水中砷的原子荧光光谱测定结果的不确定度评定

目的 对原子荧光光谱法测定水中砷含量的不确定度来源及其对测量不确定度的影响进行分析。方法 利用相对标准不确定度进行测量不确定度的评定。过程采用直观的因果图，建立有效的数学模型，利用相对标准不确定度分量进行测量不确定度评定，并在砷含量为1．7μg/L的水样测定中，获得其相对标准不确定度为3．4％，有效自由度为25。结论 原子荧光光谱法对水中砷浓度测量不确定度影响因素中，工作曲线拟合产生的不确定度较大。     

氯仿稀释法测定高浓度含酚废水

4-AAP萃取分光光度法测定挥发酚方法中，当挥发酚浓度超出校准曲线范围时，一般将水样稀释后重新分析测定。本文采用氯仿稀释萃取液测定吸光度，通过公式换算求得挥发酚浓度，试验表明，该方法准确可靠，操作简便快捷。     

纳氏比色法测定NH3—N的改进

减少显色剂中ＨｇＣＬ２、ＫＩ的含量，以聚乙烯醇作胶体稳定剂，显著提高了显色剂的稳定度和显色的稳定度。以ＫＯＨ和酒石酸作缓冲液，保持恒定的显色碱度，同时也隐蔽了金属离子的干扰，从而大大降低了空白吸光度和检出限。废水预处理，通过条件实验，确定稀释比．稀释水样用絮凝沉淀法或蒸馏法处理，蒸馏时用磷酸盐缓冲液，并降低硼酸吸收液的浓度，提高了回收率。     

用分光光度法测定有机质的研究

在强酸性溶液中、165℃和催化剂作用的条件下,土壤中的有机碳被K2Cr2O7迅速氧化,而K2Cr2O7中的Cr6+还原成Cr3+,Cr3+在600nm波长上有特征吸收,其吸光度与有机碳的浓度成正比。根据吸光度可计算出土壤有机质的含量。实验证明试剂和工作曲线的斜率有很好的稳定性和重现性。分光光度法测定有机质快速、准确。     

红外光度法测定石油类和动植物油常见问题探讨

根据石油类在波数为2930cm-1、2960 cm-1、3030 cm-1全部或部分谱带处有物征吸收的原理,采用红外光度测油仪和水样絮凝富集技术测定石油类、动植物油。     

BHTTT试剂的合成与高灵敏,选择性的光度法测定痕量钴

应用乙二胺代替丙胺,巧妙地合成了 BHTTT 试剂,产率由48％提高到65％,截至目前为止,尚未见报道。研究了 Co(Ⅱ)-BHTTT—吐温-80显色配位体系的特性。在 pH5.0～9.5范围内,显色体系光谱吸收峰(λmax)为385nm,试剂空白λmax 为225nm,对比度(Δλ)较高,Δλ=160nm。摩尔吸光系数ε_(385)=2.35×10~5L.ml~(-1).cm~(-1).在低浓度吐温80和 DL-半胱胺酸盐酸盐存在下(具有相当高的选择性),Co(Ⅱ)与BHTTT 组成比为1∶2.在0.5～10ug/50ml 范围内,服从比尔定律.检出最低浓度0.005mg/L,测定上限为0.5mgCo/L.此方法已成功地应用到测定玫瑰花、当归根、人发、环境水样和钢铁中痕量钴.     

快速分光光度法测定环境空气中的一氧化碳

介绍了用基于钯(Ⅱ)被一氧化碳还原的灵敏分光光度法测定一氧化碳。所得单体钯在氯存在下在酸性介质中与碘酸盐作用产生ICL_n~-类物质,它容易用焦宁G以离子对形式萃入苯中。在535nm处测定革取物吸光度使得可以测定低至1μl/l的空气中的一氧化碳。讨论了干扰气体的影响。本法适用于汽车排出的气体和环境空气中一氧化碳的测定。     

双最大吸收光度法测定水中（Zn^2^＋）

在ＰＨ７ＨＡｃ—ＮａＡｃ溶液中，锌Ｚｎ２＋与５—Ｂｒ—ＰＡＤＡＰ反应，显色液由黄色变红色。本文依据有色溶液吸光度（Ａ）与入射波长（λ）及显色物质浓度（Ｘ）数学关系研究双最大吸收光度定量法测定水中锌。该方法可将黄色褪色和红色生色双重定量联合起来定量Ｚｎ２＋，分析灵敏度较高。实验表明，ＲＳＤ≤２％，检出限０．０１ｕｇ／ｍＬ，加标回收率９７．５％—１０５％。     

