Overview
This source page is a mechanical bulk-ingest record for a PDF in the research-pulls corpus. 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:
- consumed 81.4% of scrap tires generated in the U.S. in 2017, which includes tire-derived fuel (> 43%), tire crumb
- rubber (TCR) applications (≈ 25%), civil engineering products (≈ 7.9%), and other markets (≈ 7.4%), and accounts
- for more than 205 million scrap tires. About 25% and 22% of the TCR were used in sports surfacing and play-
- For example, Cd ranging from 0.09 to 1.39 mg/kg and levels of Pb from 1.9 to 33.1 mg/kg were found in com-
- m2/day), relative humidity of 0% (dry) and 75% (wet) with a constant temperature of 55 °C in air was achieved
- values, and the SemiQuant survey measurements were validated by the recoveries of 95% for chromium, 85%
- for lead, 83% for cadmium, and 80% for copper.
- was transferred to a 15 mL Falcon tube (m8) and weighed (m9). The solution was diluted with 2% HNO3 (v/v)
- of signal at 115 u was 4.3% throughout the measurement, which verified the stability of the instrument. One of
- fraction. Except for Se which was below the detection limit, acceptable recoveries in the range of 71–103% were
- digestion system (Anton Paar, Ashland, VA, USA). A 2.0 mL aliquot of (67–70) % mass fraction HNO3 (Sigma
- shown in Table S2 to be within 82–105%, which validated the method.
- at 0% RH. Each replicate was cut into a quarter circular shape with a surface area of S = 0.0075 ft2. For each RH,
- fell in the following ranges for other metals: 100 μg/g to 1000 μg/g for Na, Mg, Al, K, Co; 10 μg/g to 100 μg/g
- play on the playgrounds. Excepting Se, which was below the 1.8 μg/g detection limit, the ranges of measured
- to 75% percentile range, vertical lines indicate the median, and open squares represent the mean value for their
- Tl were undetectable (UD). The unit for ISR, μg/ft2 is used because it is used in the regulatory standard. Use the
- i.e., the higher the bulk content was, the higher the surface release (Fig. 1). Ranges of ISRs were: 10–100 μg/ft2
- followed this pattern under the 0% RH condition, except for Pb in Sample S2 (green tile), which followed the
- second growth-and-level-off release (GLR) pattern. Under the wet, i.e., 75% RH, condition, the releases of As
- contrast, the release patterns of the three metals in Sample S6 (black tile) changed from the CR under the 0% RH
- Similar CR patterns were observed for As and Cu (Fig. 3b,c, RH = 0%) though the rate of release differed for
- Table S1), indicating the significance of weathering on the release of the two elements.
- release. The release of Tl adhered to this pattern under the 0% RH condition (Fig. 3d) with a half-year induction
- as measured by the SemiQuant method (Table S1). A similar ICR pattern was also observed for Tl under the
- 75% RH condition with the release rate at ≈(0.10 ± 0.03) μg/ft2/y (p = 0.005 to 0.006) after the half-year point.
- about 30–80% of their ISR values and no marked humility effect was observed.
- observed at the 1.57-year of weathering mark under the 0% RH condition. No significant cumulative releases
- μg/g, respectively. These measured replications show a relatively larger RSD of > 20%, compared to Pb (≈5%),
- As (≈9%), Cu (≈12%), Tl (≈6%), Cr (≈10%), Ba (≈10%), indicating a highly inhomogeneous distribution of Sb
- same reasoning to Cd, which also has a similarly large RSD of 24%, one would expect that the SiR could take
- Collected in Table 1 are the regulatory or advisory limits for the bulk contents of the 10 selected metals from
- bulk content standards for other toxic elements were converted to surface content equivalent as listed in Table 1.
- Table 1. The release models of 10 selected metals and the potential exposure to children. SR: Step Release,
- Accumulated Release, SiR: Singular Release, 75H: 75% Humidity, 0H: 0% Humidity, na: not applicable. *only
- shown in Fig. 3, the rate of release is calculated as the slope defined by the neighboring two points. Table 2 lists the
- equal those listed in Table 2. A comparison of the maximum accumulation in Table 2 to the inferred exposure
- limits in Table 1 shows that all metals on the TCR tiles are at or below the inferred exposure limit except for Sb
- Table 2. Maximum rate of release of metals from TCR surface in µg/ft2/month*. *Be is excluded because its
-
- Benoit, G. & Demars, S. Evaluation of organic and inorganic compounds extractable by multiple methods from commercially
Methods (brief)
- mercially available TCR mulch after strong acid digestion with microwave25. Twenty four metals were identified
- The amount of metal from MSR was determined by ICP-MS (inductively coupled plasma mass spectrometry).
- Selection of samples. Six samples of commercially available TCR playground tiles were provided volun-
- specification of Samples S1 through S6 is as follows:
- Sample # Materials Surface color Manufacturer
- SemiQuant measurements of metals in the samples. Three replicates of each in the above sample
- list were prepared for the SemiQuant survey measurement by a model 7500cs ICP-MS (Agilent, Santa Clara,
- CA, USA). Prior to microwave digestion of the TCR tiles, each replicate was transferred to a cleaned model
- mill and render the sample brittle for cryo-milling. Each replicate was homogenized at 15.0 Hz for 4 min and
- transferred into a clean vessel. About 0.25 g of the sample was weighed on a balance (m1), and transferred into
- a Teflon EasyPrep microwave vessel for digestion in a Mars 6 microwave (CEM, Matthews, NC, USA). Approxi-
- the sample was digested at the pressure of 800 psi and temperature of 220 °C for 15 min. The temperature ramp
- speed was 25 °C/min from room temperature to 220 °C. The replicates from Samples S1 to S3 were fully digested
- but those from Samples S4 to S6 contained white precipitates in powder form which were centrifuged out before
- ICP-MS analysis. All digested replicates were diluted to about 50 g in pre-weighed 60 mL low-density polyethyl-
- After the solution was measured by the ICP-MS, the mass fraction of each element in the tile sample was
- where MCPS and RhCPS are the respective ICP-MS intensities of the targeted element and Rh in counts per second
- For quality assurance, duplicate samples of SRM 2859 Restricted Elements in Polyvinyl Chloride were pro-
Implications
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Verification notes
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wiki/sources/pages before creation. - Full-PDF read:
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
The five most recent substantive edits to this page, classified major (evidence or structure moved), correction (a published value or statement was wrong and has been fixed), or minor (narrative rewritten without changing the underlying evidence). Each description is derived from what the edit did to this page; the linked commit is the authoritative record, routine regeneration passes are excluded, and the full version history lives in git. When DOI minting comes online (see schema docs), each entry below will also link to a version-pinned DataCite DOI.