Building spectral libraries for wetlands land cover classification and hyperspectral remote sensing

Recent advances in remote sensing provide opportunities to map plant species and vegetation within wetlands at management relevant scales and resolutions. Hyperspectral imagers, currently available on airborne platforms, provide increased spectral resolution over existing space-based sensors that can document detailed information on the distribution of vegetation community types, and sometimes species. Development of spectral libraries of wetland species is a key component needed to facilitate advanced analytical techniques to monitor wetlands. Canopy and leaf spectra at five sites in California, Texas, and Mississippi were sampled to create a common spectral library for mapping wetlands from remotely sensed data. An extensive library of spectra (n=1336) for coastal wetland communities, across a range of bioclimatic, edaphic, and disturbance conditions were measured. The wetland spectral libraries were used to classify and delineate vegetation at a separate location, the Pacheco Creek wetland in the Sacramento Delta, California, using a PROBE-1 airborne hyperspectral data set (5m pixel resolution, 128 bands). This study discusses sampling and collection methodologies for building libraries, and illustrates the potential of advanced sensors to map wetland composition. The importance of developing comprehensive wetland spectral libraries, across diverse ecosystems is highlighted. In tandem with improved analytical tools these libraries provide a physical basis for interpretation that is less subject to conditions of specific data sets. To facilitate a global approach to the application of hyperspectral imagers to mapping wetlands, we suggest that criteria for and compilation of wetland spectral libraries should proceed today in anticipation of the wider availability and eventual space-based deployment of advanced hyperspectral high spatial resolution sensors.     

The effect of air mass origin on the ambient concentrations of Be and Pb in Islamabad, Pakistan

Concentration of radionuclides ²¹⁰Pb and ⁷Be, having half lives of 22.3 years and 53.29 days, respectively, in the surface air samples of Islamabad (33.38° N, 73.10° E and Altitude ∼536 m asl.) are measured. The non-destructive technique of gamma-spectrometry, with a high purity germanium HPGe detector, was employed for the analysis of all samples. The annual average concentrations of ²¹⁰Pb and ⁷Be in the surface air samples were determined as 0.284 ± 0.15 and 3.171 ± 1.14 mBq m⁻³, respectively. Our results have shown a seasonal variation of the concentration of ⁷Be in air samples with high values for the spring season. High concentrations for ²¹⁰Pb are obtained when air masses originate from plain areas of Pothohar region, located in the South-West, West and North West of Islamabad. Our values of concentrations show a nice agreement with the relevant reported results.     

The interaction of boron with goethite: experiments and CD-MUSIC modeling

Boron (B) is an essential element for plants and animals growth that interacts with mineral surfaces regulating its bioavailability and mobility in soils, sediments, and natural ecosystems. The interaction with mineral surfaces is quite important because of a narrow range between boron deficiency and toxicity limits. In this study, the interaction of boric acid with goethite (α-FeOOH) was measured in NaNO₃ background solution as a function of pH, ionic strength, goethite and boron concentration representing as adsorption edges and isotherms. Boron adsorption edges showed a bell-shaped pattern with maximum adsorption around pH 8.50, whereas adsorption isotherms were rather linear. The adsorption data were successfully described with the CD-MUSIC model in combination with the Extended Stern (ES) model. The charge distribution (CD) of inner-sphere boron surface complexes was calculated from the geometry optimized with molecular orbital calculations applying density functional theory (MO/DFT). The CD modeling suggested dominant binding of boric acid as a trigonal inner-sphere complex with minor contributions of a tetrahedral inner-sphere complex (at high pH) and a trigonal outer-sphere complex (at low pH). The interpretation with the CD model is consistent with the spectroscopic observations.     

Cell absorption induced desorption of hydrophobic organic contaminants from digested soil residue

