Especiação e grau de saturação de fósforo em latossolo tratado com lodo de esgoto

Abstract

Phosphorus speciation and degree of phosphorus saturation of an Oxisol amended with sewage sludge Because of the population and industrial increase in the great urban centers, the amount of generated sewage sludge (SS) has also increased, and it constitutes, today, one of the great problems of modern society. The most viable alternative seems to be the land disposal of the sludge, since it is a source of nutrients as N, P, Ca, organic matter (OM) etc. However, the indiscriminate use can cause damages to the environment, as the eutrophication of aquifers, caused by phosphorus accumulation in the soil. Research regarding the behavior of P in soil is of common occurrence. However, the ones that quantify the adsorption, bioavailability, speciation of soil solution and losses of nutrients in areas amended with SS are scarce. The present study was carried out with samples of a Rhodic Hapludox, (RH) collected in a field experiment of the Embrapa Meio-Ambiente, located in Jaguariúna (SP), in which SS was added since 1999. Samples were collected in 2003, at the depths of 0-0.1, 0.1-0.2, and 0.2-0.4m, after five years of SS application. Treatments were: T1 = absolute control; T2 = Amount of SS calculated on basis of N concentration; T3 = Twice of SS amount applied in the T2, and T4 = Four times the SS amount in the T2. The objectives of this study were to evaluate the ionic speciation of P in soil solution and the risk of P losses in the RH by means of the degree of phosphorus saturation (DPS).

Extratores químicos empregados na determinação de P como indicadores ambientais em solos tratados com lodo de esgoto

“…O GSP é calculado utilizando-se a fórmula [(P ox /(α(Al ox +Fe ox )))x100] ( %), em que os teores de P, Fe e Al são medidos por meio de extração com ácido oxálico e oxalato de amônio, conhecido por remover P dos óxidos amorfos de Fe e Al no solo (Jordão, 2006), e o valor α é um fator empírico que se baseia nos diferentes solos e em suas propriedades (van der Zee & van Riemsdijk, 1986). Portanto, o GSP leva em conta tanto o fator P intensidade como o fator capacidade, considerando, consequentemente, a variabilidade da perda de P graças ao tipo de solo e ao risco de perda de P do solo para as águas superficiais.…”