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排序方式: 共有162条查询结果,搜索用时 15 毫秒
1.
Spatial structure analysis and kriging analysis have been identified to be useful tools in illustrating the spatial patterns of variables. Taihu Lake is one of the largest fresh water lakes in China, and has suffered serious eutrophication in recent years due to the rapid economic development and growing environmental pollution in the Taihu Catchment. In this paper, spatial structural analysis, kriging interpolation and eutrophication assessment were carried out for chlorophyll a in the lake. Studies show that spherical model could be applied to fit all experimental variograms. Positive nuggets were observed for three directions except NE–SW direction. The variograms show some anisotropy with anisotropic ratio falling within 1.76. The spatial structural patterns of chlorophyll a in the lake were affected by factors such as distribution of pollution sources, water flow and wind. Two-dimensional ordinary block kriging was applied for interpolation process. An eutrophication assessment map was also made based on a water-quality evaluation standard. Results show that the content of chlorophyll a in Taihu Lake was quite high. The whole lake has suffered serious eutrophication. However, the eutrophic situation varied in space. Higher contents of chlorophyll a appeared mainly in the northern part of the lake. 相似文献
2.
水中余氯测定方法进展 总被引:5,自引:0,他引:5
综述了水体中余氯的分析方法研究进展,对每种分析方法的原理、测定条件、干扰因素及其消除方法、检测限、线性范围及应用对象做了较为详细的论述。 相似文献
3.
《环境科学学报(英文版)》2023,35(4):29-39
Residual ammonium is a critical parameter affecting the stability of mainstream partial nitritation/anammox (PN/A), but the underlying mechanism remains unclear. In this study, mainstream PN/A was established and operated with progressively decreasing residual ammonium. PN/A deteriorated as the residual ammonium decreased to below 5 mg/L, and this was paralleled by a significant loss in anammox activity in situ and an increasing nitrite oxidation rate. Further analysis revealed that the low-ammonium condition directly decreased anammox activity in situ via two distinct mechanisms. First, anammox bacteria were located in the inner layer of the granular sludge, and thus were disadvantageous when competing for ammonium with ammonium-oxidizing bacteria (AOB) in the outer layer. Second, the complete ammonia oxidizer (comammox) was enriched at low residual ammonium concentrations because of its high ammonium affinity. Both AOB and comammox presented kinetic advantages over anammox bacteria. At high residual ammonium concentrations, nitrite-oxidizing bacteria (NOB) were effectively suppressed, even when their maximum activity was high due to competition for nitrite with anammox bacteria. At low residual ammonium concentrations, the decrease in anammox activity in situ led to an increase in nitrite availability for nitrite oxidation, facilitating the activation of NOB despite the dissolved oxygen limitation (0.15–0.35 mg/L) for NOB persisting throughout the operation. Therefore, the deterioration of mainstream PN/A at low residual ammonium was primarily triggered by a decline in anammox activity in situ. This study provides novel insights into the optimized design of mainstream PN/As in engineering applications. 相似文献
4.
Residual dynamics of thiacloprid in medical herbs marjoram, thyme, and camomile and in soil 总被引:2,自引:0,他引:2
Thiacloprid is a new insecticide of the chloronicotinyl family. To assess its risk after application, residual characteristics of thiacloprid in marjoram, thyme, and camomile and in soil were studied under field conditions. The active ingredient was extracted from the plant material using a mixture of acetone-water. After filtration, the extract was concentrated to the aqueous phase, diluted with water, and portioned against ethyl acetate on a matrix solid phase dispersion column. Thiacloprid was extracted from soil using a mixture of methanol-water, filtered, and re.extracted (clean up) with dichloromethane. The residues were quantified using HPLC-MS-MS. The methods were validated by recovery experiments. Thiacloprid residues in marjoram, thyme, and camomile and in soil persisted beyond 10, 14, 14, and 21 d but no residues were detected after 14, 21, 21, and 28 d, respectively. The data obtained in this study indicated that the biexponential model is more suitable than the first-order function to describe the decline of thiacloprid in fresh marjoram, fresh thyme, and dried camomile flowers with half-life (t1/2) of 1.1, 0.7, and 1.2 d, respectively. However, both the first-order function and biexponential model were found to be applicable for dissipation of thiacloprid in soil with almost the same t1/2 values of 3.5 and 3.6 d. The results indicated that thiacloprid dissipates rapidly and does not accumulate in the tested herbs and in soil. 相似文献
5.
The use of quantitative data for constructing prognostic maps of the dynamics of ecosystem degradation and restoration by
nonlinear simulation methods is a topical field of landscape ecology. This method of dynamic cartography is based on fiberwise
comparison of data on the state of Chernye Zemli (the Kalmyk Republic, Russia) in different years and the detailed analysis
of the period on which the prognosis was based. For this purpose, materials of repeated aerial and satellite photography obtained
during a long period (1954–1993) were used. Comparison of maps characterizing the dynamics of Chernye Zemli between 1958 and
1993 allows prognostic electronic maps for the next 10–15 years (with a five-year interval) to be drawn and land prognosis
for the next 20–30 years (1998–2023) to be obtained.
