The Proceedings of the Eighth International Conference on Creationism (2018)

released by the volcano. As mentioned earlier, the pre-Flood oceanic crust may have been higher in arsenic than the continental crust. However, there was presumably some arsenic in the continental crust. A good deal of this would have been have been released by the massive weathering associated with the Flood. Ultimately, the arsenic would probably have been dissolved in water as AsO 3 3- or AsO 4 3- , once again with varying degrees of protonation. Taken together, these sources (hydrothermal, volcanic, and mechanical weathering) would have mobilized a great deal of arsenic, much of it being deposited as sulfide minerals but some being truly dissolved as well. How that arsenic would have interacted with the environment and where it would ultimately have resided is dependent on the chemistry of arsenic itself and of the Flood waters, which we will consider next. THE CHEMISTRY OFARSENIC IN THE FLOOD WATERS The geochemistry of arsenic is highly complex, dominated by changes in oxidation state and solubility. In almost any water conditions there are some forces moving the arsenic towards dissolving in the water and some promoting precipitation out of the water. We cannot simply say “arsenic minerals in the Flood waters would have dissolved” or “arsenic minerals in the Flood waters would have remained insoluble”. Rather, we have to consider the possible conditions of the waters and the factors that would promote precipitation or dissolution under those conditions. Throughout the Flood, there was a great deal of hydrothermal activity, with the fluids both mixing with pre-Flood seawater and infiltrating into rock. These hydrothermal fluids were almost certainly rich in arsenic. Most hydrothermal fluids are chemically reducing and of low to neutral pH, so arsenic within them would have been the more reduced As 3+ form, H 3 AsO 3 . Modern studies have found a wide variety of arsenic concentrations in hydrothermal waters and hot springs, ranging from 0.0003 to 47 ppm (Henke 2009a). Yellowstone geothermal water has been reported to have arsenic concentrations from 0. 16 to 10 ppm, Waiotapu geothermal waters in New Zealand range from 0.710- 6.5 ppm, and El Tatio geothermal in Chile averages a stunning 45-50 ppm As (Bowell et al. 2014). It is reasonable to assume that the hydrothermal waters of the flood would have contained ppm level concentrations of arsenic as well. Hydrothermal fluids also can have extremely high sulfide concentration, with a recent source reporting an average of approximately 1 wt% H 2 S (10,000 ppm) for magmatic- hydrothermal fluids and 1.0 X 10 -4 to 1% (1-10,000 ppm, with concentration decreasing with temperature) for metamorphic fluid (Fontbote et al. 20173). Another work suggested an average of 5.0 mM H 2 S (170 ppm) for deep sea hydrothermal vents (Jannasch 1989). When these fluids cooled either upon mixing with the relatively colder ocean waters or infiltration into existing rock layers, the arsenic would precipitate as sulfides. The exact mineral that would form would have depended on the composition and temperature of the fluid In the presence of significant amounts of iron and at temperatures between 450°C and 150°C, arsenopyrite or arsenian pyrite (FeS 2 containing from 0.02-6% As) would precipitate first. At lower temperatures (below 150-200°C) and in the absence of iron, realgar and orpiment would precipitate; if the temperature drops quickly enough and iron is abundant, all three minerals could form (Henke 2009a). In that situation, one would expect to find both As-sulfides and pyrite with As incorporated into its structure as it formed; the As-containing pyrite would probably predominate (Saunders et al. 2008). As(OH) 3 in volcanic vapor reacts with H 2 S, FeS 2 , and CuCl to form enargite (Cu 3 AsS 4 ) and tennantite (Cu 12 As 4 S 13 ) (Henley, Mavrogenes, and Tanner 2012; Henley and Berger 2012). As long as they are exposed to only reducing conditions, which in natural waters generally corresponds to a relatively low oxygen content, the arsenic would remain in these minerals. So as long as these minerals were buried and/or exposed only to water depleted of oxygen by the massive amount of decay attendant to the Flood, the arsenic would remain trapped in them, where they either remained stable until undergoing weathering more recently (Mukherjee et al. 2014) or remain trapped today. This is consistent with the current distribution of arsenic in the crust, where most of the toxin is associated with sulfides, especially pyrite (Bowell et al. 2014). Such arsenic would pose no threat to life immediately post-Flood. However, arsenic does not always remain precipitated in sulfides; these minerals can release arsenic under oxidizing conditions. Pyrite and arsenopyrite dissolve in the presence of oxygenated- water to release Fe 3+ , SO 4 2- , and any arsenic associated with the minerals. This is how acid mine drainage is created today, which is a modern route of arsenic release. This process is encouraged by certain bacteria and oxidizing chemicals such as nitrates (Henke 2009a; Lazareva et al. 2015). Both realgar and orpiment can also oxidize under these conditions with realgar initially converting to orpiment and then both converting to H 3 AsO 3 . Even in a low oxygen environment, high concentrations of carbonate (CO 3 2- ) can also dissolve orpiment (Henke 2009a). Orpiment would be less stable than realgar and arsenopyrite under those conditions, but all three minerals would be likely to release at least some of their arsenic. So there are mechanisms by which some of the arsenic sulfides could dissolve. We would expect this dissolved arsenic to be in the +3 oxidation state and assuming a pH of 9 or below, it would take the form of H 3 AsO 3 , which is rather unreactive (Henke and Hutchison 2009). In the presence of oxygenated water, the arsenic would slowly oxidize to As 5+ . This process is very slow in and of itself, but the rate can be increased by the presence of Fe 3+ , manganese oxides, nitrates, organic matter, and some microorganisms (Henke and Hutchison 2009). We would expect most of these to be present in the Floodwaters. Iron would be especially common due to its high abundance in the crust and because one primary method of arsenic release is oxidation of iron sulfides, generating Fe 3+ right alongside the arsenic. Therefore we would expect the dissolved As to be oxidizing to As 5+ , in the form of H 3 AsO 4 (at extremely low pH), H 2 AsO 4 - , HAsO 4 2- , and AsO 4 3- . Added to this arsenic released from sulfides would be the arsenic mobilized by other sources in the Flood. While roughly 2/3 of the arsenic in a volcanic system is believed to be in the gas phase rather than the ash (Henley and Berger 2013), there would still be a great deal in the ash. Much of this would be leached into the Floodwaters, presumably as AsO 4 3- with varying degrees of protonation based on the pH of Hutchison and Bortel ◀ Fate of Arsenic in the Flood ▶ 2018 ICC 231