Abstract
Among the environmental emerging concern rare earth elements, lanthanum (La) is one of the most common and reactive. Lanthanum is widely used in numerous modern technologies and applications, and its intense usage results in increasing discharges into the environment, with potentially deleterious consequences to earthlings. Therefore, we exposed the important food resource and powerful monitoring tool Manila clam to two environmentally relevant concentrations of La (0.3µg L-1 and 0.9µg L-1) for 6days, through water, to assess the bioaccumulation pattern in the gills, digestive gland, and remaining body. The La bioaccumulation was measured after 1 (T1), 2 (T2), and 6 (T6) days of exposure. Lanthanum was bioaccumulated after 2days, and the levels increased in all tissues in a dose-dependent manner. When exposed to 0.3µg L-1, the enrichment factor pattern was gills > body > digestive gland. However, when exposed to 0.9µg L-1, the pattern appears to change to gills > digestive gland > body. Tissue portioning appears to be linked with exposed concentration: In higher exposure levels, digestive gland seems to gain importance, probably associated with detoxification mechanisms. Here, we describe for the first time La bioaccumulation in these different tissues in a bivalve species. Future studies dealing with the bioaccumulation and availability of La should connect them with additional water parameters (such as temperature, pH, and major cations).
Highlights
Most high technology equipment relies on rare earth elements (REE) to be manufactured, such as electric and hybrid vehicles, smartphones, and digital cameras (Wall, 2014)
REE exists in very low concentrations in non-contaminated seawater, they are known to be bioaccumulated by marine organisms (Palmer et al, 2006; Pernice et al, 2009)
One hundred and fifty Manila clam individuals were randomly assigned to fifteen 5-L glass tanks, with continuously aerated, filtered, and UV-irradiated natural seawater directly pumped from the ocean (38°70′99.7′′N and 9°48′69.2′′W), into three treatments: control (La = 0 μg L−1), low La concentration (La = 0.3 μg L−1), and high La concentration (La = 0.9 μg L−1)
Summary
Most high technology equipment relies on rare earth elements (REE) to be manufactured, such as electric and hybrid vehicles, smartphones, and digital cameras (Wall, 2014). Insufficient public knowledge on its recycling accoupled with inefficient recycling methodologies culminates in REE build-up in the environment (Tansel, 2017), highlighting the urgent need to study their speciation, availability, and ecotoxicological behavior and impacts. This has led to REE being considered contaminants of environmental emerging concern. Rare earth elements enter aquatic ecosystems through domestic and industrial wastewater discharges and leaching of REE enriched soils. REE exists in very low concentrations in non-contaminated seawater (in the pg L −1 range; Wang & Yamada, 2007), they are known to be bioaccumulated by marine organisms (i.e., squids, krill, Nautilus) (Palmer et al, 2006; Pernice et al, 2009)
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