THE DISTRIBUTION AND FUNCTION OF DENITRIFICATION GENES: EXPLORING AGRICULTURAL MANAGEMENT AND SOIL CHEMICAL IMPLICATIONS

Denitrification is a microbially-mediated process that converts nitrate (NO3-) to dinitrogen (N2) gas and has implications for soil fertility, climate change, and water quality. Using PCR, qPCR, and T-RFLP, the effects of environmental drivers and land management on the abundance and composition of functional genes were investigated. Environmental variables affecting gene abundance were soil type, soil depth, nitrogen concentrations, soil moisture, and pH, although each gene was unique in its spatial distribution and controlling factors. The inclusion of microbial variables, specifically genotype and gene abundance, improved denitrification models and highlights the benefit of including microbial data in modeling denitrification. Along with some evidence of niche selection, I show that nirS is a good predictor of denitrification enzyme activity (DEA) and N2O:N2 ratio, especially in alkaline and wetland soils. nirK was correlated to N2O production and became a stronger predictor of DEA in acidic soils, indicating that nirK and nirS are not ecologically redundant.

RISK FACTORS FOR NONMEDICAL PRESCRIPTION ANALGESIC USE AMONG COLLEGE STUDENTS: RESULTS OF A PROSPECTIVE STUDY

Purpose—Nonmedical Prescription Analgesic (NPA) use is a serious public health concern and studies on risk factors for NPA use are lacking. This investigation used preexisting data from a landmark longitudinal, prospective study of college students, the College Life Study (CLS), to examine the longitudinal relationship between four suspected risk factors—affective dysregulation, conduct problems, depressive symptoms, and general psychological health—and NPA use. Methods—The sample was comprised of 1,253 young adults originally recruited as first-year college students from a large, mid-Atlantic university. Results—10.5% (n=103) of the participants during year 3 of the study reported past year NPA use, of which 55.3% (n=57) were male and 81.6% (n=84) were white. Affective dysregulation and conduct problems were found to be significantly and longitudinally (baseline to year 3) associated with incident NPA use after controlling for gender, parents’ education, and race/ethnicity. Conclusions—Affective dysregulation and conduct disorder are longitudinally associated with NPA use among college students. These findings might aid in prevention efforts to reduce NPA use among college students.