Characterization of respirable volcanic ash from the Soufriere Hills volcano, Montserrat, with implications for human health hazards
Characterization of respirable volcanic ash from the Soufriere Hills volcano, Montserrat, with implications for human health hazards
复制标题
DOI：
10.1007/s00445-002-0266-6
复制
发表时间：
2003-07-01
影响因子：
3.5
通讯作者：
Williamson, BJ
中科院分区：
文献类型：
--
作者：
Horwell, CJ;Sparks, RSJ;Williamson, BJ
蒙特塞拉特岛苏弗里埃尔山火山长期喷发时产生的火山灰含有可吸入颗粒（小于 4 微米）和方英石（一种结晶二氧化硅多晶型物）。方英石的可吸入颗粒可引起硅肺病，从而增加了火山灰危害呼吸道健康的可能性。本研究考虑了影响人类接触可吸入火山灰的一些主要因素，即可吸入火山灰的成分和比例，以及空气中悬浮颗粒物的成分和浓度。对苏弗里夫山火山灰沉积物（穹顶塌陷火山灰沉积物、穹顶塌陷火山碎屑流基质、火神爆炸灰和混合灰）代表性样品中可吸入颗粒的组成、尺寸分布和比例（按重量计）进行了表征。圆顶塌陷的火山灰沉积物比其他火山灰样品，尤其是圆顶塌陷火山碎屑流沉积物的基质，明显富含可吸入颗粒（12 wt%）。在可呼吸部分中，与其他原生火山灰类型（0.4-5.6 数量%）相比，穹顶塌陷灰含有最高比例的结晶二氧化硅颗粒（20-27 数量%，其中 97 重量% 是方英石）。圆顶塌陷灰中结晶二氧化硅的富集在非常细的颗粒部分（亚2微米）中最为明显。结果被解释为由于火山碎屑流破碎过程中显着的尺寸分级，导致细粉耗尽的穹顶塌陷基质和富含细粉的穹顶塌陷灰沉积。对于所有样品类型，低于 4 微米的部分占低于 10 微米部分的 45-55 wt%。对过滤器收集的风沉积物、火山泥沉积物和空气悬浮灰样品进行了表征。这些样品显示可吸入部分中结晶二氧化硅的富集（10-18%）。结果与环境中的火山灰具有混合来源但主要源自穹顶塌陷喷发一致。然而，与原生灰样品相比，返工灰中的可吸入灰分含量较低（接近 3 wt%）。研究发现，蒙特塞拉特岛道路车辆重新悬浮的火山灰颗粒浓度随着距地面高度的增加而呈指数下降，这表明儿童与成人相比，接触的颗粒物浓度更高：0.9 m（两岁儿童的高度）处的 PM4 浓度是 1.8 m（成人高度）处的 3 倍。重新悬浮的道路颗粒的成分与风重新悬浮的成分相似。
Volcanic ash, generated in the long-lived eruption of the Soufriere Hills volcano, Montserrat, is shown to contain respirable (sub-4 mum) particles and cristobalite, a crystalline silica polymorph. Respirable particles of cristobalite can cause silicosis, raising the possibility that volcanic ash is a respiratory health hazard. This study considers some of the main factors which affect human exposure to respirable volcanic ash, namely, the composition and proportions of respirable ash, and the composition and concentrations of airborne suspended particulates. The composition, size distribution and proportion (by weight) of respirable particles in representative samples of the Soufriefe Hills tephra (dome-collapse ash-fall deposits, dome-collapse pyroclastic-flow matrix, Vulcanian explosion ash and mixed ash) have been characterized. Dome-collapse ash-fall deposits are significantly richer in respirable particles (12 wt%) than the other tephra samples, in particular the matrices of dome-collapse pyroclastic-flow deposits Q wt%). Within the respirable fraction, dome-collapse ash contains the highest proportion of crystalline silica particles (20-27 number%, of which 97 wt% is cristobalite), compared with other primary tephra types (0.4-5.6 number%). This enrichment of crystalline silica in the dome-collapse ash is most pronounced in the very fine particle fraction (sub-2 mum). The results are explained as being due to significant size fractionation during fragmentation of pyroclastic flows, resulting in a fines-depleted dome-collapse matrix and a fines-rich dome-collapse ash deposit. For all sample types, the sub-4 mum fraction comprises 45-55 wt% of the sub-10 mum fraction. Aeolian deposit, lahar deposit and airborne samples of suspended ash, collected on filters, were characterized. These samples show enrichment of crystalline silica in the respirable fraction (10-18 number%). The results are consistent with ash in the environment having a mixed origin but originating predominantly from dome-collapse eruptions. The reworked ash, however, contains low proportions of respirable ash (similar to3 wt%) compared to primary ash samples. The concentration of ash particles re-suspended by road vehicles on Montserrat is found to decrease exponentially with height above the ground, indicating higher exposure for children compared with adults: PM4 concentration at 0.9 m (height of two-year-old child) is 3 times that at 1.8 m (adult height). The composition of the re-suspended road particles is similar to that re-suspended by the wind.