An-Najah Staff

Harmful effects of acid rain have been considered a serious problem. In this paper we have studied the ability of several common types of leaves to mitigate the effect of acid rain via the ability of these leaves to act as buffers in water.

The pH of leaf suspensions of cypress, pine, oak, cinchona and ficus leaves has been determined and its variation with time has been followed. The buffer capacities for these leaf suspensions have also been determined at several times over a long period of time. The effect of dilution on this buffer capacity has been studied. The speeds at which the various leaf suspensions adjust their pH value when disturbed have been studied.

The capability of the various leaves studied here to act as a buffer can be arranged in the order:

Uptake of cadmium from aqueous solutions by beech leaves has been studied. The effect of several factors on both rate and amount of this uptake has been studied. These factors include concentration of leaves, concentration of cadmium, pH, competing ions and drying leaves. The pattern of the curves showing the loss of cadmium from solution has been explained. Applicability of the Freündlich adsorption isotherm on the present results has been examined and the parameters of this isotherm have been calculated. The order of reaction between cadmium ions and beech leaves has been determined and a mechanism for this reaction has been suggested.

Decaying leaves have been proven capable of partially removing lead from polluted water. Several factors affecting the removal process have been studied. These include the concentration of lead ions, concentration of leaves, drying leaves, degree of crushing of leaves, leaf extracts, pH, agitation and presence of competing and of complexing agents. The relative capability of some common types of leaves for the removal of lead from water has been studied.
The release of lead from leaves saturated with lead ions has been studied under the effect of varying pH, addition of competing ions and the addition of complexing agents.
The results of the present work indicate that the interaction between lead ions and leaves is mainly an adsorption process and fit the Freundlich adsorption isotherm whose parameters have also been calculated. A fractional order of reaction (0.7) has been determined for the reaction between lead ions and leaves using two methods of evaluation. A mechanism in which film diffusion being the most probable limiting step has been suggested.

Several factors affecting the growth and the metal uptake of pepper plants treated with cadmium solutions have been studied. These include concentration of cadmium, type of treatment, type of soil, plant species, and some properties of solutions used for treatment such as acidity, degree of salinity and temperature.
Cadmium had an obvious effect on the growth of pepper plants. Foliar‐treated plants were affected more than root‐treated plants. The least degree of growth‐inhibition and of cadmium uptake was found in plants grown in soils with high organic matter content. Various species of pepper plants acted very differently towards cadmium treatment. Both growth‐inhibition and cadmium uptake was increased in plants treated with acidic, saline and hot solutions.