本研究主要致力於(1)探討可呼吸性粉塵於濾紙上之均勻性(Uniformity)對使用直接分析(Direct-on filter; DOF)配合X光繞射(XRD)分析方法進行石英含量分析之影響；(2)探討石英粒徑分布對XRD定量分析及其對現場採集之樣本分析之影響；(3)研發可適用於DOF XRD分析結晶型二氧化矽（Crystalline silica）之新型濾紙握持器(Filter holder)。
於第一部份之研究，空氣樣本於鑄造廠中三作業場所（包括：造模、拆模及噴砂區）進行採集，空氣樣本同時以三種可呼吸性粉塵採樣器(包括：25-mm aluminum cyclone、nylon cyclone、及IOSH cyclone)進行採集，樣本採集後將分析其可呼吸性粉塵於濾紙上之均勻性及石英之含量，其中石英含量將以DOF XRD及NIOSH 7500分析方法分別進行分析。可呼吸性粉塵於濾紙上之均勻性以25-mm aluminum cyclone最佳，nylon cyclone次之，而IOSH cyclone最差。結果亦發現即使具有最佳均勻性之採樣器(25-mm aluminum cyclone)，其樣本以DOF XRD進行分析所得之石英含量仍為標準分析方法之1.152.89倍。因此建議未來應發展濾紙握持器以使可呼吸性粉塵於濾紙上之均勻性與NIOSH 7500 方法相同(=0.78)。本研究依據樣本之均勻性及石英濃度開發修正因子(conversion factor，Cf)，可使用前述因子來修正DOF XRD之石英濃度，前述修正因子現階段僅適用於鑄造廠。
於第二部份之研究中，本研究使用液相沉積裝置將石英分塵區分為不同之粒徑，共計取得7個接近單粒徑分布純石英粉塵，前述石英粉塵之質量中數粒徑(MMAD)為0.70μm–10.84μm，前述樣本將依據NIOSH 7500方法評估其單位之XRD強度（Unit intensity; UI）。結果發現UI隨著純石英粉塵之MMAD之增加而增加(UI由0.63增加至1.14)。為了評估前述之影響對於現場採集樣本之衝擊，本研究將於7個不同之作業環境中，同時進行全塵量及可呼吸性粉塵之採集。結果於全塵量之樣本(MMAD = 5.18μm–16.7μm； GSD=2.08–2.88)發現，由於其粒徑大於石英標準品（NIST-SRM 1878），因此其石英濃度均有低估之趨勢(Cf=0.775–0.834)，然可呼吸性粉塵(MMAD= 1.37μm–3.95μm；GSD=1.98–2.87)之樣本發現，其粒徑可能較大於或小於石英標準品，因此其石英之濃度可能有低估或高估之狀況(Cf =0.881–1.09)。為修正現場採集樣本之量測濃度，本研究將應用樣本之石英粒徑分布及其UIs研發修正模式，對於可呼吸性部份之修正因子(CRf)其模式為CRf =1.50－0.67×[1-exp(-0.69×MMAD)]。如果收集樣本之石英粒徑不屬於本研究之粒徑範圍中時，其CRf應需要小心使用。
於第三部份之研究，首先依據NIOSH 7500分析方法來評估粉塵於濾紙上之均勻度(=0.78)，前述均勻度將作為本研究開發濾紙握持器之目標均勻度，不論25-mm aluminum cyclone或nylon cyclone使用濾紙握持器時均需符合目標均勻度。於實驗室測試結果發現新型濾紙握持器之設計為出氣端角度為120°與長度為50mm。現場驗證工作於鑄造廠中三作業場所進行，可呼吸性粉塵將同時以四種採樣組合同時採集，包括：nylon cyclones搭配傳濾紙匣與新型濾紙握器(依序定義為T-Nylon與N-Nylon)，與25-mm aluminum cyclone搭配傳濾紙匣與新型濾紙握器(依序定義為T-AL與N-AL)。結果發現4種採樣組合所採集之可呼吸性粉塵濃度並未具有差異，此結果可推論4種採樣組合於收集可呼吸性粉塵具相似之效能。以T-Nylon與T-AL採集之樣本以DOF XRD進行分析，結果發現其石英濃度高於NIOSH-7500方法所得之濃度，另一結果亦發現以N-Nylon及N-AL所採樣之樣本以DOF XRD進行分析，其濃度與NIOSH-7500分析之濃度未具有差異。綜合前述結果可發現，本研究所開發之新型濾紙握持器適合用於可呼吸性樣本之採集，並可搭配DOF XRD進行可呼吸性二氧化矽之樣本分析，運用濾紙握持器將有助於減少石英分析時之人力及費用。

The present study were set out (A) to investigate the effects of uniformities of deposition of respirable particles on filter on determining their quartz contents by using the DOF XRD method; (2) to investigated the effects of the quartz particles size on XRD quantifications and its implications for field collected sample; and (C) to develop A new filter holder suitable for using the DOF XRD method for analyzing crystalline silica samplesFor the first part study, field samplings were conducted in three workplaces of a foundry plant, including the molding, demolding, and bead blasting, respectively. Three respirable aerosol samplers (including a 25-mm aluminum cyclone, nylon cyclone, and IOSH cyclone) were used side-by-side to collect samples from each selected workplace. For each