Neighborhood-scale lead (Pb) speciation in Akron, Ohio (USA) soils: primary sources, post-deposition diagenesis, and high concentrations of labile Pb.

Lead (Pb) poses a significant risk to infants and children through exposure to contaminated soil and dust. However, there is a lack of information on Pb speciation and distribution at the neighborhood-scale. This work aimed to determine: (1) the distribution of acid-extractable (labile) Pb and other metals ([M]AE) in two neighborhoods in Akron, Ohio (USA) (Summit Lake and West Akron; n = 82 samples); and (2) Pb speciation and potential sources. Total metal concentration ([M]T) and [M]AE was strongly correlated for Pb and Zn (R2 of 0.66 and 0.55, respectively), corresponding to 35% and 33% acid-extractability. Lead and Zn exhibited a strong positive correlation with each other (R2 = 0.56 for MT and 0.68 for MAE). Three types of Pb-bearing phases were observed by electron microscopy: (1) galena (PbS)-like (5-10 µm); (2) paint chip residuals (10-20 µm); and (3) Pb-bearing Fe-oxides (20 µm). Isotope ratio values for PbAE were 1.159 to 1.245 for 206Pb/207Pb, and 1.999 to 2.098 for 208Pb/206Pb, and there was a statistically significant difference between the two neighborhoods (p = 0.010 for 206Pb/207Pb and p = 0.009 for 208Pb/206Pb). Paint and petrol are the dominant sources of Pb, with some from coal and fly ash. Lead speciation and distribution is variable and reflects a complex relationship between the input of primary sources and post-deposition transformations. This work highlights the importance of community science collaborations to expand the reach of soil sampling and establish areas most at risk based on neighborhood-dependent Pb speciation and distribution for targeted remediation.

A Validity Study Applying the Rasch Model to the American Association for the Advancement of Science Force and Motion Sub-Topic Assessment for Middle School Students.

The purpose of this research was to investigate the reliability of the scores produced and validity of the inferences drawn from the American Association for the Advancement of Science (AAAS, 2018) force and motion sub-topic assessment for middle school students. The assessment of student outcomes in STEM is an international focus in K-12 education. Project 2061, initiated by the AAAS, focuses on addressing challenges related to standards and assessments. This study informs this effort through testing a 14-item multiple-choice test constructed of questions from the AAAS item bank. Two samples of eighth-grade students participated (N = 1777). Rasch analysis applying the dichotomous model (Rasch, 1960) indicated sufficient item separation and reliability. Thirteen items fit the Rasch model and one item was removed for misfit. Further support for construct validity was observed with 78 percent of item ordering aligned with that predicted by physics educators and stability of measures for 11 items across the two samples. One item exhibited significant differential item functioning by gender and minority status in science. After inspection by physics educators, no bias in item wording or context was determined. Recommendation for additional items is made to increase item targeting and variance explained by the Rasch linear measure.