title: Retrospective analysis of heavy metal contamination in Rhode Island based on old and new herbarium specimens.
abstract: OBJECTIVE
  Herbarium specimens may provide a record of past environmental conditions, including heavy metal pollution. To explore this potential, we compared concentrations of copper, lead, and zinc in historical and new collections from four sites in Rhode Island, USA.
  
  
  METHODS
  We compared historical specimens (1846 to 1916) to congener specimens collected in 2015 at three former industrial sites in Providence, Rhode Island, and one nonindustrial site on Block Island. Leaf material was prepared by UltraWAVE SRC Microwave Digestion, and heavy metal concentrations were measured by inductively coupled plasma-atomic emission spectroscopy.
  
  
  RESULTS
  Heavy metal concentrations in the historical and new specimens were measurable for all elements tested, and levels of copper and zinc were comparable in the historical and 2015 collections. By contrast, the concentration of lead declined at all sites over time. Significant variability in heavy metal concentration was observed between taxa, reflecting their varied potential for elemental accumulation.
  
  
  CONCLUSIONS
  It seems clear that herbarium specimens can be used to evaluate past levels of pollution and assess local environmental changes. With careful sampling effort, these specimens can be a valuable part of environmental science research. Broadening the possible applications for herbarium collections in this way increases their relevance in an era of reduced funding for collections-based research.
authors.affiliation: Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook Street, Providence, Rhode Island 02912 USA.
authors.forename: Sofia M
authors.initials: SM
authors.lastname: Rudin
authors.affiliation: Department of Earth, Environmental, and Planetary Sciences, Brown University, 324 Brook Street, Providence, Rhode Island 02912 USA.
authors.forename: David W
authors.initials: DW
authors.lastname: Murray
authors.affiliation: Brown University Herbarium, Department of Ecology and Evolutionary Biology, Brown University, 34 Olive Street, Box G-B225, Providence, Rhode Island 02912 USA.
authors.forename: Timothy J S
authors.initials: TJ
authors.lastname: Whitfeld
keywords: Rhode Island; heavy metals; herbarium specimens