Environmental Engineering Reference
In-Depth Information
As a result, decreased amounts of de-icing salts were applied on streets and decreased
accumulation of ions occurred in street soil. Besides, Cl
−
as anions are more leach-
able from the soil and a more rapid decrease compared to Na
+
occurred. Cl
−
usually
follow the water and do not take part in chemical reactions, while Na
+
participate
in chemical processes in the soil and are to a great extent retained in the upper part
of the soil profile
[16]
. Thereby summer soil sampling results did not show the real
situation with Na and Cl
−
pollution before the vegetation season had started.
A different situation was stated with K (Fig.
2
). In the vast majority of sampling
sites in 2005 the concentrations of K in the soil were lower compared to the park.
It was consistent with other studies in urban areas where soil contained construction
and demolition waste
[13, 17]
. The decrease of K concentrations was stated almost
for all studied sites from March to July, mainly due to K uptake by plants. Better K
status in soil samples was found in the vegetation season of 2007. In most of the
studied street sites, the level of K was the same as in the park, or slightly elevated.
It showed a tendency to increase from June to August, probably due to application of
K containing fertilizers. In general, the concentrations of K in soil samples during 2005
and 2007 ranged from 85.10 ± 13.38 mg/kg (Site 5) to 318.90 ± 46.22 mg/kg (Site 8).
When comparing results from 2 years, the level of K in street soil samples was
statistically significant higher in June 2007, in contrast to Na. Less amounts of Na
in the street soil, which could displace K in the exchange sites in the soil, resulted in
an improved K/Na ratio in 2007. In total, the K/Na ratio in the soil samples from the
park ranged from 4.15 to 13.48. In the street soils, the K/Na ratio were 0.13-6.45
for healthy limes, for medium damaged limes up to 4.82, and for damaged trees
0.07-2.66. It means that the small K/Na ratio in street soil samples had additive
harmful impact on the tree status.
Plants
. In general, the concentrations of Na and Cl
−
in lime leaves increased
during the summer of 2005 and 2007, showing opposite trends as those in the soil.
The K content in lime leaves decreased (Fig.
3
), thereby harmfully affected the tree
status. The analysis of plant material showed that the soil salinity induced increased
Na and Cl
−
concentrations in lime leaves in sites with higher soil salinity during
2005 and 2007. During the vegetation seasons, Na ranged from 0.01% in June to
1.93% in August, which was up to 48 times higher than values from the park. The Cl
−
concentrations in the leaves from the vast majority of street sites were significantly
higher than those of the park site at all sampling times, as well as higher than the
Na concentrations in lime leaves. The highest Cl
−
concentrations, found in Site 4 in
July (3%) and August (2.90%), were more than 25 times above the background
level. As the lime tree decayed in autumn, this concentration could be characterized
as especially toxic to lime trees. In general, concentrations of Cl
−
in leaves higher
than 2% were harmful to lime trees, causing tree decay.
The lowest concentrations of Na and Cl
-
in lime leaves were found in sites situated
about 3.5 m from the carriageway (sites: 8, 10, 11, 13, 15), as well as sites 12 and 14.
These limes were characterized as healthy.
There were no significant correlation between the element concentrations in soil
and leaves, except the concentrations of Na in July 2005 (r = 0.39; n = 30). The results
showed negative medium close correlation between the level of K in soil of
