Biogeochemical specialization of macrophytes and their role as a biofilter in the Selenga delta

• Published in: GEOGRAPHY, ENVIRONMENT, SUSTAINABILITY
• Main Authors: G. Shinkareva L., M. Lychagin Yu., M. Tarasov K., J. Pietroń, M. Chichaeva A., S. Chalov R.
• Other Authors: Work was done with financial support of following grants: “Comprehensive assessment of the impact of the Selenga basin on Lake Baikal” (RGS, No. 06/2015-И),“Development of the atlasmonograph “The Selenga Basin: hydrological and landscape-geochemical analysis” (RGS, 13/2016-P), Spatio-temporal analysis of the migration of chemical elements and compounds in natural and anthropogenic landscapes” (No. 14-27-00083), RGS-RFBR “Geochemical barrier zones in freshwater river deltas of Russia” (No. 23/2017 / RGSRFBR), RFBR “Long-term river variability the influx of water, sediment and chemicals into Lake Baikal” (No. 17-29-05027). In addition, the work was supported by WSP Sverige AB (project K3502010). The field visits were also done as a part of expedition Selenga-Baikal and the Baikal expedition of the Russian Geographical Society in 2011-2018.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Russian Geographical Society 2019
• Subjects: biogeochemistry;deltaic environment;heavy metals and metalloids in aquatic systems;macrophytes;hyperspectral images; Butomus umbellatus
• Online Access: https://ges.rgo.ru/jour/article/view/827; https://doi.org/10.24057/2071-9388-2019-103

This study aims to evaluate the biofiltration ability of higher aquatic vegetation of the Selenga delta as a barrier for heavy metals and metalloids (HMM) flows into the Lake Baikal. Main aquatic vegetation species have been collected from deltaic channels and inner lakes: Nuphar pumila, Potamogeton perfoliatus, P. pectinatus, P. natans, P. friesii, Butomus umbellatus, Myriophyllum spicatum, Ceratophyllum demersum, Phragmites australis. Analysis of the obtained data showed that regardless of the place of growth hydatophytes spiked water-milfoil (M. spicatum) and the fennel-leaved pondweed (P. pectinatus) most actively accumulate metals. Opposite tendencies were found for helophytes reed (Ph. australis) and flowering rush (B. umbellatus), which concentrate the least amount of elements. This supports previous findings that the ability to concentrate HMM increases in the series of surface – floating – submerged plants. Regarding river water, the studied macrophyte species are enriched with Mn and Co, regarding suspended matter – Mo, Mn and B, regarding bottom sediments – Mn, Mo and As. We identified two associations of chemical elements: S-association with the predominant suspended form of migration (Be, V, Co, Ni, W, Pb, Bi, Mn, Fe and Al) and D-association with the predominant dissolved form of migration (B, U, Mo, Cr, Cu, Zn, As, Cd, Sn and Sb). Due to these associations three groups of macrophytes were distinguished – flowering rush and reed with a low HMM content; small yellow pond-lily and common floating pondweed with a moderate accumulation of S-association and weak accumulation of D-association elements; and clasping-leaved pondweed, fennel-leaved pondweed, and pondweed Friesii accumulating elements of both S and D groups. The results suggest that macrophytes retain more than 60% of the total Mn flux that came into the delta, more than 10% – W, As, and from 3 to 10% B, Fe, Co, Mo, Cd, V, Ni, Bi, Be, Cu, Zn, Cr, U, Al. The largest contribution is made by the group of hydatophytes (spiked water-milfoil and pondweed), which account for 74 to 96% of the total mass of substances accumulated by aquatic plants.