Electro-chemical charge characteristics of surface-subsurface region of selected soils in the tropics

Abstract

A study was conducted to investigate the relation between soil chemical, mineralogicalproperties and surface charge characteristics of selected tropical soils in West Bengal, India.The objectives of this study were to analyse the electro-chemical charge characteristics ofsurface-subsurface soils in accordance with point of zero charge (PZC) and pH-dependentcharge. Subsoil’s generally have higher PZC than corresponding surface horizons and pHdependent surface charges are maximum in upper layer than that of other. Relatively lowervalue of PZC (or pH0) along the depth, mostly affected by organic matter, clay content free Feand Al oxides. Result shows that PZC (or pH0) values decrease with increasing organic mattercontent and increase with increase in sesquioxides content. The PZC of the charge-pH curvesin Diamond Harbour soil (DH) (0-45cm) was on the acid side of the zero point titrationindicate that the samples possess permanent negative charge and in Raigunj soil (RG) (30-45cm) was on basic side possess slight permanent positive charge. Amount of surface chargereduces along the depth (subsurface region) than corresponding surface region except in RG(30-45cm) due to considerable increase in positive charges by presence of various electrolyteor synthetic hematite as $α-Fe_2O_3$. PZC has the strong negative correlation with pH-dependentcharge (r= -0.85707*) that supports the superiority of the present study. Regression valuealso supports the strong dependency of electrochemical surface charge on PZC and organicmatter content of corresponding soil layers (R2= 0.971474).