Evaluation of the Effect of Land Use and Soil Properies on the Amount of Lead in Shiraz Urban Watershed Soils, Using Geostatistics and Digital Soil Mapping

Urbanization has led to environmental challenges; one of these challenges is heavy metal contamination in which is a serious concern for the public health and health of watershed residents issues. One of the heavy metals that play a major role in soil pollution in urban ecosystems is Lead (Pb). Pb has been used by humans for a long time, and in recent decades, leaded gasoline is one of the main sources of this pollutant in urban watersheds. The use of digital soil mapping using the functions available in geostatistics has changed the zoning of soil pollution compared to the old methods and can lead to the optimal management of soil pollution while land use can also have a great impact on this management. The aim of this research is to determine the amount of Pb heavy metal in soil and its relationship with land use.

The study area was Shiraz urban watershed with an area of ​​41133 hectares, as a part of the Maharloo lake watershed, located in the central part of Shiraz township, Fars province in the south of Iran. Soil moisture and temperature regims of study area are xeric and thermic respectively. The studied land uses were bare lands, urban parks, gardens and mountain range lands In order to determine the physical and chemical properties of the soil, 30 soil samples were taken from the depth of 0 to 20 cm from each land use. Geographic information system (GIS) and spherical and exponential variogram geostatistical models were used to produce digital maps. Kriging method was also used to estimate the physical and chemical properties, and the amount of Pb.

Based on the results of this research, the difference in soil chemical properties such as reaction, equivalent calcium carbonate and the amount of organic matter in different uses was significant. Also, the amount of cation exchange capacity and lead pollution was significant at the level of 0.01. The results of this research showed that in urban watershed soils of Shiraz, the amount of Pb was influenced by some chemical characteristics of the soil such as organic matter and cation exchange capacity. In the studied area in different land uses, the trend of Pb contamination was as follows: mountain range lands < gardens < urban parks < bare lands.

Conclusions and suggestions:

The results of current research showed that different land uses can affect the amount of Pb. Considering the problem of soil pollution in urban watersheds and the important effect of land use on its amout, it is suggested to carry out research and urban development projects for detailed investigations of land use and its relationship with other environmental characteristics, including soil pollution. It is also suggested to carry out more local and thematic researches in urban ecosystems on the effect of various types of plant species on the amount of heavy metals in the examined soil, so that by planting that type of vegetation, soil decontamination can be helped.