RESUMEN
Heavy metal contamination in urban environments, particularly lead (Pb) pollution, is a health hazard both to humans and ecological systems. Despite wide recognition of urban metal pollution in many cities, there is still relatively limited research regarding heavy metal distribution and transport at the household-scale between soils and indoor dusts-the most important scale for actual human interaction and exposure. Thus, using community-scientist-generated samples in Indianapolis, IN (USA), we applied bulk chemistry, Pb isotopes, and scanning electron microscopy (SEM) to illustrate how detailed analytical techniques can aid in interpretation of Pb pollution distribution at the household-scale. Our techniques provide definitive evidence for Pb paint sourcing in some homes, while others may be polluted with Pb from past industrial/vehicular sources. SEM revealed anthropogenic particles suggestive of Pb paint and the widespread occurrence of Fe-rich metal anthropogenic spherules across all homes, indicative of pollutant transport processes. The variability of Pb pollution at the household scale evident in just four homes is a testament to the heterogeneity and complexity of urban pollution. Future urban pollution research efforts would do well to utilize these more detailed analytical methods on community-sourced samples to gain better insight into where the Pb came from and how it currently exists in the environment. However, these methods should be applied after large-scale pollution screening techniques such as portable X-ray fluorescence (XRF), with more detailed analytical techniques focused on areas where bulk chemistry alone cannot pinpoint dominant pollution mechanisms and where community scientists can also give important metadata to support geochemical interpretations.
Asunto(s)
Contaminantes Ambientales , Metales Pesados , Contaminantes del Suelo , Humanos , Monitoreo del Ambiente/métodos , Plomo , Contaminación Ambiental , Contaminantes Ambientales/análisis , Metales Pesados/análisis , Ciudades , Suelo , Medición de Riesgo , Contaminantes del Suelo/análisis , ChinaRESUMEN
This study shows thallium (Tl) concentrations in Brassica juncea (Indian mustard) tissue are more than an order of magnitude higher (3830 µg/kg) than that of the substrate (100 µg/kg) and are strongly influenced by the underlying mineralogy; i.e., Tl bioaccessibility depends on the mineral structure: K-feldspar > Mn nodule > hendricksite mica. The majority of Tl for all substrates is contained in edible parts of the plant, i.e., leaves (41% of total Tl, on average) ≥ flower stems (34%) > seed pods (11%) ≈ stems (10%) > flowers (3%). We also show that Tl isotope fractionation induced by B. juncea is substantial, at nearly 10 ε205Tl units, and generates systematic plant-specific patterns. Progressive plant growth strongly fractionates Tl isotopes, discriminating against 205Tl as the plant matures. Thus, 205Tl values are systematically higher in the early formed stem (ε205Tlavg = +2.5) than in plant elements formed later (ε205Tlavg = -2.5 to +0.1), which demonstrates the large degree of translocation and the associated effects during plant growth. This study establishes the potential of Tl isotopes as a new tool for understanding heavy metal (re)distribution during anthropogenic and geologic processes and the utility of such information in environmental and health-related planning and in phytomining or bioprospecting.