In silico study of possible roles of relative humidity in chemical speciation on ambient particulate matter using PHREEQC
2021
Rosales, C. M. F. | Lamorena, R. B.
One of the components of ambient particulate matter (PM) that contributes to its possible toxicity are metals. Moreover, other factors in the environment, such as the presence of water as indoor humidity, can also affect the behavior of PM either physically or chemically. Chemically, the presence of water may affect the forms or species in which the metal is present. The present study aims to utilize PHREEQC, a geochemical modeling software, in the evaluation of species formation of metals in particulate matter. From all these runs, it was found that the possible roles of water in metal speciation in particulate matter are as follows: (1) in the presence of water as relative humidity (RH), metals in PM may be hydroxylated, which may facilitate further uptake of water and affect the reactivity of the PM, (2) in addition to the RH, the volume of the room may affect the species concentrations present, and (3) inferences may be made regarding the possible initial form of the metals, which may be oxides, as shown by the formation of hydroxylated metals upon exposure of metals to water vapor. These observations give a brief insight into how water may possibly interact and affect the possible toxicity of metal species in PM.
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