Assessing the quality of pipe borne water using Magnetic Susceptibility Measurements
Magnetic susceptibility measurements and chemical analysis were performed on samples of water taken from the academic and residential areas of the Kwame Nkrumah University of Science and Technology (KNUST) campus, Kumasi. The aim of these measurements was to see if water delivered through metallic pipes was clean. Magnetic susceptibility measurements were performed using the Bartington MS2 magnetic susceptibility meter, with MS2G single frequency sensor and the chemical analysis was performed with the Varian SpectrAA 220FS Atomic Absorption Spectrometer. Results of the measurements showed that the water samples had negative magnetic susceptibility (χ) values of the order of 10 –5 and were thus diamagnetic. The χ values obtained for the samples were between –1.3  10 -6 SI and –1.23  10 -5 SI for the Academic Area (sampled colleges) and –3.0  10 -7 SI and –8.7 10 -6 SI for the Residential Area (sampled Halls of residence). Chemical analysis of the samples showed variation in the concentrations of iron and zinc. Regression analysis of their concentrations with their χ values revealed zinc to have a strong inverse relationship with a correlation coefficient of 73%. Although the study showed some level of metallic contamination in the water samples of average concentration of 0.03mg/l, these were well below the concentration of 3mg/l which is of detrimental concern as outlined by the World Health Organization (WHO). This makes drinking water from the study area safe for drinking.
Magnetic viscosity, quadrature susceptibility, and frequency dependence of susceptibility in single‐domain assemblies of magnetite and maghemite
Neel has derived an expression relating the decay of viscous remanent magnetization and the variation of susceptibility with frequency in noninteracting single-domain assemblies of ferrimagnetic oxides, such as magnetite. This theory is extended to obtain a relationship for the quadrature susceptibility in such a sample. Measurements of these three parameters for soil samples and artificially prepared samples that contain single-domain magnetite or maghemite grains are described; the results obtained are in good agreement with theory.
Experimental investigation of the geotechnical properties and microstructure of lime-stabilized saline soils under freeze-thaw cycling
Abstract The Song-Nen Plain in northeastern China holds one of the three largest expanses of soda saline-alkali soil in the world. Due to its disadvantageous geotechnical properties, the saline soil in this area is unable to meet the needs of construction projects. This study evaluates the stabilizing effect of adding lime to such soils. Specifically, it investigates how the physicochemical and mechanical properties and microstructure of soda saline-alkali soil are altered by lime and how these changes are affected by both freeze-thaw cycling and the duration of curing. The results reveal that adding lime to saline soil transforms clay particles into sand and silt particles and causes the pore size distribution (PSD) to become bimodal, with small-pore and macropore populations. An increase in lime content leads to an increase in the unconfined compressive strength (UCS) but a gradual decrease in both the cation exchange capacity (CEC) and plastic index. Freeze-thaw cycles break up coarse particles and aggregate finer particles, increasing the diameter of macropores and decreasing the USC; however, the effect on specimens with >9% lime is negligible. It is further shown that the geotechnical properties of the soil change immediately after the addition of lime, indicating that the cation exchange reaction takes place very quickly. Furthermore, the pozzolanic reaction leads to an increase in the percentage of sand-sized particles and a decrease in porosity after 28 days of curing. Overall, these results indicate that it is feasible to use lime to improve the engineering properties of soda saline-alkali soil in this area.