collected sample, the uniformity of the deposition of respirable dusts on the filter was measured and its free silica content was determined by both the DOF XRD method and NIOSH 7500 XRD method (i.e., the reference method). A same trend in measured uniformities can be found in all selected workplaces: 25-mm aluminum cyclone〉nylon cyclone〉IOSH cyclone. Even for samples collected by the sampler with the highest uniformity (i.e., 25-mm aluminum cyclone), the use of the DOF XRD method would lead to the measured free silica concentrations 1.152.89 times in magnitude higher than that of the reference method. A new filter holder should be developed with the minimum uniformity comparable to that of NIOSH 7500 XRD method (= 0.78) in the future. The use of conversion factors for correcting quartz concentrations obtained from the DOF XRD method based on the measured uniformities could be suitable for the foundry industry at this stage.
For the second part of study, seven nearly mono-dispersed pure quartz dusts (mass median aerodynamic diameter (MMAD)=0.70–10.84 μm) were prepared by a liquid sedimentation device and their unit XRD intensities (UI) were measured per NIOSH Method 7500. Results show that UI is increased as the increase in the MMAD of the pure quartz dust (the UI increased from 0.63 to 1.14). To examine the impact of the above results on quantifying field collected samples, both total dust and respirable dust samplings were conducted at seven different workplace environments. Results show that the quartz particles contained in all collected total dust samples (the MMAD=5.18–16.7 μm, and the GSD= 2.08–2.88) were coarser in their particle sizes than that of the reference quartz standard (NIST-SRM 1878) leading to a consistent underestimation on their measured total quartz particle concentrations (the conversion factor (Cf) were 0.775–0.834). But for respirable dust samples (the MMAD=1.37–3.95 μm, and the GSD=1.978–2.87), since collected quartz particle sizes could be either finer or coarser than that of the reference standard, either under- or overestimation of their measured respirable quartz particle concentration were found in the present study (the Cf were 0.881–1.09). To correct measured concentrations of field collected samples, correcting models were developed based on MMADs of the collected quartz particle samples and their corresponding UIs. The correcting factor for respirable fraction (CRf) was CRf =1.50－0.67×[1-exp(-0.69×MMAD)]. However, the obtained CRf should be the used with caution if collected samples were found with the quartz particle sizes fell outside the size range of the present study.
