Posteruptive impacts of pyroclastic deposits from basaltic andesite stratovolcanoes on surface water composition

Abstract

Volcanic ash deposition following explosive eruptions can pose significant hazards for water quality, human health, agriculture, and infrastructure functionality. Many studies have examined how fresh ash deposition may lower the pH of, and introduce a range of potentially toxic elements into, exposed surface waters. However, no study has yet determined the effects on water composition as a result of mechanical pyroclast disaggregation and production of new fresh particle surfaces and increasingly fine grained particles. Such disaggregation could result from natural posteruptive processes such as debris avalanches, lahars, or fluvial/aeolian transport and human activities such as cleanup efforts or mining of pyroclastic deposits. The posteruption time scales of pyroclast disaggregation may vary from months in moist tropical or temperate environments to years or decades in arid settings. Here we show, for the first time in experimental studies, that mechanical milling of pyroclasts will introduce a range of elements into exposed waters, including Al, which can be toxic at elevated levels, and Na, which increases the electrical conductivity of solutions. The pH of leaching solutions also increases by several log units. Such dramatic changes on the experimental scale may have implications for surface water composition in posteruptive settings, necessitating longer‐term risk assessments for ecosystem health and consideration of the role of pyroclastic deposits in element cycling in volcanically active regions.

Suspended sediment transport diversity in river catchments following the 2014 phreatic eruption at Ontake Volcano, Japan

“…The elevated EC values in the Akagawa River are attributed to the erosion, reworking, and entrainment of eruptive material and lahar deposits that contain minerals such as plagioclase feldspar and smectite (Kataoka et al 2018). These minerals contain sodium and calcium, and previous studies have demonstrated that these elements show a positive correlation with EC values in leachate experiments on pyroclastic deposits (Genareau et al 2016). Plagioclase is prone to chemical weathering (e.g., Nesbitt and Young 1996), and the acidity of the Akagawa River may have enhanced the dissolution of plagioclase grains.…”

Bubbles and Dust: Experimental Results of Dissolution Rates of Metal Salts and Glasses From Volcanic Ash Deposits in Terms of Surface Area, Chemistry, and Human Health Impacts

“…The elevated concentrations of dissolved ions leached from volcanic ash, such as Cl, F, Al, Fe, Mn, As, Cd, Cr, Cu, Pb, Se, and Zn, can chemically alter the water, leading to a change in pH or toxic bioaccumulation, which can render the water unsafe for human and animal consumption (Flaathen & Gislason, 2007;Genareau et al, 2016;Stewart et al, 2006;Wilson et al, 2010). Certain metals are of particular concern for bioaccumulation because they may be toxic in low concentrations and do not degrade.…”

“…Volcanic ash eruptions produce well-known hazards, but the geochemical impacts on ecosystems and human health are not as well understood. Health hazards associated with volcanic eruptions include inhalation dangers and water contamination, which can lead to increased cancer risk, kidney damage, and skeletal and dental fluorosis (Baxter & Ancia, 2002;Genareau et al, 2016;Horwell et al, 2003;Ivhhn.org, 2018). After deposition and subsequent leaching in soils or water bodies, volcanic ash leachates may have both poisoning and fertilizing potential; by contaminating water and vegetation, making it unsafe for human and animal consumption, but also enriching volcanic soils with critical nutrients in the long term.…”

“…Numerous previous ash leachate studies have been conducted in both the field and the laboratory, including analysis of leachate chemistry from a range of compositions from andesitic to basaltic ash (Bosshard-Stadlin et al, 2017;Cangemi et al, 2017;Flaathen & Gislason, 2007;Frogner et al, 2001;Frogner Kockum et al, 2006;Genareau et al, 2016;Jones & Gislason, 2008;Witham et al, 2005). Similar leachate studies have used previously weathered ash (Genareau et al, 2016;Jones & Gislason, 2008), while others used unhydrated pristine ash (Cronin et al, 2014;Gislason et al, 2011;Olgun et al, 2011) to explore various environmental geochemical conditions and processes that follow volcanic eruptions. For this study, pristine ash is used and is defined as natural ash, collected immediately after an eruption, prior to being altered naturally by precipitation (unhydrated) or mechanically in the lab.…”

Sustained effects of volcanic ash on biofilm stoichiometry, enzyme activity and community composition in North- Patagonia streams

“…Son ecosistemas biogeoquímicamente muy activos debido al fuerte contacto entre la atmósfera, las riberas y el lecho bentónico (Liu et al 2008). Una característica hidromorfológica muy importante en este tipo de ecosistemas es el alto cociente entre el borde del arroyo y su área (Vannote et al 1980 (Genareau et al 2016).…”