Fate and agricultural consequences of leachable elements added to the environment from the 2011 Cordón Caulle tephra fall

CAROL STEWART; HEATHER CRAIG; SALLY GAW; THOMAS WILSON; GUSTAVO VILLAROSA; VALERIA OUTES; SHANE CRONIN; CHRISTOPHER OZE

JOURNAL OF VOLCANOLOGY AND GEOTHERMAL RESEARCH

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2016

0377-0273

The June 2011 eruption of Cordón Caullevolcano, Chile, dispersed tephra over ~ 350,000 km2,including productive agricultural land. This resulted in the death of nearlyone million livestock. Two distinct environments were affected: a proximaltemperate Andean setting, and the semi-arid Argentine steppe farther from thevolcano. The purpose of this study was to better understand the fate andagricultural consequences of leachable elements added to the environment bythis large silicic tephra fall. Tephra, soil and surface water samples acrossthe depositional area were collected both immediately after the eruption(tephra and water) and nine months afterwards (tephra, soil and water). Tephrasamples were analysed following a new hazard assessment protocol developed bythe International Volcanic Health Hazard Network (IVHHN). Water-extractable elementconcentrations in freshly-collected tephra were very low to low compared toother eruptions, and showed no trends with distance from the volcano. Surfacewater analyses suggested short-term changes to water composition due to therelease of elements from tephra. No effect on the fertility of soils underlyingtephra was apparent after nine months. Water-extractable fluorine (F) infreshly-collected tephra ranged from 12 to 167 mg/kg, with a median valueof 67 mg/kg. Based on parallels with the 11?12 October 1995 eruption ofRuapehu volcano, New Zealand, we conclude that F toxicity was a possiblecontributing factor to the large-scale livestock deaths as well as to chronicfluorosis widely reported in wild deer populations across the Cordón Caulletephra depositional area. Finally, we recommend that effective response towidespread tephra fall over agricultural areas should include: (1) rapid,statistically representative field sampling of tephra, soils, surface watersupplies and forage crops; (2) analysis using appropriate and reliablelaboratory methods; (3) modelling both short and long-term impacts on theecosystem, especially for elements that may generate chronic hazard; (4) timelydissemination of results to agricultural agencies; (5) longitudinal samplingand monitoring to adapt impact models; and (6) developing reliable animalfatality diagnoses through autopsies and chemical analysis.