within individual sites indicated that two sites (Units 1 and 3) had the greatest effects on immune function and hematology of cotton rats. Cotton rat populations inhabiting abandoned landfarms reached maximum densities half that of reference populations, and had lower rates of survival. Toxicity indices indicated that both metal and PAH concentrations affect survival and population density. Cotton rat populations had more variable sex ratios and lower proportion of juveniles than populations from reference sites. No treatment differences were observed in the weight of epidymides, testes, uteri, or ovaries. Assemblages inhabiting landfarms were dominated by cotton rats, however harvest mice (Reithrodontomys fulvescens) were replaced by deer mice (Peromyscus maniculatus ). Contaminated sites were characterized by an increase in house mice (Mus inusculus) and an absence of voles (Microtus spp.). The results of this study suggest that residual petrochemical waste affects mammals from the cellular through the community level.