Jakob Ronit, Roth Anja, Haas Karsten, Krupp Eva M, Raab Andrea, Smichowski Patricia, Gómez Darío, Feldmann Jörg
Trace Element Speciation Laboratory Aberdeen, Department of Chemistry, University of Aberdeen, Meston Building, Meston Walk, Aberdeen, Scotland, UK.
J Environ Monit. 2010 Feb;12(2):409-16. doi: 10.1039/b915867g. Epub 2009 Nov 17.
Biovolatilisation of arsenic as their arsines in the form of AsH(3), and mono-, di and trimethylarsine has often been determined under laboratory conditions. Although environmental point sources such as landfill sites or hot springs have been characterised, only limited knowledge is available on how widespread the formation of volatile methylated arsenic compounds are in the environment. Here we studied the atmospheric stability of the different arsines and quantified their oxidation products in atmospheric particulate matter (PM(10)) in two locations in Argentina. The atmospheric half-life of the arsines range from 19 weeks for AsH(3) to 2 d for trimethylarsine (TMAs) at 20 degrees C in the dark, while during simulated daytime conditions the stability is reduced for all arsines and in particular for the methylated arsines by three orders of magnitude which suggests that TMAs can only be dispersed at night. At both locations the arsenic concentration was in all samples below 1 ng As m(-3), which is considered as rural background for arsenic. The oxidation products, i.e. methylarsonate (MA), dimethylarsinate (DMA) and trimethylarsine oxide (TMAO) were identified by using HPLC-ICP-MS/ES-MS in more than 90% of the 49 PM(10) samples taken from 8 sampling points at the two geographically different locations. TMAO was the predominate organoarsenicals in both locations (66 and 69%, respectively) while DMA was determined to be between 13 and 19% of all organoarsenicals at the two locations. The concentration of the organoarsenicals ranged from 4 to 60 pg As as TMAO m(-3), while the maximum concentration for DMA and MA were 16 and 6 pg As m(-3), respectively. No difference in terms of the concentration or distribution of the organoarsenicals in the PM(10) samples was identified as significant. Since the two locations were different in climate and industrial impact and sampled in different seasons, these data suggest that methylated arsenicals do occur as background chemicals in the environment. Due to the low atmospheric stability of the methylated arsines, it is suggested that biovolatilization of arsenic as methylated arsines is a widespread phenomenon. More studies however are necessary to identify the major sources and determine the flux of the volatilization process in order to determine whether or not the process has environmental significance.
在实验室条件下，常对砷以砷化氢（AsH₃）、一甲基胂、二甲基胂和三甲基胂形式进行生物挥发作用的测定。尽管诸如垃圾填埋场或温泉等环境点源已被表征，但对于挥发性甲基化砷化合物在环境中的形成有多广泛，人们了解有限。在此，我们研究了不同胂类在大气中的稳定性，并对阿根廷两个地点大气颗粒物（PM₁₀）中的氧化产物进行了定量分析。在20℃黑暗条件下，胂类在大气中的半衰期从砷化氢的19周至三甲基胂（TMA）的2天不等，而在模拟白天条件下，所有胂类尤其是甲基化胂类的稳定性降低了三个数量级，这表明三甲基胂只能在夜间扩散。在两个地点，所有样品中的砷浓度均低于1 ng As m⁻³，这被视为砷的农村背景值。通过使用HPLC - ICP - MS/ES - MS，在从两个地理位置不同的地点的8个采样点采集的49个PM₁₀样品中，超过90%的样品鉴定出了氧化产物，即甲基胂酸（MA）、二甲基胂酸（DMA）和三甲基胂氧化物（TMAO）。TMAO是两个地点主要的有机砷化合物（分别为66%和69%），而DMA在两个地点所有有机砷化合物中的占比为13%至19%。有机砷化合物的浓度范围为4至60 pg As（以TMAO计）m⁻³，而DMA和MA的最大浓度分别为16 pg As m⁻³和6 pg As m⁻³。在PM₁₀样品中，未发现有机砷化合物在浓度或分布方面存在显著差异。由于这两个地点在气候和工业影响方面不同且在不同季节采样，这些数据表明甲基化砷化合物作为环境中的背景化学物质确实存在。由于甲基化胂类在大气中的稳定性较低，有人认为砷以甲基化胂类形式进行生物挥发是一种普遍现象。然而，需要更多研究来确定主要来源并确定挥发过程的通量，以便确定该过程是否具有环境意义。
