Abstract

A radish species was grown in a sandy loamy soil either unpolluted or polluted by increasing concentrations of crude oil added to watering solutions during one month under controlled laboratory conditions. This procedure was set to evaluate the impact of oil pollution of the substrate on the elemental uptake by plants. In summary, the increasing pollution by crude oil to the soil has not a univocal impact: the changing elemental contents in the roots and leaves of the cultivated radishes are never single trended with the amount of oil pollution, showing in turn that they are not provided by the spilled oil. The most significant elemental increase occurs in the leaves of the radishes grown in the soil polluted by 10 ml of oil and in the roots of those grown in the soil polluted by 4 ml of oil. In the detail, the significant effects of the oil pollution induce in the leaves: (1) similar behaviors for Ca, K, P, Mg, Fe and Al; (2) the highest impact on Ca, K, P, Mg and Al at the intermediate 10-ml pollution; (3) the highest uptake at the high side of pollution for Fe, Mn, Zn, Ni, Co, Cr and Pb; and (4) no significant impact on the uptake of the REEs. Oil pollution on the plant roots impacts: (1) an increased Ca, Fe, Al and Si uptake, often only in the case of the highest pollution, while P’s uptake decreases; (2) an increase of the microbial population by a factor of about 2.5 at low pollution and a dramatic decrease at higher pollution; (3) an uptake of REEs only at the highest degree of pollution by a specific increase of the light REEs.

The translocation roots-to-leaves indicates a decrease of Ca to the leaves when oil pollution increases, while remaining state for K and P with a slight decrease when pollution is at its maximum. The total biomass increases in the soil at low levels of pollution, decreases at intermediate levels and remains the same at high levels of pollution. The increase of most of elements at low level of oil supply is correlated with an increase in microorganism density, which suggests that availability of elements in soil can be attributed to an increase in organic activity, which has been stimulated by the oil pollution.