Wood preservation facilities, ammoniacal copper zinc arsenate: chapter C-3

3. Environmental Effects

Ammonia, copper, zinc and arsenic are found naturally in the environment. Considerable variation occurs in natural concentrations of copper, zinc and arsenic in soils and waters (5).

3.1 Aquatic Toxicity

In considering the aquatic toxicity of ACZA, the following points should be borne in mind:

• The valence of arsenic, copper and zinc may change in the environment, and these changes may reduce or enhance the toxicities of the elements. No studies have been reported in the literature on valence inter-conversion of copper, zinc or arsenic in soils, groundwater or surface runoff water at or from ACZA facilities. Nonetheless, it is known that reduced forms of copper rarely occur in aqueous environments (6). A limited study to assess arsenic speciation in samples of soil and water in the vicinity of chromate copper arsenate (CCA) facilities showed that the samples contained at least 97% of the original pentavalent form of arsenic (7). A similar predominance of the pentavalent form is assumed at ACZA facilities.

The guidelines and limits for copper, zinc and arsenic noted in Table 3 are based on total concentrations. They reflect the recommendations of many scientific reviews that indicate that the current state of knowledge does not enable water quality limits to be based on either valence state or dissolved fractions in water (8).

Canadian limits for ammonia, arsenic, copper and zinc in aquatic environments are listed in Table 3, and these limits are subject to change from time to time. Recurrent review of these limits is recommended.

Provincial guidelines are applicable and should be consulted. Provincial guidelines may differ from or be more specific than national guidelines. Provincial regulations may require additional measures that may enhance, but not reduce, protection.