Agriculture Reference
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NaCl/l were predicted near roads with an annual use of 20-250 tons NaCl per km road
(dual to multiple lane motorways), and that stabilisation occurred after 700 years. The
consequences for the environment can be groundwater of insufficient quality for drinking
water. Direct or indirect release to lakes can give hypolimnetic conditions and prevention of
biannual full circulation with reduced oxygen levels (Bækken et al., 2006). Release into
creeks can give negative effects to biologic systems (Meland, 2010).
Winter season NaCl (tons) Sand(tons)
2005/2006 166,000 435,000
2006/2007 137,000 386,000
2007/2008 160,000 484,000
2008/2009 200,000 443,000
2009/2010 201,000 417,000
Table 2. Total consumption of road salts and sand on Norwegian national roads (the
Norwegian public roads administration, www.vegvesenet.no).
2.2 Organic de-icing chemicals
Organic salts such as Potassium Formate, Potassium Acetate and Calcium Magnesium
Acetate are used on runways and some roads (US EPA, Amundsen et al., 2008). These
chemicals are more costly than the inorganic salts, but are used because they are degradable
and less corrosive. Normally these chemicals are also released directly into the ground next
to the road or runways.
Propylene glycol, Ethylene glycol and Diethylene glycol are the main constituents of de-
icing chemicals used to keep planes and other vehicle surfaces free of ice. The de-icing at
airport takes place on special de-icing platforms which normally collect the surplus
chemicals with subsequent re-cycling or treatment in treatment plants (Øvstedal & Wejden,
2007). Estimations from Oslo airport, Gardermoen, suggest that 80% is collected at the de-
icing platforms, about 10% is released to the local environment at take-off, and 10% leaves
with the planes (Øvstedal & Wejden, 2007). Still many airports in the world do not collect
the de-icing chemicals and they are released into the local environment (US EPA).
The treatment of water contaminated with organic de-icing chemicals is usually based on in-
situ or off-situ aerobic and/or anaerobic degradation. The tested techniques vary from
constructed wetlands, reed beds, constructed soil filters (Roseth and Bjørnstad, 1998; Roseth
et al., 1998) natural soil profiles (French et al., 2001, Jaesche et al., 2006) to more conventional
wastewater treatment plants (Rusten et al., 1999). The chemicals are supplied during the
frozen season which may vary geographically but falls roughly between October to April.
The objective of using de-icing chemicals is to reduce the freezing point of water, hence
water will remain in a fluid state below 0C and can infiltrate into the ground as long as
there are open pores. Water containing de-icing chemicals may therefore infiltrate the
ground prior to the main snow melting period. The preferential melt-out of de-icing
chemicals was shown by French & van der Zee (1999) as also shown for other chemicals
stored in snow (Johannesen and Henriksen, 1978). Although the organic de-icing chemicals
are degradable and the top soil hosts large amounts of bacteria and fungi, the temperatures
are negative or close to zero, and there is little degradation during this period. Half lives of
Propylene Glycol and Acetate under field conditions throughout melting period and into
the summer ranged between 15-46 days (French et al., 2001). Degradation rates of other
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