采用四硼酸锂-偏硼酸锂混合熔剂(67∶33),硝酸锂为氧化剂,溴化锂为脱模剂,熔融制作样片,利用X射线荧光光谱仪,用土壤、水系沉积物和海洋沉积物等标准物质拟合校准曲线,系统研究了熔剂、稀释比、脱模剂、熔融温度与时间对测定结果的影响,并分析了产生这些影响的机理,优化改进了X射线荧光光谱(XRF)法同时测定海洋沉积物中主量组分(Na2O、MgO、Al2O3、SiO2、P2O5、K2O、CaO、Fe2O3、MnO、Ti2O)的分析方法。结果表明,当样品与混合熔剂在熔融稀释比例为1∶10的条件下混合均匀,在700℃预氧化200 s,升温至1050℃熔融10 min,实验优化获得高质量的熔片,较大的稀释比与未知烧失量(loss on ignition,缩写为LOI)校正结合,无需对样品烧失量进行校正,简化了分析步骤。对海洋沉积物标准物质GBW07314进行精密度考察,各组分含量的相对标准偏差(RSD)为0.32%~2.05%,方法检出限为70~270μg/g。对海洋沉积物、水系沉积物、岩石矿物和土壤4类标准样品进行准确度考察,测定值与标准推荐值无显著性差异。表明方法准确可靠,能满足地质与地理类海洋沉积物、水系沉积物、岩石矿物和土壤等样品准确定量分析。
Biogenic elements and six phosphorus （P） fractions in surface sediments from the Changjiang Estuary and adjacent waters were determined to investigate the governing factors of these elements, and further to discuss their potential uses as paleo-environment proxies and risks of P release from sediment. Total organic carbon （TOC） and leachable organic P （Lea-OP） showed high concentrations in the estuary, Zhejiang coast and offshore upwelling area. They came from both the Changjiang River and marine biological input. Biogenic silicon （BSi） exhibited a high concentration band between 123 and 124°E. BSi mainly came from diatom production and its concentration in the inshore area was diluted by river sediment. Total nitrogen （TN） was primarily of marine biogenic origin. Seaward decreasing trends of Fe-bound P and Al-bound P revealed their terrestrial origins. Influenced by old Huanghe sediment delivered by the Jiangsu coastal current, the maximum concentration of detrital P （Det-P） was observed in the area north of the estuary. Similar high concentrations of carbonate fluorapatite （CFA-P） and CaCO3in the southern study area suggested marine calcium-organism sources of CFA-P. TOC, TN and non-apatite P were enriched in fine sediment, and Det-P partially exhibited coarse-grain enrichment, but BSi had no correlation with sediment grain size. Different sources and governing factors made biogenic elements and P species have distinct potential uses in indicating environmental conditions. Transferable P accounted for 14%-46% of total P. In an aerobic environment, there was low risk of P release from sediment, attributed to excess Fe oxides in sediments.
