Arsenic speciation in Portuguese in situ lichen samples.

In this work, 29 lichen samples collected in situ and representative of high loadings, medium loadings and zero loadings for factors related to natural and anthropogenic emission sources, were analyzed to determine arsenic contents and its species extractability. The studied sites showed As values between 430 and 5590 microg kg(-1). The cationic forms were extracted at most of the sites varying between 0.5% and 6.6%. Extracted anionic forms were not detected in any of the sites. In a few other sites the % of extracted As(III)--more toxic--exceeds the equivalent value of As(V). It is concluded that arsenic in native Parmelia sulcata Taylor under the form of As(V) either was kept unchanged or was partially transformed into As(III) (more frequent) or partially transformed into As(III) and dimethylarsinic acid (DMAA) or partially transformed into DMAA.