EFFECT OF LEAD AND HYDROGEN ON THE ALTERATION OF SELECTED CHEMICAL PROPERTIES OF ARABLE SOILS

摘要

The concept of this study was based on the evaluation of the impact of lead (Pb) and hydrogen protons (H~+) on selected chemical characteristics of two arable soils: Light loamy sand (No. 1); and Silty soil (No. 2). The targeted chemical alterations of the soils concerned pH changes, water soluble forms of Pb and displaced alkaline cations as induced by Pb and H incorporation. Preliminarily, the amounts of exchangeable alkaline cations (ExAC = Ca_(ex)+ Mg_(ex)+K_(ex)+Na_(ex)) were extracted by using 1 mole CH_3COONH_4 dm~(-3), pH 7.0 and these amounts were used for calculating amounts of Pb and H to be incorporated as follows: lead as Pb(NO_3)_2 and hydrogen in the form of HCl at spiking rates corresponding to 0, 5, 10, 30, 60, 100, 150, 200, 300, 400, 500 and 1000% of ExAC. Lead and H-spiked soils were incubated for 16 weeks at 18°℃ and kept at 75-85% WHC (water holding capacity). Amounts of Pb and H incorporated into soils were different and varied by a factor of 1.36 between soils No. 1 and No. 2 in the case of Pb and 1.47 for H~+, respectively. Lead and hydrogen effects on soil chemical properties can be first observed throughout pH changes, which were more pronounced for H treatments as compared to Pb ones. The direct impact of Pb and H over the soils buffering capacities was decidedly acute for H. Water extractable Ca for Pb and H-spiked soils revealed that the amounts of Ca displaced at Pb spiking rates of 1000% ExAC were 17 and 36 times higher than the control, respectively for soils No. 1 (Light loamy sand) and No. 2 (Silty soil), whereas for H, the impact was much more higher and represented 31 and 50 times, respectively. The joint impact of both elements, i.e., Pb contamination and simultaneous acidification are the core agroenvironmen-tal concern.