Amelioration effects of biochar on Cd contaminated soils

Biokreda (BK) kao stabilna forma organske tvari sa velikom reaktivnom (adsorpcijskom) površinom dugoročno povećava sadržaj ugljika u tlu, te potencijalno proizvodne mogućnosti na metalima kontaminiranim tlima. Uz pretpostavku da će velika aktivna površina BK na sebe adsorbirati (imobilizirati) određene forme metala u kontaminiranom tlu, u ovome istraživanju je testiran učinak dvije doze BK (1% i 4% m/m) na vegetacijske parametre i mineralni sastav industrijske konoplje (Cannabis sativa, L.) te kemijske promjene u Cd kontaminiranom tlu. Aplikacija niže doze BK nije značajno utjecala na visinu stabljike, dok je viša doza BK povećala visinu stabljike test kulture za 21% u odnosu na kontrolnu varijantu. Dodatak BK nije značajnije utjecao na promjer stabljike, broj etaža listova te masu listova, kao i na biomasu cijele test kulture u svježem i suhom stanju u odnosu na kontrolnu varijantu. Dodatak niže doze BK je povećao masa korijena u odnosu na kontrolnu varijantu za 21% u suhom i 22% u svježem stanju, odnosno za 39% u suhom stanju i 54% u svježem stanju pri višoj dozi BK. Koncentracija Cd, Cu i Pb u korijenu test kulture je sa aplikacijom BK smanjena za 58%, 37% i 58% (kod niže doze BK ), odnosno za 68%, 39% i 62% (kod više doze BK), pojedinačno u odnosu na kontrolnu varijantu. Koncentracija Cd u listu test kulture je sa dodatkom BK smanjenja u odnosu na kontrolnu varijantu za 30% kod niže doze BK, odnosno za 50% kod više doze BK. Koncentracija Zn u listu je sa dodatkom BK smanjena za 29% u odnosu na kontrolnu varijantu. U stabljici test kulture je pri višoj dozi BK koncentracija Cd smanjena za 40% u odnosu na kontrolnu varijantu, dok na koncentraciju preostalih metala u stabljici aplikacija BK nije značajnije utjecala. Dodatkom BK nije značajnije promijenjen pH vodenog perkolata testiranoga tla nakon perioda inkubacije, za razliku od električne provodljivost koja je smanjena sa 9,5 dS/m kod kontrolne varijante na 7,8 dS/m. Koncentracija većine analiziranih teškim metala je ostala nepromijenjena u vodenom perkolatu tla nakon inkubacije, izuzev Cu čija je koncentracija porasla. Primjena BK ima veliki potencijal u gospodarenju tlima koja su kontaminirana Cd i ostalim teškim metalima, te su nužna daljnja istraživanja kako bi se utvrdio utjecaj BK na test kulture i razne druge (a)biotske čimbenike.Biochar (BK) as a stable form of organic matter with a large reactive (adsorptive) surface increases the carbon content in the soil long-term, as well as potential production on metal-contaminated soils. With the assumption that the large active surface of BK will adsorb (immobilize) certain forms of metals in contaminated soil, we tested the effect of two doses of BK (1% and 4% m/m) on vegetative parameters and mineral composition of industrial hemp (Cannabis sativa, L.) and chemical changes in Cd contaminated soil. The application of a lower dose of BK did not significantly affect the stem height, while a higher dose of BK increased the stem height of the test culture by 21% compared to the control variant. The addition of BK did not significantly affect the diameter of the stem, the number of tiers of leaves and the weight of the leaves, as well as the fresh and dry biomass of the entire test culture compared to the control variant. The addition of a lower dose of BK increased root mass compared to the control variant by 21% in dry and 22% in fresh state, or by 39% in dry state and 54% in fresh state at a higher dose of BK. The concentration of Cd, Cu and Pb in the roots of the test culture was reduced with the application of BK by 58%, 37% and 58% (at a lower dose of BK), respectively, i.e., by 68%, 39% and 62% (at a higher dose of BK), respectively in compared to the control variant. The concentration of Cd in the leaf of test culture was reduced with the addition of BK compared to the control variant by 30% at a lower dose of BK, i.e., by 50% at a higher dose of BK. With the addition of BK, the concentration of Zn in the leaf was reduced by 29% compared to the control variant. In the stem of the test culture at a higher dose of BK, the concentration of Cd was reduced by 40% compared to the control variant, while the concentration of the remaining metals in the stem was not significantly affected by the application of BK. The addition of BK did not significantly change the pH of the aqueous percolate of the tested soil after the incubation period, in contrast to the electrical conductivity which was reduced from 9.5 dS/m in the control variant to 7.8 dS/m. The concentration of most analyzed heavy metals remained unchanged in the aqueous soil percolate after incubation, with the exception of Cu which concentration increased. The application of BK has great potential in the management of soils contaminated with Cd and other heavy metals, and further research is necessary to determine the impact of BK on the test culture and various other (a)biotic factors