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681.
面向铀尾矿库放射性核素污染WSN监测中,由于监测环境制约,针对该条件下节点密度低、带状分布网络连通性差等问题,为保证一定定位精度,提出一种新的定位算法。新内点测试利用RSSI值与海伦公式判断是否在三角形内外,无需未知节点周围其他节点信息,并采用Grid-SCAN寻找概率模型选取点,使该算法满足低密度条件的定位并减少其计算量。约束范围内计算网格内各点RSSI值的概率,并以最大概率坐标为定位结果。经过仿真,新算法较APIT算法在定位精度上提高了55%~69%。 相似文献
682.
亚热带茶园土壤酸度特征研究——以福建省武夷山市为例 总被引:2,自引:0,他引:2
调查测试福建省武夷山市60个茶园6个土类120个土层的土壤酸度指标,分析茶园土壤酸度特征,结果表明:福建省武夷山市茶园0~20cm土层土壤平均pH值为4.52,其中pH < 4.5的重度酸化土壤占总调查样本的55.00%;20~40cm土层土壤平均pH值为4.52,pH < 4.5占53.33%;茶园红壤、紫色土、粗骨土0~20cm、20~40cm土层土壤平均pH值均低于4.5,茶园土壤酸化严重.总体上茶园土壤中交换性Al3+的数量和相对比例随交换性酸总量增加而增大,交换性H+的相对比例则呈相反的变化特征,交换性Al3+占交换性酸的比例为76.67%~98.40%;茶园土壤pH值与交换性酸、H+和Al3+均呈极显著的负相关关系,相关系数分别为-0.61、-0.46和-0.59.茶园土壤酸碱缓冲性能随着土壤pH值的降低呈现下降趋势;总体上茶园土壤pH值与盐基饱和度呈极显著正相关关系, 土壤pH值与盐基饱和度的正相关主要受到交换性Ca2+、Mg2+饱和度的制约.但不同土壤类型表现不一,体现了茶园土壤酸度的复杂性、多样性. 相似文献
683.
以同时模拟未来大气CO2浓度和温度升高的田间开放式气候变化平台为依托,研究CO2浓度升高(CE)、升温(WA)以及两者同时升高(CW)对麦田土壤基础呼吸和微生物丰度、群落结构的影响.结果表明:CE对土壤基础呼吸没有影响,但是WA显著提高了土壤基础呼吸,在抽穗和成熟期分别增加了51.6%和38.5%.在分蘖期,土壤细菌和真菌丰度没有显著变化;而在抽穗和成熟期,CW和WA处理显著降低了真菌丰度,降低幅度分别达到32.1%~50.2%和32.0%~37.4%.通过对T-RFLP数据分析发现,CE、CW和WA处理对麦田土壤真菌和细菌群落结构没有显著影响,但是在一定程度上改变了古菌群落结构.与对照相比,CE处理真菌多样性提高了7.1%~8.2%,CW和WA处理真菌多样性分别降低了5.3%~13.5%和22.1%~33.6%;在分蘖和抽穗期,CE、CW和WA处理土壤细菌多样性比对照显著提高. 相似文献
684.