For the third part study, the target uniformity of the deposition of particles on a filter (=0.78) was determined according to NIOSH-7500 method, and was used as a guideline for developing a new filter holder suitable for both the nylon cyclone and 25-mm aluminum cyclone. A new filter holder with an120° outlet angle and a 50mm cowl length was identified based on repetitive laboratory tests. Field validations were conducted on three selected workplaces in a foundry plant. For any given workplace, two nylon cyclones respectively mounted with a traditional and a newly developed filter holder (denoted as T-Nylon and N-Nylon, respectively) , and two 25-mm aluminum cyclone respectively mounted with a traditional and the newly developed filter holder (denoted as T-AL and N-AL, respectively) were used to collected respirable dust samples. Results show that no significant difference was found among the respirable dust concentrations for samples collected from the T-Nylon, N-Nylon, T-AL and N-AL suggesting that all testing cyclones shared a very similar performance as a pre-selector for collecting the resparable dust. The quartz concentrations for samples collected from T-Nylon and T-AL analyzed using the DOF XRD method were found to be higher than that of the NIOSH-7500. On the other hand, quartz concentrations for samples collected from N-Nylon and N-AL, while analyzed using the DOF XRD method, were found with no significant difference from those analyzed using the NIOSH-7500 method. It is concluded that the developed filter holder is suitable for collecting and analyzing respirable free silica samples using the DOF XRD method, which will be beneficial to industries for reducing both cost and manpower on crystalline silica analysis as in comparison with the use of the NIOSH-7500 method.

Abstract (Chinese) i
Abstract (English) iii
Acknowledgements vi
Table of contents vii
List of Tables xi
List of Figures xiii
Terminology xvi
Chapter 1 Introduction 1
1.1 General 1
1.2 Objectives and Significance 4
Chapter 2 Literature review 5
2.1 Definition of Crystalline silica 5
2.2 The health effect and exposure limit for crystalline silica 5
2.3 Sampling and analytical methods 7
2.4 DOF XRD method 8
2.5 The particle size affecting the accuracy and precision for the analysis of crystalline silica 11
Chapter 3 Material and Methods 27
3.1 Research Framework 27
3.2 Experimental section 31
3.2.1 Part-I: the effects of uniformities of deposition of respirable particles on filter on determining their quartz contents by using the DOF XRD method. 31
3.2.2 Part-II: the effects of the quartz particles size on XRD quantifications and its implications for field collected sample 35
3.2.3 Part-III: A new filter holder suitable for using the DOF XRD method for analyzing crystalline silica samples 44
Chapter 4 Results and Discussions 49
4.1 Part-I: the effects of uniformities of deposition of respirable particles on filter on determining their quartz contents by using the DOF XRD method. 49
4.1.1 Respirable dust concentrations of the three selected workplaces 49
4.1.2 Respirable quartz concentrations of the three selected workplaces 50
4.1.3 Comparisons of respirable quartz concentrations obtained from the NIOSH 7500 and DOF XRDs 51
4.1.4 Effects of uniformity of the deposition of respirable particles on filters on quantifying quartz concentrations by using the DOF XRD method 52
4.2 Part-II: the effects of the quartz particles size on XRD quantifications and its implications for field collected sample 58
4.2.1 Separated pure quartz dusts. 58
4.2.2 Effect of quartz particle size on measured XRD intensities. 59
4.2.3 True quartz concentrations and their conversion factors for the field collected samples. 59
4.2.4 Respirable quartz concentrations and their conversion factors for the field collected samples. 62
4.3 Part III: A new filter holder for DOF analyzing crystalline silica samples using the XRD 72
4.3.1 The target uniformity 72
4.3.2 The development of the new filter holder 72
4.3.3 Field validation: Respirable dust concentrations of the three selected workplaces 73
4.3.4 Field validation: Uniformities for samples collected from the three selected workplaces 74
4.3.5 Field validation: Respirable quartz concentrations for samples collected from the three selected workplaces s 75
Chapter 5 Conclusions and Future Research 80
5.1 Conclusion 80
5.1.1 Part-I: the effects of uniformities of deposition of respirable particles on filter on determining their quartz contents by using the DOF XRD method. 80
5.1.2 Part-II: the effects of the quartz particles size on XRD quantifications and its implications for field collected sample 81
5.1.3 Part III: A new filter holder for DOF analyzing crystalline silica samples using the XRD 82
5.2 Future Research 82
Chapter 6 References 84
Appendix I: Reynolds number for the new filter holder with three types of cowl length 90

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