Laboratory Simulation Of The Weathering Process Of Granite With Oxalic Acid And Succinic Acid

Mineral weathering is a common and important geochemical process occurring on the earth's surface.Granite is widely distributed in Heilongjiang Province that is also an important soil forming rock.The weathering of granite is mainly done by microorganisms,especially in the early stage of soil formation.The biochemical weathering of lichen fungi was mainly achieved through the secretion of low molecular organic acids(oxalic acid,succinic acid,usnic acid etc.).In this paper,the biological weathering processes of granite induced by oxalic acid and succinic acid were simulated in laboratory so as to reveal the role of organic acids in soil formation,element migration and transformation of loacl forest area.The main conclusions are as follows:1.Oxalic acid and succinic acid both induced the weathering of granite,in which the solubility of oxalic acid was higher than that of succinic acid.On the day of 0,the concentrations of Al,Fe and Si ions under oxalic acid treatment were all much higher than those of succinic acid.The electron microscope results also showed that the dissolution rate of granite powder is higher under oxalic acid treatment.2.The content of each ion induced by oxalic acid did not increase significantly with the increase of its concentration,however the content of each ion induced by succinic acid increased obviously with the increase of acid concentration.The ion content treated with50mmol/L oxalic acid solution was similar to that of 10mmol/L oxalic acid,while the ion content treated with 50mmol/L succinic acid was generally higher than that of 10mmol/L succinic acid solution.3.Under the same concentration of organic acid treatments,the concentrations of different ions in the solutions fluctuated with treatment time,and the fluctuation induced by oxalic acid was greater than that of succinic acid.4.Under oxalic acid treatment,the ions,such as aluminum,iron,calcium,magnesium and manganese,would react with oxalic acid,so the concentrations of aluminum,iron,calcium,magnesium and manganese ions in solutions were all kept at a very low level.Especially Iron and aluminum ions,they were released from granite in the beginning,but as time went by their concentrations decreased dramatically.But the ionic concentration growths induced by succinic acid were relatively stable,and did not change dramatically with time.5.The contents of potassium and sodium ions induced byoxalic acid were stable only with a small increase,and the contents of iron and aluminum ions on 0 days were much higher than those of other days.The change curve of silicon ion concentration was a bit like as those of iron and aluminum ions,but the content of silicon ions on 0 days did not open the gap with other days.Manganese,magnesium and calcium ion concentration curves were the same.Under succinic acid treatment,except of iron ion,the change curves of otherion concentrations were not significant different,and their concentrations increased with the increase of acid concentration,but iron ion concentration was similar to manganese,magnesium and calcium concentrations.6.Compared with succinic acid,more ions were released from granite treating with oxalic acid,however,they entered into the soil with the form of oxalic acid and metal ions complex.Conversely,most of the metal ions dissolved by succinic acid directly entered into the soil.