Vegetation stress detection through chlorophyll a + b estimation and fluorescence effects on hyperspectral imagery

Physical principles applied to remote sensing data are key to successfully quantifying vegetation physiological condition from the study of the light interaction with the canopy under observation. We used the fluorescence-reflectance-transmittance (FRT) and PROSPECT leaf models to simulate reflectance as a function of leaf biochemical and fluorescence variables. A series of laboratory measurements of spectral reflectance at leaf and canopy levels and a modeling study were conducted, demonstrating that effects of chlorophyll fluorescence (CF) can be detected by remote sensing. The coupled FRT and PROSPECT model enabled CF and chlorophyll a + b (Ca + b) content to be estimated by inversion. Laboratory measurements of leaf reflectance (r) and transmittance (t) from leaves with constant Ca + b allowed the study of CF effects on specific fluorescence-sensitive indices calculated in the Photosystem I (PS-I) and Photosystem II (PS-II) optical region, such as the curvature index [CUR; (R675.R690)/R2(683)]. Dark-adapted and steady-state fluorescence measurements, such as the ratio of variable to maximal fluorescence (Fv/Fm), steady state maximal fluorescence (F'm), steady state fluorescence (Ft), and the effective quantum yield (delta F/F'm) are accurately estimated by inverting the FRT-PROSPECT model. A double peak in the derivative reflectance (DR) was related to increased CF and Ca + b concentration. These results were consistent with imagery collected with a compact airborne spectrographic imager (CASI) sensor from sites of sugar maple (Acer saccharum Marshall) of high and low stress conditions, showing a double peak on canopy derivative reflectance in the red-edge spectral region. We developed a derivative chlorophyll index (DCI; calculated as D705/D722), a function of the combined effects of CF and Ca + b content, and used it to detect vegetation stress.     

Investigation of Child Restraint System (CRS) Compatibility in the Vehicle Seat Environment

Objective: Child restraint system (CRS) misuse is common and can have serious consequences to child safety. Physical incompatibilities between CRS and vehicles can complicate the installation process and may worsen CRS misuse rates. This study aims to identify the most common sources of incompatibility between representative groups of CRS and vehicles.

Methods: Detailed dimensional data were collected from 59 currently marketed CRS and 61 late model vehicles. Key dimensions were compared across all 3,599 theoretical CRS/vehicle combinations and the most common predicted incompatibilities were determined. A subset of 34 physical installations was analyzed to validate the results.

Results: Only 58.2% of rear-facing (RF) CRS/vehicle combinations were predicted to have proper agreement between the vehicle's seat pan angle and the CRS manufacturers’ required base angle. The width of the base of the CRS was predicted to fit snugly between the vehicle's seat pan bolsters in 63.3% of RF CRS/vehicle combinations and 62.2% of forward-facing (FF) CRS/vehicle combinations. FF CRS were predicted to be free of interaction with the vehicle's head restraint in 66.4% of combinations. Roughly 90.0% of RF CRS/vehicle combinations were predicted to have enough horizontal clearance space to set the front seat in the middle its fore/aft slider track. Compatibility rates were above 98% regarding the length of the CRS base compared to the length of the vehicle seat pan and the ability of the top tether to reach the tether anchor. Validation studies revealed that the predictions of RF CRS base angle range vs. seat pan angle compatibility were accurate within 6%, and head restraint interference and front row clearance incompatibilities may be more common than the dimensional analysis approach has predicted.

Conclusions: The results of this study indicate that RF CRS base angles and front row clearance space, as well as FF CRS head restraint interference, are frequent compatibility concerns. These results enable manufacturers, researchers, and consumers to focus their attention on the most relevant CRS/vehicle incompatibility issues in today's market.     

Lability of drinking water treatment residuals (WTR) immobilized phosphorus: aging and pH effects

Time constraints associated with conducting long-term (>20 yr) field experiments to test the stability of drinking water treatment residuals (WTR) sorbed phosphorus (P) inhibit improved understanding of the fate of sorbed P in soils when important soil properties (e.g., pH) change. We used artificially aged samples to evaluate aging and pH effects on lability of WTR-immobilized P. Artificial aging was achieved through incubation at elevated temperatures (46 or 70 degrees C) for 4.5 yr, and through repeated wetting and drying for 2 yr. Using a modified isotopic ((32)P) dilution technique, coupled with a stepwise acidification procedure, we monitored changes in labile P concentrations over time. This technique enabled evaluation of the effect of pH on the lability of WTR-immobilized P. Within the pH range of 4 to 7, WTR amendment, coupled with artificial aging, ultimately reduced labile P concentrations by > or = 75% relative to the control (no-WTR) samples. Soil samples with different physicochemical properties from two 7.5-yr-old, one-time WTR-amended field sites were utilized to validate the trends observed with the artificially aged samples. Despite the differences in physicochemical properties among the three (two field-aged and one artificially aged) soil samples, similar trends of aging and pH effects on lability of WTR-immobilized P were observed. Labile P concentrations of the WTR-amended field-aged samples of the two sites decreased 6 mo after WTR amendment and the reduction persisted for 7.5 yr, ultimately resulting in > or = 70% reduction, compared to the control plots. We conclude that WTR application is capable of reducing labile P concentration in P-impacted soils, doing so for a long time, and that within the commonly encountered range of pH values for agricultural soils WTR-immobilized P should be stable.     

Environmental Surveillance of Polioviruses in Rio de Janeiro,Brazil, in Support to the Activities of Global Polio Eradication Initiative

Wild polioviruses still remain endemic in three countries (Afghanistan, Pakistan, and Nigeria) and re-emergency of wild polio has been reported in previously polio-free countries. Environmental surveillance has been used as a supplementary tool in monitoring the circulation of wild poliovirus (PVs) and/or vaccine-derived PVs even in the absence of acute flaccid paralysis cases. This study aimed to monitor the presence of polioviruses in wastewater samples collected at one wastewater treatment plant located in the municipality of Rio de Janeiro, Brazil. From December 2011 to June 2012 and from September to December 2012, 31 samples were collected and processed. RD and L20B cell cultures were able to isolate PVs and non-polio enteroviruses in 27/31 samples. Polioviruses were isolated in eight samples (type 1 Sabin = 1, type 2 Sabin = 5, and type 3 Sabin = 2). Vaccine-derived polioviruses were not detected nor evidence of recombination with other PVs or non-polio enterovirus serotypes were observed among the isolates. The Sabin-related serotypes 2 and 3 presented nucleotide substitutions in positions associated with the neurovirulent phenotype at the 5′-UTR. Changes in important Amino acid residues at VP1 were also observed in the serotypes 2 and 3. Environmental surveillance has been used successfully in monitoring the circulation of PVs and non-polio enteroviruses and it is of crucial importance in the final stages of the WHO global polio eradication initiative. Our results show the continuous circulation of Sabin-like PVs and non-polio enteroviruses in the analyzed area during the study period.     

Editorial: Special Institutional Thematic Issue: National Research Center for Statistics and the Environment,University of Washington

Environmental and Ecological Statistics -