Angebotene Bachelorarbeit

Arsenic in Taro

Betreuer: Britta Planer-Friedrich, Jeany Werner

Taro (Colocasia esculenta) is one of the World´s oldest food crops (ref1) with research indicating its use 28,000 years ago on the Solomon islands (ref2). Probably originated in southeast Asia Taro has spread throughout the world early on. Today it is an important staple food in the Pacific Islands, Asia and Africa, where it is cultivated mainly for its starch- and mineral rich tubers.(ref3) However, there are studies indicating the potential of taro to accumulate heavy metals like cadmium (Cd) (ref4), lead (Pb) (ref4,5), mercury (Hg) (ref5) and arsenic (As) (ref5-8), there is hardly information on arsenic speciation. Furthermore, one of the two main cultivations methods of taro is under wetland-irrigated (flooded) conditions(ref9), which resembles the cultivation of rice in paddy fields. Recent studies have shown that paddy soil pore waters are a source of methylated Thioarsenates(ref10) - like the highly toxic(ref11) Dimethylmonothioarsenate (DMMTA) - which can then be taken up, translocated and accumulated within the rice plant.(ref12,13) Since there is no information on methylated thioarsenates in taro, we would like to investigate their importance (and distribution) in this plant. Therefore, the aim is to analyze an initial set of taro samples for arsenic (and other elements) content, including arsenic speciation analysis. The study could also include field sampling of (wetland) taro plants (and associated soil/porewater).

Literature:

1. Rao, V. R., Matthews, P. J., Eyzaguirre, P. B., & Hunter, D. (2010). The Global Diversity of Taro: ethnobotany and conservation.

2. Loy, T. H., Spriggs, M., & Wickler, S. (1992). Direct evidence for human use of plants 28,000 years ago: starch residues on stone artefacts from the northern Solomon Islands. Antiquity, 66(253), 898-912.

3. Chaïr, H., Traore, R. E., Duval, M. F., Rivallan, R., Mukherjee, A., Aboagye, L. M., ... & Lebot, V. (2016). Genetic diversification and dispersal of taro (Colocasia esculenta (L.) Schott). PloS one, 11(6), e0157712.

4. Bindu, T., Sumi, M. M., & Ramasamy, E. V. (2010). Decontamination of water polluted by heavy metals with Taro (Colocasia esculenta) cultured in a hydroponic NFT system. The Environmentalist, 30, 35-44.

5. Essumang, D. K., Dodoo, D. K., Obiri, S., & Yaney, J. Y. (2007). Arsenic, cadmium, and mercury in cocoyam (Xanthosoma sagititolium) and watercocoyam (Colocasia esculenta) in Tarkwa a mining community. Bulletin of environmental contamination and toxicology, 79, 377-379.

6. Kundu, R., Pal, S., & Bandopadhyay, P. (2013). Response of Taro to Arsenic Contamination in the Ganga Basin of Eastern India. JOURNAL OF ROOT CROPS, 37(2), 168. Retrieved from http://journal.isrc.in/index.php/jrc/article/view/42

7. Alam MG, Snow ET, Tanaka A. Arsenic and heavy metal contamination of vegetables grown in Samta village, Bangladesh. Sci Total Environ. 2003 Jun 1;308(1-3):83-96. doi: 10.1016/S0048-9697(02)00651-4. PMID: 12738203.

8. Thathong, V., Tantamsapya, N., Yossapol, C., Liao, C. H., Wirojanagud, W., & Padungthon, S. (2019). Role of Colocasia esculenta L. schott in arsenic removal by a pilot-scale constructed wetland filled with laterite soil. Heliyon, 5(2), e01233.

9. Yamanouchi, H., Tokimura, K., Miura, N., Ikezawa, K., Onjo, M., Minami, Y., & Kajiya, K. (2022). Effects of flooding cultivation on the composition and quality of taro (Colocasia esculenta cv. Daikichi). Journal of the Science of Food and Agriculture, 102(4), 1372-1380.

10. Wang, J., Kerl, C.F., Hu, P. et al. Thiolated arsenic species observed in rice paddy pore waters. Nat. Geosci. 13, 282–287 (2020). https://doi.org/10.1038/s41561-020-0533-1

11. Moe, B.; Peng, H.; Lu, X.; Chen, B.; Chen, L. W. L.; Gabos, S.; Li, X. F.; Le, X. C. Comparative cytotoxicity of fourteen trivalent and pentavalent arsenic species determined using real-time cell sensing. J. Environ. Sci. 2016, 49, 113– 124, DOI: 10.1016/j.jes.2016.10.004

12. Kerl, C. F., Schindele, R. A., Brüggenwirth, L., Colina Blanco, A. E., Rafferty, C., Clemens, S., & Planer-Friedrich, B. (2019). Methylated thioarsenates and monothioarsenate differ in uptake, transformation, and contribution to total arsenic translocation in rice plants. Environmental science & technology, 53(10), 5787-5796.

13. Colina Blanco, A. E., Kerl, C. F., & Planer-Friedrich, B. (2021). Detection of thioarsenates in rice grains and rice products. Journal of Agricultural and Food Chemistry, 69(7), 2287-2294.