The physicochemical and structural characteristics of Cu²⁺ contaminated undisturbed loess

The effects of Cu²⁺ on the physicochemical and structural characteristics of undisturbed loess were studied in order to formulate effective strategies for environmental protection, soil pollution prevention and remediation, and to provide theoretical support for the engineering construction of contaminated sites. The particle size distribution, CaCO₃ content and pH value of Cu²⁺ contaminated loess samples were determined. The SEM images and particle size contents of the samples were obtained by scanning electron microscopy and laser particle size analyzer. The influence mechanism of Cu²⁺ on the microstructure of undisturbed loess was analyzed by means of fractal theory. The compression test of Cu²⁺ contaminated undisturbed loess was carried out, and the comprehensive structural potential of the sample was analyzed. The results show that with the increase of Cu²⁺ content, the clay content increases first and then decreases, and then increases and then decreases, while the powder content decreases first and then increases, and the sand content remains unchanged. The content of CaCO₃ decreased linearly. The pH value decreases rapidly at first, and then remains unchanged. The comprehensive structural potential of the contaminated loess samples first increased and then decreased, and then increased and then decreased. In general, the incorporation of heavy metal Cu²⁺ leads to the decrease of soil pH value, the dissolution of the main cementing material calcium carbonate, and the change of the form and composition of clay aggregates due to the electrostatic attraction and van der Waals forces between clay particles, thus affecting the compactness and structural strength of soil.