Zinc, copper and nickel concentrations in ryegrass grown on sewage sludge‐contaminated soils of different pH

Abstract

Sewage sludges containing high concentrations of zinc, copper and nickel were added separately to samples of two soils, a silty clay loam and a sandy loam, on which pH levels between 4.5 and 7.5 had been established; there were also treatments with sludge of low metal content or no-sludge. Soil-sludge mixtures were either continuously cropped with ryegrass or kept uncropped in pots in the glasshouse for 6 months. Zinc and nickel concentrations in 0.1 M calcium chloride extracts of soils from the cropped pots and in solutions displaced from the fallow pots decreased with increasing pH over the range tested, but copper concentrations remained steady above pH 5.5; individual metal concentrations in ryegrass tops followed the same pattern with pH as those in extracted solutions. Squared correlation coefficients (R') between shoot metal concentrations and concentrations of metals in EDTA, DPTA or calcium chloride extracts or displaced solutions, when taken over all soil, pH and sludge treatments, were >0.60 (P<O.OOl). Ryegrass yield reductions occurred on soils contaminated with each of the three metal sludges when soil pH was 5.5 or below.

Soil profile as a natural membrane for heavy metals from wastewater

“…Furthermore results indicate that the average concentration of zinc in the whole soil profile was at the level of purity by first-class Polish standards for groundwater (500 µg dm -3 ), while the concentration of cadmium in the profile from 15 to 75cm meets the requirements for fifth class of purity (> 10 µg dm -3 ) and in the lowest part of soil profile (75-90 cm) corresponds to the requirements of class fourth (10 µg dm -3 ) (PKN, 2004). Moreover, the range of Zn concentration do not appear to adversely affect microbiological processes (Gondek et al, 2010;Mann et al, 2002;Sanders et al, 2006;Singh and Agrawal, 2007). According to previous studies (Gondek et al, 2010; Guo and Marschner, 1995;Mann et al, 2002;Usman et al, 2005) , 10 6 ìg dm -3 of Zn content influences negatively most microbiological activity.…”

“…Moreover, the range of Zn concentration do not appear to adversely affect microbiological processes (Gondek et al, 2010;Mann et al, 2002;Sanders et al, 2006;Singh and Agrawal, 2007). According to previous studies (Gondek et al, 2010;Guo and Marschner, 1995;Mann et al, 2002;Usman et al, 2005) , 10 6 ìg dm -3 of Zn content influences negatively most microbiological activity.…”

“…Changes in soil reaction (pH) in the alkaline direction, high content of PO 4 2-, high content of organic matter and low moisture may retard the availability of zinc. Low reaction of soil is the primary factor that is conducive to zinc migration (Andevsson and Nillson, 1974;Sanders et al, 2006).…”

“…Changes in soil reaction (pH) in the alkaline direction, high content of PO 4 2-, high content of organic matter and low moisture may retard the availability of zinc. Low reaction of soil is the primary factor that is conducive to zinc migration (Andevsson and Nillson, 1974;Sanders et al, 2006).Cadmium is a heavy metal that is described as highly toxic to some organisms in nature (Alloway, 1990;Mann, 2002). Cadmium belongs to a group of elements that display very rarely physiological function.…”

Study of the Effect of pH on the Toxicity and Bioaccumulation of Cadmium on Beans [Phaseolus Vulgaris]

“…The decrease in pH which is considered as a determinant factor promotes the mobility of most metals by dissolving metal salts or the destruction of the retention phase [2]. It also influences the solubility and speciation of the metal and thus its toxicity as reported by [4]- [7]. PH has become a key variable in the bioavailability of Cd.…”