Forecasting heavy metal pollution of soils in an administrative district of Belarus

Abstract

We tested the dynamical model of migration based on balance equations, for a predictive assessment of soil pollution by heavy metals: lead, cadmium, zinc and copper, at the level of an administrative district. As the main input components of the balance, we took into account the flows of metals caused by atmospheric depositions, weathering of parent materials and input with fertilizers (on agricultural lands); the expenditure part of the balance is described by flows of metals with the infiltration subsurface flow and consumption for buildup of the vegetation biomass or the removal with the harvest. It is found that given the continuation of the existing level of loads (scenario 1), for the calculated period (40 years) in the soils of natural ecosystems the concentrations of the four elements can decrease substantially or remain at the previous level. Changes will make up 0.2–0.8% for lead, 0.5–5 for cadmium, 0.8–4 for copper, and 0.3–1.5% for zinc of their total content levels in the soil. In the soils of agricultural lands, provided that the aforementioned conditions are observed, the total content of lead will increase by 5–6.5%, cadmium by 1–1.2%, copper by 2.1–3, and zinc by 12.5–16.5%. It is determined that with an increase in the flow of atmospheric deposition (scenario 2), for 40 years the soils of natural ecosystems will retain a minor negative balance of cadmium (0.001–0.004 mg/kg of the soil); for lead the negative balance in forest ecosystems will change to a minor positive balance (0.09–0.18 mg/kg of the soil), and the removal of zinc and copper will retain its previous level. In the soils of agricultural lands, with a simultaneous increase of the rates of application of organic fertilizers by 20%, the total concentrations of lead for the calculated period can increase by 7.1–9.6%, cadmium by 7–8.5, copper by 5.2–7.8, and zinc by 18.2–24.2%.