Arsenic and mercury in bird feathers: Identification and quantification of inorganic pesticide residues in natural history collections using multiple analytical and imaging techniques

Life science collections and their curated metadata are now seen as potential archives of environmental levels of trace elements. Bird feathers are especially promising material, but surface contamination might present a significant issue. The suitability of preserved specimens for environmental studies may be further limited by historical application of inorganic pesticides in the collections. Arsenic (As) and mercury (Hg) are the most significant inorganic contaminants in natural history collections since they were widely applied as pesticides from the late 18th century until the 1980s. Potential presence of As- and Hg-containing pesticide residues has also to be taken into account when members of the public are allowed to handle specimens. Even though the testing of taxidermy and anthropology museum collections for pesticide residues is becoming a common practice, it is generally done qualitatively rather than quantitatively. In this study, the concentrations of As and Hg were determined in feathers of eleven bird specimens considered for an interactive display and were found to range from 1.1 to 15,183 μg g− 1 and from < 1 to 26,960 μg g− 1, respectively. The study shows how the quantitative information can be obtained and the history of the pesticide treatment reconstructed using a combination of analytical techniques including bulk analysis by inductively coupled plasma mass spectrometry (ICP-MS) following destructive or non-destructive sampling, and spatially resolved techniques such as laser ablation (LA)-ICP-MS and scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS). Inorganic As speciation by squarewave anodic stripping voltammetry (SWASV) and localisation of pesticide residues by X-ray micro-computed tomography (μCT) can provide additional information. It is found that As is not only present as micron-sized particulate residues, but becomes incorporated into the keratin matrix of the feathers. Mercury is probably nano-particulate and fully incorporated into keratin. The history of pesticide treatment might be complicated with mixtures of chemicals involving both As and Hg compounds and more than one way of pesticide application used on the same specimen.