For several decades,elemental mercury(Hg0)has been released from artisanal and small-scale gold mining(ASGM)along the Cikaniki River in West Java,Indonesia.The refining processes associated with ASGM release significant amounts of Hg into the surrounding environment; however,Hg dispersion through air is not yet well understood.The aims of this study are to determine the speciation of Hg in air from the ASGM operation,measure Hg concentration for each ASGM operational step in real time,and reveal the distribution of atmospheric Hg concentration in the Cikaniki River Basin using a biomonitoring method.Hg2+ and Hg0 in air were collected using KCl and KMnO4 solutions,respectively.Ambient air was drawn through the solutions at a flow rate of 0.5 L min?1.Hg concentration collected in the solutions was measured by cold vapor atomic absorption spectrometry(CVAAS).Real-time measurements of Hg0 in air were performed using an EMP-2 mercury analyzer(NIC,Tokyo,Japan).Fronds of a native epiphytic fern Asplenium nidus complex were used as a biomonitor.Three or more fronds of A.nidus were collected from nine locations in March 2014.The fronds were washed with water and dried at 70°C for five days.The total mercury concentration in the fronds was determined by CVAAS after acid digestion.The Hg2+ and Hg0 concentrations in air were 130 ng m?3 and 5.6 μg m?3,respectively,inside an ASGM workplace,whereas 1.3–48 ng m?3 and 1.3–5.0 μg m?3,respectively,outside the ASGM workplace.When an amalgam was burned,Hg2+ and Hg0 concentrations elevated to 92 μg m?3 and 61 μg m?3,respectively.Although Hg0 is the primary form of Hg in the atmosphere around ASGM workplaces,a significant amount of Hg2+ is emitted during amalgam burning process.The atmospheric Hg2+ emitted is then deposited rapidly on the surrounding surfaces and/or dissolved in environmental water.Results of real-time measurements indicated clear peaks for each mining step; inside the work place,the recorded Hg concentrations were 10 μg m?3 and 45 μg m?3 for inactive and panning,respectively,whereas that for outside the workplace was 3.2–4.9 μg m?3.And the concentration exceed the detection limit(>999 μg m?3)of the mercury analyzer for amalgam burning processes in a fume hood.The distribution and trend of atmospheric Hg concentrations in the studied area were discussed with regard to the biomonitoring results.