Environmental Engineering Reference
In-Depth Information
high cost of wastewater and storm runoff treatment and pollution concerns.
Therefore, in 1997, the Japanese government requested companies to voluntarily stop
producing this preservative, and by 2003, production of CCA-treated wood had stopped
almost completely (Hata et al.
2006
; Japan Wood Protection Association
2011
).
As a result, other wood preservatives such as copper-based (CuAZ and ACQ) and
non-copper based chemicals (AAC and BAAC) became popular. By 2005, most
treated wooden planks for ground use (sill), exterior use and other materials were
treated with these chemical compounds (Japan Wood Protection Association
2011
).
Lebkowska et al. (
2003
) reported that waterborne chemicals could have a
negative impact on surface water and groundwater quality. Toxicity tests including
luminescent bacteria tests, algae growth inhibition tests and crustacean and fi sh lethal
tests were performed to determine the presence of tebuconazole, propiconazole,
3-iodo-2-propynyl butylcarbamate, cyfl uthrin, and alkyd resin. The results showed
that wood preservatives leached from wood samples by 10 % within 1 month of
exposition when impregnated with chemicals at concentrations of 18,060 mg/L.
A fi eld study done in Canada by Zagury et al. (
2003
) showed that concentrations
of CCA chemicals from treated utility poles are present in soil and groundwater.
Copper concentrations in the soil were larger than arsenic and chromium; the highest
concentrations were found to be immediately adjacent, i.e. copper 1,460 ± 677 mg kg
−1
,
arsenic 410 ± 150 mg kg
−1
, and chromium 287 ± 32 mg kg
−1
. These concentrations
decreased with distance reaching almost background levels at 0.1 m for chromium,
and 0.5 m for copper and arsenic. On the other hand, the concentrations of copper
and chromium in ground water showed to be less than 1.000 mg L
−1
and less than
0.05 mg L
−1
, respectively. In the case of chromium Cr(VI), the concentration was
less than 0.02 mg L
−1
. The same authors also concluded that soil contamination is
more strongly correlated to soil type rather than the pole age; leaching is higher in
low-organic and ion-clay soil types.
Other authors have also shown that concentrations of chemicals in soil from
treated poles become reduced as distance from the sources increases (Morrell and
Huffman
2004
; Cooper and Ung
1997
; Hingston et al.
2001
; Graham and Scott
2013
).
Robinson et al. (
2004
), found that CCA-treated poles in vineyards located in the
Marlborough Region (New Zealand) leached, which in some cases exceeded
acceptable levels for chromium and arsenic in agricultural soils set by the Australian
National Environment Protection Council's Levels for Soil and Groundwater
(NEPC
1999
). Up to 25 % of the samples exceeded the guideline levels in the soil
for arsenic and 10 % exceeded levels for chromium (100 mg/kg); in urban areas,
20 mg/kg of arsenic or chromium is considered to represent an environmental
concern. Moreover, the author highlights the fact that under certain circumstances
there may be a risk of arsenic leaching into groundwater, although further research
is necessary to ascertain this possibility.
The main impacts of leaching into soil seem to be localized. Townsend et al.
(
2001
) found that the highest concentrations of arsenic, chromium, and copper were
found within 5 cm (laterally) of the CCA-treated timber, with the metal-to-soil
levels decreasing with distance. The highest median concentrations were found in
the upper 20 cm of soil.
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