Agriculture Reference
In-Depth Information
4
Reflectance Spectroscopy as a Tool for
Monitoring Contaminated Soils
Guy Schwartz
1
, Gil Eshel
3
and Eyal Ben-Dor
2
1
Tel Aviv University, Porter School of environmental studies,
2
Tel Aviv University, Geography and human environment department,
3
Soil Erosion Research Station, Ruppin Inst., Emeck-Hefer,
Israel
1. Introduction
Soil reflectance spectroscopy is a well-known technique to assess soil properties rapidly and
quantitatively in both point (spectroscopy) and spatial (imaging spectroscopy (IS)) domains.
The quantitative approach has been developed in the past two decades by many researchers,
with much literature on the topic. Basically, this approach was adopted from other
disciplines (e.g. food, textiles), whereas the mapping approach was incorporated with
spectral-based remote sensing means. Soil contamination is an ever-growing concern, and a
reliable and environmentally friendly method is needed to rapidly detect and monitor soil
contaminants at any stage for the diagnosis of suspected contaminated areas, as well as for
controlling rehabilitation processes. Conventional methods for investigating soil
contamination based on point sampling and chemical analysis are time-consuming, costly
and sometimes incorporate the use of environmentally damaging chemicals. Soil reflectance
spectroscopy is a promising tool for the efficient detection and monitoring of soil
contaminants. Using reflectance spectroscopy measurements, several direct and indirect soil
properties, as well as soil contamination characteristics, can be extracted. Due to the vast
amount of data in soil spectroscopy, be it point or image, data-modeling processes are
required. This chapter reviews soil spectroscopy theory and its quantitative capabilities, as
well as data-modeling methods for soil spectra that are related to soil contamination.
Discussed contaminants include petroleum hydrocarbons, heavy metals such as Ni, Cr, Cu,
Cd, Hg, Pb, Zn and As, acid mine drainage and pesticides. Limitations, obstacles and
problems in recording soil spectra in the field and in the laboratory are discussed, along
with IS technology. The future potential of spectral technology and IS missions used for soil
contamination monitoring is presented, based on ongoing worldwide initiatives. This
chapter also provides some notes on how to merge this technology with other systems, such
as a penetrating spectral device for underground measurements utilizing the catheterization
approach.
1.1 Energy matter interactions
Most, if not all matter interacts with electromagnetic radiation in one way or another.
Electromagnetic radiation that is radiated onto any kind of material may be reflected,
absorbed or transmitted. For most materials, specific light interactions of a certain
