Potential utilization of orange juice industrial production’s residues for the immobilization of metals in contaminated soils

Mestrado em Engenharia Agronómica - Hortofruticultura e Viticultura / Instituto Superior de Agronomia. Universidade de Lisboa

Soil contamination with potentially toxic elements (metals and metalloids) may affect the crops in several undesirable ways, and, consequently, the human food chain. The use of organic amendments to treat the contaminated soil is a possibility that cannot be excluded and thus must be taken into account when addressing this problem, since the organic matter has a sequestration potential for metals and, additionally, has the possibility to improve the physical, chemical, and biological properties of the amended soil. The application doses of the residue evaluated equivalent to 20 and 40 t/ha were not reflected in a significant variation of the OM content in both-contaminated and non-contaminated soils, contrarywise to what was verified in the application of orange residues in a rate of 80 t/ha, which evidenced significant differences when in comparison with the non-treated samples, in both contaminated and non-contaminated soils. Concerning the pH of the soils, in the non-contaminated soil only the highest rate application registered statistical differences when in comparison with the non-treated evidence, whereas for the contaminated soil none of the application rates registered significant differences. The obtained results showed that the application of orange juice residues caused significant differences in the pseudo-total and bioavailable contents of Cu but not of Cd, in both contaminated and non-contaminated soil. However, the Cd bioavailable contents are not considered high, varying between 5.67% and 6.45% of total Cd content. Further experiments should be made in order to assess the effects that higher doses of residue can produce in the bioavailable quantities of Cd, and also to evaluate how the application of the orange juice residues can influence the extractability of other potentially toxic elements, as well as validate the possibility of using this method to the remediation of soils in a real situation under non-controlled circumstances

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