This work is aimed to present the forms of lead in soil taking in the account its' acid and basic conditions. Different forms of heavy metals in soil could have a negative impact on plants and human beings, particularly if they present in higher concentrations than maximum allowed. Various soil conditions cause the different bioavailability of some forms of heavy metals to plants. This paper considers the bioavailability of lead to some plants in acid and basic soil conditions using computer software and comparing results to those obtained by experiment in the laboratory. Obtained results in this work could be used to predict the behavior of heavy metals in different soil conditions, particularly those that are present in very small concentrations, such as lead, cadmium, etc.

Agricultural activities directly infl uence the quality of water systems. Investigations showed that application of various agro-technical measures results with the pollution of water streams with heavy metals and other polluters. Increased concentrations of heavy metals result with intake of heavy metals and their transfer to food chains, and for that reason it is necessary to monitor the content of heavy metals regularly. Broad investigations of bio-geochemical cycling of heavy metals in the region of Lake Modrac were performed with combined methodology of determination of heavy metal traces with the estimation of bioavailability, based on the determination of complexing constants for Pb, Cu, Cd and Zn. Monitoring was performed at the locations in the vicinity of agricultural soil. Th e results achieved showed that the content of organic matter in water streams presents the key factor that determines the extent of bioavailability of heavy metal traces in water systems.

Milk is a food of high biological value and as part of a properly balanced diet plays a major role in human health. The composition of milk varies depending on the origin and the animals from which it originates. Disruption of milk stability usually is the result of changes in the concentration of Ca 2+ ions. Increasing stability in this case can be achieved by the addition of phosphate, polyphosphate or citrate of an alkali metal or by removal of calcium by ion exchangers. The present salts and ions directly has effects on the physical properties of the milk, such as osmotic pressure, the freezing point and boiling point, conductivity, titratable acidity, pH, and buffering capacity of milk. Ca 2+ ions influence on the dispersity of the casein and on the amount of bound water directly influence the density and viscosity of milk. Milk acidity, density, viscosity, surface tension, refractive index, electrical conductivity are important physical - chemical indicators of the quality of the milk. The aim of this study is to examine the effect of heat treatment on the physical-chemical properties of the milk and the calcium content on which depend the quality of the final product, and to establish the correlation between certain parameters. For this research, different milk samples from different geographical regions of the Tuzla Canton were analyzed. Due to the extreme importance of the milk and dairy products in the diet of all age groups of people, monitoring of the physical-chemical properties of milk and the calcium content is of particular importance.