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Pesticides have been used for years to increase farm production by reducing and exterminating pests and plant diseases. Once they are poured into soil, physical, chemical and biological processes occur controlling the level of their persistence in the soil. This study focuses on the application of rock magnetism to study the properties of pesticide residues on soil. We investigate the effects on soil caused by dichlorodiphenyltrichloroethane (DDT) known as organochlorine (OC), a type of pesticide that is widely used by farmers. Results from the analysis of low frequency magnetic susceptibility show that addition of OC causes change in mineral type for diamagnetic and paramagnetic minerals, whereas for ferromagnetic mineral, addition of OC affects the magnetic susceptibility insignificantly. Results from the magnetic viscosity analysis indicate that addition of OC will reduce the magnetic susceptibility of soil. Based on SEM measurement, the amount of oxygen increases due to oxidation whereas Fe decreases. After OC addition the porous spaces decrease and the grain size reduces one grade from ferromagnetic to ferromagnetic and from ferromagnetic to diamagnetic. [ABSTRACT FROM AUTHOR]

Magnetic viscosity, also known as viscous magnetization, is one of the magnetic properties that rarely used in study of rock magnetism. The recent emergence of portable magnetic viscosity meter allows scientists to exploit that magnetic viscosity as the proxy parameters of processes recorded in natural materials. One of such instrument is MVM1, a new kind of magnetic viscosity meter which allow measurement of viscous magnetization to be conducted in 14 steps of time delay ranging from 10 to 100 µs. In this study, we have measured the changes of magnetic viscosity over the time delay and magnetic susceptibility in a suite of natural samples. The results show that viscous magnetization decays with time (in logarithmic scale or log t) which follows the trend of cubical-logarithmic decay. This is a unique response of fine magnetic grains, i.e. superparamagnetic grains, when that magnetization was measured in very short time delay. We then found the correlation between parameters of magnetic viscosity, S in specific range of time delay, and parameters derived from magnetic susceptibility measurements. This correlation enables the measurements of magnetic viscosity to be used in order to approximate fraction of specific size of fine magnetic grains in bulk samples. [ABSTRACT FROM AUTHOR]