The effect of sewage sludge on the growth and species composition of the sward and the content of heavy metals in plants and urban soil

摘要

The effect of sewage sludge on the growth and species composition of the sward and the content of heavy metals in plants and urban soil. The determination of the sludge fertilising infl uence for the growth and composition of the urban grasslands’ swards and heavy metals concentration in above-ground parts of the plants was the aim of the study. The study was conducted on four research plots along the main roads in Bia?ystok. The plots were seeded with two mixtures of lawn grasses (Eko and Roadside) and three doses of sludge were applied: 0 (control), 7.5 and 15 kg/m2. The study also included the determination of concentrations of Cd, Cr, Cu, Pb and Zn in soil and in the above-ground parts of lawn grasses and selected physical and chemical properties of soils fertilized with different doses of sludge. The dose of 7.5 kg/m2 increased the plant dry matter on average by 53%, the dose of 15 kg/m2 - on average by 90%. The largest effect of fertilization was found for lightest soil. Under these conditions, grass dry matter fertilized with 7.5 kg/m2 sludge was almost doubled, and fertilized with the dose of 15 kg/m2 was almost three times larger than in not fertilized areas. Perennial ryegrass (Lolium perenne L.) was the dominant species in the sward. Perennial ryegrass constituted on average 71% of all grass species in the areas fertilized with sewage sludge in the dose of 7.5 kg/m2, while on the areas fertilized with 15 kg/m2 - about 81%, and on not fertilized ones - 50% on average. Bioconcentration factor in the study allowed for estimating the plants ability to collect heavy metals present in the soil. Based on these results, it was found that the rate of bioconcentration of Cd, Cr, Cu and Pb was the highest in August, which may indicate the ease of downloading these metals by plants, particularly high mobility of metals during this period, and lower in October and June