This article reports on a study whose aim was to evaluate the impact of snow removal salts on urban soil properties and the health of roadside trees. The evaluation was done by chemical analyses of soil samples and plant matter combined with toxicity testing, performed with a Protoxkit F, a protozoan microbiotest. Samples were collected at 45 locations on three main roads in the town of Opole (Poland). The roads differed in the snow removal technology and amount of chemical substances (mostly NaCl) used on them during the winter. The study showed that when soil was exposed to a high level of NaCl, it tended to be more alkaline and also exhibited increased content of Na(+) and Cl(-). The toxic effects of the soil extract on protozoa appeared at 26.0 mg Na(+)/100 g soil dry mass (s.d.m.) and 12.0 mg Cl(-)/100 g s.d.m., whereas salt injury symptoms (chlorosis and necrosis of the edge of leaf blades) appeared at 13.2 mg Na(+)/100 g s.d.m. and 3.9 mg Cl(-)/100 g s.d.m., becoming more severe at 26.0 mg Na(+)/100 g s.d.m. and 12.0 mg Cl(-)/100 g s.d.m. because of extensive necrosis and defoliation. The lysimetric experiment, which was used to test soil samples collected from the city park area, indicated that salt plays a significant role in the pollution of soil in urban areas, with the least toxic salt being CaCl(2).
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