REYKJAVÍK, ICELAND AUGUST 11-13, 2008 - Veðurstofa Íslands

Table 4. Efficiency in treating stormwater in urban areas in %, Åstebøl et al.
(2005).
Pollutant Treatment efficiency Pollutant Treatment efficiency
Phosphorus (P) 65 Chromium (Cr) 70
Nitrogen (N) 35 Nickel (Ni) 70
Lead (Pb) 70 Mercury (Hg) 70
Copper (CU) 70 Suspended solid (SS) 85
Zink (ZN) 70 Oil 80
Cadmium (Cd) 70 PAH 85
The calculations show the discharge of stormwater pollutants from
urbanized areas after implementation of pollutant reducing measures and the
resulting average concentration in Lake Urriðavatn. The calculations show
therefore the expected increase in average concentrations in Lake Urriðavatn,
exceeding today concentration after development.
The calculations of increase in concentration are based on a model for
phosphorus loadings developed at Norwegian Institute of Water Research
(NIVA), Berge (1987). The model is based on empiric data from a large
number of shallow lakes. The model is also used to calculate the other
pollutants except nitrogen. Metals and PAH have higher natural retention in
lakes than phosphorus. The model will therefore overestimate the
concentrations in the lake for those pollutants. For nitrogen there is only
calculated dilution in the lake. Formula used to calculate the concentration in
the lake is:
1) (P)i = (P)inn/Q where: (P)I = average concentration on P in the inlet(ugP/l)
(P)inn = annual discharge of phosphorous (kgP/year)
2) (P)$ = 0,436 x (P)I x Tw -0.16 where: (P)$ = average concentration of
phosphorous in the lake (ugP/l).
Tw = lag time (year) = V (m3)/Q (m3/year)
Table 5. Environmental limitations regarding heavy metals causing biological
effects. Umhverfismálaráðuneyti Íslands (1999).
Metals (conc.) I (µg/l) II (µg/l) III (µg/l) IV (µg/l) V (µg/l)
Copper (Cu) 45
Zink (Zn) 300
Cadmium (Cd) 1.5
Lead (Pb) 15
Chromium (Cr) 75
Nickel (Ni) 225
Arsenic (Ar) 75
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