Izabela Anna Tałałaj
The aim of this paper was to determine the release of selected heavy metal from waste to leachate on active municipal landfill in north-eastern Poland. The metal mass-balance was made on the basis of measured metal levels in leachate and literature values for metal contents in municipal waste. Leachate samples were collected four times a year (quarterly). The samples were analyzed for: pH, Pb, Cu, Zn, Cr, Hg, and Cd. Additionally the waste quantity and leachate volume were recorded on analyzed landfill. The waste deposited in the analyzed landfill had the largest share of zinc, the weight of which in 2011 was estimated at 26 193 kg. Level of lead, chromium and copper were similar and ranged between 4000–5000 kg. Cadmium and mercury were deposited in the smallest amount. Concentration of heavy metals in leachate from the landfill does not exceed 0.2 mg/dm3, except for zinc, for which the value of 0.38 mg/dm3 was recorded in spring 2011. Metals concentrations in leachate can be ranged as follows: Hg <Cd <Cr <Pb <Cu <Zn. Release of analyzed heavy metals was calculated as the ratio of the metal-mass in the leachate to the metal-mass in the waste. The cadmium was the metal with the highest degree of release (0.35%), which was result of the very high cadmium concentration in spring 2011. Landfill conditions also promote the release of mercury. The release rate of the other metals was at a similar level (0.015–0.075%). Low concentrations of heavy metals in the leachate, and thus – low rate of release may be due to the formation of stable organic metal complexes. Precipitation of metals in the form of sulfides, and in the case of chromium – in the form of hydroxides, is also very important. The higher pollutant loads are released in the spring. At this time 94% of the annual loads of lead is released, 75% – of the annual loads of copper, 75% – zinc, and 96% – cadmium. This is due to the lower pH of leachate in spring. The degree of metal release can by also increased due to temporary oxidation of metal sulfides to soluble sulfates. The winter season promotes the release of mercury and chromium – at this time the 82% of the annual load of mercury is released and 54% of chromium load. Probably it is the result of reducing conditions prevailing in the winter time and the high value of pH, which affecting the growth of the chromium mobility. Conducted investigations have shown that the release of heavy metals from waste to leachate is not high and is limited by the processes favoring metal immobilization such as sorption, precipitation, and a higher value of pH. In addition, the waste contains organic matter, which at neutral to higher pH have high sorption capacity favoring metal immobilization.
składowisko odpadów komunalnych, metale ciężkie
Release of Heavy Metals on Selected Municipal Landfill During the Calendar Year
municipal landfill, heavy metals
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