三峡水域中痕量汞的分光光度法测定

聚乙烯醇(PVA)存在下[HgI4]2-与罗丹明B(RHB)形成配合物[HgI4]2--RHB-PVA,在波长610nm处有最大吸收,表观摩尔吸光系数ε = 6.02×105 L/( mol·cm).结合巯基棉(SCF)对汞的选择性吸附,实现了水样中痕量汞的分离、富集与测定.标准样品富集前后测定的相对标准偏差RSD分别为4.25%和7.40%(n=6).本法应用于三峡水域长江和嘉陵江江段中总汞的测定,回收率为90.6%～111.4%,最低检出浓度0.040μg/L,对比国控点原子荧光光谱分析法监测汞数据,结果令人满意.     

阻抑光度法测定痕量乙醇的研究

文章研究了在稀硫酸介质中,乙醇阻抑高碘酸钾氧化中性红褪色反应的各种反应条件,建立了阻抑光度法测定痕量乙醇的新方法。讨论了体系酸度、试剂浓度、反应温度、反应时间、干扰离子等因素对反应体系的影响。选择530nm作为测定波长,确定了阻抑反应的最佳条件。在所选择的试验条件下,方法的线性范围为1.0~7.0μg/25mL,检测限为4×10~(-6)g/L。表观摩尔吸光系数ε=3.68×10~4L/mol·cm。对该方法进行了精密度测定,其相对标准偏差RSD5%。该方法用于水样中痕量乙醇含量的测定,并进行了加标回收试验,平均回收率为98.6%~98.7%。     

AN APPLICATION RUNOFF MODEL STRATEGY FOR UNGAGED WATERSHEDS1

ABSTRACT: Mathematical models for predicting watershed surface flow responses are available, most of which are elaborate nonlinear numerical surface and channel flow models linked with infiltration models. Such models may be used to make predictions for ungaged areas, assuming an acceptable fitting of the model to the topography and roughness of the real system. For some application purposes, these models are impractical because of their complexity and expensive computer solutions. A procedure is developed that uses a complex model of an ungaged area to derive a simpler parametric nonlinear system model for repetitious simulation with input sequences. The predicted flow outputs are obtained with the simpler model at significant savings of money and time. The procedures for constructing a complex kinematic model of a 40 acre (161,880 m²) reference watershed and deriving the simpler system model are outlined. The results of predictions from both models are compared with a selected set of measured events, all having essentially the same initial conditions. Peak discharges ranged from 3 to 118 ft³/sec (0.085 to 3.34 m³/sec), which includes the largest event of record. The inherent limitations of lumped systems models are demonstrated, including the bias caused by their inability to model infiltration losses after rainfall ceases. Computer costs and times for the models were compared. The derived simple model has a cost advantage when repeated use of a model is required. Such an applications hydrologic model has an engineering tradeoff of reduced accuracy, and lumping bias, but is more economical for certain design purposes.     

Conversion of temperate forests into heaths: Role of ecosystem disturbance and ericaceous plants

Fire and logging in nutrient-poor temperate forests with certain ericaceous understory plants may convert the forests into heaths. The process of disturbance-induced heath formation is documented by using examples ofCalluna in western Europe,Kalmia in Newfoundland, andGaultheria (salal) in coastal British Columbia. In a cool, temperate climate, rapid vegetative growth ofCalluna, Kalmia, and salal following disturbance results in increasing organic accumulation (paludification), nutrient sequestration, soil acidification, and allelochemicals. These are thought to be the main reasons to conifer regeneration failure in disturbed habitats. If continuation in forest is a land-use objective, then temperate forests with an ericaceous understory should not be logged unless effective silvicultural methods are devised to control the ericaceous plants and restore forest regeneration. Preharvest vegetation control may be considered as an option. Failure to control the understory plants may lead to a long-term vegetation shift, from forest to heathland, particularly in nutrient-poor sites. Successful methods of controllingKalmia andGaultheria, however, have yet to be developed. While theKalmia- andGaultheria- dominated heathlands are undesirable in Canada and the Pacific Northwest, a wide range ofCalluna heathlands of western Europe are being conserved as natural and seminatural vegetation.     

