Technologically critical elements in marine environments: evaluation of rare earth elements in the risk to human health and as a tool in predicting anthropic influence
Name: SUELLEN GERONIMO CORDEIRO
Publication date: 16/04/2024
Examining board:
Name |
Role |
|---|---|
| CLÉSIA CRISTINA NASCENTES | Examinador Externo |
| EDUARDO SCHETTINI COSTA | Examinador Interno |
| GEISAMANDA PEDRINI BRANDAO ATHAYDE | Presidente |
| JEFFERSON RODRIGUES DE SOUZA | Coorientador |
| MARIA TEREZA WEITZEL DIAS CARNEIRO LIMA | Examinador Interno |
Pages
Summary: This study, firstly, different calibration strategies were evaluated for determining rare earth elements (REE) in marine sediment by inductively coupled plasma mass spectrometry (ICP-MS). The strategies used were external calibration (SC - standard calibration), standard calibration with acid matching (SCAM), standard addition calibration (SA), and a non-conventional multi-isotopic calibration (MICal), all performed under the same operational conditions. The non-conventional calibration strategy, MICal, proved to be a viable alternative for determining these analytes. However, since this strategy has limitations that would make it unfeasible to study all REE, an analytical performance study of the determination procedure for REE, Th, and U by ICP-MS with collision cell (using helium gas) at 1350W power was conducted using SC. The figures of merit were established, and method accuracy was verified by analyzing the certified reference material (CRM) of estuarine sediment – BCR 667, obtaining concentration values that indicated accuracy. Thus, the REE were determined in marine sediment samples collected along approximately 210 km of coastline at a depth of 10 meters. The distribution profile of REE was evaluated using Post Archean Australian Shale (PAAS) as a normalizer, revealing a more significant enrichment of lutetium at the sampling stations. Enrichment of heavy REE was observed compared to light and intermediate REE, along with positive anomalies of cerium (Ce) and europium (Eu) at most sampling stations, suggesting anthropogenic contributions. Higher concentrations of REE were found in the oxide and hydroxide (OXI-HID) fraction, as well as in the residual fraction (RES). Using the total concentration of REE and their concentration in geochemical fractions in Principal Component Analysis (PCA), there was a tendency to form two distinct groups, with most stations north of the mouth of the Doce River grouped due to higher concentrations. To evaluate the toxic potential of REE, bioaccessibility tests were conducted using marine sediment matrices, along with complementary cytotoxicity and bioaccumulation tests for the elements La, Ce, Eu, and Gd. Human health risk assessment through dermal absorption and oral ingestion was performed using the hazard quotient (HQ). After simulating gastric (SBET) and gastrointestinal (PBET) digestion, it was observed that Ce and Nd had higher absorption capacities in the human body (> 2 µg.g -1 ). La and Y showed intermediate concentrations (close to 1 µg.g -1 ), while the other elements showed concentrations below 0.5 µg g-1 . The results of the bioaccumulation test conducted with fibroblast cells (L929) indicated that La and Eu had a 25% probability of intracellular accumulation, while Ce and Gd showed 1%. Cell viability tests exposed to standard REE solution in 2% v.v-1 HNO3 (100 g.mL1 ) or aqueous solution of La2O3, Gd(NO3)3, Ce(NO3)3, and Eu2O3 (1000 g.mL-1 ) did not demonstrate cytotoxic effects on fibroblast cells. HQing values were higher than HQderm values, suggesting that REE pose greater risks to human health through oral ingestion than through dermal absorption. However, considering the obtained ingestion hazard quotient (HQing) and dermal hazard quotient (HQderm) (<1), it is suggested that there is no significant risk of non-cancerous effects. The results of this study corroborate the potential of REE as indicators of anthropogenic contribution in marine sediments and emphasize the importance of their monitoring and the establishment of appropriate regulatory policies that include them.
