Understanding the dynamics of black carbon and associated contaminants in glacial systems

Abstract

More than one billion people depend upon glaciers for water, yet this exploitation is seldom underpinned by science-led water management practice. Previous work has detected that glaciers store and then subsequently release contaminants to downstream ecosystems, revealing a potentially harmful legacy that needs to be managed in conjunction with contemporary atmospheric pollution and climate change. Remarkably, while several classes of harmful organic pollutants have been considered in this context, almost no attention has been given to black carbon, a dark aerosol that is host to several adsorbed contaminants and that greatly increases glacier melt by enhancing the absorption of solar radiation. The future impact of black carbon upon glacier melt and contaminant release cannot be managed until we know how much historical black carbon is stored in Earth's glaciers. Further, as the residence time of ice within many mountain glaciers is between 100 and 1000 years, major changes in these impacts can be anticipated in the near future. A case is therefore made for using glacier dynamic models to understand the distribution of postindustrial, contaminated ice within glaciers, so that their impacts upon melt water quantity and quality can be forecast. A research framework is proposed that ranges from high flux, dynamic glaciers which are replete with postindustrial ice, to low flux, polar glaciers which are unlikely to become replete before they disappear. Research into the processing of contaminants following their melt-out is also required, because microbial processes will lead to their bioflocculation and biodegradation on glacier surfaces. © 2014 Wiley Periodicals, Inc. How to cite this article:WIREs Water 2014Water , 1:141-149. doi: 10.1002Water /wat2.1016 INTRODUCTION P eople's dependence upon water supply from glacier ice is far greater than is immediately apparent. It ranges from the consumption of groundwaters replenished by Pleistocene ice sheets in urban communities such as Chicago, through the hydroelectric power production of Norway, Switzerland, and New Zealand, to the collection of surface runoff from glaciers for irrigation and * Correspondence to: a.j.hodson@sheffield.ac.uk 1 Department of Geography, University of Sheffield, Sheffield, UK 2 Arctic Geology, University Centre in Svalbard, Longyearbyen, Norway Conflict of interest: The author has declared no conflicts of interest for this article. domestic use in rural parts of the Himalayas and Andes. Historically, the use of glacial melt waters for irrigation in Asia has involved farmers sprinkling ash over glaciers to enhance melting. The effect of the ash is to reduce the surface reflectance of the ice and thus increase the absorption of solar radiation. As a consequence of industrialization during the so-called Anthropocene, the atmospheric deposition of carbonaceous particles (hereafter black carbon or 'BC') is having precisely the same effect (see Box 1). Several potentially harmful classes of persistent organic pollutants (POPs) are also known to ...

Impact of impurities and cryoconite on the optical properties of the Morteratsch Glacier (Swiss Alps)

“…Furthermore, snow grain packing also plays a critical role in affecting the albedo of both clean and dirty snow . High SDI and I imp values are found across the ELA (equilibrium line altitude; located approximately at 3000 m, following Zekollari et al, 2014), where Saharan dust layers probably associated with heavy depositions that occurred during the hydrologic year 2014(Di Mauro et al, 2015Varga et al, 2014) appear on the glacier surface. The presence of outcropping dust across and above the ELA of an Alpine glacier during the summer season further decreases its reflectance and enhances the melt at higher altitude, where new snow and firn are directly exposed to solar radiation.…”

“…The Alps rise on the top of the Po river plain, one of the most industrialized and densely populated areas of Europe. As a consequence, the presence of anthropogenic activities is expected to strongly influence the geochemical and radiative characteristics of cryoconite (Baccolo et al, 2017;Cook et al, 2015;Hodson, 2014;Tieber et al, 2009).…”

Post-Depositional Biodegradation Processes of Pollutants on Glacier Surfaces

“…Cryoconite in holes has higher concentration of organic matter and inorganic nutrients (nitrogen, phosphorus...) than the surrounding ice and supraglacial sediments [35,36]. This characteristic leads, on the one hand, to the incorporation of hydrophobic compounds such as POPs into the cryoconite organic matter [6] and, on the other hand, it promotes the presence of biodiverse and active microbial communities [37], which can biodegrade the contaminants.…”

“…The organic contaminants in these remote areas are referred to as persistent organic pollutants (POPs), which consist of several groups of chemicals with similar structures and physical-chemical properties that are extensively used worldwide in agriculture (pesticides), industrial and health applications. Recent studies have revealed that alpine environments are affected by the presence of POPs [4][5][6]. These chemicals are ubiquitous, show long-range transport potential, and many of them are hydrophobic.…”

Effect of Atmospheric Deposition and Weathering on Trace Element Concentrations in Glacial Meltwater at Grand Teton National Park, Wyoming, U.S.A.

“…Glaciers on the Tibetan Plateau are currently an important sink in the global Hg cycle, but with a warming climate they may become a Hg source that could endanger ecosystems and human health in the region (Huang et al, 2012). Glacier dynamic models project future increases in contaminant releases from glacier melt (Hodson, 2014).…”