BIOLOGICAL INDICATORS AND BIOLOGICAL EFFECTS OF ESTUARINE/COASTAL POLLUTION1

ABSTRACT: Sustained interest in and concern about the health status of the aquatic environment has resulted in extensive research focused on (1) effects of pollution on survival, growth, and reproduction of resource species at all life stages; (2) diseases of fish and shellfish, as they may be related to pollution and as they may serve as indicators of environmental stress; and (3) contaminant body burdens in fish and shellfish - their effects on the aquatic animals and their potential effects on humans. Effects, lethal and sublethal, of pollutants on life history stages of fish and shellfish have been documented, as have impacts on local stocks in badly degraded habitats, but as yet there has been no adequate quantitative demonstration of effects on entire aquatic species - probably because of the difficulty in sorting out relative effects of the many environmental factors that influence abundance. Sublethal effects, especially those that result in disease, have been examined intensively, and some diseases and disease syndromes have been associated statistically with pollution. Other pollution indicators (biochemical, physiological, genetic, behavioral, and ecological) have also received some attention, as have body burdens of contaminants in aquatic species. Research, especially that conducted during the past decade, has done much to clarify the many pathways and toxic effects of contaminants on aquatic animals, and has also helped to identify mechanisms for survival of fish and shellfish in the presence of environmental changes caused by human activities.     

Using Paleo Reconstructions to Improve Streamflow Forecast Lead Time in the Western United States

In water stressed regions, water managers are exploring new horizons that would help in long‐range streamflow forecasts. Oceanic‐atmospheric oscillations have been shown to influence streamflow variability. In this study, long‐lead time streamflow forecasts are made using a multiclass kernel‐based data‐driven support vector machine (SVM) model. The extended streamflow records based on tree ring reconstructions were used to provide a longer time series data. Reconstructed data were used from 1658 to 1952 and the instrumental record was used from 1953 to 2007. Reconstructions for oceanic‐atmospheric oscillations included the El Niño‐Southern Oscillation, Pacific Decadal Oscillation, Atlantic Multidecadal Oscillation, and North Atlantic Oscillation. Streamflow forecasts using all four oscillations were made with one‐year to five‐year lead times for 21 gages in the western United States. This is the first study that uses both instrumental and reconstructed data of oscillations in SVM model to improve streamflow forecast lead time. SVM model was able to provide “satisfactory” to “very good” forecasts with one‐ to five‐year lead time for the selected gages. The use of all the oscillation indices helped in achieving better predictability compared to using individual oscillations. The SVM modeling results are better when compared with multiple linear regression model forecasts. The findings are statistical in nature and are expected to be useful for long‐term water resources planning and management.     

Journalists' views of advertiser pressures on agricultural news

All major journalism ethical codes explicitly state that journalists should protect editorial copy from undue influence by outside sources. However, much of the previous research on agricultural information has concentrated on what information various media communicate (gatekeeping studies) or communication's role in increasing innovation adoption (diffusion studies). Few studies have concentrated specifically on organizational and structural constraints that might adversely affect agricultural journalists' ethical standards; those that have, focus largely on farm magazines. A study of newspaper reporters who cover agricultural news found that the most pressing ethical concern is the effect of advertiser (agri-business) pressure on editorial copy, and that their concerns in general parallel those of farm magazine writers and editors. The majority reported being in situations in which they might be exposed to advertiser pressure, including pressures to change or withhold editorial copy. Large minorities suggested that advertising pressures affect the overall environment in which agricultural journalists work, and more than one in ten said they allow advertiser pressures to influence editorial decisions. The newspaper reporters who cover agricultural beats showed slightly more resistance to advertiser pressure than did farm magazine editors in a parallel study.     

