REMEDIATION NEEDS OF AGRICULTURALLY USED SOILS

Whereas prominent attention is being paid to the harsh remediation of severely polluted soils, especially of old loads in urban, industrial and military areas, spatial remediation of agriculturally used soils i s still neglected. Criteria are developed for identification of these sites, based on assessments of mobilities' of hazardous trace elements in soils, their transfers into plants and reaching critical contents in crops, threatening the food chain and/or the crop production. Exper iments with the immobilization of trace elements by liming proved thei r high efficiency in expressive decreasing of elements mobilities and transfers of elements, the mobility of which is pH-dependent (Tab. I). Significant correlation was found in dystric Cambisols between soil p H and contents of Cd, Zn and Ni in testing plants (spinach > radish) a nd soil-plant transfers in the following sequence of elements: Zn, Cd, Ni (Tab. II). Experiments were conducted with remediation of soils by dung, compost and muck. The muck shows the most expressive effects on pH and humus quality, especially (Tab. III) in dystric Cambisols (les s in Arenosols). The organic amendments display their impacts strongly on mobile species of trace elements, less expressively on potentially mobilizable ones (Figs 1, 2) in the sequence dung < compost < muck (m aterial of sapric Histosols). This fact is reflected also in the conte nt of trace elements Cd, Zn, Ni in carrots (Fig. 4). The effects depen d upon the soil units. Whereas in dystric Cambisols the application of all organic ameliorative substances manifests itself in decreasing th e trace element mobilities, the effects decline in Arenosols and are n il in Chernozem (Fig. 3). The same statement can be made about the con tent of Cd in carrots (Fig. 5). The sequential anal:ysis proved (Fig. 6) that positive effects of organic amendments on decreasing trace ele ments mobility and their transfer into plants are not only due to thei r neutralising effects but also due to their capability to incorporate them into organic bonds. The most expressive effects were found after application of muck into dystric Cambisols.