Production of perchlorate by laboratory simulated lightning process

Balaji Rao, Suhas Mohan, Andreas Neuber, William Andrew Jackson

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24 Scopus citations


Perchlorate (ClO 4 -), a thyroid hormone disruptor, is both naturally occurring and a manmade contaminant increasingly found in a variety of terrestrial environments. The environmental presence of ClO 4 - is considered to be the result of atmospheric formation and deposition processes. The ultimate processes, particularly heterogeneous-based reactions, leading to natural ClO 4 - formation are not well understood. Oxidation of chlorine species by an energetic source such as lightning is considered to be one of the potential heterogeneous sources of natural ClO 4 -. Currently, there is very little information available on lightning-induced ClO 4 -. We designed a laboratory electrical discharge reactor capable of evaluating ClO 4 - formation by the oxidation of "dry" sodium chloride (NaCl) aerosols (relative humidity (RH) <70%) in electrical discharge plasma at voltages and energies up to 24 kV and 21 kJ, respectively. Similar to other non-electrochemical ClO 4 - production processes, the amount of ClO 4 - produced (0.5-4.8 μg) was 3 orders of magnitude lower than the input Cl - (7.1-60.1 mg). The amount of ClO 4 - generated increased with peak voltage (V) and theoretical maximum discharge energy with ΔClO 4 -/ΔV=0.28× 10-3 μg V -1 (R 2=0.94) and ΔClO 4 -/ΔE=0.44× 10-3 μg J -1 (R 2=0.83). The total ClO 4 - generated decreased with an increase in relative humidity from 2.8±0.1 μg (RH̃46%) to 0.9±0.1 μg (RH̃62%) indicating that the presence of moisture inhibits the formation of ClO 4 -. Additional modifications to the reactor support the hypothesis of ClO 4 - formation due to the action of plasma on Cl - aerosols as opposed to direct oxidation on the surface of the electrodes. Finally, the contribution of lightning-induced ClO 4 - in North America is calculated to have a wide range from 0.006×10 5 to 5×10 5 kg/year and is within the range of the measured ClO 4 - depositional flux in precipitation samples obtained across the USA (0.09× 105-1.2×10 5 kg/y).

Original languageEnglish
Pages (from-to)275-287
Number of pages13
JournalWater, Air, and Soil Pollution
Issue number1
StatePublished - Jan 2012


  • Deposition
  • Lightning
  • Natural
  • Perchlorate


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