Environmental Indicators of Habitat Quality in a Migratory Freshwater Fish Fauna

/ In general, diadromous (and particularly amphidromous and catadromous) freshwater fishes decline in frequency of occurrence, change age/size structure, and probably also decline in abundance with increasing elevation and distance upstream from the sea. In freshwater fish faunas with a high proportion of migratory species, as in New Zealand, these changes in occurrence and abundance result in a breakdown of the relationship between fish abundance and habitat quality, making application of the index of biotic integrity (IBI) as a measure of habitat quality problematical since the index depends on the relationship between population metrics and habitat quality. An alternative approach applicable to assessing temporal changes in habitat quality and that uses a large database on fish distributions, involves analysis of the distribution of species across their natural distributions. In this paper we generate curves of occurrence of species across ranges of altitude and distance inland and show, through comparisons of data subsets, that the curves are consistent estimators of species' occurrence and therefore useful as indicators of habitat quality.     

Monitoring Ecosystems in the Sierra Nevada: The Conceptual Model Foundation

Monitoring at large geographic scales requires a framework for understanding relationships between components and processes of an ecosystem and the human activities that affect them. We created a conceptual model that is centered on ecosystem processes, considers humans as part of ecosystems, and serves as a framework for selecting attributes for monitoring ecosystems in the Sierra Nevada. The model has three levels: 1) an ecosystem model that identifies five spheres (Atmosphere, Biosphere, Hydrosphere, Lithosphere, Sociocultural), 2) sphere models that identify key ecosystem processes (e.g., photosynthesis), and 3) key process models that identify the "essential elements"that are required for the process to operate (e.g., solar radiation), the human activities ("affectors") that have negative and positive effects on the elements (e.g., air pollution), and the "consequences"of affectors acting on essential elements (e.g., change in primary productivity). We discuss use of the model to select attributes that best reflect the operation and integrity of the ecosystem processes. Model details can be viewed on the web at http://www.r5.fs.fed.us/sncf/spam_report/index.htm(Appendix section).     

基于碳同位素组成的大气NMHCs光化学寿命研究

利用热解析-气相色谱-同位素质谱联用仪测定了兰州市冬季和夏季昼夜大气非甲烷烃(NMHCs)的稳定碳同位素组成.结果表明,兰州市冬季大气NMHCs的δ13C值为-30.5‰～-24.3‰,夏季为-31.9‰～-24.2%,受燃煤烟气排放的影响,冬季大气NMHCs的δ13C值明显大于夏季;冬季大气NMHCs的δ13C值夜晚大于白天,夏季不同时间点C4、C5化合物的同位素值相差不大,正己烷和正庚烷的δ13C值白天比夜晚要高.利用"碳氢化合物同位素时钟"计算出正己烷和1-丁烯在兰州市夏季大气中的平均光化学寿命分别约为6d和25min.     

浅议“创模”指标的变化与发展

根据“十五”、“十一五”期间“创模”指标体系,分析了各阶段指标体系差异和变化,而最新的指标体系能更全面地反映环境质量。同时,“创模”指标的变化趋势分析表明,“创模”指标的发展必然是反映当时的环保工作重点,“创模”的基本条件门槛会不断提升,“创模”指标的内涵会不断丰富,以确保国家环境保护模范城市的先进性和示范性。     

三唑酮在水体系中的光化学降解研究

系统研究了在天然日光和高压汞灯照射下三唑酮在蒸馏水、人工海水和天然海水中的光降解情况.结果表明,天然日光照射下,三唑酮在三种介质中降解较慢.高压汞灯较天然日光能够更有效地激发三唑酮的降解,且降解符合一级动力学规律.在300 W高压汞灯照射下,三唑酮在蒸馏水、人工海水和天然海水中的半寿期分别为54.14 min、144.38 min、177.69 min.三唑酮在蒸馏水中的光降解速率大于其在天然海水中的,这主要是由于天然海水中存在的阴、阳离子和其它特殊的物质所引起的.同蒸馏水中的光反应相比,人工海水中的离子抑制了三唑酮的光降解反应.在500 W高压汞灯照射下,三唑酮的反应速率明显提高.实验发现溶液中加入重金属离子(Cu2+、Pb2+、Cd2+)能够改变三唑酮的光降解速率.     

Agroecosystem functional assessment and its difficulties

Agroecosystem functional assessment indicators provide a necessary bridge between decision-makers and scientists. The development of acceptable indicators, however, remains a difficult task because the current knowledge and understanding of ecosystems is not sufficient to allow an objective assessment of all ecosystem functions. These difficulties were summarized from three perspectives. First, there are difficulties in individual function assessment. Of the four functions associated with agroecosystems-energy flow, materials cycling,information flow and value flow-data on material cycling and information flow remain difficult to obtain and the indicators relatively immature. Secondly, there are difficulties of integration. During the assessment process, the integration of the agroecosystem functions remains the biggest obstacle. Until now, there has been no practical or effective methodology established to resolve the problem. At present, the makeshift approach has been to weight the various indicators and then add them together. Thirdly, there is the problem of obscure concepts and concept confusion. When assessments of agroecosystems are conducted, concepts such as structure, function, benefit,and resource utilization are used extensively. To date, no logical relationship (either real or implied) has been developed between any of these concepts. Are they causes and results such that the relationship between them is linear, or are they independent from one another such that the relationship is parallel? Thus far, the essence of this question is yet to be explored.     

