No abstract

No abstract

Changes in magnetic and chemical properties of soil during the growth of tomato plants (Lycopersicon esculentum) are examined in this study. The synthetic soils, prepared from sand, topsoil and organic material, were treated with magnetite powder (\5 lm) in order to simulate metal contamination. Six soil treatments were prepared from two soil types: controls, low-contamination and highcontamination treatments (0.01 and 0.05 g of magnetite powder/kg soil, respectively). Overall, the contaminated soils had a greater decrease in magnetic susceptibility (MS) than the controls, and the difference in MS decrease between the treatments was found to be statistically significant for both soil types. Potential reasons for the overall MS decrease were explored, and among them, trace element uptake by plants probably had a minor contribution as the concentration differences of Fe and other trace elements (Ni, Mn) between treatments were not statistically significant. In soils, oxidized and weakly magnetic minerals (maghemite, goethite and hematite) were common after plant growth, when compared with the untreated (background) soil. Such mineral transformations could have contributed to the overall MS decrease. The results show that exposure to Fe contaminants can affect plant growth and suggest that plant growth can measurably change the magnetic properties of their growth media. While the potential variables affecting plant growth were controlled as much as possible, there still remains the potential that biotic and abiotic chemical reactions could have affected the results. Thus, continuous monitoring of the changes in soil magnetic and chemical properties in more complex soil-plant systems is needed.

In order to assess the use of magnetic methods to study vertical migration behavior of metal pollutants in natural soils, a controlled experiment was performed near Belle River, Ontario, Canada. The soil at the site consists primarily of clay-rich glacial till overlain by localized alluvium. Twenty PVC tubes (16″×8″) were inserted vertically into the ground as test capsules. Magnetite powder (<5 μm) was distributed on the surface of the soil inside ten tubes (10 grams/tube) to simulate anthropogenic contamination, while the other ten were used as controls. While the surficial magnetic susceptibility (MS) remained fairly stable in controls, decreases of 15-60% were observed in contaminated soil tubes. Post-test MS profiles from soil cores in contaminated tubes show that the magnetic signal is strongest at depths between 4 and 6 cm. Magnetic measurements and chemical analysis (using SEM-EDS) on soil layers with enhanced magnetic signal indicate the presence of iron containing particles, likely magnetite. Overall, the results suggest that magnetite powder migrated vertically downwards at a rate of ∼14 cm/year over the four month period, probably as a result of rainwater infiltration. Such magnetic methods and chemical analytical techniques are useful in the investigation of migration of metal pollutants and the potential depth of soil contamination.

The Dang valley consists of several patches of confined and unconfined aquifer systems. Drilling data reveals that the northern portion of the study area has more permeable surfaces than the southern and central portions. Annual domestic draft and safe yield were calculated to be 7.43 x106 m3/year and 3.16 x 107 m3/year, respectively. The fact that the safe yield is higher than the annual draft indicates the presence of good groundwater potential in the study area. Key words: terrace, lithology, aquifer, tubewell, yield, draft, piezometric surface, water table Himalayan Journal of Sciences 1(2): 119-122, 2003