Jinglan Feng Pengtuan Hu Fei Zhang Jianhui Sun 《Environmental geochemistry and health》2016,38(6):1241-1253
The levels, potential sources and ecological risks of hexachlorocyclohexanes (HCHs) and dichlorodiphenyltrichloroethanes (DDTs) in Yellow River of Henan section, a typical agricultural area in China, were investigated. Surface water samples and suspended particulate matters (SPMs) were collected from 23 sites during two seasons. In wet season, the residues of ∑HCHs (α-HCH, β-HCH, γ-HCH and δ-HCH) and ∑DDTs (p,p′-DDT, o,p′-DDT, p,p′-DDE, p,p′-DDD) ranged from 41.7 to 290 and 4.42 to 269 ng/L in surface water, while those varied from 0.86 to 157 and 1.79 to 96.1 ng/g dw in SPM, respectively. Moreover, in surface water, the levels of HCHs and DDTs in wet season were much higher than those in dry season. The reverse was true for residues of HCHs and DDTs in SPM. Compared with the large rivers in other regions, the levels of HCHs and DDTs in the studied area ranked at high levels and the residual concentrations might cause adverse biological risk, especially for ∑HCHs during wet season. Distributions of HCHs and DDTs delineated that the input of tributaries made a significant effect on the residue of HCHs and DDTs in the mainstream. ∑HCHs in surface water were consist of 26.7 % α-HCH, 30.0 % β-HCH, 37.9 % γ-HCH and 5.45 % δ-HCH and those in SPM contained 5.16 % α-HCH, 22.1 % β-HCH, 60.5 % γ-HCH and 12.2 % δ-HCH on average. Combined with ratios of α-HCH/γ-HCH in surface water (0.70) and in SPM (0.09), the results strongly indicated that lindane was recently used or discharged in the studied area. The mean percentage of DDTs′ isomers were 28.7 % p,p′-DDT, 29.8 % o,p′-DDT, 28.1 % p,p′-DDE and 13.4 % p,p′-DDD in surface water, while those were 12.5 % p,p′-DDT, 31.8 % o,p′-DDT, 30.5 % p,p′-DDE and 25.1 % p,p′-DDD in SPM. The ratios of (DDE + DDD)/∑DDTs and o,p′-DDT/p,p′-DDT revealed that the DDTs in the studied area mainly derived from long-term weathering of technical DDTs residue and the input of dicofol. 相似文献
685.
Liuyan WU Lijuan JIA Xiaohan LIU Chao LONG 《Frontiers of Environmental Science & Engineering》2016,10(3):482-490
Adsorption isotherms of methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate and ethyl propionate on hypercrosslinked polymeric resin (ND- 100) were measured at 303K, 318K and 333K,respectively, and well fitted by Dubinin–Astakhov (DA) equation. The plots of the adsorbed volume (q v ) versus the adsorption potential (ε) at three different temperatures all fell basically onto one single curve for every ester. A predicted model based on DA equation was obtained on the basis of adsorption equilibrium data of methyl acetate, ethyl acetate and ethyl propionate at 318K. The model equation successfully predicted the adsorption isotherms of methyl acetate, ethyl acetate and ethyl propionate on ND-100 at 303K, and 333K, and also gave accurate predictive results for adsorption isotherms of the other two ester compounds (propyl acetate and isopropyl acetate) on ND-100 at 303K, 318K and 333K. The results proved the effectiveness of DA model for predicting the adsorption isotherms of ester compounds onto ND-100. In addition, the relationship between physico-chemical properties of adsorbates and their adsorption properties was also investigated. The results showed that molecular weight, molar volume and molar polarizability had good linear correlations with the parameter E (which represents adsorption characteristic energy) of DA equation. 相似文献
686.
Shou ZHAO Dongxin WANG Chenghong FENG Ying WANG Zhenyao SHEN 《Frontiers of Environmental Science & Engineering》2016,10(1):19-27
Metal speciation can provide sufficient information for environmental and geochemical researches. In this study, based on the speciation determination of Cu and Zn in the Yangtze Estuary sediments, roles of eight geochemical controls (i.e., total organic carbon (TOC), clay, Fe/Mn in five chemical fractions and salinity) are fully investigated and sequenced with correlation analysis (CA) and principal components analysis (PCA). Results show that TOC, clay and Fe/Mn oxides are key geochemical factors affecting the chemical speciation distributions of Cu and Zn in sediments, while the role of salinity appears to be more indirect effect. The influencing sequence generally follows the order: TOC>clay>Mn oxides>Fe oxides>salinity. Among the different fractions of Fe/Mn oxides, residual and total Fe content, and exchangeable and carbonate Mn exert the greatest influences, while exchangeable Fe and residual Mn show the poorest influences. 相似文献
687.
