Resumo

DOMINGUES, H. et al. Copper concentrations in surface runoff water in a soil to which a copper rich urban biosolids was applied. Rev. de Ciências Agrárias [online]. 2007, vol.30, n.2, pp.326-334. ISSN 0871-018X.

Agricultural land spreading of urban biosolids (UB) contributes to increase soil fertility and also for its recycling, but the concentrations of some metals may restrict the application rates. In this work, the copper (Cu) concentrations in surface runoff water (SRW) were evaluated, in a field experiment of application of UB with a high Cu concentration (2042 mg kg^-1) with a sown pasture mixture. The field experiment was a randomised block design, with three UB rates from Évora (L0 = 0, L1 = 12, and L2 = 24 t/ha), and two replicates. It was established on a Haplic Luvisol, in Mértola, with a mean slope of 15%. Erosion devices of zinc plate (4 m²) were installed in each plot (48 m²) to which polyethylene reservoirs were connected (80 L) to collect the SRW. The SRW sampled in 2002 (seven dates), 2003 (five dates) and 2004 (two dates) were analysed for Cu. According to the Decreto-Lei nº 236/98, which sets out requirements for the water quality, the SRW Cu concentrations were lower than the emission value (1,0 mg L^-1) for the wastewater discharge and they were also lower than the maximum recommended value (0,2 mg L^-1) for irrigation water. From the data obtained in 2002, about 75397 years would be required to drain the Cu added to the soil through the UB L2 rate. From the results got in 2004, about 47123 and 100016 years would be needed to remove the Cu from the UB L1 and L2 rates, respectively. As regard to 2003, it was not possible to quantify the loss of the element, as the Cu concentration at the L0 rate was higher than at the other rates. The Cu from the application of this UB had a reduced dragging and will not be pollutant to the surface-water and groundwater resources of the region.

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