Effect of heavy metals on peppermint and cornmint

Abstract

Heavy metal pollution of agricultural soils and air is one of the most severe ecological problems on a world scale and in Bulgaria in particular. The biggest sources of pollution in Bulgaria are some non-ferrous metals smelters, such as the Non -Ferrous Metals Combine (NFMC) near Plovdiv, situated on very fertile soils. Vegetable, arable and animal production in this area results in contaminated produce with excessive amounts of Cd, Pb, Cu, Mn and Zn.In order to discover some crops which could be grown on these areas without contamination of the end product, we conducted (in 1991-1993) field experiments in the vicinities of NFMC near Plovdiv. As experimental material we used Mentha piperita L. (cv Tundza and Clone No 1) and Mentha arvensis var piperascens Malinv. (cv . Plants have been grown on three Plots: Plot No 1 -at a distance of 400 m from the source of pollution; Plot No 2 -at 3 km from the source of pollution and on a control Plot -in the experimental gardens of University of Agriculture in Plovdiv, at 10 km from the source of pollution. It was established that heavy metal pollution of soil and air at a distance of 400 m from the source of pollution decreased the yields of fresh herbage by 9-16% and the yield of essential:oil by up to 14% compared to the control, but did not negatively affect the essential oil content and its quality.Oils obtained from Plot 1 at a distance of 400 m from the source of pollution have not been contaminated with heavy metals.Cultivar response to heavy metal pollution was established. A positive correlation between Pb concentration in leaves and in essential oil was found.Heavy metal concentration in the plant parts was found to be in order: for Cd roots > leaves > rhizomes > stems; Pb roots = leaves > rhizomes = stems; Cu roots > rhizomes = stems = leaves; Mn roots > leaves > stems = rhizomes; Zn leaves > roots > stems = rhizomes.The tested cultivars of peppermint and cornmint could be successfully grown in highly heavy metal polluted areas, as in the area around NFMC near Plovdiv, without contamination of the end product -the essential oils.Despite of the yield reduction (up to 14%), due to heavy metal contamination, mint still remained a very profitable crop and it could be used as substitute for the other highly contaminated crops.

Development of mint (Mentha piperita L.) grown on biosolids: evaluation of productivity and essential oil content

“…With time, mint plants seemed to have adjusted to the cultivation conditions in the presence of biosolids, because they no longer showed differences in dry matter values when grown in the presence of different levels of solids residues. These results were in agreement with those of Zheljazkov and Nielsen (1996) and Scora and Chang (1997), because the mint plants were capable of developing without accumulation of these metals in their tissues. When mint plants were evaluated as for dry matter of stem plus petiole (Fig.…”

“…In all evaluation periods, a higher value for root dry matter was observed in the plants grown without biosolid. The increase in the residue levels was accompanied by a decrease in root dry matter, which suggested the phytoremediator action of mint plants (Zheljazkov and Nielsen, 1996;Scora and Chang, 1997). Maisonnave et al (2002) observed that the roots of grass plants grown on biosolids assimilated high levels of heavy metals obstructing their translocation to other plant parts.…”

“…However, there are restrictions for the use of biosolids from sewage of metropolitan regions because of mineral imbalance, high levels of heavy metal (Bettiol and Camargo, 2000), ammonia volatilization and increase of soil salinity, when the residue is applied at elevated concentrations (Bugbee, 2002). Zheljazkov and Nielsen (1996) reported a decrease from 9 to 16% of mint fresh matter grown in high concentrations of Cd, Pb, Cu, Mn and Zn.…”

The response of chamomile (Matricaria chamomilla L.) plants to soil zinc supply

“…Ren et al (1993) observed increased synthesis of ginsenosides in Panax quinquefolium L. plants. On the other hand, field experiments with Mentha piperita L. and Mentha arvensis L. grown on strongly contaminated soil in the vicinity of a smelting plant for non-ferrous metals, showed a decreased yield of fresh herbage but the content of essential oil was not affected by contamination of soil with heavy metals (Zheljazkov and Nielsen 1996).…”

Low-cost agricultural measures to reduce heavy metal transfer into the food chain - a review

“…Similar results were obtained for peppermint and cornmint, where no heavy metal contamination was found in the essential oils. Despite of the yield reduction (up to 14%) caused by heavy metal contamination, mint still remained a very profitable crop and it could be used as substitute for other crops (Zheljazkov and Nielsen 1996a). Other industrial crops suggested for cultivation on metal contaminated soils were fibre plants like flax, cotton, hemp (e.g., Yanchev et al 2000, Angelova et al 2004 and energy crops, such as Salix trees and reed canary grass (Börjesson 1999).…”