Influence of latitudinal zonality on some chemical properties of urban soils

In this study, the database of properties of urban soils was created to assess the influence of zonal features of natural factors of soils, situated in urban areas. The database contains more than 135 cities located in different natural zones all over the world from the Arctic tundra to equatorial tropics. A comparison based on two features: soil organic carbon (SOC) and water-extracted pH. A number of statistical indicators such as average value, minimum and maximum values, standard deviation, variation, correlation coefficients were calculated for each zone and feature. The analysis of the results showed that the variation in carbon content values in urban soils is significantly higher in comparison with background soils. This fact can be explained by the influence of anthropogenic factor on the processes of organic matter reduction and accumulation in the soil. At the same time the average carbon content in urban soils in most cases is much higher than in natural soil and in general, there is a trend: the difference between SOC in urban and natural soils increases to the north and gradually decreases to the south. However, a comparative analysis of soil-bioclimatic zones neither in climatic nor in facial series there is no trend can be observed. This means that the characteristics of the SOC of urban soils are not zonal and the observed trend can be explained by the intensity of human impact. The comparison of the average values of pH in the urban and natural has not shown any statistically significant difference. However the comparison of maximum values of water-extracted pH for the groups showed a clear pattern in northern hemisphere: increasing of the alkalinity in the humid and semihumid areas from the one side, and acidification in the more southern arid and semi-arid areas from the other side, that may indicate the presence of zonal trend