N. Pirrone et al., TRENDS OF AMBIENT CONCENTRATIONS AND DEPOSITION FLUXES OF PARTICULATETRACE-METALS IN DETROIT FROM 1982 TO 1992, Science of the total environment, 162(1), 1995, pp. 43-61
Ambient air concentrations of the particulate trace metals Fe, Zn, Pb,
Ni, Cr, Cd, Be and Hg have been measured since the early 1980s at sev
en urban sites across the metropolitan area of Detroit. Trace metals s
uch as Fe, Zn, Ni and Cr were found to be more abundant at industrial
sites, while Pb and Cd concentrations were highest at commercial sites
. Be and Hg ambient concentrations did not show any large variations a
mong land use categories on an annual average basis. The largest incre
ases in ambient concentrations between two consecutive years were a 20
fold increase for Fe in industrial areas (Winter 1988), a 21-fold inc
rease for Zn in a residential area (Summer 1986), a 5-fold increase fo
r Ni in commercial areas (Winter 1992), a 10-fold increase for Cr in i
ndustrial and commercial areas (Spring 1982), a 5-fold increase for Cd
in commercial areas (Fall 1987), a 27- and 24-fold increase for Be in
residential and industrial areas, respectively; and a 6-fold increase
for Hg in residential areas. Pb did not show a large increase between
2 consecutive years (< 1%); however a 6-fold decrease was observed in
residential areas during the summer of 1992. Selected US market param
eters were used as indicators of emission source activity and their te
mporal trends were compared with those of the ratio between maximum (C
(max)) and average (C(average)) ambient concentrations of trace metals
observed in Detroit. Good agreement was found between the trend in th
e C(max)/C(average) ratio and the trend in US production and consumpti
on, import and export, and the price of metal-based products. A dynami
c model was used to calculate the dry deposition flux of trace metals
associated with total suspended particulate matter and its temporal va
riation by land-use category accounting for the variation of meteorolo
gical parameters, surface roughness, and ambient concentration. This m
odel showed that the seasonal variability in meteorological parameters
may yield a 40-50% variation in the dry deposition velocity of partic
ulate trace metals on an annual basis. It also showed that deposition
fluxes are generally higher in industrial areas than in residential an
d commercial areas. Finally, temporal trends of the ambient concentrat
ion and dry deposition flux of particulate trace metals are provided f
or the 1982-1992 period using a simple regression of seasonal data obt
ained at each sampling site. Ambient concentrations and dry deposition
fluxes of Fe, Pb, Cr, Cd and Be are characterized by downward trends
with annual decreases in the range of -1 to -11% using 1982 as the ref
erence year. Trace metals such as Zn, Ni and Hg show an upward trend w
ith annual increases in the range of 0.4-9%.