基于地理加权回归模型的葡萄园土壤砷含量高光谱反演

以吐鲁番盆地葡萄园土壤中砷(As)为研究对象,分析15种光谱变换下的土壤光谱反射率数据与土壤As含量的相关性,构建土壤As含量预测的偏最小二乘回归(PLSR)模型和地理加权回归(GWR)模型.结果表明:葡萄园土壤原始光谱率(R)经一阶微分( FD)、平方根一阶微分(SRFD)、平方根二阶微分( SRSD)、倒数二阶微分...     

渭-库绿洲耕层土壤砷含量高光谱估测研究

以新疆渭干河-库车河三角洲绿洲耕层土壤为研究对象,通过对原始光谱反射率(R)、包络线去除(CR)和一阶微分(R′)变换光谱数据结合连续小波变换生成小波系数,筛选出与砷含量具有极显著相关性的特征波段(P<0.001),运用偏最小二乘回归、BP神经网络、随机森林回归及支持向量机回归分析方法建立耕层土壤砷含量的高光谱估测模型。结果表明,经一阶微分结合连续小波变换处理后,光谱数据与砷含量之间的相关性提升尤为明显。综合考虑各模型估测精度及稳定性,认为R′-CWT-2⁶-SVMR模型可作为研究区耕层土壤砷含量的最佳估算模型,其训练集和验证集的决定系数(R²)分别为0.753和0.740,均方根误差(RMSE)分别为1.350 mg/kg和1.819 mg/kg,相对分析误差(RPD)分别为2.03和2.00。     

空间关联随机森林模型结合Sentinel-2影像估算潍北地区裸土期土壤盐分

土壤盐分含量(SSC)是评价土地退化和肥力水平的重要指标,实现SSC状态和空间分异的快速准确监测对区域环境的优化管理极为关键。选取潍北平原为研究区,野外采集233处土壤样品并获取同时相Sentinel-2多光谱影像,进一步将特征光谱波段和构建的最优光谱指数作为输入自变量,测试得到的SSC实测值为因变量,最后将空间关联函数引入到随机森林中去建立基于空间关联随机森林算法的SSC遥感估算模型,完成区域尺度上的SSC反演估算与空间制图。结果表明：影像的B3、B8和B11是SSC的特征波段,通过波段比值变换能够增强卫星光谱信号对SSC的吸收响应,筛选得到的最优光谱指数分别为RI₃₄(波段3和波段4的反射率比值)、RI₇₁₁(波段7和波段11的反射率比值)、ND₆₁₁(波段6和波段11的反射率归一化值)和D₄₅(波段4和波段5的反射率差值);仅用特征波段或最优光谱指数来构建模型不能取得满意的SSC估算精度,空间关联随机森林模型的SSC估算精度要高于随机森林模型;在将上述特征波段和最优光谱指数共同输入空间关联随机...     

Landsat5 TM遥感影像上太湖蓝藻水华反射光谱特征研究

利用ENVI遥感软件的FLAASH工具对2005年10月17日大规模蓝藻水华暴发的太湖Landsat5 TM影像进行大气校正处理,反演获得蓝藻水华和其他地物类型的遥感反射率图像,提取了不同集聚程度蓝藻水华的可见波段至近红外波段反射率数据,并与陆生植被、无蓝藻水面等地物的光谱反射率进行了比较。研究表明,与陆生植被、无蓝藻水面相比,蓝藻水华在TM2波段和TM4波段具有更高的反射率,在可见光波段整体反射率略高于陆生植被,在TM5、TM7波段则受水的影响反射率很低。从蓝藻水华、陆生植被的细胞生理结构、生长环境、复杂的遥感反射、散射及透射模型方面初步讨论了光谱差异的原因。     

