Biophysical forest type characterisation in the Colombian Amazon by airborne polarimetric SAR

Fully polarimetric C-, L-, and P-band data were collected by NASA's AirSAR system in May 1993 at the Araracuara test site, a well-surveyed forest reserve in the center of the Colombian Amazon. The area is characterized by a high diversity of forest types, soil types, and flooding conditions. In this paper a polarimetric classification technique is used to assess AirSAR's potential for forest structural type mapping and, indirectly, forest biophysical characterization. Field observations were made at 23 0.1 ha plots to obtain additional quantitative descriptions on forest structure and ground surface conditions, but also to assess the suitability of existing map legends for synthetic aperture radar (SAR) mapping. It could be shown that a new type of legend leads to physically better interpretable results. it method based on iterated conditional modes is introduced and is shown to yield radar-derived classifications with a high level of agreement with the landscape-ecological map, as well as with the ground observations. The following results may indicate the high level of accuracy obtained: 15 classes can be differentiated, the average radar classification agreement ranges from 68 o 94ødepending on the type of classification and approach), and for only a few classes the agreement is less than 70&Eth;The relation between physical forest structure and polarimetric signal properties is studied explicitly using polarimetric decomposition. A new method is introduced based on the decomposition of polarimetric coherence, instead of power. It is based on simple physical descriptions of the wave-object interaction. The accuracy of the complex coherence estimation is described using the complex Wishart distribution. Thus, several interesting physical relations between polarimetric signal and forest structure can be revealed. The physical limitations of this technique and its relation with sample size are indicate

Exploration of factors limiting biomass estimation by polarimetric radar in tropical forests

Direct inversion of radar return signals for forest biomass estimation is limited by signal saturation at medium biomass levels (roughly 150 ton/ha for P-band). Disturbing factors such as forest structural differences-and, notably, at low biomass levels, terrain roughness, and soil moisture variation-cause further complications. A new and indirect inversion approach is proposed that may circumvent such problems. Using multifrequency polarimetric radar the forest structure can be assessed accurately. Ecological relationships link these structures with biomass levels, even for high biomass levels. The LIFEFORM model is introduced as a new approach to transform field observations of the complex tropical forest into input files for the theoretical UTARTCAN polarimetric backscatter model. The validity of UTARTCAN for a wide range of forest structures is shown. Backscatter simulations for a wide range of forest structures, terrain roughness, and soil moisture clearly show the limitations of the direct approach and the validity of the proposed indirect approach up to very high levels of biomass

Application of solar photocatalytic ozonation for the degradation of emerging contaminants in water in a pilot plant

10.1016/j.cej.2014.08.067Aqueous mixtures of six commonly detected emerging contaminants (acetaminophen, antipyrine, bisphenol A, caffeine, metoprolol and testosterone), selected as model compounds, were treated by different solar-driven photochemical processes including photolysis, photocatalytic oxidation with Fe(III) or TiO2, photo-Fenton and single, photolytic and photocatalytic ozonations. Experiments were carried out in a compound parabolic collector photoreactor. It was found that photolysis and photocatalytic oxidation using Fe(III) are not effective for the complete removal of the selected contaminants, while TiO2 photocatalysis, photo-Fenton, single, photolytic and photocatalytic ozonations can rapidly remove them and decrease total organic carbon to some extent. The combination of photocatalytic oxidation and ozonation considerably enhances the system efficiency by reducing the ozone demand and energy requirements to completely remove the contaminants. Results also demonstrate that, at the operational conditions applied in this work, the contaminant removal and mineralization by ozone processes takes place in the slow kinetic regime, therefore the application of the ozone combined processes studied instead of single ozonation is recommended. Kinetic considerations on the application of solar photocatalytic processes for mineralization have been also assessed