Root Uptake of Cobalt in Common Vegetables
Authors:
- Students:
- Aditya Dave
- Summer Leung
- Somya Mehta
- Shreya Mukunthan
- Siri Nayakanti
- Charlotte Nordahl
- Tejas Shetty
- Dhruv Syngol
- Teachers:
- Vanessa Troiani
- Mentors:
- Olga Antipova (Argonne National Laboratory, XSD-MIC)
Advanced Photon Source Sector 2: Microscopy
Cobalt is a chemical element with the atomic number of 27 on the periodic table. As a transition metal next to Iron and Nickel, cobalt can be found in small deposits in rocks, water, plants, animals, industrial processes, and even everyday objects like batteries or tools. In lower concentrations that are below 1.8 mg/L, Cobalt is an essential trace element in humans because of its important role in the formation of amino acids, proteins in nerve cells, neurotransmitters, along with being a necessary component of vitamin B12 (Czarnek et al., 2015). Within plants, cobalt fuels the process of nitrogen fixation, allowing plants to appropriately use nitrogen for their innate processes. However, when thrown into flux, Cobalt can become deadly. Concentrations of Cobalt greater than 1.8 mg/L can potentially lead to asthma, hard metal lung disease,contact allergy, and an increased risk of cancer (Wahlquivst et al., 2020). Plants, fruits, and vegetables are some of the main transporters in which metals enter the body, but the way in which they take up Cobalt remains obscure. Cobalt can enter the environment from both natural sources and human activity, and is present in the soil, water, and air; of this exposure, food is the largest source of cobalt intake (Agency for Toxic Substances and Disease Registry (ATSDR). 2004). High concentrations of cobalt are found in the soil and air near mines, such as by the United State’s newest cobalt mine in Idaho, which is expected to play a significant role in the electric transportation industry. (Siegler & Whitney, 2022). Human exposure includes inhalation, ingestion, or contact of the skin to cobalt; repeated exposure can cause difficulty breathing and lead to chronic lung problems including asthma and pulmonary fibrosis (ATSDR, 2004). Cobalt poisoning has been further documented in prosthetic hip associated cobalt toxicity, or PHACT, from prosthetics, which has been known to cause systemic toxic effects including peripheral neuropathy, sensorineural hearing loss, vision loss, and cognitive decline (Venkatraman et al., 2020). The planned experiment will be to grow cucumber, corn, lentil, basil and Arabidopsis thaliana seeds in petri dishes with a 1% agar 1% sucrose growth medium. 20 of each plant’s seeds will be sterilized and planted into the gel. They will undergo vernalization for 2 days, then be grown under 23° white light for 7 days. The control plants will then be extracted from the gel to cut 1.5-2 mm root tips. Meanwhile, the experimental group will be exposed to a Cobalt concentration of 1.8 mg/L for 1 hour of incubation. Roots of these plants are then also cut. All roots get scanned with 5x5 μm step size and 5 msec dwell time at 13.7 KeV (or 10.5 KeV). Data will be collected using XRF-MAPS to measure all major element concentrations.
The Beamline 2-ID-E contains the necessary high resolution and sensitivity to see and analyze the plant tissues. This specific area utilizes full fluorescence spectra to be shown at each pixel, which is how Cobalt concentration uptake is measured for each specimen. The collected spectra can be analyzed by using the custom MAPS software and calibrated and quantified by using AXO thin film standard. From this, we can further understand how plants are a pathway for Cobalt to enter the human body. Our hypothesis is that the plants grown in environments containing increasingly concentrated levels of Cobalt will take up increased levels of Cobalt, more so than would occur naturally as a result of natural Cobalt levels present in an environment. This, in turn, would have detrimental effects to plant well-being, as well as animal/human wellbeing, via consumption. By finding the relative amount of cobalt taken up by different plants in different environments, we can then learn what kinds of plants are suitable to grow in a cobalt-contaminated area, those with Cobalt uptake below the “safe” level.