An Integrated Geochemical and Mineralogical Approach for the Evaluation of Zn Distribution in Long-Term Sludge-Amended Soil

This research work was designed to compare the Zn distribution in a long-term sludge-amended soil with that in a control soil. Two complementary approaches were performed: 1) a geochemical approach at the metric scale of the bulk soil horizons and 2) a mineralogical approach at the micrometric scale of the primary minerals weathering microsites. The geochemical approach revealed that Zn in the control soil was inherited from the weathering parent-rock. Its concentration was always lower than in the amended soil where Zn was supplied at the surface by the spread sludges and moves downwards. The mineralogical approach showed that the clay minerals, produced by the weathering of the primary minerals (amphiboles and plagioclases), or filling the fissure network were made up of smectites (saponite and montmorillonite) at the bottom and kaolinite at the top of the two soil profiles. Each clay mineral, with its specific sorption capacity, controlled the Zn distribution within the soil: the smectites produced by the amphiboles had high sorption capacity and favored Zn retention in the upper horizons of the soil. Conversely, the kaolinites produced by the plagioclases had lower sorption capacity, did not retain Zn in the surface horizons, and allowed it to migrate to deeper horizons where it was sorbed onto the montmorillonites.

Prediction of Thermal Conductivity and Specific Heat of Native Maize Starch and Comparison with HMT Treated Starch

Specific heat(Cp)and effective thermal conductivity(λ)of native maize starch(NS)were measured by DSC and transient heat transfer method,respectively,at different moisture contents and temperatures.The dependency of temperature(T)and moisture content(W)on the two parameters were investigated.The thermophysical properties of treated starch(TS)by four hydrothermal processes(RP-HMT,IV-HMT,DV-HMT and FV-HMT)were measured and compared to native strach.Hydrothermal treatments were performed at 3 bars(133°C)for 10 min.For Cp andλmeasurements,moisture content varied for NS from 5 to 21.5%d.b.and from 8.8 to 25%d.b.,respectively,and was fixed at 6%d.b.for TS.Empirical models were developed to specific heat and effective thermal conductivity,using a multiple regression algorithm with subsequent statistical analysis.The proposed models for NS based on T and W predict Cp andλwith a mean absolute error of 3.5%and 1.3%,respectively.Large differences in specific heat were observed between TS and NS.In a temperature range of 40 to 160°C,Cp values varied from 1.964 to 2.699 for NS and 1.380 to 2.085(J.g-1.°C-1)for TS.In contrast,the conductivity of NS was almost identical to that of treated starch by FV-HMT,followed in an increasing order by those treated by DV-HMT,RP-HMT,and IV-HM processes.

Distribution and Mobility of Zn,Pb and Cd in a Sewage Sludge-Amended Soil

The distribution of the metallic trace elements (MTE) Zn, Pb and Cd in a sludge-amended soil and their partitioning in specific soil microystems are studied by comparing their contents in amended and control soils. This comparison is achieved at the metric scale of the bulk soil horizons and at the micrometric scale of the weathering microsites (weathering rock-forming minerals and their specific weathered products). The chemical analyses of the MTE in the bulk samples do not show any anthropic contamination of the amended soil with repeated sewage sludge spreading. The chemical analyses of the