Release flux of mercury from different environmental surfaces in Chongqing, China.

An investigation was conducted to estimate mercury emission to the atmosphere from different environmental surfaces and to assess its contribution to the local mercury budget in Chongqing, China. Mercury flux was measured using dynamic flux chamber (DFC) at six soil sites of three different areas (mercury polluted area, farmland and woodland) and four water surfaces from August 2003 to April 2004. The mercury emission fluxes were 3.5+/-1.2-8.4+/-2.5 ng m(-2) h(-1) for three shaded forest sites, 85.8+/-32.4 ng m(-2) h(-1) for farming field, 12.3+/-9.8-733.8+/-255 ng m(-2) h(-1) for grassland sites, and 5.9+/-12.6-618.6+/-339 ng m(-2) h(-1) for water surfaces. Mercury exchange fluxes were generally higher from air/water surfaces than from air/soil surfaces. The mercury negative fluxes were found in tow soil sites at overcast days (mean=-6.4+/-1.5 ng m(-2) h(-1)). The diurnal and seasonal variations of mercury flux were observed in all sites. The mercury emission responded positively to the solar radiation, but negatively to the relative humidity. The mercury flux from air/soil surfaces was significantly correlated with soil temperature, which was well described by an Arrhenius-type expression with activation energy of 31.1 kcal mol(-1). The annual mercury emission to the atmosphere from land surface is about 1.787 t of mercury in Chongqing.