Lead, Cadmium, and Zinc Contamination of Aspen Garden Soils and Vegetation

Abstract

Samples of old silver mine dump materials, garden soils contaminated with mine dump materials, noncontaminated garden soils, and vegetation grown in these gardens were collected to determine the extent of Pb, Cd, and Zn contamination in Aspen, CO. Total HNO3‐HCIO4‐HF‐soluble and NH4HCO3‐DTPA (AB‐DTPA)‐extractable metals in mine dump materials and soils, respectively, were determined by inductively coupled plasma atomic emission spectrometry (ICPS). Plant samples were diegested with HNO3 and analyzed by ICPS. Total metals ranged from 135 to 21 700 mg kg−1 Pb, from 13.3 to 223 mg kg−1 Cd, and from 144 to 20 000 mg kg−1 Zn in mine dump materials. The AB‐DTPA‐extractable metals ranged from 9.2 to 808 mg kg−1 Pb, from 0.2 to 14.2 mg kg−1 Cd, and from 8.4 to 484 mg kg−1 Zn in garden soils. Many of the mine dump materials and soils contained sufficient quantities of Pb and Cd to pose potential health risks if the contaminated materials were ingested. Plant tissues were sampled from the above gardens. In general, leafy tissue concentrations of Pb, Cd, and Zn were highest. Root and other tuber crops were intermediate, lower than leaves, but higher than fruits. The range of concentrations of metals in the leafy tissues were from <5.0 to 45 mg kg−1 for Pb, from 0.6 to 11.9 mg kg−1 Cd, and from 16 to 444 mg kg−1 for Zn. In the roots, metals ranged from <5.0 to 12 mg kg−1 Pb, from 0.5 to 3.6 mg kg−1 Cd, and from 19 to 150 mg kg−1 Zn. Vegetable fruits contained <5.0 mg kg−1 Pb, from <0.5 to 2.7 mg kg−1 Cd, and from 46 to 107 mg kg−1 Zn. Members of the species Brassica oleracea did not accumulate Pb in leaves, even when grown on highly contaminated soils, but accumated Cd and Zn. It was concluded that old mine dump materials have contaminated garden soils placed on them with Pb, Cd, and Zn. The contaminated material poses a health hazard, especially for children. These potential health risks caused the USEPA to list the site on the National Priority List (Superfund sites). The USEPAh as completed its REMEDIAL INVESTIGATION/FEASIBILITY STUDY of Aspen mine dumps and has scheduled implementation of remedial action (clean up) to begin in 1991.

Accumulation and implications of cadmium, cobalt and manganese in soils and vegetables irrigated with city effluent

“…A concentration of 0.10 mg Cd kg −1 plant material on a dry weight basis is generally considered critical 22. Boon and Soltanpour35 observed higher concentrations of Cd in leaves of vegetables such as lettuce, radish, tomato and carrot than in the respective roots or fruits. In the present study the higher concentration of Cd in plant samples could be partially due to bioaccumulation, since the Cd content of the soils on which they were grown was below the permissible limit.…”

Accumulation of heavy metals by vegetables grown in mine wastes

“…Stream sediments and resultant floodplain soils that are downstream of historic mines may be attractive as amendments to increase the productivity of home gardens. This would pose concerns, as lead, cadmium, arsenic, and other heavy metals accumulate in the leaves and roots of vegetable plants [6, 7, 10, 17, 21]. Metal accumulation depends on plant species, chemical species, and soil condition [19, 22–26].…”

Trace Metal Contamination in Community Garden Soils across the United States

“…High levels of trace metals were also found in the leaves of plants than in any other area [33], with high concentrations of metals being found in leafy vegetables such as lettuce or cabbage, which might be due to strong transpiration throughout the leaves as they are the main part of the plant used for photosynthesis. Root vegetables are speculated to have high concentrations of metals because lead, cadmium, and arsenic are not nutrients like copper and zinc, so they are stored in the root of the vegetable [44].…”

“…Both urban and nonurban gardeners should be aware of this exposure pathway and should attempt to limit trace metal uptake of plants in their soil. This can be carried out by applying a 10% volume-toweight ratio of biochar and compost to limit the availability of trace metals, mainly lead, and avoiding growing too many root crops or leafy crops, as they tend to uptake more trace metals than fruits or nightshade vegetables [5,17,33].…”