太湖氮磷浓度与水质因子的关系

在2003年10月27、28日和2004年8月19日的太湖水质试验数据基础上,研究与探讨了氮浓度、磷浓度与叶绿素a浓度、悬浮物浓度和CDOM(Colored Dissolved Organic Matter)浓度之间的定量关系。研究结果表明:①在2003年10月份和2004年8月份,太湖梅梁湾地区水体的氮、磷浓度介于1~4mg/L和0.1~0.3mg/L,该浓度恰好处于易发生水华的营养物质浓度供应区间;②与2004年8月19日相比,2003年10月27、28日的太湖藻类处于低增长、高消亡状态;③在太湖梅梁湾地区,氮、磷浓度与CDOM浓度、叶绿素a浓度和悬浮物浓度之间存在较强的线性相关性,其相关系数大于0.557;④在太湖水体中,磷浓度、CDOM浓度、叶绿素a浓度和悬浮物浓度的四因子关系模型比氮浓度、CDOM浓度、叶绿素a浓度和悬浮物浓度的四因子关系模型的相关系数高。     

MODIS影像监测海州湾叶绿素a浓度的研究

利用海州湾海域2004～2006年的水质监测资料,选择同期成像质量良好的MODIS Terra 1B影像,分别在单波段因子和波段组合与叶绿素a浓度之间进行相关分析,发现近红外波段和绿波段、红波段的比值因子、差值因子以及仿植被指数因子与叶绿素a浓度相关性较高.用这些因子建立叶绿素a浓度的回归模型,其中因子F7(24)的二次多项式模型的R2达到0.801,平均相对精度达到65%以上,且模型具有较高的泛化能力,不仅证明了利用MODIS 1B影像监测海面叶绿素a浓度的可行性,而且对于监测该海域赤潮和富营养化状况具有重要的现实意义.     

去除叶绿素a影响的泥沙反演模型

通过遥感方法反演自然水体中泥沙浓度时,大量藻类的存在影响泥沙的反演精度,如何消除这种影响是提高水体中泥沙反演精度的关键.文章通过对一定叶绿素a浓度下不同浓度泥沙的光谱曲线研究,分析光谱曲线特征位置的漂移和数值变化,寻找去除叶绿素a影响的光谱范围和特征位置,通过相关性分析,建立多个模型,并从中选取最佳模型.     

基于Landsat系列卫星分析1985—2015年东平湖叶绿素a浓度变化趋势

基于Landsat-5 TM数据和地面同步水质监测数据发现,近红外波段与红色波段比值与叶绿素a实测浓度存在较高相关性,并以此建立了提取水体表层叶绿素a浓度的遥感信息模型。经验证,该模型用于叶绿素a浓度反演的精度良好,平均相对误差为14.5%。将该模型应用于Landsat卫星系列数据,提取了东平湖1985-2015年每年度丰水期叶绿素a浓度信息,得到共31幅东平湖叶绿素a浓度分布图,并对其进行了时空分析。结果表明：1985-2015年,东平湖叶绿素a平均浓度范围为32.4~81.4 μg/L,空间分布上一般表现为湖周边浅水区高于湖中心深水区,且空间差异变化明显;时间序列上,东平湖叶绿素a浓度表现出一定的波动性,在1987、1988、1992年出现较高值,总体看来,在95%置信水平上秩相关系数为-0.592,浓度呈下降趋势。     

环境卫星CCD影像在太湖湖泛暗色水团监测中的应用

太湖地区2009年5月11日、2010年8月21日、2011年7月28日和2011年9月24日的环境卫星CCD影像显示,在太湖西部沿岸带、竺山湖等水域存在湖泛暗色水团现象。由于环境CCD缺少辅助反演气溶胶信息的2.1um波段,试验了基于空气自动监测子站获得的与环境卫星CCD成像时间接近的地面能见度测量数据进行FLAASH大气校正的方法,反演结果总体上符合水体光谱特征。提取了湖泛水体、对照水体阳区在CCD各波段的光谱反射率数据统计特征。结果表明,和对照水体相比,湖泛水体在环境卫星CCD的可见光—近红外波段具有较低的反射率,与人眼观察湖泛水色暗黑的感官一致,另一方面,湖泛水域由于仍有一定的藻类存在,在环境卫星CCD近红外（波段4 ）具有比可见光（波段3）略高的反射率,其规律与基于Landsat ETM的湖泛暗色水团遥感分析结果相一致。     

紫外光诱导荧光分析仪结合多元线性回归算法在城市河流常规污染指标监测中的应用

为建立一种针对城市河流水体常规污染指标的快速原位监测方法,首次运用紫外光诱导荧光分析仪对扬州市60条城市河流进行水体三维荧光光谱(EEM)测量,形成了具有多样性的水质样本集合.利用峰值拾取法、相关性分析和主成分分析3种方式从三维荧光光谱中提取溶解性有机物(DOM)污染信息,结合多元线性回归算法(MLR),建立与化学需氧...     