基于支持向量回归机的煤层瓦斯含量预测研究

为了对煤层瓦斯含量进行准确预测,应用支持向量回归机(SVR)理论建立煤层瓦斯含量预测模型,结合现场实测数据利用支持向量机(SVM)工具箱进行模型的求解及预测,并从均方根误差、希尔不等系数和平均绝对百分误差3个不同误差指标与人工神经网络预测模型进行比较分析。研究结果表明:SVR模型其预测精度及可行性高于神经网络模型,而且运算快,实时性较好,用于煤层瓦斯含量的预测较理想,具有良好的应用前景,可以为煤矿瓦斯防治提供理论依据。     

流动注射化学发光测定痕量亚硝酸根的研究

基于NO_2~-对I_2-EDTA光化学反应的抑制作用和I_2与鲁米诺的化学发光反应,建立了痕量亚硝酸根的流动注射化学发光分析方法.试验并选择了最佳条件,测定了天然水中亚硝酸根的含量,回收率在93—103.5％,方法线性范围为1.0×10~(-7)—4.0×10~(-6)mol.L~(-1),检测限为1.1×10~(-6)mol.L~(-1).对2.0×10~(-7)mol·L~(-1)NO_2~-进行测定,相对标准偏差为2.2％.     

Nitrate and natural organic matter in aqueous solutions irradiated by simulated sunlight

By means of simulated sunlight, the influence of natural organic matter (NOM) on the photochemical degradation of halogenated pesticides in the absence and presence of nitrate as a precursor of the highly reactive OH radicals in aqueous solutions and freshwater was investigated. Solutions of dichlorprop or terbutylazine (a) in phosphate-buffered demineralized water containing nitrate and/or NOM and (b) in natural freshwaters were irradiated by a 1000-W Xe short-arc lamp. The collimated beam was filtered using a combination of optical filters (WG 320 and WG 295) to simulate the solar spectrum under summer midday conditions. In the absence of nitrate and NOM, the pesticides were degraded photolytically by simulated sunlight. The degradation rates depended on the absorption spectrum in the UVB range and the quantum yield of the degradation. The photochemical degradation of the pesticides was faster in the presence of nitrate due to the sunlight-induced formation of OH radicals. In the absence of nitrate, low concentrations of NOM of a brownwater lake accelerated the degradation due to the formation of reactive species by NOM. At higher concentrations of NOM, the inner filter effect of NOM lowered the degradation rates. In the presence of 50 mg l−1 nitrate, NOM decreased the degradation rate significantly. In case the natural water samples were used as a matrix for the experiments (nitrate concentrations between 2 mg l−1 and 15 mg l−1, DOC concentrations below 2.3 mg l−1), NOM acted mainly as a radiation filter and as a scavenger of OH radicals. As a consequence, in most freshwater systems, the accelerating effect of NOM by the formation of reactive species is of minor importance compared to the inner filter effect and to radical scavenging.     

SOLUBLE SUGAR COMPOSITION OF POND‐CYPRESS: A POTENTIAL HYDROECOLOGICAL INDICATOR OF GROUND WATER PERTURBATIONS1

ABSTRACT: Pond‐cypress, a deciduous conifer, is a dominant canopy species in depressional wetlands of the southeastern Coastal Plain (SCP). Extensive premature decline and death of pond‐cypress trees in central Florida have been attributed to hydroperiod alterations due to excessive withdrawals of ground water from the Floridan aquifer. One factor identified in the decline process is basal decay, which may be related to the presence of Botryosphaeria rhodina and Fusarium species (nonaggressive, facultative fungal pathogens). These fungi have been cultured from sapwood tissue of declining pond‐cypress associated with ground water mining, but not from pond‐cypress away from ground water mimng areas. In this experiment, differences in soluble (nonstructural) carbohydrate composition of branch tips were evaluated for one‐and two‐year old, nursery‐grown (unsheltered) pond‐cypress, following a year of growth under treatment conditions (control, fungal inoculation, water stress, and fungal inoculation plus water stress) in a growth chamber. Results from two methods of wet chemical analysis were compared (trimethylsilyl methylglycoside‐Method A, and alditol acetate ‐ Method B). Three pentoses (arabinose, rhamnose, and xylose) and three hexoses (galactose, glucose, and mannose) were identified in branch tips from both age classes. A fourth hexose (fucose) also was identified in samples from the younger trees. The acidic sugar, galacturonic acid, was identified in both age classes using Method A. Results suggest that prolonged water stress is correlated with greater relative concentrations of the neutral soluble sugars rhamnose (P = 0.02), xylose (P = 0.02), and galactose (P = 0.02), in addition to the acidic sugar galacturonic acid (P = 0.01), for Method A, and arabinose (P = 0.02) for Method B. These results also suggest that in the absence of water stress, the fungal pathogen B. rhodina does not penetrate to the sapwood of the trees, and that inoculation with this fungal pathogen is not correlated with differences in relative concentrations of nonstructural, soluble carbohydrates, based on Method A analysis. Empirical evidence suggests that pond‐cypress trees in depressional wetlands respond similarly to anthropogenic perturbations of ground water, but not to natural periods of drought in the absence of such perturbations. Therefore, pond‐cypress appear to be integrators of groundwater perturbations. Greater concentrations of the soluble sugars identified in this study in pond‐cypress branch tips may be hydroecological indicators of such anthropogenic perturbations as unsustainable yield from the regional aquifer and adverse impacts from aquifer storage and recovery (ASR) activities in the SCP.