Microscopic characterisation of black crusts on different substrates

15/04/2017

lack crusts on different substrates (carbonate and silicate stones, cement-based mortar and carbonate detrital deposits) in urban environments were characterized microscopically by analysing their morphologies and compositions. The objective of this article is to study the interaction between the substrate and the crust and the influence of the environmental conditions on the crust development. On the one hand, the internal structure and morphology of each sample were evaluated with stereo and scanning electron microscopies. On the other hand, the black crust composition was accessed by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron microscopy in backscattered electron mode combined with energy dispersive x-ray spectroscopy. The results of these analytical techniques provided interesting information about the composition and the mineralogical phases present in the collected black crusts. In most of the cases, gypsum was detected as the main component exhibiting different habits. Calcite was also detected in all the evaluated gypsum black crusts; its presence was attributed to different origins. The substrate-crust interaction was also evaluated, contributing to distinguish different crust development processes in relation to the substrate. In carbonate substrates (limestones, mortar and carbonate detrital deposits), it was detected a continuous diffuse boundary related to the replacement of Ca-carbonate by Ca-sulphate, while this boundary was significantly more defined for the granitic stone. This study shows that the substrate, the presence of different construction materials, (e.g. mortars), the motor exhaust particulate substances and the concentrations of atmospheric pollutants, the marine influence as well as biological or other anthropogenic compounds are decisive factors in the development of the black crust. Some ideas about the establishment of conservation strategies are also shown.

Autores da comunidade :

• 

  C

  Carla Sofia Almeida da Rocha

  ist27936

  Afiliações e fontes

  IST > CERENA

  Centro de Recursos Naturais e Ambiente

  De: scopus

  ID: 2-s2.0-85028268063

  De: orcid

  ID: 36509663

• 

  M

  Manuel Francisco Costa Pereira

  ist13225

  Afiliações e fontes

  IST > CERENA

  Centro de Recursos Naturais e Ambiente

  IST > CEPGIST

  Centro de Petrologia e Geoquímica

  IST > DECivil

  Departamento de Engenharia Civil, Arquitetura e Ambiente

  De: orcid

  ID: 38618583

  De: cienciavitae

  ID: 1506610

  De: scopus

  ID: 2-s2.0-85028268063

AO - Versão original do autor

Elsevier

Science of the Total Environment

291

306

584-585

15

10.1016/j.scitotenv.2016.12.080

earth-and-related-environmental-sciences - Ciências da Terra e Ciências do Ambiente

eng - Inglês

https://publons.com/publon/19580389/