Assessing the impact of hydrocarbon leakages on vegetation using reflectance spectroscopy I.D. Sanches a,⇑ , C.R. Souza Filho a , L.A. Magalhães a , G.C.M. Quitério a , M.N. Alves b , W.J. Oliveira c a Geoscience Institute, University of Campinas (UNICAMP), P.O. Box 6152, 13083-970 Campinas, SP, Brazil b CPQBA, University of Campinas (UNICAMP), P.O. Box 6171, 13081-970 Campinas, SP, Brazil c PETROBRAS, Engenharia/IETEG/ETEG/EAMB, Av. Almirante Barroso, 81, 12° andar, Centro, 20031-000 Rio de Janeiro, RJ, Brazil article info Article history: Received 14 May 2012 Received in revised form 21 January 2013 Accepted 21 January 2013 Available online 28 February 2013 Keywords: Reflectance spectroscopy Contamination Liquid hydrocarbons Vegetation Red edge Brachiaria brizantha abstract This paper assesses the capability of hyperspectral remote sensing to detect hydrocarbon leakages in pipelines using vegetation status as an indicator of contamination. A field experiment in real scale and in tropical weather was conducted in which Brachiaria brizantha H.S. pasture plants were grown over soils contaminated with small volumes of liquid hydrocarbons (HCs). The contaminations involved volumes of hydrocarbons that ranged between 2 L and 12.7 L of gasoline and diesel per m 3 of soil, which were applied to the crop parcels over the course of 30 days. The leaf and canopy reflectance spectra of contam- inated and control plants were acquired within 350–2500 nm wavelengths. The leaf and canopy reflec- tance spectra were mathematically transformed by means of first derivative (FD) and continuum removal (CR) techniques. Using principal component analysis (PCA), the spectral measurements could be grouped into either two or three contamination groups. Wavelengths in the red edge were found to contain the largest spectral differences between plants at distinct, evolving contamination stages. Wave- lengths centred on water absorption bands were also important to differentiating contaminated from healthy plants. The red edge position of contaminated plants, calculated on the basis of FD spectra, shifted substantially to shorter wavelengths with increasing contamination, whereas non-contaminated plants displayed a red shift (in leaf spectra) or small blue shift (in canopy spectra). At leaf scale, contaminated plants were differentiated from healthy plants between 550–750 nm, 1380–1550 nm, 1850–2000 nm and 2006–2196 nm. At canopy scale, differences were substantial between 470–518 nm, 550–750 nm, 910–1081 nm, 1116–1284 nm, 1736–1786 nm, 2006–2196 nm and 2222–2378 nm. The results of this study suggests that remote sensing of B. brizantha H.S. at both leaf and canopy scales can be used as an indicator of gasoline and diesel contaminations for the detection of small leakages in pipelines. Ó 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS) Published by Elsevier B.V. All rights reserved. 1. Introduction The Brazilian pipeline system that provides transportation for petroleum and its derivatives comprises a structure of 11,000 km of pipes running all across the country and through widely differ- ent landscapes. Although environmental and operational variables are taken into consideration when those pipelines were designed and installed, the wearing of material in older pipes, collapses of terrain, and sudden changes in pressure and temperature, among other reasons, can cause small clefts and consequent leakage of hydrocarbons (HCs). Therefore, monitoring pipelines and nearby landscape features crossed by them is of the utmost importance from the perspectives of economy, environment and health. Leaks are currently monitored by the petroleum industry through techniques used to detect changes in pressure, tempera- ture and flow along the pipeline. The task, however, is not simple, considering that pumps being switched out or set in motion will provoke pressure variations similar to those provoked by leaks, which makes monitoring difficult. In addition, these methods are inefficient at detecting small leaks (those below 1% of the pipe’s flow capacity). The benefits of detecting small leaks include pre- venting them from occurring during long periods (i.e., impacting the environment without being noticed) and controlling small leaks before they become large and able to cause greater impacts. Leaks of HCs have an influence on the soil and vegetation with which they are associated. In the soil, the main influences are microbiological alterations, neomineralisation (e.g., calcite, pyrite), bleaching (discoloration of red soils), electrochemical alterations 0924-2716/$ - see front matter Ó 2013 International Society for Photogrammetry and Remote Sensing, Inc. (ISPRS) Published by Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.isprsjprs.2013.01.007 ⇑ Corresponding author. Tel.: +55 19 35214535. E-mail addresses: iedasanches@ige.unicamp.br (I.D. Sanches), beto@ige.uni- camp.br (C.R. Souza Filho), luciola@ige.unicamp.br (L.A. Magalhães), giuliana@i- ge.unicamp.br (G.C.M. Quitério), mnopper@cpqba.unicamp.br (M.N. Alves), wilsonjo@petrobras.com.br (W.J. Oliveira). ISPRS Journal of Photogrammetry and Remote Sensing 78 (2013) 85–101 Contents lists available at SciVerse ScienceDirect ISPRS Journal of Photogrammetry and Remote Sensing journal homepage: www.elsevier.com/locate/isprsjprs