用TM影像进行湖泊水色反演研究的人工神经网络模型

利用人工神经网络技术进行了湖泊水色遥感的反演研究,在同步实验的基础上了构造了包含一个隐含层的BP神经网络模型,利用TM卫星影像反演悬浮物、COD_Mn、溶解氧、总磷、总氮和叶绿素浓度反演精度较高,相对误差基本在25%以下,同时分析了该人工神经网络反演模型的误差来源,改进措施以及应用前景.研究表明,在进行小规模的同步监测的基础上,此模型可用于湖泊水质调查、分析和评价.     

基于GF-1 WFV影像和BP神经网络的太湖叶绿素a反演

叶绿素a浓度是可直接遥感反演的重要水质参数之一,常用来评价湖泊水体的富营养化程度.太湖是典型的二类水体,光学性质复杂,应用一类水体线性反演模式拟合较为片面且难以找到最佳拟合模型.BP神经网络模型具有模拟复杂非线性问题的功能.为研究高分一号卫星16m多光谱相机WFV4结合BP神经网络进行太湖叶绿素a浓度监测的可行性,实验利用GF-1 WFV4影像和实时的地面采样数据,建立了BP神经网络模型,同时采用波段比值经验模型进行对比.经精度检验,BP神经网络模型预测值与实测值之间的可决系数R2高达0.9680,而波段比值模型的R2为0.9541,且均方根误差RMSE由波段比值模型的18.7915降低为BP神经网络模型的7.6068,平均相对误差e也由波段比值模型的19.16%降低为BP神经网络模型的6.75%.结果证明,GF-1 WFV4影像应用BP神经网络模型反演太湖叶绿素a浓度较波段比值模型精度有所提高.将经过水体掩膜的GF-1 WFV4影像用于训练好的BP神经网络反演太湖叶绿素a浓度分布,结果显示,叶绿素a高浓度区集中分布在湖心区北部、竺山湾、梅梁湾区域,与之前的研究一致.本文研究结果验证了采用BP神经网络模型对GF-1 WFV4影像进行太湖叶绿素a浓度反演的可行性.     

太湖叶绿素a浓度预测模型初探

以太湖2005年的监测资料为基础,运用多元统计回归和BP人工神经网络方法构建模型,探求叶绿素a与水深、水温、营养盐等10项环境因子之间的关系,通过验证发现BP模型对叶绿素a浓度的拟合值与叶绿素a浓度的实测值之间的均方误差为220．3059,优于统计回归模型的235．4569;此外对两种模型进行了灵敏度测试,结果都显示总磷不是太湖叶绿素a浓度的限制因子,而水深、水温、总氮的变化对叶绿素a浓度影响显著。本研究对太湖叶绿素a浓度预测模型的建立是十分有意义的。     

面向GF-1WFV数据的闽江下游叶绿素a反演模型研究

叶绿素a浓度是可直接遥感反演的重要水质参数之一,常用来评价水体的富营养化程度.为建立适合于闽江下游叶绿素a浓度的反演模型,利用地面采样数据,结合GF-1 WFV光谱响应函数,选用多元回归、BP神经网络和随机森林方法,构建了叶绿素a浓度反演模型;并根据验证数据与实测值之间的决定系数(R~2)、均方根误差(RMSE)和平均相对误差对模型反演结果进行了比较.结果发现,随机森林模型的R~2为0.895,RMSE为1.994 mg·m~(-3),平均相对误差为11.502%,是3种模型中最优的.为了评估模型的性能,进一步比较了WFV影像像元反射率反演的叶绿素a浓度值与相应的实测值.结果表明,随机森林模型同样具有较高的精度,其R~2为0.709,RMSE为3.540 mg·m~(-3),平均相对误差为25.616%.本研究可为闽江下游水环境的监测提供一定的理论依据和技术参考.     

基于中巴地球资源1号卫星的太湖表层水体水质遥感

利用CBERS 1的CCD数据和准同步地面监测数据,结合水体组分的光谱特征,建立了太湖表层水体叶绿素a和总氮的遥感信息模型.将模型用于2000 09 16太湖表层水体,所得结果较客观地反映了叶绿素a和总氮的分布趋势,表明利用CBERS 1的CCD数据进行湖泊表层水体水质指标监测具有重要的现实意义和应用前景.由于地面监测站位有限,模型在浅水草型湖泊———东太湖的适用性受到一定限制,说明同步性好、覆盖广的地面监测对于水质遥感信息模型的准确性和适用性至关重要.     

