PM07 Pollutant Chemistry Transport, Cycling and Fate
Exhibit Hall
8:00 AM - Monday
(PM086) Bioavailability of heavy metals in sludge-amended chilean soils.
Mendoza, J1, Garrido, T1, Castillo, G2, 1 Universidad de Chile. Facultad de Ciencias Químicas y Farmacéuticas, Santiago, Chile2 Universidad de Chile. Facultad de Ciencias Físicas y Matemáticas, Santiago, Chile
ABSTRACT- The Chilean government has proposed a set of regulations to establish health quality requirements, limits in heavy-metal contents, and rates of application of stabilized sludges from sewage treatment. However, there are no studies on heavy-metal availability in Chilean soils amended with sludge. The purpose of this study was to assess the effect of two kinds of sludge produced in Chile on heavy-metal availability for two frequent crops, sorghum and lettuce, grown in acid and neutral soil. Applying both types of sludge increased heavy-metal total content and this correlated positively with the applied dose. Applying a dose in the 0 to 30 ton/ha range, such as recommended by regulations, sparingly increases total metal content. Higher doses (100ton/ha), equivalent to six successive applications will have an effect only on those metals highly contained in the sludge. For the sludges under study, the metal increase in the soil showed the order Zn> Cu> Pb. Sludge addition modified the soil pH, so that in acid soil sludge increased the pH, with a consequent increase in the plant yield (Pichilemu soil). In neutral soil (Rancagua soil), though, it did not. Additionally, changes in pH produced by the sludge would explain the increase in the amount of Cu and Zn absorbed by the plants. Sludge processed at a compact plant of activated sludge, compared with sludge from a facultative stabilization pound caused a higher increase in element uptake and translocation to the aerial part of the plant. The parameters cation exchange capacity, metal extractable with DTPA or MgCl2, and organic matter showed no relation with heavy-metal absorption but they would be related to metal mobility in the soil profile. Funded by Universidad de Chile, Project TNAC018-02/01
Key words: sludge amended soil, bioavailability of heavy metal, absorption of elements, metal mobility