PNNL

Abstract

The N-nitrosodimethylamine (NDMA) degradation rate and mineralization rate were measured in two aquifer sediments that received treatments to create oxic, reducing, and sequential reducing/oxic environments. Chemically reduced sediments rapidly abiotically degraded NDMA to nontoxic dimethylamine (DMA) to parts per trillion levels, then degraded to further products. NDMA was partially mineralized in reduced sediments (6 to 28 percent) at a slow rate (half-life 3,460 h) by an unknown abiotic/biotic pathway. In contrast, NDMA was mineralized more rapidly (half-life 342 h) and to a greater extent (30 to 81 percent) in oxic sediments with propane addition, likely by a propane monooxygenase pathway. NDMA mineralization in sequential reduced sediment followed by oxic sediment treatment did result in slightly more rapid mineralization and a greater mineralization extent relative to reduced systems. These increases were minor, so aerobic NDMA mineralization with oxygen and propane addition was the most viable in situ NDMA mineralization strategy.