@article{sowers_harrington_polizzotto_duckworth_2017, title={Sorption of arsenic to biogenic iron (oxyhydr)oxides produced in circumneutral environments}, volume={198}, ISSN={["1872-9533"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85007364750&partnerID=MN8TOARS}, DOI={10.1016/j.gca.2016.10.049}, abstractNote={Arsenic (As) is a widespread and problematic pollutant that can be derived from natural or anthropogenic sources. Iron (oxyhydr)oxides readily sorb As and thus play critical roles in As cycling in terrestrial environments; however, little is known about the affinity and mechanism of As sorption by biogenic iron (oxyhydr)oxides formed in circumneutral environments. To investigate this, we conducted sorption isotherm and kinetics experiments to compare As(V) and As(III) sorption to synthetic 2-line ferrihydrite and iron biominerals harvested from the hyporheic zone of an uncontaminated creek. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify both As(V) and As(III), and X-ray absorption spectroscopy (XAS) was utilized to obtain As and Fe K-edge spectra for As(V) and As(III) sorbed to environmentally collected and laboratory produced Fe(III) minerals. All environmental Fe(III) biominerals were determined to be structurally similar to 2-line ferrihydrite. However, environmental Fe(III) biominerals have a surface area normalized affinity for As(V) and for As(III) that is greater than or equivalent to synthetic 2-line ferrihydrite. Whereas the extent of sorption was similar for As(III) on all minerals, As(V) sorption to environmental Fe(III) biominerals was approximately three times higher than what was observed for synthetic 2-line ferrihydrite. Structural modeling of EXAFS spectra revealed that the same surface complexation structure was formed by As(V) and by As(III) on environmental Fe(III) biominerals and ferrihydrite. These results suggest that, despite similarities in binding mechanisms, Fe(III) biominerals may be more reactive sorbents that synthetic surrogates often used to model environmental reactivity.}, journal={GEOCHIMICA ET COSMOCHIMICA ACTA}, author={Sowers, Tyler D. and Harrington, James M. and Polizzotto, Matthew L. and Duckworth, Owen W.}, year={2017}, month={Feb}, pages={194–207} }
 @article{kang_sowers_duckworth_amoozegar_heitman_mclaughlin_2013, title={Turbidimetric Determination of Anionic Polyacrylamide in Low Carbon Soil Extracts}, volume={42}, ISSN={["1537-2537"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84887582502&partnerID=MN8TOARS}, DOI={10.2134/jeq2013.07.0279}, abstractNote={Concerns over runoff water quality from agricultural lands and construction sites have led to the development of improved erosion control practices, including application of polyacrylamide (PAM). We developed a quick and reliable method for quantifying PAM in soil extracts at low carbon content by using a turbidimetric reagent, Hyamine 1622. Three high-molecular weight anionic PAMs differing in charge density (7, 20, and 50 mol%) and five water matrices, deionized (DI) water and extracts from four different soils, were used to construct PAM calibration curves by reacting PAM solutions with hyamine and measuring turbidity development from the PAM-hyamine complex. The PAM calibration curve with DI water showed a strong linear relationship ( = 0.99), and the sensitivity (slope) of calibration curves increased with increasing PAM charge density with a detection limit of 0.4 to 0.9 mg L. Identical tests with soil extracts showed the sensitivity of the hyamine method was dependent on the properties of the soil extract, primarily organic carbon concentration. Although the method was effective in mineral soils, the highest charge density PAM yielded a more reliable linear relationship ( > 0.97) and lowest detection limit (0.3 to 1.2 mg L), compared with those of the lower charge density PAMs (0.7 to 23 mg L). Our results suggest that the hyamine test could be an efficient method for quantifying PAM in environmental soil water samples as long as the organic carbon in the sample is low, such as in subsurface soil material often exposed at construction sites.}, number={6}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={Kang, Jihoon and Sowers, Tyler D. and Duckworth, Owen W. and Amoozegar, Aziz and Heitman, Joshua L. and McLaughlin, Richard A.}, year={2013}, pages={1902–1907} }