Release of cadmium, copper and lead from urban soils of Copenhagen

- Total Cd, Cu and Pb concentrations were elevated 5-27 times in the urban soils.
- Cd and Pb are potentially available from acid leachable and reducible soil fractions.
- Up to 78, 18 and 15% of total soil Cd, Cu and Pb could be acid leached.
- Initial Cd and Pb release rates increase 10 fold with pH decrease of 2 and 3 units.
- The mobility of Cu and Pb were higher in urban compared to agricultural soils.

We studied the bonding and release kinetics of Cd, Cu and Pb from different soils in the older metropolitan area of Copenhagen. Total Cd, Cu and Pb concentrations were elevated 5-27 times in the urban soils compared to an agricultural reference soil, with Cd and Pb in mainly mobilisable pools and Cu in strongly bound pools. The soils were subjected to accelerated leaching studies in Ca(NO3)2 or HNO3 solutions resulting in release up to 78, 18 and 15% of total Cd, Cu and Pb soil concentrations over a period of 15 weeks. The relative initial Cd and Pb release rates increased 10 fold when pH decreased 2 and 3 units, respectively, while increases in Cu release rates were only seen at pH below 4. The total leachable Cu and Pb pools were higher in urban soils compared the agricultural reference soil but not for Cd.