贝类生物作为海洋生态系统监测的理想标识, 以Ca为内标进行元素比例变化的分析, 将有可能获知气候演化及贝类生长等有用信息。 区别于其他技术, 微区激光诱导击穿光谱技术(Micro-LIBS: micro-probe laser induced breakdown spectroscopy)应用于贝类贝壳探测时, Ca的特征发射谱线将分布于整个光谱探测区间, 如何选择合适谱线作为内标是Ca内标法用于贝壳成分元素分析的关键。 以Ca元素为内标进行贝壳成分元素的Micro-LIBS探测, 通过归一化Ca元素全谱谱线、 最强离子谱线Ca Ⅱ 393.3 nm和不同强度原子谱线(Ca Ⅰ 422.7 nm/Ca Ⅰ 487.9 nm)为内标情况下Sr/Ca元素比例变化的比较, 结果发现相较于Ca离子线Ca Ⅱ 393.3 nm和强度较弱原子线Ca Ⅰ 487.9 nm, 以Ca元素全谱强度或最强原子线Ca Ⅰ 422.7 nm为内标时, Sr/Ca分布在贝壳分析区域内变化较小, 其浮动分别小于7%和10%, 符合贝壳分析区域为同一生长周期的纹理特征, 较为准确地反映了贝壳的生长发展; 同时, 应用Ca全谱强度为内标对贝壳成分元素分析发现, 元素比例Li/Ca, K/Ca, Na/Ca相较于Mn/Ca, 具有明显的相似特征, 说明海水富含轻质元素在贝壳生长分布上具有明显的相似性。 研究结果表明, 较强Ca原子线或全谱强度比Ca离子线更适合作为内标用于贝壳成分元素的微区LIBS分析, 证明了Micro-LIBS用于贝壳分析的可行性。

The shellfish has been extensively applied as a proxy for marine ecosystem monitoring, and the climate evolution or the shell growth might be derived from the elementary spatial distribution when using calcium (Ca) as the internal reference. Differed from other technique, the calcium emission lines are spread all over the wavelength range when applying Micro-probe Laser Induced Breakdown Spectroscopy (Micro-LIBS) to analyze the shell. So it is crucial to select a suitable calcium line for the shell elementary analysis. In this paper, the scallop shell composition was analyzed by comparing calcium internal references of total-line, atomic line (Ca Ⅰ 422.7 nm/Ca Ⅰ 487.9 nm) and ionic line (Ca Ⅱ 393.3 nm). It was found that, the fluctuation of Sr/Ca ratio was less than 7% and 10% in the investigated area when using total-line and strongest atomic line (Ca Ⅰ 422.7 nm) as the reference respectively, which was in agreement with the shell growth development. What’s more, the obtained results indicated that the element ratio Li/Ca had a high correlation to K/Ca and Na/Ca rather than Mn/Ca, so the light elements might be accumulated in a same pattern during the shell growth development. It was suggested that Micro-LIBS was a practical way for the seashell investigation, and a better elementary analysis could be achieved by using the internal reference of calcium total-line or the strong atomic line, while not in case of calcium ionic line.