Transfer of Cd, Pb, Ra and U from Phosphogypsum Amended Soils to Tomato Plants

摘要

About 170 million tons of phosphogypsum (PG) are annually generated worldwide as a byproduct of phosphoric acid factories. Agricultural uses of PG could become the main sink for this waste, which usually contains significant radionuclide (from the ~(238)U-series) and toxic metals concentrations. To study PG effects on pollutant uptake by crops, a completely randomised greenhouse experiment was carried out growing Lycopersicum esculentum Mill L. on a reclaimed marsh soil amended with three PG rates (treatments), corresponding to zero (control without PG application), one, three and ten times therntypical PG rates used in SW Spain (20 Mg ha~(-1)). The concentrations of Cd, Pb, U (by inductively coupled plasma mass spectroscopy) and ~(226)Ra and ~(210)Po (by γ-spectrometry and α-counting, respectively) were determined in soil, vegetal tissue and draining water. Cadmium concentrations in fruit increased with PG rates, reaching 44±7 μg kg~(-1) formula weight with ten PG rates (being 50 μg kg~(-1) the maximum allowed concentration by EC 1881/2006 regulation). Cd transfer factors in non-edible parts were as high as 4.8 ± 0.5 (dry weight (d.w.)), two orders of magnitude higher than values found for lead, lead, uranium and radium concentrations in fruit remained below the corresponding detection limits-0.5 and 0.25 mg kg~(-1) and 0.6 mBq kg~(-1), respectively (in a d.w. basis). ~(238)U (up to 7 μg kg~(-1) d.w.) and ~(210)Po (up to 0.74 Bq kg~(238) d.w.) could be measured in some fruit samples by α-spectrometry. Overall, the concentrations of these metals and radio-nuclides in the draining water accounted for less than 1% of the amount applied with PG.