Total suspended matter observation in the Pearl River estuary from in situ and MERIS data

Based on the cruise data collected in the Pearl River estuary (PRE) in May 2008, an empirical two-band model by using the ratio of R _rs at 629 and 671 nm was established to retrieve total suspended matter (TSM) concentration with the determination coefficient (R²) of 0.854, mean relative error (MRE) of 7.483%, and root-mean-square error (RMSE) of 1.295 mg L^???1. To match with medium resolution imaging spectrometer (MERIS) bands, in situ remote sensing reflectance was re-sampled to the bandwidth of 10 nm. The relationship between TSM and re-sampled R _rs at 620 nm (MERIS band 6) and 665 nm (MERIS band 7) are obtained (R² = 0.748, RMSE = 1.697 mg L^???1, MRE = 8.785%, n = 13). Additionally, to map the spatial distribution of TSM in the PRE, MERIS level_1B data were calibrated using a multiple linear regression model based on in situ R _rs. Another dataset collected in the PRE in January 2004 was used to validate the two-band model and also applied to map TSM distribution from MERIS image. The comparison between measured TSM values and modeled ones showed satisfactory results (R² = 0.753, MRE = 22.199%, and RMSE = 2.603 mg L^???1).     

Influence of High Levels of Total Suspended Solids on Measurement of Cod and Bod in the Yellow River, China

Using the Yellow River, China, the study explores the problem of the use of COD and BOD₅ as water quality management parameters in the presence of very high levels of suspended sediment (TSS) that characterize this river. Although the amount of natural organic matter per unit of suspended sediment of the Yellow River is not high, the very high concentration of mineral sediment in the Yellow River results in a large concentration of organic matter, which artificially inflates the laboratory values of COD and, as a consequent, leads to greatly exaggerated reports of pollution of the Yellow River. BOD₅ can more accurately reflect the pollution of the Yellow River than COD; however, measured values of BOD under-report the actual values due to settling of the sediment in the incubation chamber resulting in values that are 21.6--38.3% less than the actual values. Therefore corrections are required for laboratory COD and BOD values so that the values are not artifacts of the sediment regime. Our work provides new insight into this phenomenon and demonstrates how correction factors may be determined and used with pollution data. Our work also suggests that the actual pollution levels of the Yellow River are probably not as high as reported by monitoring agencies.     

A Numerical Model for the Transport of Chromium and Fine Sediments

A mathematical model which represents the transport processes of heavy metals and fine sediments in a fluvial stream was developed. The model consists of a three-equation system: the first one for total chromium concentration in the water column, C _Tw, the second one for total suspended sediment concentration, S _w, and the third one for chromium concentration in bed sediments, r. The third equation represents the chromium exchange between the water column and bed sediments by two processes: diffusion of soluble chromium and erosion/deposition of chromium sorbed to sediments. The basic assumption of the model is the instantaneous equilibrium. The main parameters are the partition coefficients in the water column and bed sediments, the depth of the active bed sediment layer, and the mass transfer coefficient between the water column and sediment pore water. The numerical model approximates the equations of advection–dispersion for chromium in water and suspended sediments by using a Eulerian third-order scheme. Numerical vs. analytical solutions were considered satisfactory for different initial, boundary, and sedimentological conditions. In order to estimate the impact of a chromium side discharge, the model was implemented for the Salado River in a reach of 65.6-km long (Santa Fe, Argentina). The results showed the effect of chromium discharge on almost the whole reach, then the vulnerability of the water quality in the Salado River when the flow was low was evidenced. When comparing the computed and measured results, the former showed a reasonable representation of the presence of chromium in water and bed sediments.     

