Study On The Change Pattern Of Resistivity Of Organophosphorus Pesticide Contaminated Loess

The high-quality development of the Yellow River Basin has brought long-term economic growth to the west while also exacerbating the site contamination problem in the western loess region.In recent years,with the deepening of environmental protection concept,the treatment and remediation of contaminated sites have become a research hotspot.Resistivity,as an inherent property of soil,varies significantly before and after soil contamination,and is a good characterization of physical and mechanical properties and microscopic characteristics of soil.In this paper,the basic physical and mechanical properties and electrical properties of the soil were tested by artificially formulating different pesticide contaminants in Yangling loess,and the electrical prediction equations applicable to organophosphorus pesticide contaminated sites were proposed.The main research contents and results are as follows:(1)The physical and mechanical changes of organophosphorus pesticide contaminated soil were investigated in depth.The test results showed that the clay content of all three pesticide contaminated soils decreased continuously with the increase of pesticide concentration;the p H value of glyphosate contaminated soil did not change significantly,while the p H value of glufosinate and trichlorfon contaminated soil decreased significantly;the liquid limit and plasticity index showed a decreasing trend,while the plastic limit did not change significantly;the electrical conductivity showed a significant increasing trend;the compressive strength without lateral limit decreased continuously,and the damage form of contaminated soils showed weakly softening plasticity.With the increase of water content,the damage form transitions from brittle damage to plastic damage.(2)The two-phase electrode method was used to conduct electrical resistivity tests on contaminated soils,and the effects of pesticide type,pesticide content,moisture content,porosity,saturation and curing time on soil resistivity were analyzed.The results showed that the resistivity of all three pesticide contaminated soils decreased with the increase of pesticide content,decreased with the increase of water content,increased with the increase of porosity,decreased with the increase of saturation,and showed a trend of increasing and then decreasing with the increase of action time,and reached the peak at 15 d.The orthogonal analysis was used to discriminate the major and minor influences of each factor,and the above influencing factors were integrated to propose the resistivity prediction formula for organophosphorus pesticide contaminated soil.(3)X-ray diffraction tests and energy spectrum analysis tests revealed that the intrusion of pesticides changed the mineral and elemental contents of the soil.Scanning electron microscopy tests revealed that pesticides were mainly adsorbed on the clay-grained minerals in the soil,and the macropores in the soil increased with the increase of pollutant concentration.The inter-particle contact mode gradually transitioned from face-to-face contact to edge-to-face contact and edge-to-edge contact.The quantitative analysis of the IPP software showed that the small pore area did not change significantly after the soil was polluted by pesticides,but the large pore area increased in different degrees.