Deceased 相似文献
6.
从活性污泥的絮凝特点、有机物与 NH 4-N 的微生物代谢过程等方面探讨前处理残余铝对曝气池活性污泥的影响规律.结果显示,随着进水Al3 浓度的不断增加,污泥瞬时沉降速度明显增加,而对污泥沉降比影响不大.Al3 对COD去除率基本上没有影响,而对废水中 NH 4-N 氧化过程的影响却非常明显,随着活性污泥中Al3 的逐渐增加, NH 4-N 去除率出现了先升后降的变化趋势. NH 4-N 去除率下降的趋势与Al3 对微生物细胞膜电解质透性的影响规律呈负相关关系,说明Al3 对氨氧化微生物种群的干扰作用最强. 相似文献
7.
长三角典型区土壤重金属有效态的协同区域化分析、空间相关分析与空间主成分分析 总被引:11,自引:8,他引:3
以昆山市为典型区,采集了126个表层土壤样品,通过多元统计学、地统计学与GIS技术相结合,采用基于协同区域化理论的因子克立格法探讨了长三角多个土壤重金属有效态的区域分异,并在剖析不同空间尺度有效态重金属的空间结构特征基础上,应用空间相关分析和空间主成分分析来揭示引起这种分布格局的成因和污染来源,结果表明,昆山土壤有效态重金属服从正态或对数正态分布,变异系数较大,有效态Cd污染最重.重金属有效态在空间上可划分为块金尺度、小空间尺度(15 km左右)和大空间尺度(40 km左右),它可用3个尺度的实验(交叉)变异函数的协同区域化模型线性拟合.空间相关分析中,Cd和Zn在3个尺度中的相关性均极显著,且元素在小尺度和大尺度的相关性比块金尺度更强,大尺度的负相关特征较其它尺度明显.空间主成分分析表明,不同尺度的空间污染来源不同.重金属有效态第一、二主成分的空间分布格局结果表明重金属有效态含量与工业活动、污水灌溉和土壤性质密切相关. 相似文献
8.
Ravikumar KVG Debayan Ghosh Mrudula Pulimi Chandrasekaran Natarajan Amitava Mukherjee 《Frontiers of Environmental Science & Engineering》2020,14(1):16
9.
Mapping the Spatial Variability of Plant Diversity in a Tropical Forest: Comparison of Spatial Interpolation Methods 总被引:4,自引:0,他引:4
Hernandez-Stefanoni JL Ponce-Hernandez R 《Environmental monitoring and assessment》2006,117(1-3):307-334
Knowledge of the spatial distribution of plant species is essential to conservation and forest managers in order to identify
high priority areas such as vulnerable species and habitats, and designate areas for reserves, refuges and other protected
areas. A reliable map of the diversity of plant species over the landscape is an invaluable tool for such purposes. In this
study, the number of species, the exponent Shannon and the reciprocal Simpson indices, calculated from 141 quadrat sites sampled
in a tropical forest were used to compare the performance of several spatial interpolation techniques used to prepare a map
of plant diversity, starting from sample (point) data over the landscape. Means of mapped classes, inverse distance functions,
kriging and co-kriging, both, applied over the entire studied landscape and also applied within vegetation classes, were the
procedures compared. Significant differences in plant diversity indices between classes demonstrated the usefulness of boundaries
between vegetation types, mapped through satellite image classification, in stratifying the variability of plant diversity
over the landscape. These mapped classes, improved the accuracy of the interpolation methods when they were used as prior
information for stratification of the area. Spatial interpolation by co-kriging performed among the poorest interpolators
due to the poor correlation between the plant diversity variables and vegetation indices computed by remote sensing and used
as covariables. This indicated that the latter are not suitable covariates of plant diversity indices. Finally, a within-class
kriging interpolator yielded the most accurate estimates of plant diversity values. This interpolator not only provided the
most accurate estimates by accounting for the indices' intra-class variability, but also provided additional useful interpretations
of the structure of spatial variability of diversity values through the interpretation of their semi-variograms. This additional
role was found very useful in aiding decisions in conservation planning. 相似文献
10.
Yu-Pin Lin Bai-You Cheng Tsun-Kuo Chang 《Environmental pollution (Barking, Essex : 1987)》2010,158(1):235-244
This study identifies the natural background, anthropogenic background and distribution of contamination caused by heavy metal pollutants in soil in Chunghua County of central Taiwan by using a finite mixture distribution model (FMDM). The probabilities of contaminated area distribution are mapped using single-variable indicator kriging and multiple-variable indicator kriging (MVIK) with the FMDM cut-off values and regulation thresholds for heavy metals. FMDM results indicate that Cr, Cu, Ni and Zn can be individually fitted by a mixture model representing the background and contamination distributions of the four metals in soil. The FMDM cut-off values for contamination caused by the metals are close to the regulation thresholds, except for the cut-off value of Zn. The receiver operating characteristic (ROC) curve validates that indicator kriging and MVIK with FMDM cut-off values can reliably delineate heavy metals contamination, particularly for areas lacking background information and high heavy metal concentrations in soil. 相似文献