BEHAVIOR OF HEAVY METALS IN THE SOIL-PLANT SYSTEM

Abstract

Relationships between heavy metals, soils and plants may be studied in objective manner in field conditions. A long-term field experiment was set up with some microelements at Karoly Robert College on a slightly acidic clay soil. Four levels (0, 30, 90 and 270 hg element*ha-1) of microelements were added to plots separately at initiation. Different crops (winter wheat, maize and sunflower) were grown each year. In addition to yield evaluation, soil tests and plant analyses were completed yearly. In the first year of the experiment nearly the total amount of applied elements could be detected in the ploughed layer in mobile form. Two years later only about one-third of the applied elements were traced in available forms. With time there was a fixation of these elements in less mobile/soluble forms and they stayed mainly in the cultivated soil layer. Cd remains mobile in the soil-plant system for a long time. It accumulated both in the vegetative and generative parts of plants with no observed symptoms of toxicity and yield loss. Pb can enter both the vegetative and generative plant organs, however its accumulation cannot be increased with increasing Pb loads of the soil. Pb has low mobility in the soil-plant system. Hg and As cannot translocate into the grain even their extremely high concentration in the soil. Grain, as a generative organ, proved to be resistant tot these micropollutants. The non-essential elements Cd, Cr and Pb can translocate into the grain, so they can pollute the food chain. -------------------------------------------------------- A nehezfem-talaj-noveny kapcsolat-rendszer egzakt szabadfoldi kiserletekben tanulmanyozhato megbizhatoan. A Karoly Robert Főiskolan szabadfoldi nehezfem-terhelesi tartamkiserletet allitottunk be gyengen savanyu agyag talajon, 8 mikroelemmel negy terhelesi szinten (0/30, 90 es 270 kg elem/ha). A parcellakon minden evben mas-mas jelzőnovenyt termesztettunk (őszi buza, kukorica, napraforgo). A termes merese mellett evente talaj- es novenyvizsgalatokat vegeztunk. A kiserlet első eveben a kiszort elemek csaknem teljes mennyisege mobilis formaban volt kimutathato a szantott retegben. Ket evvel kesőbb mar csak kb. ketharmad reszuk volt kimutathato felvehető formaban. Idővel az elemek oldhatosaga/felvehetősege csokkent es a művelt talajretegben maradtak. A Cd hosszu ideig megtartotta mozgekonysagat a talaj-noveny rendszerben. Dusulasa a vegetativ es generativ novenyi reszekben is megfigyelhető volt fitotoxikus tunetek es termes csokkenes nelkul. Az Pb beepult a vegetativ es a generativ novenyi reszekbe, de talajterheles hatasara dusulasa nem volt igazolhato. Csak kis mertekben mozgekony a talaj-noveny rendszerben. Az As es a Hg meg extrem magas talajterheles eseten sem epult be a szemtermesbe. A szem, mint generativ szerv genetikailag vedett e szennyezőkkel szemben. A noveny szamara nem esszencialis elemek kozul a Cd, Cr es az Pb bekerultek a szemtermesbe, es igy terhelhetik a taplaleklancot.