GEOCHEMICAL CONTROLS ON METAL DISTRIBUTION WITHIN BRASSICA JUNCEA: IMPLICATIONS FOR METAL POLLUTION AND SOURCING

Metal pollution entering the food chain poses a serious environmental and human health concern, particularly for plant species that have demonstrated an ability to hyperaccumulate a variety of metals and still thrive. One such family of hyperaccumulators is the Brassicaceae family, which includes produce, such as turnips, cabbage, and broccoli, along with a variety of mustard plants. Brassicaceae have been shown to accumulate a variety of metals at a much higher concentration than the underlying substrate, in some cases resulting in weight percentages of various metals within edible plant parts. This behavior can result in metal accumulation to such a degree that human consumption can result in serious adverse health effects, even when these plants are grown in areas with relatively low geologic metal contents. While it has been observed that mineralogical and soil compositions can greatly influence the mobility and availability of various metals and that many plants, particularly those of the Brassicaceae family, can bioaccumulate metals to a great extent, there has been very little work attempting to connect these two realms.

Here, we explore the geochemical controls on metal distribution within greenhouse trials of Brassica juncea, a member of the Brassicaceae family. B. juncea thrives in a variety of geologic environments prone to unusual metal accumulations, such as various ore-forming systems and areas with advanced hydrothermal alteration, among others, making it an ideal candidate for controlled study and, ultimately, comparison with field-based studies. Preliminary results indicate biologic signatures of heavy metals within B. juncea may be heavily influenced by the underlying mineralogy. While this may pose a human health risk, the idea that biochemical signatures of plants may be influenced by the underlying geology also presents certain opportunities, namely: (1) plant-based extraction of metals with economic or environmental benefit; (2) sustainable soil management and risk minimization; and (3) long-term (multi-seasonal or multi-generational), less labor-intensive geochemical sampling.