Volcanic ash leachate compositions and assessment of health and agricultural hazards from 2012 hydrothermal eruptions, Tongariro, New Zealand

摘要: Abstract After almost 80 years of quiescence, the upper Te Maari vent on Mt. Tongariro erupted suddenly at 2352 h (NZ time) 6 August 2012. The short-lived hydrothermal eruption distributed a fine ash minor volume (~ 5 × 10 5  m 3 ) over 200 km from source. threat further eruptions prompted an investigation possible health and agricultural impacts any future this volcano, particularly since most recent large-scale falls in New Zealand 1995–1996 had generated significant problems, including livestock deaths. Deposited was sampled between volcano as soon after eruption. Two sub-lobes were identified different areas displayed subtly leaching properties. first initial small lobe directed NNE, likely formed drifting low-level clouds associated with lateral explosive blast surges. main fall lobe, eastward, sourced vertical plume that rose up to c. 8 km. Ash higher concentrations F Al, single-step leaches well totals three, sequential extractions. Further, showed proportion soluble Al extracted leach, compared totals. A linear relationship single highly (Pearson correlation coefficient r = 0.987 for 1:20 ratios r = 0.971 1:100), suggesting presence alumino-fluoride complexes (AlF x + 3 − x ). An even more 1:1 ratio is largest concentration leached ions Ca SO 4 , which correspond crystalline gypsum throughout newly excavated system. Although no fresh magma event, shallow intrusion prior explosion apparently provided contents volcanic gas dissolved within fluids adhering ejected particles. This ubiquitous dominated components these deposits leading complex profile. study carried out here human hazard assessment (particularly S) not straightforward, because solubility may be characterised by simple studies. In case S, agriculturally important, saturation effects are apparent using normal protocols also imply need modification standard methods.