Environmental Engineering Reference
In-Depth Information
17.2.3
CuAZ (Copper, Boron, and Azole) and ACQ
(Ammonical Copper Quaternary)
Another preservative with a higher copper concentration than CCA also proved to
be a better alternative for wood treatment due to its low leaching rate (Li et al.
2011
),
although Wang and Wang (
2011
) showed that the copper fi xation rate in CuAZ-
treated bamboo was similar to that of CCA, suggesting similar copper loss in both
wood treatments.
In 2007, the majority of lumber in the USA was treated with ACQ, due to its
reliability (Home Builders Association
2007
). Likewise, this compound was widely
used in Japan (Miyauchi
2008
); as arsenic was not present in the formula, ACQ
contains a high copper concentration, much like CuAz. Copper-leaching has shown
to be continuous from treated wood due to rainfall, albeit in lesser quantities as
wood weathers (Hasan et al.
2010
).
The release and environmental impact of copper from ACQ- (Ammonical copper
quaternary) treated wood was evaluated in a wetland boardwalk study (US-FFS
2000
). Elevated levels of copper were detected in rainwater, soil, and sediment
collected adjacent to sites with treated wood. The rainwater collection indicated that
the release of copper peaked 6 months after construction, reaching average release
rates of 35
g per cm
2
/in. of rain (US-FFS
2000
). Much lower average release rates
(approximately 5
ʼ
g/cm
2
/in. of rain) were observed 11.5 months after construction.
The relatively high release of copper during the fi rst 6 months of this study was
refl ected in the concentrations of copper detected in the soil; geometric mean soil
concentrations were elevated by approximately 169 kg/min (fl ow rate) directly
under the edge of the boardwalk. Copper mobility was greater in the sediment than
in the soil. Despite the accumulation of copper detected in the environment, no
signifi cant impact was detected on the quantity or diversity of aquatic insects at the
site (Lebow
2004
). A wide description and characteristics of ACQ is available at
Treatedwood.com (
2012
).
ʼ
17.2.4
AAC (Alkyl Ammonium Compounds) and BAAC
(Quaternary Ammonium Borate)
ACC is also a component of ACQ (Ibach
1999
), and its effi ciency as a preservative
depends on the type of tree species on which it is applied and the specifi c chemical
formulation (Hedley et al.
1982
). Although leaching inevitably occurs, it can be
greatly reduced with proper chemical fi xation (Ohio-DOA
2003
). Due to its apparent
low toxicity and biodegradability, AAC is still used in China and other countries
(Huai'An Huize
2013
).
Considering the low environmental impact of AC and ACQ, both are commonly
used in Japan, particularly in the treatment of wooden bridges (Shuichi et al.
2001
).
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