Behavior of KCl sorbent traps and KCl trapping solutions used for atmospheric mercury speciation: stability and specificity

Abstract

Abstract. Atmospheric mercury speciation is of paramount importance for understanding the behavior of mercury once it is emitted into the atmosphere as gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particulate-bound mercury (PBM). GOM and PBM can also be formed in the atmosphere; their sampling is the most problematic step in the atmospheric mercury speciation. GOM sampling with speciation traps composed of KCl sorbent materials and KCl trapping solutions are commonly used sampling methods, although the research conducted with them at ambient air concentrations is limited. The results of the specificity test demonstrated that the KCl sorbent traps are highly specific when using new traps, while their specificity drops dramatically when they are reused. The results of the stability test indicated that the highest Hg2+ losses (up to 5.5 % of Hg2+ loss) occur when low amounts of Hg2+ (< 1 ng) are loaded, due to a reduction of Hg2+ to Hg0. KCl trapping solutions have also been considered as a selective trapping media for GOM in atmospheric samples. A dimensionless Henry law constant was experimentally derived and was used to calculate the solubility of elemental Hg in KCl solution. The degree of GEM oxidation was established by purging elemental Hg calibration gas into a KCl solution and determining the GOM trapped using aqueous-phase propylation liquid–liquid extraction and gas chromatography–atomic fluorescence spectrometry (GC-AFS) measurement. A positive GOM bias was observed due to the solubility and oxidation of GEM in KCl trapping solutions, strongly suggesting that this approach is unsuitable for atmospheric mercury speciation measurements.

Atomic spectrometry update – a review of advances in environmental analysis

“…A novel signal-enhancement strategy for LIBS analysis of soil combined 201 APGD and cylindrical (plasma) connement. The LODs of 2,31,21,35,49,67,43,20 and 18 mg kg −1 for Ba, Cu, Eu, La, Lu, Ni, Ti, Y and Yb, respectively, were signicantly better than the values (10,133,102,175,262,356,246,158 and 105 mg kg −1 , respectively) achievable using conventional LIBS. An alternative approach involved 202 addition of 15% KI to soil samples to increase plasma temperature and electron density.…”

“…Although sampling into impingers containing HNO 3 /H 2 O 2 best preserved volatile trapped Sb species, preconcentration onto solid-phase traps containing AgNO 3 -impregnated silica gel was preferable for remote locations and for achieving a lower method LOD. The performance of both KCl-impregnated sorbent traps and KCl-liquid impinger samplers, widely used to trap gaseous oxidised mercury (GOM), were evaluated 20 using a novel 197 Hg radiotracer procedure. Reduction of some of the collected Hg 2+ species to Hg 0 resulted in losses from the sorbent traps even when spiked only with a mass (<1 ng) typical of that collected when clean ambient air is sampled.…”

Measurement of Atmospheric Mercury: Current Limitations and Suggestions for Paths Forward

“…Then, during a 30 min period, while the system samples Hg-free air, the denuder and particulate filter are sequentially heated, and released Hg goes through a pyrolyzer, then enters the Tekran 2537 unit where Hg 0 concentrations are determined. KCl-coated denuders in the Tekran system have been demonstrated to be biased low by up to 50%, due to reactions with ozone that reduce GOM, collection of different Hg compounds with unequal efficiency, passivation due to water vapor, and decreased efficiency over time. ,,− Repetative heating decreases the collection efficiency, therefore, denuders should not be used for long periods without recoating . It is important to consider that the denuder performance will vary according to location.…”