太湖富营养化控制机理模拟

建立了一个将三维风生湖流模型,水质模型和富营养化模型耦合的数学模型,该模型不仅可以对太湖的风生湖流,总磷、总氮、COD等水质要素进行模拟,还可以模拟藻类在太湖中的生长和消亡情况以及其随风生湖流迁移的规律;在模型中,还考虑了水温、总氮、总磷和太阳辐射等环境生态因子对藻类生长率的影响,并且将模拟结果与1998年太湖的实测资料进行了对比,结果表明:该模型对风生湖流、总磷、总氮的模拟都是切合实际的,以叶绿素a浓度描述的藻类浓度的模拟值也能较好的拟合实测值。     

冰封期乌梁素海冰层中营养盐垂直分布特征分析

针对我国北方湖泊冰封期较长的特点,以乌梁素海为研究对象,通过冰封期采集的冰样和水样,对乌梁素海营养盐在水体中的垂向分布特征进行分析,冰封期过程中,冰体中的冰-水界面冰层中各营养盐浓度均大于其他冰层营养盐浓度,其中总氮、总磷、COD和氨氮在冰-水界面浓度分别是冰表层浓度的2.28倍、3.23倍、1.12倍和1.56倍。而水体中浓度均大于冰层中营养盐浓度。总体上水体中营养盐浓度超标,整个乌梁素海富营养化严重。     

内蒙古乌梁素海富营养化与环境因子的相关分析

文章利用2008年6～10月对乌梁素海水体的测定结果,以最能表现水体富营养化状态进程的叶绿素a为基准因子,分析了叶绿素a的时空分布特征。运用分层聚类分析法将乌梁素海现有的20个测点分成四类,然后应用修正的卡尔森营养状态指数对四类测点的水质进行评价,找出各类测点及总测点中与叶绿素a显著相关的环境因子,最后建立了多元逐步回归方程。2008年乌梁素海各测点叶绿素a的平均值为6.314mg/m3,变幅1.54～26.87mg/m3;在8、9月出现高峰,7、10月居中,6月最低,整个区域呈现较明显的东北高西南低的分布趋势。依据修正的卡尔森营养状态指数公式,计算得出乌梁素海TSIM平均值为65.1(53),全湖处于富营养化状态。应用SPSS统计分析软件进行相关分析的结果表明叶绿素a与BOD5、悬浮物、浊度、总磷都呈极显著正相关,与透明度呈极显著负相关,与pH值和溶氧呈显著负相关。综合逐步回归方程表明,影响乌梁素海叶绿素a的环境理化因子因不同类型的测点各有所不同,但主要的影响因子有浊度、悬浮物、总磷、总氮、硝酸盐氮和亚硝酸盐氮。     

河流水质采样策略与频率对氮磷负荷估算的影响

为探究适合的流域水质监测频率与采样策略,提高氮磷污染物负荷估算的精度,基于云南省洱源县凤羽河流域2011～2013年间逐日流量与总氮、总磷浓度的每日数据,在7d/次,14d/次,21d/次,28d/次4种采样频率下设定了3种不同的采样情景(情景a:普通随机取样、情景b:随机取样的基础上增加降水量超过10mm的水样样品采集,情景c:随机取样的基础上增加降水量超过25mm的水样样品采集).基于采样频率与采样情景的组合,利用LOADEST模型估算的总氮与总磷负荷,并与逐日连续水量水质数据计算的实测值进行比较,评估了不同取样频率和取样情景下LOADEST模型的负荷估算精度.结果表明:在LOADEST模型的估算过程中,同种采样频率下,增加降雨时期的浓度数据将会提高LOADEST模型的模拟精度;在降雨事件期间进行加密采样,不仅加大了工作量,且增加的采样次数过多(如情景b)使总氮的RMSE值由1.92增至2.26,总磷的RMSE值由0.08增至0.19,高估氮磷负荷,模型模拟精度降低.在四种不同的采样频率下,情景c中总氮的RMSE值范围为1.92～2.07,总磷的RMSE值范围为0.06～0.13,...     

