Copper and Lead Levels in Crops and Soils of the Holland Marsh Area—Ontario

Abstract

AbstractA study has been made of the occurrence, distribution, and concentrations of the heavy metals copper (Cu) and lead (Pb) in the soils crops of the important horticultural area north of Toronto known as the Holland Marsh. The soils are deep organic mucks (> 85% organic mtter), derived by the drainage of black marshland soils, which has been carried out over the past 40 years. A comparison is made between the Pb and Cu concentrations in undrained, uncultivated areas of the Marsh and in the intensively used horticultural area. Analyses show a marked accumulation of Cu in surface layers of cultivated soils, with a mean surface concentration of 130 ppm, declining to 20 ppm at a 32‐cm depth. Undrained (virgin) soils of the same marshes had < 20 ppm at all depths. Lead concentrations also declined through the profile, from concentrations of 22 to 10 ppm. In comparison, undrained areas had elevated Pb levels. Cultivation appeared to have increased Cu, but lowered Pb in the marsh. Copper and lead levels found in the crops were generally higher in the young spring vegetables than in the mature fall ones. Leafy crops, especially lettuce (Lactuca L.) and celery (Apium graveolens), accumulated higher Pb levels in their foliage compared with levels in root crops. Cultivation procedures, including past pesticide applications and fertilizer additions, appeared to be principal sources of Cu. Mobility from the soil and into the plant for these elements in the marsh muck soils is discussed.