A survey of soil lead levels in the city of Winnipeg
Krawchuk, Bert Paul.
Lead has been mined and used for thousands of years. Today, lead is the most common non-ferrous heavy metal pollutant of the environment. In particular soils by major roadways and around smelters have been found to be contaminated by lead. A survey of soil was carried out in the city of Winnpeg during the period September 1978 to September 1979. Seventy-five sites, ranging from residential through heavily trafficked arteries to industrial areas were sampled on a seasonal basis. In the winter a number of snow samples were collected and examined. The samples were prepared using a nitric-perchloric acid digest. Extracts were analysed for lead by atomic absorption spectroscopy. An extraction of 95% or better was obtained. The survey found high lead-in-soil levels (>1000 ug Pb/g soil) beside major arteries and at busy intersections. As well, high lead-in-soil levels were found in areas surrounding secondary lead smelters. Snow samples showed the same trend, high lead levels along major arteries, low lead levels in residental areas. Lead levels in roadside soil are traffic volume dependent. Soils from along major routes had lead-in-soil levels greater than 1000 ug/g while residential area soils gave levels of less than 500 ug/g. The three smelter sites were found to have high lead-in-soil levels (1,000 to 12,000 ug/g) in the soil around them. A factor influencing the lead level observed in the soil was found to be site location of the sampling point within the area of study. As well, site history (topography, physical disruption of the soil) is believed to be a factor for the lead observed in the soil at that site. The salt spred during the winter was found to reduce the accumulated lead levels along major arteries from fall to spring.