Development of Automatic and Countinuous Measurement Equipment and Monitoring System for Chemical Composition of Rain Water

为监测雨水中阴阳离子浓度，研制了一套自动连续测量系统。该系统主要由自动换样器、自动进样器和离子色谱仪三个部分组成。自动取样器和进样器由定时器控制，能定时自动连续地将雨样送入离子色谱仪，雨样进入阴离子分离柱，可分离主要阴离子(Cl、NO_3和SO_4~(2-))和有机酸(HCOO和CH_3COO)。然后，分离出的阴离子用电导检测器检测，部分有机酸自动回注到离子色谱柱(ICE)进行测定。因此，该系统可在20分钟内连续测定雨水样品中的阴离子和有机酸。还可用另一流动装置同时测定雨水样品中的阳离子(Na~+、K~+、NH_4~+)。用2 mM NaS_2CO_3/4mMNaHCO3阴离子分析和0.05 mM H_2SO_4有机酸分析为淋洗液，5 mM HNO_3为阳离子分析试剂，对日本横滨庆应大学的雨水进行了为期一年的采样分析。按规定的时间间隔连续采集雨水，用离子色谱仪对雨水中的主要阴阳离子进行分析。该系统对于研究城市和偏远地区降雨对气溶胶和气体的去除过程是非常有效的。

An automatic and continuous measurement system was developed for the monitor-ing of anion and cation concentrations in rain water. This system is primarily composed of three sub aystems - an automatic sample changer, an sutomatic sample injector, and an ion chromatograph. The automatic samplechanger and sample in-jector are controlled by a timer and they are able to automatically and continu-ously transfer rain samples into ion chromatograph at regular intervals.The rain sample is injected into anion separation column which is able to separate major anion (Cl, No_3, and SO_4^<2->) and organic acids (HCOO and CH_3COO). Then, the separated anion is detarmined by electrical conductivity detector and a portion of organic acids is automatically reinjected into ion chromatography exclusion (ICE) column and determined. Therefore, anion and organic acids in the rain sample can be continuously determined within 20 minutes by this system. Cation(Na^+, K^+, and NH_4^+) in the rain sample also can be simultaneously deter-mined by using another flow kine for ionchromatography analysis. 2mM Nas_2CO_3/4mMNaHCO_3 for anion analysis and 0.05mM H_2SO_4 for organic acids analysis are used as an eluent, and 5mM HNO_3 is used for cation analysis to get a sufficient separ ation among ions.By uging this system, rain waters have been sampled and analyzed at Keio Uni-versity in Hiyoshi, Yokohama, Japan for one year, 1995. The rain water was con-tinuously sampled at regular intervals bytnis system and major anion and cation in the rain water were immediately analyzed by ion chromatography. This system is very effective for investigating the removal processes of aerosols and gases by rain in urban and remoe regions.