Environmental Fate and Partitioning

Environmental fate analysis integrates information on the chemical behaviour of the substance with the properties of the receiving environment. The objective of fate analysis is to determine the multimedia distribution of the substance after its release into the environment. This includes consideration of the persistence and bioaccumulation of the substance in the environment.

Level III fugacity modelling (CEMC, 2002) predicts the following fate for DNOC (estimated for the neutral form of DNOC) released into different media:

• With releases solely to water (as would be expected from the stated use), the majority of DNOC would remain in water (99%), with a minor amount partitioning to sediments (1%). Loss of the substance from the aquatic environment at steady state will be mainly a result of transport (~55% advection) out of the “unit world” and degradation (~45%).
• With emissions solely to air, the majority of DNOC would partition to soil (91%) and water (7%).
• With releases solely to soil, the majority of DNOC would remain in soil (98%), with some transfer to water (2%).

The following information was considered in evaluating whether DNOC meets the criteria for persistence and bioaccumulation as defined under the Persistence and Bioaccumulation Regulations of CEPA 1999:

• Persistence:
  
  
  1. in air, estimated half-life of 8 hours to 129 days (U.S. EPA, 1986b; Atkinson, 1987; Howard et al., 1991);
     
  2. in surface water, half-life ranges from 3 to 5 weeks (Mill and Mabey, 1985; Kelly et al., 1994; IPCS, 2000);
     
     
  3. in sediments, half-life is estimated to be 150 days (EPI version 3.11);
     
  4. in soil, half-life ranges from 14 hours to less than 2 months (Callahan et al., 1979; HSDB).
     
• Bioaccumulation:
  
  
  1. bioaccumulation factor (BAF) of 25 calculated for DNOC (Gobas and Arnot, 2003).
     

Persistence criteria are half-lives of greater than or equal to 2, 182, 365 and 182 days for air, water, sediment and soil, respectively.

Bioaccumulation criteria are BAFs or bioconcentration factors (BCFs) of greater than or equal to 5000 or a log Kow of greater than or equal to 5.0.

Based on the Persistence and Bioaccumulation Regulations, DNOC is persistent in air and not bioaccumulative.