Pharmaceuticals and personal care products (“PPCPs”) have been detected in freshwater systems world-wide. Intrinsically biologically active, PPCPs have the potential to act on non-target organisms at sub-toxic concentrations including microbes involved in base food web processes. Denitrification is a microbe mediated process in which nitrate is reduced to di-nitrogen gas (N2), effectively removing nitrogen from aquatic systems. The ultimate step in the denitrification process is the conversion of nitrous oxide (N2O) to N2 mediated by the nitrous oxide reductase enzyme, encoded by the nosZ gene. Chemical inactivation or mutation of nosZ will result in failure to complete this last reduction step; thus increasing the production of N2O, a strong greenhouse gas. To date, few studies have examined the effect of PPCPs on denitrification in the environment and to our knowledge no studies have applied nosZ gene quantification to define the effects of PPCPs on denitrification. This study will explore the relationship between denitrification rate, N2O production and nosZ gene abundance in the presence of four PPCPs: acesulfame (30-200 ng/L), amoxicillin (30-200 ng/L), diphenhydramine (20-100 ng/L) and triclosan (5-80 ng/L). The effects of these PPCPs on denitrification will be examined in sediments across a land use gradient from three constructed wetlands. Denitrification rates will be measured using 15N-labelled NO3- and nosZ will be quantified by targeted PCR in the presence of environmentally relevant PPCPs concentrations.