Qiuying CHEN Jingling LIU Feng LIU Binbin WANG Zhiguo CAO 《Frontiers of Environmental Science & Engineering》2016,10(1):46-52
Surface sediments of rivers can exhibit spatial and temporal variations in contaminant concentrations that may significantly affect risk evaluations. As to pollution control and remediation of watershed, large-scale and further background data on PAHs in China were required urgently. Spatial distribution and compositional characteristics of 16 polycyclic aromatic hydrocarbons (PAHs) in surface sediments from Haihe River Basin were investigated. A method based on effects range (ER) was used to assess ecosystem risk of ∑PAHs (the total of 16 PAH) sensitively and accurately. The results indicated that ∑PAHs content levels ranged from 257 to 16901 μg·kg−1 dry weight. The lower rings predominated in the samples, and 2-, 3-, 4-, 5- and 6-ring PAHs accounted for 12%, 21%, 30%, 30%, and 7% respectively in total PAHs. The ratio of Fl / (Fl+ Py) uniformly distributed in the interval 0.20–0.80, indicating that it may be affected by petroleum origin, oil combustion, biomass and coal combustion jointly. ∑PAHs in Cetian (S6), Dongwushi (S19), Handan (S20), Aixinzhuang (S21) and Tianjin (S37) exceeded effects range low (ERL), in which biologic effects were in a medium level with an adverse effect on biologic organisms. Thus, it is necessary to strengthen the PAHs monitoring and research of the Haihe River Basin. 相似文献
688.
Rufeng LI Chenghong FENG Dongxin WANG Baohua LI Zhenyao SHEN 《Frontiers of Environmental Science & Engineering》2016,10(2):381-389
Successive sediment suspensions often happen in estuary, yet little research has probed into the difference in the release behaviors of organic compounds among different suspensions. This study took polycyclic aromatic hydrocarbons (PAHs) as typical organic contaminants and investigated the release behaviors between two successive suspensions with a particle entrainment simulator (PES). Results showed that successive sediment suspensions lowered the concentration of dissolved PAHs in the overlying water via facilitating the re-adsorption of dissolved PAHs onto the suspended particles. Fast-release and slow-release periods of PAHs were successively observed in the both suspensions. The concentration changes of dissolved PAHs in the second suspension were generally similar with but hysteretic to those in the first suspension. More vigorous desorption and re-absorption of PAHs were induced in the second suspension. Successive sediment suspensions obviously decreased the concentrations of mineral composition and organic matters in the overlying water, which significantly affects multiphase distribution of PAHs. 相似文献
689.
Feng Zhang Shengsong Yu Jie Li Wenwei Li Hanqing Yu 《Frontiers of Environmental Science & Engineering》2016,10(3):531-538
Modification of electrode surface with carboxylic acid terminated alkanethiol self-assembled monolayers (SAMs) has been found to be an effective approach to improve the extracellular electron transfer (EET) of electrochemically active bacteria (EAB) on electrode surface, but the underlying mechanism behind such enhanced EET remains unclear. In this work, the gold electrodes modified by mercapto-acetic acid and mercaptoethylamine (Au-COOH, Au-NH2) were used as anodes in microbial electrolysis cells (MECs) inoculated with Geobacter sulfurreducens DL-1, and their electrochemical performance and the bacteria-electrode interactions were investigated. Results showed that the Fe(CN) 6 3–/4– redox reaction occurred on the Au-NH2 with a higher rate and a lower resistance than that on the Au or the Au-COOH. Both the MECs with the Au-COOH and Au-NH2 anodes exhibited a higher current density than that with a bare Au anode. The biofilm formed on the Au-COOH was denser than that on bare Au, while the biofilm on the Au-NH2 had a greater thickness, suggesting a critical role of direct EET in this system. This work suggests that functional groups such as–COOH and-NH2 could promote electrode performance by accelerating the direct EET of EAB on electrode surface. 相似文献
690.