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(W/EH057) Effect of several species of cadmium on phosphatase in a soil treated with sewage sludge. Gomez, Ignacio1, Marco, Begoņa2, Mataix, Jorge2, Navarro Pedreņo, Jose2, Mataix Beneyto, Jorge2, 1 2 ABSTRACT- A laboratory experiment was carried out with a calcareous agricultural soil of Alicante for three months under wet and temperature controlled. The soil was treated with sewage sludge from the wastewater treatment plant of Altea (Alicante) (40 g/kg d.w. soil). With the objective to determine the effects of cadmium species (soluble, exchangeable and complexed) on phosphatase activity, several treatments with different doses of cadmium were applied. The treatments established were: T0 (control soil), TL (soil+sewage sludge), T1 (soil+sewage sludge+Cd 40 mg/kg d.w.), T2 (soil+sewage sludge+Cd 80 mg/kg d.w.), T3 (soil+sewage sludge+Cd 200 mg/kg d.w.). The metal was added to the soil as cadmium chloride in desionized water solution used for irrigation along the experiment. The chemical speciation of the metal was done: water extraction to obtain the soluble fraction, ammonium acetate 1 M extraction for the exchangeable fraction and NaOH 1 M extraction for the complexed fraction. Cadmium was measured by atomic absorption spectrometry. The enzymatic activity of the phosphatase was determined from the liberation of p-nitrophenol (PNP), using p-nitrophenol phosphate (PNPP) as substrate. The p-nitrophenol liberated was measured with an UV-spectrometer. The results showed that the addition of sewage sludge increased significantly the activity of the enzyme and was no affected by cadmium. In the first sampling period, the activity was clearly higher in the treatments with sewage sludge, and also in the highest cadmium treatment where the activity reached values of 602 mmol PNP/g h opposite to the 55 mmol PNP+/g h obtained in the control treatment (T0). In the fifth samplig period a light increment of enzymatic activity in the control treatment (T0) was observed (117 mmol PNP/g h). In the rest of treatments, the values were around 352-440 mmol PNP/g h. These facts may indicated that the sewage sludge acted as a buffer to the chemical changes of the soil. Key words: phosphatase, cadmium, sewage sludge |