Impact of Diwali celebrations on urban air and noise quality in Delhi City,India

A study was conducted in the residential areas of Delhi, India, to assess the variation in ambient air quality and ambient noise levels during pre-Diwali month (DM), Diwali day (DD) and post-Diwali month during the period 2006 to 2008. The use of fireworks during DD showed 1.3 to 4.0 times increase in concentration of respirable particulate matter (PM₁₀) and 1.6 to 2.5 times increase in concentration of total suspended particulate matter (TSP) than the concentration during DM. There was a significant increase in sulfur dioxide (SO₂) concentration but the concentration of nitrogen dioxide (NO₂) did not show any considerable variation. Ambient noise level were 1.2 to 1.3 times higher than normal day. The study also showed a strong correlation between PM₁₀ and TSP (R ² ≥ 0.9) and SO₂ and NO₂ (R ² ≥ 0.9) on DD. The correlation between noise level and gaseous pollutant were moderate (R ² ≥ 0.5). The average concentration of the pollutants during DD was found higher in 2007 which could be due to adverse meteorological conditions. The statistical interpretation of data indicated that the celebration of Diwali festival affects the ambient air and noise quality. The study would provide public awareness about the health risks associated with the celebrations of Diwali festival so as to take proper precautions.     

Comparison of different semi-empirical algorithms to estimate chlorophyll-a concentration in inland lake water

Based on in situ water sampling and field spectral measurement from June to September 2004 in Lake Chagan, a comparison of several existing semi-empirical algorithms to determine chlorophyll-a (Chl-a) content was made by applying them to the field spectra and in situ chlorophyll measurements. Results indicated that the first derivative of reflectance was well correlated with Chl-a. The highest correlation between the first derivative and Chl-a was at 680 nm. The two-band model, NIR/red ratio of R_710/670, was also an effective predictor of Chl-a concentration. Since the two-band ratios model is a special case of the three-band model developed recently, three-band model in Lake Chagan showed a higher resolution. The new algorithm named reverse continuum removal relies on the reflectance peak at 700 nm whose shape and position depend strongly upon chlorophyll concentration: The depth and area of the peak above a baseline showed a linear relationship to Chl-a concentration. All of the algorithms mentioned proved to be of value and can be used to predict Chl-a concentration. Best results were obtained by using the algorithms of the first derivative, which yielded R ² around 0.74 and RMSE around 6.39 μg/l. The two-band and three-band algorithms were further applied to MERIS when filed spectral were resampled with regard to their center wavelengths. Both algorithms showed an adequate precision, and the differences on the outcome were small with R ² = 0.70 and 0.71.     

Assessment of Chlorophyll-a Concentration and Trophic State for Lake Chagan Using Landsat TM and Field Spectral Data

In this study, we present the digital evaluation of Landsat TM data and field spectral measurements for retrieving chlorophyll-a (chl-a) concentration and trophic state index in Lake Chagan of Northeast China. Chl-a concentration of the lake can be estimated from the band ratio (TM4/TM3) and the field spectral data at 670 nm (absorption peak) and at 700 nm (reflectance peak). The results show that the best determination coefficient (R ²) is 0.67 from the TM data, by which chl-a distribution can be mapped. Based on chl-a determination from laboratory analysis, field spectral and TM data, the modified trophic state index (TSI_M) was applied to assess the lake’s trophic state. With the available data in Lake Chagan, each algorithm demonstrates the similar result for assessing the lake’s chl-a and trophic state. Our results indicate that Landsat TM and field spectral data could be used effectively to determine chl-a concentration and evaluate the trophic state of Lake Chagan in the study.     

Assessment of water quality based on Landsat 8 operational land imager associated with human activities in Korea

