Changes on chemical fractions of heavy metals in Chilean soils amended with sewage sludge affected by a thermal impact

Abstract

Forest fires are frequent in central-southern Chile; high temperatures may affect chemical fractions of heavy metals (Cu, Zn, Ni, Pb, Cd, Mo, Cr, and Mn) naturally present in soils and those coming from sewage sludge amendment. Changes in exchangeable, sorbed, organic, carbonate, and residual heavy metals fractions, evaluated by sequential extraction, were observed after heating at 400 • C in 2 amended volcanic soils. Most significant heavy metals in these samples were Cu, Zn, Pb, and Ni. A significant increment in the total content of organic matter and metal ions, such as Zn and Cu, was observed in amended soils with respect to controls. In all samples, sorbed and exchangeable forms represent <10% of the total amount, while organic and carbonate fractions represent 24 and 48%, respectively. The thermal treatment of amended soil samples results in a redistribution of the organic fraction, mainly into more insoluble carbonate and residual fractions such as oxides. Finally, the thermal impact is much more important on sewage sludge amended soils if a heavy metal remediation process is considered, reducing the mobility and solubility of heavy metals supported by sewage sludge, minimising leaching and promoting accumulations in surface horizons.Additional keywords: heavy metal pollution, forest fire, chemical fractions, volcanic soils, sewage sludge, waste disposal.

CHEMICAL FRACTIONS OF Al IN VOLCANIC SOIL AMENDED WITH CELLULOSE WASTE

“…According to the well-known buffer capacity of volcanic soils, the pH of amended samples goes down to the control soil pH after an incubation period of 2 months. Therefore, in amended Chilean volcanic soils, after some time the CEC or the excess of previously adsorbed metals may be released to the soil solution [12].…”

“…Also, these are acid and show considerable quantities of iron oxides and organic matter, while its variable charge, which is pH and ionic strength dependent, is one of its singular features. Furthermore, they possess a high cationic exchange capacity (CEC) and a high accumulation of P as phosphate [12]. As mentioned above, these soils present acidity problems.…”

Sewage Sludge Disposal and Applications: Self-heating and Spontaneous Combustion of Compost Piles - Trace Metals Leaching in Volcanic Soils After Sewage Sludge Disposal

“…Fractionation data show that Zn and Cu are mainly associated with highly insoluble fractions, such as carbonates and residual fraction. In control soils the total heavy metal content follows the sequence Zn > Cu > Ni > Pb for Collipulli soil, and Cu > Zn > Ni> Pb for Ralún soil (Antilen et al 2006). On the other hand, the Zn and Cu release patterns for the sludge and sludge ash were similar (Figure 16), with the accumulated amounts released by the sludge considerably higher than those of the sludge ash.…”

“…The thermal treatment of amended soil samples results in a redistribution of the organic fraction, mainly into more insoluble carbonate and residual fractions such as oxides. Finally, the thermal impact is much more important in soils amended with sewage sludge if a heavy metal remediation process is considered, reducing the mobility and solubility of heavy metals supported by sewage sludge, minimizing leaching, and promoting accumulation in surface horizons (Antilen et al, 2006). Column leaching experiments were conducted to test the ability of Chilean volcanic soils to retain the mineral constituents and metals in sewage sludge and sludge ash incorporated into the soils.…”

Sukcesije biljnih zajednica na pozaristima planine Vidlic

“…Повезаност кружења тешких метала у природи и биљкама са шумским пожарима помињe већи број аутора (Antiléan et al, 2006;Szyczewski et al, 2009). Емисију тешких метала у ваздушну средину која потиче од пожара у шумама и преријама пoмиње Ross (1994).…”