Screening Campaign of Air Quality in Hanoi City

Abstract:

Within the frame of the Swiss-Vietnamese Clean Air Program (SVCAP), a project under a
bilateral agreement of the two governments, the air pollution of Hanoi was screened at a
100 locations with the passive sampling method. One hundred sites in and around Hanoi
were selected for the monitoring of SO2, NO2 and BTX. These sites were classified into
traffic hot spots sites (6), industrial hot spots sites (8) sites in rural areas (5) and the rest
in city background areas in eight inner districts covering about 120 km2. In reality, of the
81-city background sites, only 45 can be regarded as "true" background, the remaining
36 sites are on roadside locations.

Maps of NO2, SO2 and BTX were constructed that help predict the pollution levels at any
areas inside 8 inner districts by ArcGIS Software. Kriging technique was applied. In
summer (wet season), the levels of air pollutants are generally lower than during the
winter period (dry season) especially if Hanoi experiences an inversion. This is a
meteorological phenomena, where ground temperature is lower than above (formation of
a stable cold temperature “lake”). The variations of NO2 average concentrations of
8 inner districts can be statistically explained by the population density. This linear
relationship reflects the district emission density of motorbikes, as well as the ground
level atmospheric dispersion capacity. Both factors result in the high concentrations of
pollutants in crowded districts and low pollution in Tay Ho district. For SO2, no significant
relationship between pollutant concentrations and population density was found. “Thanh
Xuan”, an old industrial area of Hanoi with the population density ranked fourth, is most
SO2 polluted.).

Keywords: diffusive sampling, mapping, public health, kriging, benzene