Agriculture Reference
In-Depth Information
mechanisms that apply have been widely documented elsewhere. In the next sections these
processes and how they can be measured and modeled will be presented and we suggest
how this knowledge can be used in planning of management strategies. The focus of this
chapter is on processes near the surface and in the unsaturated zone. In the conclusions we
discuss challenges still unresolved.
2. De-icing chemicals
There are two types of de-icing chemicals; non-degradable inorganic salts and degradable
organic compounds. Table 1 shows de-icing chemicals and their associated chemical oxygen
demand in the case of complete degradation. For the inorganic salts, the only means of
reduction is dilution.
Chemical oxygen
demand (COD)
1)
Group
Name
Chemical formula
Inorganic
salts
Sodium Chloride
NaCl
0
Magnesium Chloride
MgCl
2
0
Potassium Chloride
KCl
0
Organic salts
Potassium Formate
KCOOH
0.35
Sodium Formate
NaCOOH
0.35
Calcium Magnesium
Acetate
CaMg(CH
3
COO)
4
4.28
Sodium Magnesium
Acetate
NaMg(CH
3
COO)
3
3.21
Potassium Acetate
KCH
3
COO
1.07
Sodium Acetate
NaCH
3
COO
1.07
Others
Propylene Glycol
CH
3
CHOCH
2
OH
1.69
Ethylene Glycol
HOCH
2
CH
2
OH
1.29
Diethylene Glycol
(HOCH
2
CH
2
)
2
O
Fructose/glucose/Sodi
um Chloride
C
6
H
12
O
6
/ C
6
H
12
O
6
/NaCl
Urea (H
2
N)
2
CO 2.13
2)
Table 1. Most commonly used de-icing chemicals.
1)
Chemical oxygen demand (COD) mg/l
based on standard stoichiometrical calculations assuming complete degradation
2)
assuming
reduction to NH
4
.
2.1 Inorganic salts
Some examples of total use of salts on Norwegian national roads per winter season are
given in Table 2. The average salt consumption in 2009/2010 was 14 tons per km high
priority roads.
Negative consequences of increased salt concentration along roads have been documented
(e.g. Nystén and Suokko, 1998; Oberts et al., 2000). Howard & Maier (2007) simulated
increased NaCl concentrations in groundwater due to urbanisation near Lake Ontario.
According to their Visual Modflow simulations, maximum concentrations of 5000 mg
