Total gaseous mercury measurements at four sites of the Mexico City Metropolitan Area during a short period

摘要

This work reports the results of total gaseous mercury (TGM) measurements during short periods (14 days) at four different sites of the Mexico City Metropolitan Area (MCMA) using a Tehran mercury vapor analyzer (Model 2537A), with an integration time of 5 minutes. The instrument was calibrated daily using an internal mercury permeation source. TGM was measured at two stations of the air monitoring network of Mexico City: Xalostoc (XAL) (19 deg 31 min N; 99 deg 04 min W) and San Agustin (SAG) (19 deg 31 minN; 99 deg 01 min W) during February and March 2003. Both sites are located NE of the City and correspond to an industrial and residential area, respectively. The third monitoring site was located at Iztapalapa (IZT) (19 deg 21 min N; 99 deg 04 min W), SE of MCMA, where TGM measures were made from 11/02 to 01/03; this area is characterized to be both an industrial and a highly populated residential area. The fourth monitoring site (from 01/03 to 2/03) was Tecamachalco (TEC) (19 deg 26 min N; 99 deg 13 min W), which is located NW of MCMA in a mainly residential area, however nearby there are a military base and a chemical analysis laboratory. TGM median concentrations for the 25 and 75% percentiles were: 21.64, 9.03, 10.09 and 51.04 ng centre dot m~(-3) for the sites XAL, SAG, IZT and TEC, respectively. Maximum TGM concentrations within 95% percentiles were detected recorded at the TEC (108 ng centre dot m~(-3)) and XAL (86 ng centre dot m~(-3)) sites. Variations among sites could be attributed to the characteristic activities of these areas. An assessment of potential anthropogenic mercury sources and their influence on our measurement site are here discussed. Data of air pollutant concentrations (O3, CO, SO2, NO2 and PM_(10)) and meteorological parameters (temperature, relative humidity, wind speed, wind direction) were also analyzed in order to determine some possible correlation with TGM data.