基于环境一号卫星数据的太湖叶绿素a浓度反演

环境一号卫星在大型水体水环境监测与评价中具有独特的优势。为探求遥感影像在水体叶绿素a浓度反演中的应用,基于环境一号卫星CCD数据和同步实测叶绿素a浓度值,通过影像辐射定标、大气校正和几何精校正等预处理获取水体反射率,分别将单波段和不同特征波段组合的反射率与实测叶绿素a值进行皮尔逊相关分析,选取R20.8的波段组合进行建模,通过对3种波段组合反演结果对比和精度验证,发现基于CCD数据第4波段与第3波段反射率比值的二次模型具有良好的反演效果,模型预测值与实测值的最小相对误差为0.76%,平均相对误差10.99%,均方根误差为0.007 6 mg/L,明显低于实测叶绿素a浓度的平均值;最后基于该模型实现了太湖叶绿素a浓度反演,并对叶绿素a的时空分布进行了初步分析。     

Evaluation of phytoextracting cadmium and lead by sunflower, ricinus, alfalfa and mustard in hydroponic culture

Soil contaminated with heavy metals cadmium(Cd)and lead(Pb)is hard to be remediated.Phytoremediation may be a feasible method to remove toxic metals from soil,but there are few suitable plants which can hyperaccumulate metals.In this study,Cd and Pb accumulation by four plants including sunflower(Helianthus annuus L.),mustard(Brassica juncea L.),alfalfa(Medicago sativa L.), ricinus(Ricinus communis L.)in hydroponic cultures was compared.Results showed that these plants could phytocxtract heavy metals, the ability of accumulation differed with species,concentrations and categories of heavy metals.Values of BCF(bioconcentration factor)and TF(translocation factor)indicated that four species had dissimilar abilities of phytoextraction and transportation of heavy metals.Changes on the biomass of plants,pH and Eh at different treatments revealed that these four plants had distinct responses to Cd and Pb in cultures.Measurements should be taken to improve the phytoremediation of sites contaminated with heavy metals,such as pH and Eh regulations,and so forth.     

Oxidation of As(Ⅲ) by potassium permanganate

The oxidation of As(Ⅲ) with potassium permanganate was studied under conditions including pH, initial As(Ⅲ) concentration and dosage of Mn(Ⅶ). The results have shown that potassium permanganate was an effective agent for oxidizing of As(Ⅲ) in a wide pH range. The pH value of tested water was not a significant factor affecting the oxidation of As(Ⅲ) by Mn(Ⅶ). Although theoretical redox analyses suggest that Mn(Ⅶ) should have better performance in oxidization of As(Ⅲ) within lower pH ranges, the experimental results show that the oxidation efficiencies of As(Ⅲ) under basic and acidic conditions were similar, which may be due to the adsorption of As(Ⅲ) on the Mn(OH)2 and MnO2 resulting from the oxidation of As(Ⅲ).     

Chlorobenzenes in waterweeds from the Xijiang River （Guangdong section） of the Pearl River

The Xijiang River is the major source of water for about 4.5 millions of urban population and 28.7 millions of rural population. The water quality is very important for the health of the rural population. The concentration and distribution of chlorobenzenes (CBs) in both water and waterweeds collected from 4 stations in the Xijiang River (Gangdong section) of the Pearl River in April and November were determined. The result showed that nearly every congener of CBs was detected. The total contents of CBs (∑CBs) in the river water ranged from 111.1 to 360.0 ng/L in April and from 151.9 to 481.7 ng/L in November, respectively. The pollution level of CBs in the water in April was higher than that in November. The contents of ∑ CBs in waterweeds ranged from 13.53×102 μg/g to 38.27×102μg/g dry weight (dw). There was no significant difference between April and November in waterweeds. The distribution of CBs in roots, caulis, and leaves of Vallisneria spiralis L. showed different patterns. The leaves mainly contained low-molecular-weight CBs(DCBs), whereas the roots accumulated more PCBs and HCBs. The average lgBCFlip (bioconcentration factor) of CBs ranged from 0.64 to 3.57 in the waterweeds. The spatial distribution character of CBs in the Xijiang River was: Fengkai County ＜ Yunan County ＜Yun'an County ＜ Gaoyao County according to the ∑CBs, and the pollution deteriorated from the upstream to the downstream of the Xijiang River. Further analysis demonstrated that the discharge of waste containing CBs may be the main source of CBs pollution in the Xijiang River.     

