Drew Meyers Paracoccus denitrificans

Agriculture: 73%, 17% from Nitrate runoff Wastewater: 3% UNEP 2013 N2O Report

Labile Carbon and NO 3 - from treated wastewater

Labile Carbon and NO 3 - from treated wastewater NO 3 - from agricultural runoff

Labile Carbon and NO 3 - from treated wastewater NO 3 - from agricultural runoff Aerobic Respiration: Labile Carbon + Oxygen  CO 2 +H 2 O + energy

Labile Carbon and NO 3 - from treated wastewater NO 3 - from agricultural runoff Aerobic Respiration: Labile Carbon + Oxygen  CO 2 +H 2 O + energy Anaerobic Respiration: Some bacteria use Nitrate as an electron acceptor. This is the process of Denitrification.

Labile Carbon and NO 3 - from treated wastewater NO 3 - from agricultural runoff Complete Denitrification Process, <0.5mg Oxygen/L: NO 3 -  NO 2 -  NO + N 2 O  N 2 Redox Rxn: 2 NO 3 − + 10 e − + 12 H + → N H 2 O

Labile Carbon and NO 3 - from treated wastewater NO 3 - from agricultural runoff Incomplete Denitrification Process: Conditions are not completely anoxic NO 3 -  NO 2 -  N 2 O

Labile Carbon and NO 3 - from treated wastewater NO 3 - from agricultural runoff Incomplete Denitrification Process: Conditions are not completely anoxic NO 3 -  NO 2 -  N 2 O N 2 O leaves water, enters atmosphere

O 3 +hv  O 2 + O( 1 D) N 2 O + hv  N 2 + O( 1 D) N 2 O + O( 1 D)  N 2 + O 2 or  2 NO 3 – 4% of N2O loss in stratosphere results in Nitric Oxide (NO)

O 3 +hv  O 2 + O( 1 D) N 2 O + hv  N 2 + O( 1 D) N 2 O + O( 1 D)  N 2 + O 2 or  2 NO NO + O 3  NO 2 + O 2 NO 2 + O  NO +O 2 3 – 4% of N2O loss in stratosphere results in Nitric Oxide (NO)

O 3 +hv  O 2 + O( 1 D) N 2 O + hv  N 2 + O( 1 D) N 2 O + O( 1 D)  N 2 + O 2 or  2 NO NO + O 3  NO 2 + O 2 NO 2 + O  NO +O 2 Net Rxn: O 3 + O  2 O 2