岩溶滴水中痕量磷的测定及其古环境意义

Determination of trace phosphate in cave dripping water and its paleoenvironment significance

为解决因洞穴滴水中磷酸盐含量低而无法了解磷的存在形式和分布特征这一问题,借鉴经典氢氧化镁共沉淀法,开发了集分离-富集-测定于一体的共沉淀-磷钼蓝分光光度法,用于定量测定岩溶滴水中PO34-。通过4个回收实验表明,岩溶滴水中痕量磷的回收率分别是99%、102%、95%和96%,达到定量分析的要求。对湖北清江和尚洞内HS4滴点2005—2012年的滴水样品中的磷酸盐进行测定,结果表明滴水PO34-(以P计)最大浓度为12.1μg/L,最小浓度为0.1μg/L,平均值为4.55μg/L。洞穴滴水中磷的浓度呈现季节波动,总体上夏、秋季高,冬、春季低,与同期的温度和滴水速率的季节变化相一致,较好地响应了气候和环境的变化。

The existence form and distribution of phosphorus can not be completely known due to low concen- tration of phosphate in cave dripping water. In order to resolve the above problem, the molybdophosphoric- blue spectrophotometry method,which set separation-enrichment-measurement in one process, for quantitatively measuring POI content in dripping water is developed in light of the classic method MAGIC. Four recovery tests show that the recovery rate of trace phosphate is 99%, 102%, 95% and 96% respectively, up to the requirement of quantitative analysis. Test of phosphates in dripping-water samples collected during 2005--2012 from the HS4 drop site in Heshang Cave,Hubei Province show that max content is 12.1μg P/L and minimum 0.1μg P/L, averages 4.55μg/L. The concentration of phosphate in cave dripping-water presents seasonal fluctuations, high in summer and fall, low in spring and winter, which is consistent with homo-chronous temperature and water-dripping velocity and well responses the changes of climate and environment.