Degradation of 2,4-dichlorophenol with a novel TiO2/Ti-Fe-graphite felt photoelectrocatalytic oxidation process

Degradation of 2,4-dichlorophenol(2,4-DCP)was studied in a novel three-electrode photoelectrocatalytic(PEC)integrative oxidation process,and the factors influencing the degradation rate,such as applied current,flow speed of O_2,pH,adscititious voltage and initial 2,4-DCP concentration were investigated and optimized.H_2O_2 was produced nearby cathode and Fe~(2 )continuously generated from Fe anode in solution when current and O_2 were applied,so,main reactions,H_2O_2-assisted TiO_2 PEC oxidation and E-Fenton reaction,occurred during degradation of 2,4-DCP in this integrative system.The degradation ratio of 2,4-DCP was 93% in this integrative oxidation process,while it was only 31% in E-Fenton process and 46% in H_2O_2-assisted TiO_2 PEC process.So,it revealed that the degradation of 2,4-DCP was improved greatly by photoelectrical cooperation effect.By the investigation of pH,it showed that this integrative process could work well in a wide pH range from pH 3 to pH 9.     

Effect of copper on the degradation of pesticides cypermethrin and cyhalothrin

The influence of coexisting copper (Cu) ion on the degradation of pesticides pyrethroid cypermethrin and cyhalothrin in soil and photodegradation in water system were studied.Serial concentrations of the pesticides with the addition of copper ion were spiked in the soil and incubated for a regular period of time,the analysis of the extracts from the soil was carried out using gas chromatography (GC).The photodegradation of pyrethroids in water system was conducted under UV irradiation.The effect of Cu~(2 ) on the pesticides degradation was measured with half life (t_(0.5)) of degradation.It was found that a negative correlation between the degradation of the pyrethroid pesticides in soil and Cu addition was observed.But Cu~(2 ) could accelerate photodegradation of the pyrethroids in water.The t_(0.5) for cyhalothrin extended from 6.7 to 6.8 d while for cypermethrin extended from 8.1 to 10.9 d with the presence of copper ion in soil.As for photodegradation,t_(0.5) for cyhalothrin reduced from 173.3 to 115.5 rain and for cypermethrin from 115.5 to 99.0 min.The results suggested that copper influenced the degradation of the pesticides in soil by affecting the activity of microorganisms.However, it had catalyst tendency for photodegradation in water system.The difference for the degradation efficiency of pyrethroid isomers in soil was also observed.Copper could obviously accelerate the degradation of some special isomers.     

Effects of arsenic on seed germination and physiological activities in wheat seedlings

The effects of arsenic(As)were investigated on seed germination,root and shoot length and their biomass and some other factors to elucidate the toxicity of As.The results showed low concentrations of As(O-1 mg/kg)stimulated seed germination and the growth of root and shoot,however,these factors all decreased gradually at high concentrations of As(5-20 mg/kg).The contents Of O2-,MDA,soluble protein and peroxidase(POD)activity all increased with increasing As concentrations.Soluble sugar content,ascorbate peroxidase(APX),and superoxide dismutase(SOD)activities decreased at low concentrations of As,and increased at high concentrations of As.While acetylsalicylic acid(ASA)and chlorophyll contents,catalase(CAT)activity displayed increasing trend when the concentrations of As was lower than 1 mg/kg,and then decreasing trend.By polyacrylamide gel electrophoresis(PAGE).As induced the expression of POD isozymes of wheat seedlings.As induced the expression of CAT isozymes but inhibited the expression of SOD isozymes of wheat seedlings at concentrations lower than 1 mg/kg.However,As inhibited the expression of CAT isozymes but induced the expression of SOD isozymes at concentrations higher than 5 mg/kg.The results indicated As could exert harmfulness in the early development stage of wheat at inappropriate concentrations.     

Bioconcentration kinetics of PCBs in various parts of the lifecycle of the tadpoles Xenopus laevis

Polychlorinated biphenyls （PCBs） in Xenopus laevis have been reported only for a few congeners. Additionally, there is very little information on the ability of Xenopus laevis to bioconcentrate PCBs. To address these issues, the tadpole Xenopus laevis was exposed to Aroclor 1254 mixtures in water at room temperature for 110 d followed by an additional 110 d of nonspiked PCBs in the water for the control group. During the whole process, bioconcentration factors （BCFs） of PCBs ranged from 1180 to 15670. For most PCB congeners, the highest and lowest bioconcentrations of the kinetic curves were found to be remarkably simultaneous, respectively. All 141 PCB congeners under the same experimental conditions had no linear correlation on the lgBCF versus lgKow relationship. The relationship between lgBCFs and lgKow followed a parabolic pattern indicative of selective bioconcentration, suggesting that the kinetic curves of the PCB congeners observed in the lifecycle of the tadpoles may be concentrated due to the amphibian special species and internal metabolism. In contrast, lgBCFs for PCBs were inversely related to lgKow, suggesting that a metabolism of the higher Kow PCB congeners occurred. These results support the author＇s conclusion that the tadpole Xenopus laevis plays major roles in the bioconcentration of PCB congeners, and demonstrated that the exposure kinetic curves of PCB congeners are complex. Besides the amphibian metamorphous development, the lifecycle of the tadpole Xenopus laevis also may be of importance in determining the bioconcentration of PCB congeners.     

