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:

Decaying leaves have been found capable of resisting the effects of acid rain via their ability to buffer water.

In a previous study the buffering action of five common types of leaves (cypress, oak, pine, cinchona and ficus) was investigated. In the present study the effects of several factors on the buffering ability of these leaves have been studied. These factors are acidity, presence of foreign ions, concentration of leaves and location.

The studied factors have been found not to affect the pattern of variation of pH of the leaf suspensions with time but to affect the pH value reached by these suspensions.

Ficus leaves have shown a distinct copability of neutralizing acidic waters.

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.