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THE INFLUENCE OF PH ON THE MOBILITY OF HEAVY METALS IN AGRICULTURAL SOIL FROM IALOMITA AREA

Luciana Vrancuta

Abstract

The aim of the study was to assess the influence of the soil pH, from ploughed soil layer from the Ialomita region, on the mobility of heavy metals (Cadmium, Copper, Manganese and Zinc), estimated by heavy metals extractable contents in DTPA-TEA-CaCl2. Because heavy metals exist in soil in different solid-phase forms that vary in terms of availability, total content of metals in soil are poor indicators of toxicity. In order to assess a risk of heavy metal pollution in soil should consider both mobile and availability fractions of pollutants. The soil samples were collected from sites which are located in the proximity of the most important industrial centers from the region and where the agriculture land is owned by small landowners in the neighboring villages who practice subsistence agriculture. The samples were taken from cultivated soils where dominated crops were maize and the soil pH values varied between 7.2 and 8.1. Areas of interest were determined using geomatic techniques, remote sensing and geographic information systems. The results revealed that mobility of Cd, Cu and Zn in soil depends on soil pH. The decrease of the pH values (from the maxim value of 8.1 to the minim value of 7.2) lead to increasing of the contents of mobile Cd (from 0.030 mg/kg to the 0.070 mg/kg), Cu (from 1.56 mg/kg to 4.69 mg/kg) and Zn (from 2.67 mg/kg to 8.23 mg/kg). The value of soil pH is an important characteristic for soil fertility and plant growth, and is one of the most important factors determining the activity of heavy metals in soil. Therefore, for these analyze, the soil pH interval proper for the availability of heavy metals (Cd, Cu, Mn and Zn) in soils is comprised between 7.16-7.21. Average values of the pseudo-total and mobile contents were used to estimate the relative solubility of metals (percent of pseudo-total concentration in soil) ? RS (%), as ratio between DTPA-TEA-CaCl2 extractable content of heavy metals in soil and pseudo-total metal content in soil. RS (%) for Cd, Cu and Zn is influenced by the variation of soil pH. In the case of Mn, there have not been noticed any substantial changes of RS following the rise in pH levels of the soil.

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DOI resolver: doi.org/10.5593/sgem2019/3.2/s13.068

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