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Abstract Despite international regulation, polychlorinated biphenyls (PCBs) are routinely detected at levels threatening human and environmental health. While previous research has emphasized trophic transfer as the principle pathway for PCB accumulation, our study reveals the critical role that non-trophic interactions can play in controlling PCB bioavailability and biomagnification. In a 5-month field experiment manipulating saltmarsh macro-invertebrates, we show that suspension-feeding mussels increase concentrations of total PCBs and toxic dioxin-like coplanars by 11- and 7.5-fold in sediment and 10.5- and 9-fold in cordgrass-grazing crabs relative to no-mussel controls, but do not affect PCB bioaccumulation in algae-grazing crabs. PCB homolog composition and corroborative dietary analyses demonstrate that mussels, as ecosystem engineers, amplify sediment contamination and PCB exposure for this burrowing marsh crab through non-trophic mechanisms. We conclude that these ecosystem engineering activities and other non-trophic interactions may have cascading effects on trophic biomagnification pathways, and therefore exert strong bottom-up control on PCB biomagnification up this coastal food web.more » « less
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Excellent contact passivation and selectivity are prerequisites to realize the full potential of high‐material‐quality perovskite solar cells, first to maximize the
internal voltage (or quasi‐Fermi‐level separation)iV within the absorber, then to translate this highinternal voltage into a highexternal voltageV . Experimental quantification of contact passivation and selectivity is, thus, key to improving device performance. Here, open‐circuit measurements ofiV ocandV oc, combined with surface photovoltage measurements, are used to systematically quantify the passivation—usingiV ocas a metric—and the selectivity—defined asS oc =V oc/iV oc—of a range of common carrier transport layers to wide‐bandgap (1.67 eV) perovskite absorbers. The resulting solar cells suffer from large voltage deficits, particularly when NiOx is used as the hole transport layer, even though it provides better passivation than its polymer‐based counterparts (PTAA and PTAA/PFN). This indicates a poor selectivity of NiOx (S oc < 0.81 for NiOx ‐based devices), whereas devices using polymer‐based hole transport layers exhibit high selectivity (S oc = 0.94–0.95). In agreement with recent reports, this low selectivity is attributed to the formation of an interlayer of non‐perovskite material with high resistance to holes at the perovskite/NiOx interface. These measurements also imply that the selectivity of the C60‐based electron transport layers is relatively good.