Antioxidant capacity in urban soils

Abstract

The quality of soils in 31 urban green areas in Pisa was assessed in terms their soil antioxidant systems by measuring antioxidant capacity (TEAC) and phenol substances, soil basal respiration, community level physiological profile (CLPP), expressed as average well color development (AWCD), community metabolic diversity (CMD), the Shannon–Weaver index (H), and soil enzyme activities. The urban results were compared to an extra-urban control area (near the S. Rossore-Migliarino-Massaciuccoli Natural Park). The soils of the greenspaces of Pisa city were mostly sandy, subalkaline, lightly calcareous, with a rather high (mean of 3.27 ± 1.24 gC 100 g−1 dry soil) and variable (1.32–7.57 gC 100 g−1 dry soil) organic matter content. There were little differences in the functional diversity (AWCD) of soil microbial communities. Dehydrogenase, catalase, alkaline phosphatase, B-glucosidase and lipase showed little variability among soils while arylsulphatase, protease and urease activities varied within a fairly wide range of values. Values of the alkali-and water-soluble TEAC of urban soils varied within quite large ranges (2.53–11.45 mM g−1 soil and 0.11–2.91 mM g−1 dry soil, respectively) and were generally higher than those of control. TEAC and phenol substances, both in alkaline and water extracts, were closely correlated (r > 0.850, P ≤ 0.01) and were also positively correlated with soil organic C, AWCD, CMD and, H. With the exception of dehydrogenase, the soil antioxidant system showed positive correlations with the enzymatic activities and soil basal respiration. The antioxidant system and soil basal respiration can be considered useful indicators of the soil biological status and soil quality in the examined urban soils