Natural attenuation of coal combustion waste in river sediments

Abstract

The weathering of coal combustion products (CCPs) in a lotic environment was assessed following the Tennessee Valley Authority (Kingston, TN) fly ash release of 2008 into surrounding rivers. Sampled materials included stockpiled ash and sediment collected from 180 to 880 days following the release. Total recoverable concentrations of heavy metals and metalloids in sediment were measured, and percent ash was estimated visually or quantified by particle counts. Arsenic and selenium in sediment were positively correlated with percent ash. For samples collected 180 days after the release, total concentrations of trace elements downstream of the release were greater than reference levels but less than concentrations measured in stockpiled ash. Total concentrations of trace elements remained elevated in ash-laden sediment after almost 2.5 years. A sequential extraction procedure (SEP) was used to speciate selected fractions of arsenic, copper, lead, nickel, and selenium in decreasing order of bioavailability. Concentrations of trace elements in sequentially extracted fractions were one to two orders of magnitude lower than total recoverable trace elements. The bulk of sequentially extractable trace elements was associated with iron-manganese oxides, the least bioavailable fraction of those measured. By 780 days, trace element concentrations in the SEP fractions approached reference concentrations in the more bioavailable water soluble, ion exchangeable, and carbonate-bound fractions. For each trace element, the percentage composition of the bioavailable fractions relative to the total concentration was calculated. These SEP indices were summed and shown to significantly decrease over time. These results document the natural attenuation of leachable trace elements in CCPs in river sediment as a result of the loss of bioavailable trace elements over time.

Arsenic relative bioavailability from diet and airborne exposures: Implications for risk assessment

“…Multiple leaching methods are in use and vary in specific steps but commonly are initiated with water extraction, then continue with more aggressive extractants (e.g., high molarities of nitric acid, ammonium acetate) and conclude with solvents and/or acids and perhaps heat (e.g., hydroxylamine hydrochloride in 25% acetic acid at 95°C for 15 h.) to extract metals and metalloids from mineral matrices (EPRI, 2006(EPRI, , 2008a(EPRI, , 2008bMarkwiese et al, 2014). Other works have shown that As leaching from and adsorption to ash particles are pH dependent; at pH b 3 or N7 increasing amounts of As are leached or desorbed from ash particles EPRI, 2010).…”

Characterisation of coal and its combustion ash: recognition of environmental impact and remediation

“…The distribution of these elements in signi cant amounts into the different segments of nature may cause environmental pollution and health hazards (Rowe et al, 2002;Saha and Roychoudhury, 2019). Therefore, examination of these PHEs in feed coal is important for the consumption in thermal power plants from environmental aspects (Markwiese et al, 2014). Because the range of concentration of the PHEs in the coal samples is at a considerable level, a regular chemical analysis is urgently required for the burning of this fossil fuel in the thermal power plants because vulnerable exposure of the elements due to combustion may cause adverse effects on the environment (Finkelman, 2004;Saha and Roychoudhury, 2019).…”

“…Deposition and leaching of the emitted particulate matter of toxic elements in the different environmental segments such as ground and surface water, soil, and sediment causes bioaccumulation and biomagni cations in the ecological pyramid (Bhattacharyya et al 2009;Markwiese et al, 2014). This leads adverse effect into the food-chain and nally human health (Finkelman, 2004;Markwiese et al, 2014). A lab-scale bio-availability test is performed to measure the potential mobility of hazardous elements into the living system.…”

“…Regular monitoring of emission control device and modi cation of the emission control technologies are required to control atmospheric pollution from thermal power plants. Chemical characterisation of y and bottom ash as well as suitable and frequent recycling is needed to combat against leaching of PHEs into the lithosphere and hydrosphere(Bhattacharyya et al, 2009;Markwiese et al, 2014).…”

“…These are also utilised in coastal regions; embankments; and decorative purpose in the lakes, gardens, and parks(Basu et al, 2009;Ahmaruzzaman, 2010). Combustion ashes are also widely used in zeolite, geopolymer synthesis, lling of low lying area and mine as well as low cost adsorbent for removal of pollutant from air and water(Vejahati et al, 2010;Markwiese et al, 2014). One of the environmental crises of ash utilisation is the leaching of hazardous elements into the underlying water and soil(Rowe et al, 2002;.…”