中文摘要：

本研究选取海南岛北部玄武岩上不同发育时间的土壤进行研究，通过电位滴定法测定土壤的电荷零点，并结合XRD衍射测定土壤中的黏土矿物，探讨热带地区电荷零点随土壤发育程度的变化及其指示意义。结果表明：热带地区土壤电荷零点随土壤发育时间延长而升高，土壤中黏土矿物含量的变化和金属氧化物的增加是导致这一现象的主要原因，另外黏土矿物的种类和结晶程度也会影响到电荷零点的大小。电位滴定曲线的数据表明，随着土壤发育程度的加深，土壤永久负电荷减少，土壤的缓冲性能和保肥能力下降。对比其他指示土壤发育程度的指标，电荷零点大小能更好地表征热带地区土壤发育时间的长短，评估土壤发育程度强弱。

英文摘要：

The change of point of zero charge （PZC） with soil development degree and its implications for pedogenesis in tropical areas were discussed in this research. A soil chronosequence consisting of six soil profiles with age ranging from 0.09 Ma to 2.30 Ma, developed on basalt in the tropical Hainan Island, were collected. The means of potentiometric titration in different electrolyte strengths was used to measure the soil PZC, and the mineralogical composition was determined by X-ray diffraction analysis （XRD）. The results showed that the soil PZC increased with increasing basalt age and degree of soil development, which may be due to the change of clay minerals and the enrichment of iron oxides. The potentiometric titration curves indicated that the permanent negative soil charge was reducing during soil development, combined with the decline of soil fertility retention ability. Compared with some other indices, the soil PZC could be a better indicator to evaluate the soil development time and soil weathered degree.