Overview
This source page is a mechanical bulk-ingest record for a PDF in the methylmercury infant-formula research pull. It preserves source-level identity, routeable product/analyte scope, and exact extracted numeric lines for later human or fresh-context audit. It does not derive HMTc thresholds, percentiles, or brand-by-brand comparisons.
Key numbers
The worker extracted the full PDF text with layout preservation twice and compared extraction hashes before commit. The following lines are copied from numeric/table-bearing regions of the PDF and retain the source units and wording where legible:
- from Metal Influxes and metal specific (6). Understanding the underlying mech-
- U.S. Geological Survey, 345 Middlefield Road, MS 496, The biodynamic model uses empirically determined
- Menlo Park, California 94025 species-specific and metal-specific parameters to describe
- bioaccumulation in terms of fluxes (6). It predicts that metal
- Received March 10, 2009. Revised manuscript received body burden increases when metal influxes from all exposure
- May 15, 2009. Accepted May 22, 2009. routes exceed loss rates. The model takes into account metal
- Dietborne metal uptake prevails for many species in nature. aquatic species (7)) or when the influence of growth is
- copper, the difficulty to assess dietary processes such as species and environments (6), it does not necessarily provide
- Downloaded by US GEOLOGICAL SURVEY on June 29, 2009
- Metal influxes in Lymnaea stagnalis correlated linearly with organisms (9), but determining rates from those approaches
- dietborne metal concentrations over a range encompassing most is complex (10).
- constants (kuf) were, respectively, 3.3 and 2.3 times higher metal isotope tracers to investigate the relationships between
- among metals and appeared 100 times higher than efflux expose freshwater snails to a wide range of concentrations
- of enriched 106Cd, 65Cu, and 62Ni through diet for a time period
- shorter than food gut residence time (11). We ask if metal-
- off between 1500 and 1800 nmol g-1 day-1. L. stagnalis threshold” can be reached upon short-term exposures to a
- site on the plasma membrane and its internalization (1).
- stored (2). However, some accumulated metals can exert time as a function of metal influx from water (Iw), metal influx
- molecules or by forming dangerous free radicals (3). The
- (4). Specifically, metal toxicity is related to a threshold uptake rate constant from solution, and the dissolved metal
- exchanging form, i.e., detoxified pyrophosphate granules (5). (8). By capturing potential interactions if more than one
-
- Corresponding author e-mail: mcroteau@usgs.gov; phone 650- function of the rate constant for physiological loss (ke) and
- 329-4424; fax: 650-329-5590. the accumulated metal concentration. When important,
- 10.1021/es9007454 Not subject to U.S. Copyright. Publ. 2009 Am. Chem. Soc. VOL. 43, NO. 13, 2009 / ENVIRONMENTAL SCIENCE & TECHNOLOGY 9 4915
- detoxification rate is controlled by a rate constant of metal onto a 1.2 µm Isopore membrane filter (Millipore). Feces
- concentration. This assumption seems reasonable, for ex- sheeting in the former case. Feces were dried for 24 h at 50
- ample, for very slow metal efflux (e.g., Cu in the clam °C. Aliquots of water (n ) 3-5 per treatment) were taken
- Corbicula fluminea (12)) and for excretion that occurs via immediately after labeled feeding, as well as at the beginning
- gammarellus (13)). Numerous studies properly parametrized with concentrated nitric acid.
- ke (see summary tables in refs 6 and 12), but there is no Sample Preparation and Analysis. To minimize inad-
- Experimental Organisms. Freshwater snails (Lymnaea sheeting were soaked for at least 24 h in acid (15% nitric and
- stagnalis) were reared in the laboratory in moderately hard 5% hydrochloric), rinsed several times in ultrapure water,
- (14)). Three days prior to each experiment, snails of a Partially thawed L. stagnalis were dissected to remove
- restricted size range (mean soft tissue dry weight of 5.34 ( soft tissue, placed individually on a piece of acid-washed
- 0.53 mg 95% CI, n ) 158) were transferred to a 10 L glass Teflon sheeting, and allowed to dry at 50 °C for 3 days. Dried
- Labeling of Food. The benthic diatom Nitzschia palea (100 µL mg of dry wt sample-1) for 5-7 days (19). Hydrogen
- was exposed for 24 h to 65Cu, 106Cd, and 62Ni, simultaneously, peroxide (Baker Ultrex II grade, 40 µL mg of dry wt sample-1)
- or to 106Cd and 62Ni, or to 65Cu alone. Specifically, diatoms was added prior to final dilution with ultrapure water (5-10%
- were grown axenically for several generations in an S-diatom HNO3). Similar weight samples of the certified reference
- Downloaded by US GEOLOGICAL SURVEY on June 29, 2009
- medium (15). Diatoms were harvested onto a 1.2 µm Isopore material NIST-2976 (mussel tissue from National Institute of
- hardness of 40-48 mg of CaCO3 L-1; pH 7.6 (14)). Algae were digestion procedure during each analytical run.
Methods (brief)
- dominated by loss from the metabolically available pool, the were also collected either manually or harvested by filtration
- metal-rich concretions (Cu in the amphipod Orchestia and the end of depuration. Water samples were acidified
- ke (see summary tables in refs 6 and 12), but there is no Sample Preparation and Analysis. To minimize inad-
- Labeling of Food. The benthic diatom Nitzschia palea (100 µL mg of dry wt sample-1) for 5-7 days (19). Hydrogen
- was exposed for 24 h to 65Cu, 106Cd, and 62Ni, simultaneously, peroxide (Baker Ultrex II grade, 40 µL mg of dry wt sample-1)
- were grown axenically for several generations in an S-diatom HNO3). Similar weight samples of the certified reference
- hardness of 40-48 mg of CaCO3 L-1; pH 7.6 (14)). Algae were digestion procedure during each analytical run.
- resuspended into a 20 mL acid-washed glass scintillation Water and digested samples were analyzed for the
- in the Supporting Information). The pH of the exposure media mass spectrometry (ICP-MS). Specifically, all samples, blanks,
- absorbed and adsorbed metal. After exposure, labeled pump; spray chamber) into the ICP-MS (single detector;
- filter (Millipore) and rinsed with SO water. Five small sections each sample. A replicate consisted of 32 individual measure-
- of the filters holding the labeled diatoms were sampled and ments that were averaged. External standards, serially diluted
- were collected the labeled algae) were offered as food to L. calibration curves for each isotope. Certified reference
- stagnalis. Typically, L. stagnalis (a generalist herbivore (16)) riverine water samples (National Research Council Canada;
- to a 150 mL acid-washed polypropylene vial partially addition of germanium (74Ge) to all samples and standards
- exposure vial had two 4 cm diameter holes (on opposite standards after every 10 samples. Deviations from the
- collected in a freshwater lake of the San Francisco Bay delta
- concentrations inferred by the ICP-MS software from tracer
Implications
This page makes the source discoverable for category-level evidence routing. Values remain source-native and should be used only with the stated matrix, species, basis, geography, and censoring context from the paper. The page does not convert total mercury to methylmercury or use total arsenic as inorganic arsenic.
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Verification notes
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pdftotext -layoutwas run on the full PDF twice; extracted text hashes matched before the page was written. - Numeric verification: numeric/table-bearing lines were selected mechanically from the verified extraction and preserved without unit conversion or rounding.
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Update history
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