engleski

Concentrations of Lead and Cadmium in the Zagreb Air During the Period 1975-1999

Time series of average monthly lead and cadmium concentrations in the air measured during the period 1975-1999 at two sampling sites in Zagreb were analysed for trends, seasonality, and intercorrelations. The sampling sites were the city centre and the northern residential area. Periodograms showed two significant maxima for a one-year period and for a 15-year period. Polynomial smoothing of monthly averages showed a bimodal curve similar for the two sampling sites. Bearing in mind that the primary lead source in the air is vehicle exhausts, fluctuations of total suspended particulate matter in the air, and the shape of time trend curves can be attributed to the standard of living, the world oil crisis in the early eighties, the war in Croatia, and a rise in lead-free gasoline consumption. The lead concentration rise by the late seventies may be attributed to the growth of personal standard in the former Yugoslavia. The declination started in the early eighties along with the world oil crisis and was succeeded by a drop in the standard which lasted until the late eighties when the second maximum occured. The war in Croatia started in 1991 and the standard of living dropped again. An additional effect can be attributed to the rise of lead-free gasoline consumption. Just like periodograms, autocorrelation functions of lead concentrations showed a strong seasonal effect, with higher values during winter and lower during summer. The correlation coefficients and the results of regression analysis suggest that transport significantly affects in lead content in the air.

nije evidentirano

nije evidentirano