Sustainability： A view from the wind-eroded field

This article explores the assessment of sustainability in fields subject to wind erosion. In the first part, simple sustainability audits are examined, as of soil depth and nutrients. Direct measurement of these characteristics has many problems, largely because of huge variability in space and time at all scales. Modelling still has its problems, but it may be possible to overcome many of them soon. It is true that wind erosion preferentially removes soil nutrients, but there are imponderables even here. The nutrient balance in many of these soils includes considerable input from dust. In West Africa, it has been shown that the amounts of calcium and potassium that are added in dust are sufficient to fertilize dispersed crops. In mildly acidic sandy soils, such as those found on the widespread palaeo- aeolian deposits, much of the phosphorus is fixed and unavailable to plants by the time it is removed by wind erosion, so that erosion has no added downside. Most of the nutrients carried by dust have been shown to travel close to the ground （even when they are attached to dust-sized particles）, and so are trapped in nearby fallow strips, and are thus not lost to the farming system. Second, the sustalnabillty of a whole semi-arid farming system is explored. Wind erosion in semi-arid areas （like China, the Sahel and Norflawestern Europe） generally takes place on aeolian deposits of the recent geological past. Most of these soils are deep enough to withstand centuries of wind erosion before they are totally lost to production, and some of these soils have greater fertility at greater depth （so that wind erosion may even improve the soil）. Finally some remarks are made about environmental change in relation to sustainability.     

Amplification of plasmid DNA bound on soil colloidal particles and clay minerals by the polymerase chain reaction

Polymerase chain reaction(PCR)was used to amplify a 600-base pair(bp)sequence of plasmid pGEX-2T DNA bound on soil colloidal particles from Brown soil(Alfisol)and Red soil(Ultisol),and three different minerals(goethite,kaolinite,montmorillonite). DNA bound on soil colloids,kaolinite,and montmorillonite was not amplified when the complexes were used directly but amplification occurred when the soil colloid or kaolinite-DNA complex was diluted,10- and 20-fold.The montmorillonite-DNA complex required at least 100-fold dilution before amplification could be detected.DNA bound on goethile was amplified irrespective of whether the complex was used directly,or diluted 10- and 20-fold.The amplification of mineral-bound plasmid DNA by PCR is,therefore,markedly influenced by the type and concentration of minerals used.This information is of fundamental importance to soil molecular microbial ecology with particular reference to monitoring the fate of genetically engineered microorganisms and their recombinant DNA in soil environments.     

Arsenic uptake and transport of Pteris vittata L. as influenced by phosphate and inorganic arsenic species under sand cu｜ture

In order to understand the similarity or difference of inorganic As species uptake and transport related to phosphorus in As-hyperaccumulator, uptake and transport of arsenate (As(Ⅴ)) and arsenite (As(Ⅲ)) were studied using Pteris vittata L. under sand culture. Higher concentrations of phosphate were found to inhibit accumulation of arsenate and arsenite in the fronds of P. vittata. The reduction in As accumulation was greater in old fronds than in young fronds, and relatively weak in root and rhizome. Moderate increases, from 0.05 to 0.3 mmol/L, in phosphate reduced uptake of As(Ⅲ) more than As(Ⅴ), while the reverse was observed at high concentrations of phosphate (≥ 1.0 mmol/L). Phosphate apparently reduced As transport and the proportion of As accumulated in fronds of P. vittata when As was supplied as As(Ⅴ). It may in part be due to competition between phosphorus and As(Ⅴ) during transport. In contrast, phosphate had a much smaller effect on As transport when the As was supplied as As(Ⅲ). Therefore, the results from present experiments indicates that a higher concentration of phosphate suppressed As accumulation and transport in P. vittata, especially in the fronds, when exposure to As(Ⅴ); but the suppression of phosphate to As transport in the root or rhizome may be insignificant when P. vittata when exposure to As(Ⅲ) under sand culture conditions. The finding will help to understand the interaction of P and As during their uptake process in P. vittata.