利用电沉积的方法将天然水中的痕量汞离子富集到一个高纯铜棒表面，从而克服用等离子体光谱技术直接分析水样品时水珠溅射的影响和水分子对等离子体中原子辐射的淬灭效应。激光点火显著提高了火花放电的稳定性，降低了放电电压和电流，并同时增强了火花放电等离子体中汞的原子辐射。采用激光点火辅助火花诱导击穿光谱（LI-SIBS）技术，并在富集电压为7.5 V，富集时间为10 min，放电电压为4000 V的条件下实验得到天然水中汞离子的校正曲线。该技术对于水中汞离子的检出限能够达到1 μg/L质量浓度，没有附加污染和汞的记忆。

The trace Hg in natural water was electrically deposited on the surface of a high-purity copper rod which can effectively avoid the problems existed in directly analyzing aqueous solutions with plasma emission spectroscopy, such as the effect of water sputtering and atomic emissions quenching effect due to water molecules in plasma. Discharge stability is improved and the required voltage and current for stable discharge are decreased under the assistance of laser ignition in spark-induced breakdown spectroscopy (SIBS). Laser-ignition technique is able to enhance atomic emission of Hg in spark-induced plasma. The calibration curve of Hg in natural water is built with laser-ignition assisted spark-induced breakdown spectroscopy (LI-SIBS) technique under the condition of 7.5 V deposition voltage, 10 min deposition time and 4000 V discharge voltage. Detection limit of mercury reaches to 1 μg/L under current condition. There are no any additional pollution and memory effect for Hg in this rapid and sensitive technique.