@article{lopez_funk_buchwalter_2017, title={Arsenic (V) bioconcentration kinetics in freshwater macroinvertebrates and periphyton is influenced by pH}, volume={224}, ISSN={["1873-6424"]}, DOI={10.1016/j.envpol.2016.12.066}, abstractNote={Arsenic is an important environmental pollutant whose speciation and mobility in freshwater food webs is complex. Few studies have characterized uptake and efflux rates of arsenic in aquatic benthic invertebrates. Further, we lack a fundamental understanding of how pH influences uptake kinetics in these organisms or how this key environmental variable could alter dietary exposure for primary consumers. Here we used a radiotracer approach to characterize arsenate accumulation dynamics in benthic invertebrates, the influence of pH on uptake in a subset of these organisms, and the influence of pH on uptake of arsenate by periphyton - an important food source at the base of aquatic food webs. Uptake rate constants (Ku) from aqueous exposure were modest, ranging from ∼0.001 L g−1d−1 in three species of mayfly to 0.06 L g−1d−1in Psephenus herricki. Efflux rate constants ranged from ∼0.03 d−1 in Corbicula fluminea to ∼0.3 d−1 in the mayfly Isonychia sp, and were generally high. Arsenate uptake decreased with increasing pH, which may be a function of increased adsorption at lower pHs. A similar but much stronger correlation was observed for periphyton where Ku decreased from ∼3.0 L g−1d−1 at 6.5 pH to ∼0.7 L g−1d−1 at 8.5 pH, suggesting that site specific pH could significantly alter arsenic exposure, particularly for primary consumers. Together, these findings shed light on the complexity of arsenic bioavailability and help explain observed differences reported in the literature.}, journal={ENVIRONMENTAL POLLUTION}, author={Lopez, Adeline R. and Funk, David H. and Buchwalter, David B.}, year={2017}, month={May}, pages={82–88} }
 @article{lopez_hesterberg_funk_buchwalter_2016, title={Bioaccumulation Dynamics of Arsenate at the Base of Aquatic Food Webs}, volume={50}, ISSN={["1520-5851"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-84975471905&partnerID=MN8TOARS}, DOI={10.1021/acs.est.6b01453}, abstractNote={Periphyton is an important food source at the base of freshwater ecosystems that tends to bioconcentrate trace elements making them trophically available. The potential for arsenic-a trace element of particular concern due to its widespread occurrence, toxicity, and carcinogenicity-to bioconcentrate in periphyton and thus be available to benthic grazers is less well characterized. To better understand arsenate bioaccumulation dynamics in lotic food webs, we used a radiotracer approach to characterize accumulation in periphyton and subsequent trophic transfer to benthic grazers. Periphyton bioconcentrated As between 3,200-9,700-fold (dry weight) over 8 days without reaching steady state, suggesting that periphyton is a major sink for arsenate. However, As-enriched periphyton as a food source for the mayfly Neocloeon triangulifer resulted in negligible As accumulation in a full lifecycle exposure. Additional studies estimate dietary assimilation efficiency in several primary consumers ranging from 22% in the mayfly N. triangulifer to 75% in the mayfly Isonychia sp. X-ray fluorescence mapping revealed that As was predominantly associated with iron oxides in periphyton. We speculate that As adsorption to Fe in periphyton may play a role in reducing dietary bioavailability. Together, these results suggest that trophic movement of As in lotic food webs is relatively low, though species differences in bioaccumulation patterns are important.}, number={12}, journal={ENVIRONMENTAL SCIENCE & TECHNOLOGY}, author={Lopez, Adeline R. and Hesterberg, Dean R. and Funk, David H. and Buchwalter, David B.}, year={2016}, month={Jun}, pages={6556–6564} }