Water pollution such as green algae blooms and eutrophication in freshwater fatally influences both water quality and human society. Water quality issues in the 4 major rivers in Korea, including the Nakdong, have recently become a major concern. For this reason, it is essential to monitor water quality parameters (WQPs) that have a widespread characteristic to ensure maintenance of an effective water management system. The possibility of utilizing remote sensing technology for monitoring water quality on a regional scale has been recently investigated. The main objective of this study is to evaluate potential applications of the Landsat 8 Operational Land Imager (OLI) for estimating water quality in the Nakdong River, Korea. Correlations between Landsat 8 bands and in situ measurements are determined, and water quality models are established for estimating suspended solids (SS), total nitrogen (TN), chlorophyll-a (Chl-a), and total phosphorus (TP). The results demonstrate that WQPs correlated well with band reflectance values from Landsat 8. Band 5 was reasonably correlated with all WQPs, particularly with SS (R?=??0.74) and Chl-a (R?=??0.71). This study constructed multiple regression equations for WQPs based on correlation analysis through band combination and band ratio. The spatial distribution of WQPs in the Nakdong River on October 27, 2013 and May 16, 2014 indicate that the river was nearly eutrophic from human activities. Based on the results, the Landsat 8 OLI may be an appropriate data for estimating and monitoring water quality parameters on a regional scale. However, further validation is required to support the findings of this study.     

Retrieval of total suspended matter (TSM) and chlorophyll-a (Chl-a) concentration from remote-sensing data for drinking water resources

The concentrations of chlorophyll-a (Chl-a) and total suspended matter (TSM) are major water quality parameters that can be retrieved using remotely sensed data. Water sampling works were conducted on 15 July 2007 and 13 September 2008 concurrent with the Indian Remote-Sensing Satellite (IRS-P6) overpass of the Shitoukoumen Reservoir. Both empirical regression and back-propagation artificial neural network (ANN) models were established to estimate Chl-a and TSM concentration with both in situ and satellite-received radiances signals. It was found that empirical models performed well on the TSM concentration estimation with better accuracy (R ² = 0.94, 0.91) than their performance on Chl-a concentration (R ² = 0.62, 0.75) with IRS-P6 imagery data, and the models accuracy marginally improved with in situ spectra data. Our results indicated that the ANN model performed better for both Chl-a (R ² = 0.91, 0.82) and TSM (R ² = 0.98, 0.94) concentration estimation through in situ collected spectra; the same trend followed for IRS-P6 imagery data (R ² = 0.75 and 0.90 for Chl-a; R ² = 0.97 and 0.95 for TSM). The relative root mean square errors (RMSEs) from the empirical model for TSM (Chl-a) were less than 15% (respectively 27.2%) with both in situ and IRS-P6 imagery data, while the RMSEs were less than 7.5% (respectively 18.4%) from the ANN model. Future work still needs to be undertaken to derive the dynamic characteristic of Shitoukoumen Reservoir water quality with remotely sensed IRS-P6 or Landsat-TM data. The algorithms developed in this study will also need to be tested and refined with more imagery data acquisitions combined with in situ spectra data.     

Investigations of the impact of effluent from the Ok Tedi copper mine on the fisheries resource in the Fly River,papua new guinea

The Ok Tedi copper mine currently discharges overburden and partially treated ore residues into the Ok Tedi, a major tributary of the Fly River. At peak production these discharges will result in an increase in the suspended solids levels in the Fly River from a background of 76 mg L^-1 to approximately 800 mg L^-1, and an increase in median particulate copper levels from 90 g g^-1 to 1220 g g^-1. The dissolved copper levels are not expected to exceed 10 g L^-1. The Strickland River, a tributary of the Fly River, has natural suspended solids levels in excess of 500 mg L^-1 and provided a natural bioassay for the impacts of elevated suspended solids levels. The fish communities of the Strickland River were dominated by the sediment-tolerant Ariidae catfish, but the levels of biomass caught per standard sampling effort were comparable to those in the Fly River. Laboratory bioassays were performed to assess the impact of particulate associated copper. The fish fauna of the Fly River does not include any standard test species, and it is unlikely that standard species would be unaffected by the high suspended solids levels of the Fly River. Test species were selected on the basis of ecological importance. Two freshwater prawns,Macrobrachium rosenbergii andMacrobrachium sp., a catfish,Neosilurus ater, and a cladoceran,Ceriodaphnia dubia, were tested for acute toxicity and bioaccumulation of copper from particulates. There was no evidence of acute toxicity to prawns or fish, nor for bioaccumulation by prawns. Acute toxicity toC. dubia and bioaccumulation byN. ater were probably due to dissolved copper in the test environments. The test results indicated that provided dissolved copper levels did not exceed the predicted levels, there should not be toxic affects of particulate-associated copper in the Fly River.