Seasonal changes oi leachate production and water-flux-dependent leachate quality from two test cells containing 4,000 t of refuse each were investigated. Pronounced seasonal dependence of the leachate production appeared three years after the final covering of the test cells. With seasonal dependent production, a number of leachate parameters showed water-Aux-dependent trends. The dependence was quantified with results from a five-month-long sampling program using correlation coefficients. The magnitude of changes appeared to indicate alternation between methanogenic and acidogenic phases. Reasons for the la-ge variations observed were sought with the assumption that different biochemical conditions dominated in different locations in the test cells at the same time, Hypothetical configurations with various biochemical conditions In different locations were constructed and evaluated, Results from a gas extraction program, measurements of leachate production rates, and analyses of leachate and solid waste samples were used to evaluate the configurations, The evaluation identified two mechanisms as the origins of the observed phenomena: (1) biological filtration in the drainage layer; and (2) annual successive wetting of the waste material.
