Influence of Increasing Tungsten Concentrations and Soil Characteristics on Plant Uptake: Greenhouse Experiments with Zea mays

Abstract

Tungsten is largely used in high-tech and military industries. Soils are increasingly enriched in this element, and its transfer in the food chain is an issue of great interest. This study evaluated the influence of soil characteristics on tungsten uptake by Zea mays grown on three soils, spiked with increasing tungsten concentrations. The soils, classified as Histosol, Vertisol, and Fluvisol, are characteristic of the Mediterranean area. The uptake of the element by Zea mays was strictly dependent on the soil characteristics. As the pH of soils increases, tungsten concentrations in the roots and shoots of the plants increased. Also, humic substances showed a great influence on tungsten uptake, which decreased with increasing organic matter of soils. Tungsten uptake by Zea mays can be described by a Freundlich-like equation. This soil-to-plant transfer model may be useful in promoting environmental regulations on the hazards of this element in the environment.

The Dynamics of Tungsten in Soil: An Overview

“…With regard to the Wenzel SEP, the concentration of tungsten in the F1 fraction extractable by 0.05 M (NH 4 ) 2 SO 4 represents the soluble and exchangeable forms of the element, and thus the readily labile amount that has the highest environmental risk. The F1 fraction also indicates quantities that may be bioavailable to plants; however, an accurate description of this quantity can also be obtained by a single extraction with water [54] or 0.01 M calcium chloride [55].…”

“…As with all other metals [62], soil pH plays a crucial role in determining the mobility and bioavailability of tungsten. Tungstate ion behaves similarly to molybdate, and by increasing the solubility, it becomes more bioavailable as pH increases [55,63,64]. The solubility of tungstate is strongly influenced by interactions with the positively charged surfaces of minerals, such as those of metal oxides (Fe, Al, Mn), of which the surface charge is controlled by the pH of the soil, and those of the external sites of clay minerals [65].…”

Sustainable Agriculture and Soil Conservation

“…This SI collects 12 original contributions focused on soil use and management, soil conservation, as well as on the impact of some pollutants on the soil. Specifically, the SI collects nine research papers [10][11][12][13][14][15][16][17][18], two reviews [19,20] and one methodological work [21]. Eight of the twelve manuscripts considered the effects of soil use and management (topic I) [10][11][12][13][14][15][16]21], while the remaining four [17][18][19][20] evaluated the impact of some soil contaminants (e.g., crude oil, tungsten, copper and polycyclic aromatic hydrocarbons) (topic II).…”

“…Regarding the aforementioned nine investigations (i.e., research papers), seven were carried out in the field [10][11][12][13][14][15][16], while the others accounted for pot [17] or microcosm [18] experiments. From a geographical point of view, five "field open-air" investigations were carried out in Italy (three in the south [12,13,16], one in the center [15] and one in the north [10] of Italy), while the remaining investigations were in Brazil [14] and China [11].…”

“…Petruzzelli and Pedron [18] investigated the influence of the soil characteristics on the tungsten uptake by maize for three different soils-Histosol, Vertisol and Fluvisol-in the Mediterranean area. Tungsten is largely used in high-tech and military industries.…”