Keane Michael, Stone Samuel, Chen Bean
National Institute for Occupational Safety and Health, Health Effects Laboratory Division, 1095 Willowdale Rd, Morgantown, WV 26505, USA.
J Environ Monit. 2010 May;12(5):1133-40. doi: 10.1039/b922840c.
Fumes from a group of gas metal arc welding (GMAW) processes used on stainless steel were generated using three different metal transfer modes and four different shield gases. The objective was to identify and measure manganese (Mn) species in the fumes, and identify processes that are minimal generators of Mn species. The robotic welding system was operated in short-circuit (SC) mode (Ar/CO2 and He/Ar), axial spray (AXS) mode (Ar/O2 and Ar/CO2), and pulsed axial-spray (PAXS) mode (Ar/O2). The fumes were analyzed for Mn by a sequential extraction process followed by inductively coupled plasma-atomic emission spectroscopy (ICP-AES) analysis, and by X-ray diffraction (XRD). Total elemental Mn, iron (Fe), chromium (Cr) and nickel (Ni) were separately measured after aqua regia digestion and ICP-AES analysis. Soluble Mn2+, Fe2+, Fe3+, and Ni2+ in a simple biological buffer (phosphate-buffered saline) were determined at pH 7.2 and 5.0 after 2 h incubation at 37 C by ion chromatography. Results indicate that Mn was present in soluble form, acid-soluble form, and acid-soluble form after reduction by hydroxylamine, which represents soluble Mn0 and Mn2+ compounds, other Mn2+ compounds, and (Mn3+ and Mn4+) compounds, respectively. The dominant fraction was the acid-soluble Mn2+ fraction, but results varied with the process and shield gas. Soluble Mn mass percent in the fume ranged from 0.2 to 0.9%, acid-soluble Mn2+ compounds ranged from 2.6 to 9.3%, and acid plus reducing agent-soluble (Mn3+ and Mn4+) compounds ranged from 0.6 to 5.1%. Total Mn composition ranged from 7 to 15%. XRD results showed fumes had a crystalline content of 90-99% Fe3O4, and showed evidence of multiple Mn oxides, but overlaps and weak signals limited identification. Small amounts of the Mn2+ in the fume (<0.01 to ≈ 1% or <0.1 to ≈ 10 microg ml(-1)) and Ni2+ (<0.01 to ≈ 0.2% or <0.1 to ≈ 2 mg ml(-1)) ions were found in biological buffer media, but amounts were highly dependent on pH and the welding process. Mn generation rates for the fractions were tabulated, and the influence of ozone is discussed. The conclusions are that exposures to welding fumes include multiple Mn species, both soluble and insoluble, and that exposures to Mn species vary with specific processes and shield gases.
采用三种不同的金属过渡模式和四种不同的保护气体，产生了用于不锈钢焊接的一组气体保护金属电弧焊（GMAW）工艺所产生的烟尘。目的是识别和测量烟尘中的锰（Mn）物种，并确定产生锰物种最少的工艺。机器人焊接系统分别以短路（SC）模式（Ar/CO₂和He/Ar）、轴向喷射（AXS）模式（Ar/O₂和Ar/CO₂）以及脉冲轴向喷射（PAXS）模式（Ar/O₂）运行。通过连续萃取过程，随后进行电感耦合等离子体原子发射光谱（ICP-AES）分析和X射线衍射（XRD），对烟尘中的锰进行分析。经过王水消解和ICP-AES分析后，分别测量了总元素锰、铁（Fe）、铬（Cr）和镍（Ni）。在37℃下孵育2小时后，通过离子色谱法测定了在简单生物缓冲液（磷酸盐缓冲盐水）中pH值为7.2和5.0时的可溶性Mn²⁺、Fe²⁺、Fe³⁺和Ni²⁺。结果表明，锰以可溶形式、酸溶形式以及经羟胺还原后的酸溶形式存在，分别代表可溶性Mn⁰和Mn²⁺化合物、其他Mn²⁺化合物以及（Mn³⁺和Mn⁴⁺）化合物。主要部分是酸溶性Mn²⁺部分，但结果因工艺和保护气体而异。烟尘中可溶性锰的质量百分比范围为0.2%至0.9%，酸溶性Mn²⁺化合物范围为2.6%至9.3%，酸加还原剂可溶性（Mn³⁺和Mn⁴⁺）化合物范围为0.6%至5.1%。总锰成分范围为7%至15%。XRD结果表明，烟尘中晶体含量为90 - 99%的Fe₃O₄，并且显示出多种锰氧化物的迹象，但重叠和微弱信号限制了识别。在生物缓冲介质中发现烟尘中少量的Mn²⁺（<0.01至≈1%或<0.1至≈10μg ml⁻¹）和Ni²⁺（<0.01至≈0.2%或<0.1至≈2mg ml⁻¹）离子，但含量高度依赖于pH值和焊接工艺。列出了各部分的锰生成速率，并讨论了臭氧的影响。结论是，焊接烟尘暴露包括多种可溶性和不可溶性的锰物种，并且锰物种的暴露因特定工艺和保护气体而异。
