针对水体重金属污染检测的需求, 研究了以高纯石墨片为水体富集基底, 样品多次富集结合等离子体空间约束的水体重金属LIBS检测方法, 并对Pb, Cu, Cd, Ni等不同重金属元素的测量稳定性及检测限进行了分析。 实验采用波长为1 064 nm的Nd∶YAG调Q激光器, 分辨率为0.1 nm的光纤光谱仪分别对上述水体中重金属元素含量的特征光谱进行分光探测。 结果表明, 样品多次富集结合空间约束方法能够有效地提高水体重金属检测的灵敏度及稳定性并降低元素检测限, 空间约束条件下特征光谱强度增强约2.5倍, 光谱稳定性也得到提高, 相对标准偏差由非约束情况下的11.34%降低至8.77%。 对不同浓度的Pb, Cu, Cd, Ni四种重金属元素进行检测并建立定标曲线, Pb, Cu, Cd, Ni的检测限均低于国家工业废水排放标准的1/6, 满足工业废水重金属的检测需求, 为工业废水重金属的减排控制与超标排放预警监测提供了一种有效方法和技术支持。

According to the need of heavy metal pollution detection in waste water. Pure graphite flake is selected as matrix material, the LIBS method of multiple enrichment of samples combined with spatial confinement is adopted to detect the heavy metals contained in the waste water, and spectral stability and limit of detection of Pb, Cu, Cd and Ni are also analyzed. The experiments uses a wavelength of 1 064 nm Nd∶YAG Laser, and a optical spectrometer, which the resolution is less than 0.1 nm to detect the characteristic spectrum of heavy metal elements content in water. The result shows that this method serves to improve sensitivity and spectral stability of heavy metal in waste water while reducing the limit of detection of heavy metals. The intensity of characteristic spectrum are about 2.5 times better than it under the condition of non-confinement, the spectral stability has also been improved, RSD is reduced from 11.34% to 8.77% compared with non-confinement condition. The calibration curves of four heavy metal elements have been established, the limits of detection of Pb, Cu, Cd and Ni are lower than 1/6 of discharge standard of national industrial waste water, meeting the demand of heavy metal in industrial waste water online monitoring. This method provides a convincing support for discharge control and online monitoring of warning excessive discharge of heavy metal elements in industrial waste water.