Representative splits of all processed ores, soils, and sweep samples were analyzed for multiple parameters.
The same suite of lead carbonates and other secondary lead minerals was found in the plant foodstuffs as in the ores, soils, and sweep samples.
Deionized water extractions were performed on a subset of processed ores, soils, and sweep samples to model constituent release into surface waters (Hageman 2007).
Scanning electron microscopy (SEM) was performed on a subset of raw ores, processed ores, soils, sweep samples, and grain samples to determine individual particle mineralogy, chemistry, size, and shape.
In vitro bioaccessibility assessments (IVBA) were performed on a subset of processed ores, soils, and sweep samples to model toxicant bioaccessibility and bioavailability along ingestion exposure pathways (Drexler and Brattin 2007; Morman et al. 2009).
Figure 4 shows results of calculations estimating plausible ranges in daily lead uptake from inadvertent ingestion of the different processed ore, soil, and sweep samples we analyzed.
The individual miners add mercury to silt or soil; after it binds with flecks of gold, this amalgamated ore can be sifted out.
Manganese concentrations in processed ores, background soils, village soils, and sweep samples (up to 1,320 ppm) commonly exceeded the U.S. EPA RSSL of 390 ppm (U.S. EPA 2011a), and were generally higher than concentrations measured in soils from villages without ore processing [ Table 1; see also Supplemental Material, Figure S3B (http://dx.doi.org/10.1289/ehp.1206051)].
Methods: We applied diverse analytical methods to ore samples, soil and sweep samples from villages and family compounds, and plant foodstuff samples.
Low levels of water-soluble lead found in ores and soils by our water leach tests suggest the highest lead concentrations in water likely resulted from suspended particles such as lead carbonates.