Oral ingestion of contaminated soil is an important pathway of human exposure to hydrophobic organic contaminants (HOCs), particularly for children in developing countries. The mobilization potential of various contaminants from ingested soil is often characterized using an in vitro gastrointestinal model, based on the quantities of contaminants remaining in digestive fluid after digestion and separation. Recently, it was experimentally demonstrated that a large fraction of mobilized contaminants sorbed on the digested residue could be released if the dissolved fraction was removed by intestinal absorption. This hypothesis was further tested in this study. Soil spiked with dichlorodiphenyltrichloroethane and its metabolites (DDXs) and polycyclic aromatic hydrocarbons (PAHs) was digested using an in vitro gastrointestinal model. A human colon carcinoma cell line (Caco-2) was cultured in digestive fluid with or without soil residue (pre-equilibrated with the soil) for 2 h. A large proportion of the contaminants (37-68%) was sorbed on the digested residue. Without this residue, 66 ± 13% of DDXs and 73 ± 14% of PAHs dissolved in the fluid, as means and standard deviations, were absorbed by the cell monolayer after exposure. With both digestive fluid and residue, the sorbed fraction of PAHs and DDXs decreased by 38-92%, while the ratios of the cellular to the dissolved concentrations were 2.7-2.8 times higher than those without the residue. This supported the hypothesis that the cell absorption of dissolved HOCs induces desorption of the sorbed fraction from digestive residue, and the desorbed HOCs can be absorbed as well.     

Pattern Recognition Based Software for Oil Spills Identification by Gas-Chromatography and IR Spectrophotometry

For environmental control purposes, floating oil spills in harbours, off shore areas and their sources must often be identified. Pattern recognition, applied to JR spectrophotometric data (600-2000 cm m 1 range), and to chromatographic data ( n -alkanes) for the spill and various suspected sources such as oil and fuels from ships bunkers and harbour installations, can lead to definite conclusions; particularly after artificial weathering formula are used. The software application provides quick and accurate identification of the pollution source. The identification algorithm has a learning stage in which the user creates a minimal database. This database has a tree structure with classes (fuels, crude, etc.) and members representing samples from already known sources. A sample contains JR and chromatographic data and information of the originating source. A larger database means more knowledge, which conveys a better identification. When the origin of an unknown sample is searched for, the software looks for the best match through the database and displays the results in two lists; sorted by calculated similarity. One list displays the classes in which the unknown sample could be included and the other displays the possible sources. An extra check can be done by visual inspection of the overlapped graphics (unknown sample and each of the identified sources).     

局部阻抗测试技术在评定有机涂层环境失效中的应用

局部电化学阻抗谱技术(LEIS)是一种新型的电化学测试技术,可以通过测量有机涂层体系的局部阻抗,并在局部阻抗的变化、涂层电容的变化以及涂层的剥离程度之间建立起直接关系,弥补了传统电化学阻抗技术(EIS)只能反映所测面积整体平均信息的缺点,因而对评定有机涂层的环境失效有着重要意义.对该技术的测定原理、测定装置以及在评定有机涂层环境失效上的应用进行了介绍.     

流动注射梯度稀释法在原子吸收分析中的应用

提出了应用流动注射梯度稀释法与原子吸收光度法相结合,样品不经稀释便可同时测定酸雨中不同浓度的钙。方法快速简便。     

原子吸收法测定水中锌质量控制指标研究

根据地域和监测技术代表性的筛选,在11个省份中选择了70家实验室参加测试工作,通过大量的监测数据,研究了原子吸收分光光度法测定水中锌的质量控制指标。研究表明:在0.3～1.5mg/L范围内,标准样品RSD≤3.0%,RSD’≤10.0%;浓度小于等于0.5mg/L时RE在±10.0%范围内,浓度为0.5～1.5mg/L时RE在±5.0%范围内。实际样品浓度小于等于0.05mg/L时,RD≤20.0%;浓度0.05～3.5mg/L时,RD≤5.0%。加标回收率控制范围为85%～110%。     

Comparison of EC and BC and evaluation of dust aerosol contribution to light absorption in Xi'an, China

The concentrations of EC, BC and dust aerosols were determined for atmospheric samples collected from an observation station in Xi'an, China. The results show that the averaged correlation coefficient between EC and BC was founded to be 0.72 with 0.81 (n = 49) in autumn, 0.70 (n = 112) in winter and 0.69 (n = 57) in spring, respectively. Absorption coefficients of dust aerosol were estimated to be 2.7 m² g⁻¹ in autumn and 4.4 m² g⁻¹ in winter. The comparison of absorption coefficients of dust aerosol with those of BC implies that BC is the principal light-absorbing aerosol over Xi'an atmosphere. By combining thermal analysis of elemental carbon and dust contents in the aerosol samples, however, the fraction of dust absorption to total light absorption is estimated to be 19% in autumn and 31% in winter, respectively.     

原子吸收法固体进样测定土壤中镉含量的不确定度评定

利用原子吸收法固体进样装置测定土壤中镉的含量,并对其测量过程进行了不确定度评定,从而明确了测定时的主要不确定度来源是曲线拟合过程,在测定过程中需进一步改进。