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Title: The influence of soil factors and atmospheric deposition of the cadmium and lead contents of vegetables
Author: Moir, Ann Mary
ISNI:       0000 0001 3413 9711
Awarding Body: Imperial College London (University of London)
Current Institution: Imperial College London
Date of Award: 1992
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A comprehensive survey was undertaken in 94 allotments and gardens in nine English towns and cities to assess the degree of contamination of soils and vegetables by lead and cadmium. Comparisons were made with the results obtained in a smaller survey of soils and vegetables in an old lead mining area of Derbyshire and with those found in a basket survey of retail vegetables. The geometric mean lead concentration for the soils, 215 μg/g, was five times higher than values found for agricultural soils while the mean cadmium concentration, 0.47 μg/g, was similar to 'background' levels. Very much higher levels of both lead and cadmium were noted in Derbyshire soils. Lead concentrations in the vegetables ranged from <0.25 to 16.7 1ug/g dry weight and cadmium concentrations ranged from <0.03 to 10.4 μg/g. Lead concentrations were higher than background values reported by the Ministry of Agriculture, Fisheries and Food and than levels found in the basket survey of retail vegetables. However, less than 1% exceeded the UK statutory limit for lead in saleable food (1 μg/g fresh weight), whereas 13% of the Derbyshire vegetables exceeded this value. Cadmium concentrations were generally similar to background levels but several times lower than those found in Derbyshire vegetables. Multivariate analysis of the urban vegetable and soil data indicated that lead concentrations in the vegetables were largely dependent on the 'total' lead content of the soil, while soil cadmium levels (anunonium nitrate extractable and 'total') and pH were the best predictors of vegetable cadmium concentrations. The relative importance of foliar and root uptake to the lead and cadmium content of urban vegetables was assessed by means of two studies. A 109Cd study proved unsuccessful due to incomplete equilibration of the added radiotracer with the stable cadmium content of the soil. However, a control soil study indicated that soil-derived lead and cadmium contributed around 57% and 67%, respectively, to the lead and cadmium contents of leafy vegetables.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available