Amelioration effect of humic acid extracted from solubilized excess sludge on saline-alkali soil

In this study, the main characteristics and soil amendment effects on the saline-alkali soil of humic acid extracted from solubilized excess sludge (SS-HA) were investigated. The excess sludge was solubilized prior to extraction to improve the humic acid recovery rate. The structural features of SS-HA were characterized by an elemental analysis, Fourier transform infrared spectroscopy, and H-1-nuclear magnetic resonance spectroscopy, and compared with those of HA extracted from non-solubilized excess sludge (ES-HA). The results showed that extraction efficiency of humic acid was enhanced by using solubilization, although structural properties of humic acid extracted from solubilized excess sludge were almost the same as those of ES-HA. To study a utilization method of SS-HA, the soil amendment effects on saline-alkali soil by mixture of SS-HA were investigated with a model soil-column experiment. SS-HA reduced the pH of the saline-alkali soil, and the effect was immediately observed or faster than the case in which only peat is added. Moreover, the cation exchangeable capacity of the saline-alkali soil was enhanced by addition of SS-HA.