Soil pH, electrical conductivity values and roadside leaf sodium concentration at three sites in central Poland

Sodium chloride is the most often used chemical to malt ice and snow on the roads and has negative effects on the roadside environment. The main is soil erosion, changes in mineral composition of the soil and negative impact of the growth of trees. This study described differences in electrical conductivity values in soil with increasing distance from the road. Leaf sodium contents in roadside trees have been determined to assess the uptake of this element by plants. Soil samples for EC (electrical conductivity) determination were collected in the spring and autumn 2009 and 2010 from the roadside environment every 1m started at 2m to 11m from the road edge, and every year at the same place. Leaf sample for sodium content were collected in the end of August 2009 and 2010 from Acer platanoides, Acer pseudoplatanus, Tilia cordata and Fraxinus excelsior, every year at the same trees. For comparison, samples of the leaves were also collected from trees grown in the park in Skierniewice, were no salting during the winters is provided. The composition of roadside salinity varies, mostly according to the roads, but generally, at the studied roads, the EC of the soil solution followed an exponential-like decrease with distance from the road curb, reaching background levels at 7 to 10mdistance. The exponential-like EC decrease seems to be strongly slowed at 5mdistance from the road curb. Very important information is that the level of EC in the upper layer of the soil during the season decreases rapidly. Trees grown on the roadside accumulated considerable amount of sodium ions in their leaves helping to neutralize the excess of sodium in soil. However, this had negative effect on their growth. Acer platanoides and Tilia corada uptake the greatest amount of sodium ions in comparison to the same species grown in the park. Less amount of sodium ion were noted in the leaf sample of Acer peseudoplatanus and Fraxinus excelsior. Soil salinity near the studied roads had any visual effect on the trees.

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