Ingestion of contaminated soils by children during hand-to-mouth activities can be a significant exposure pathway to toxic chemicals. Bioaccessibility, which corresponds to the fraction of an ingested contaminant dissolved in the gastrointestinal tract and potentially available for absorption, can be determined by in vitro extractions and gives a conservative value of relative oral bioavailability. The goal of this study was to investigate the validity of the CDM in vitro extraction protocol, developed by Camp Dresser and Mc Kee, by assessing the influence of soil properties and Hg fractionation on bioaccessibility. Mercury bioaccessibility was determined in two pure mercury compounds, two reference materials (a soil and a sediment), and three field-collected contaminated soils. Soils and reference materials were characterized and a sequential extraction procedure was applied to the samples. Bioaccessibility of HgCl(2) was 99.8% in the gastric phase and 88.6% in the intestinal phase, whereas bioaccessibility of HgS was lower than 0.01%. In field-collected soils A, B, M, and, in ERM-CC580, mercury bioaccessibility was lower than 3.2% (below detection). In contrast, CRM 025-050 had a high Hg bioaccessibility (44.3% for gastric phase and 34.7% for intestinal phase). Gastric and intestinal bioaccessibility values were positively correlated with sulfate content in soils (r = 0.99, p < 0.001, for both gastric and intestinal bioaccessibility). In field-collected soils and ERM-CC580, the residual fraction represented near 100% of the mercury recovered, with less than 2% of mercury being in the water-soluble (F1) and CaCl(2)-exchangeable (F2) fractions. In contrast, 46% of mercury in the reference material CRM 025-050 was extracted in the CaCl(2)-exchangeable fraction. Results of the sequential extractions were in agreement with bioaccessibility values, with the sum of the water-soluble and CaCl(2)-exchangeable fractions (F1 + F2) highly correlated with intestinal bioaccessibility values (r = 0.99, p < 0.001). Hence, the sequential extraction procedure used in this study could be a simple means to help validate mercury bioaccessibility.
This article utilizes duoethnography, a collaborative research methodology, to examine the divergent experiences of students and professors in the 2012 Québec student movement. Ignited by the government’s announcement of its intention to increase tuition fees, this youth-led movement caused an unprecedented stirring of ideas, emotions, and actions. Through personal narratives, we identify four aspects of a youth-led movement for social change, and reflect on their meaning in our lives in realizing youth-adult partnerships in the context of emancipatory approaches. They are: (a) the benefit of experiential versus classroom education; (b) the nurturing effect on youth empowerment of providing structures and spaces for youth-led processes; (c) the need to align youth emancipatory theory with practice, especially in systems which regularly resist change; and (d) the unexpectedly powerful impact of youth stereotypes, especially those delivered through mainstream media, and the difficulty of overcoming them. We also identify the value of duoethnography to accentuate youth voices, strengthen adult-youth partnerships, and enrich the transformative learning of both youth and adults.
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