Evaluation of Galai CIS-1 for Measuring Size Distribution of Suspended Primary Particles in the Ocean

使用Galai CIS-1測量海水中懸浮基本顆粒粒徑分布之評估

蔡政翰(Cheng-Han Tsai)；饒恕人(Su-Ren Rau)

Terrestrial, Atmospheric and Oceanic Sciences

3卷2期（1992 / 06 / 01）

147 - 163

英文

CIS-1是一種利用遮蔽時間(time-of-transition)原理的粒徑測定儀。它使用一雷射光束掃描顆粒，藉由顆粒遮蔽光線的時間長短來決定顆粒的大小。現已有些研究，用CIS-1測量圓球狀的標準參考顆粒及均質(homogeneous)顆粒，他們發現CIS-1能夠測得令人相當滿意的數據。本文探討以CIS-l來測量與上述物質不同的海水中懸浮顆粒之準確度。海水中的顆粒由具有不同光學性質及形狀的顆粒所組成，這可能影響粒徑分析儀測量結果的好壞。本研究將8個外海及4個近岸海水中懸浮基本顆粒經由CIS-1及光學顯微鏡之影像分析所得之粒徑分佈（體積計）作比較，結果顯示兩方法所測得之數據相差不多。粒徑中間值之最大差異為1 μm或17%，而粒徑分佈之標準偏差及眾數也都很相近。至於兩方法所得之粒徑平均相對偏差（於第十及第九十百分位數間）則於2%及17.3%之區間内，12個樣本之平均值為9.7%。本研究亦發現基本顆粒之粒徑分佈於各水樣中也彼此很接近。所測得之最大顆粒沒超過16 μm，其中間粒徑都在4 μm至6 μm區間內，若將所有水樣之粒徑分佈平均後，所得之分佈，其中間值及眾數各為4.7 μm及5.5 μm。

CIS-1 is a particle sizer based on time-of-transition principle. It scans particles with a laser beam, and determines their sizes by measuring the time lengths of light obscuration by the particles. Studies have shown that CIS-1 provides good size information for standard reference spherical panicles and for homogeneous material. This study examines the accuracy of its size information by using field particles obtained in the ocean. These particles differ from the above materials in that field particles have a wide range of shape and optical properties; they may affect the performance of a particle sizer. The volume-based cumulative size distribution of primary particles in 8 offshore and 4 coastal water samples were obtained by CIS-1 and by microscopy. Their comparison generally showed good agreements. The maximum difference in the median size of the same sample was 1 μm, or 17%,and the standard deviations and the modes also were close. The average relative size deviations between the two methods varied between 2% and 17.3%.The mean of the average relative deviation among all samples was 9.7%.The results of this study also showed that the distributions of primary particles in all samples were highly similar, irrespective whether they were from offshore or coastal waters. There were no primary particles larger than 16 μm, and their median sizes were within the range of 4-6 μm. By averaging the size distributions obtained for all samples, the median size and the mode of the resulting distribution were4.7 and 5.5 μm, respectively.