Definition Procedures Have Little Effect on Performance of Environmental Classifications of Streams and Rivers

Mapped environmental classifications are defined using various procedures, but there has been little evaluation of the differences in their ability to discriminate variation in independent ecological characteristics. We tested the performance of environmental classifications of the streams and rivers of France that had been defined from the same environmental data using geographic regionalization and numerical classification of individual river valley segments. Test data comprised invertebrate assemblages, water chemistry, and hydrological indexes obtained from sites throughout France. Classification performance was measured by analysis of similarity (ANOSIM). Geometric regions defined by a regular grid and without regard to environmental variables and a posteriori classifications based on clustering the test datasets defined lower and upper bounds of performance for a given number of classes. Differences in classification performances were generally small. The ANOSIM statistics for the a posteriori classifications were around twice that of all environmental classifications, including geometrically defined regions. The hydro-ecoregions performed slightly better for the invertebrate data and the network classification performed slightly better for the chemistry and hydrological data. Our results indicate that environmental classifications that are defined using different procedures can be comparable in terms of their ability to discriminate variation of ecological characteristics and that alleged differences in performance arising from different classification procedures can be small relative to unexplained variation. We conclude that definition procedures might have little effect on the performance of large-scale environmental classifications and decisions over which procedures to use should be based primarily on pragmatic considerations.     

Urban ecological systems: scientific foundations and a decade of progress

Urban ecological studies, including focus on cities, suburbs, and exurbs, while having deep roots in the early to mid 20th century, have burgeoned in the last several decades. We use the state factor approach to highlight the role of important aspects of climate, substrate, organisms, relief, and time in differentiating urban from non-urban areas, and for determining heterogeneity within spatially extensive metropolitan areas. In addition to reviewing key findings relevant to each state factor, we note the emergence of tentative "urban syndromes" concerning soils, streams, wildlife and plants, and homogenization of certain ecosystem functions, such as soil organic carbon dynamics. We note the utility of the ecosystem approach, the human ecosystem framework, and watersheds as integrative tools to tie information about multiple state factors together. The organismal component of urban complexes includes the social organization of the human population, and we review key modes by which human populations within urban areas are differentiated, and how such differentiation affects environmentally relevant actions. Emerging syntheses in land change science and ecological urban design are also summarized. The multifaceted frameworks and the growing urban knowledge base do however identify some pressing research needs.     

Neighbourhood characteristics and urban gardens in the Toledo metropolitan area: staffing and voluntarism,food production,infrastructure, and sustainability practices

Urban gardens are important sources of sustenance for communities with limited access to food. Hence, this study focuses on food production in gardens in the Toledo metropolitan area in Northwest Ohio. We administered surveys to 150 garden managers from November 2014 to February 2015 in our attempt to better understand how neighbourhood racial composition and poverty levels are related to staffing and voluntarism, food production and distribution, the development of infrastructure, and the adoption of sustainability practices in urban gardens. The results from 30 gardens are presented in this paper. We used Geographic Information Systems to map the gardens and overlay the map with 2010 census data so that we could conduct demographic analyses of the neighbourhoods in which the gardens were located. Though the gardens were small – two acres or less – up to 46 varieties of food were grown in a single garden. Gardens also operated on small budgets. Food from the gardens was gifted or shared with friends, family, and neighbourhood residents. Gardens in predominantly minority neighbourhoods tended to have fewer institutional partners, less garden infrastructure, and had adopted fewer sustainable practices than gardens in predominantly White neighbourhoods. Nonetheless, residents of predominantly minority and high-poverty neighbourhoods participated in garden activities and influenced garden operations. Volunteering and staffing were racialised and gendered.     

Predicting deer-vehicle collisions in an urban area

Collisions with deer and other large animals are increasing, and the resulting economic costs and risks to public safety have made mitigation measures a priority for both city and wildlife managers. We created landscape models to describe and predict deer-vehicle collision (DVCs) within the City of Edmonton, Alberta. Models based on roadside characteristics revealed that DVCs occurred frequently where roadside vegetation was both denser and more diverse, and that DVCs were more likely to occur when the groomed width of roadside right-of-ways was smaller. No DVCs occurred where the width of the vegetation-free or manicured roadside buffer was greater than 40 m. Landscape-based models showed that DVCs were more likely in more heterogeneous landscapes where road densities were lower and speed limits were higher, and where non-forested vegetation such as farmland was in closer proximity to larger tracts of forest. These models can help wildlife and transportation managers to identify locations of high collision frequency for mitigation. Modifying certain landscape and roadside habitats can be an effective way to reduce deer-vehicle collisions.     

Biodiversity and biotechnology

The maintenance of biodiversity is urged from many quarters and on grounds ranging from aesthetic considerations to its usefulness, particularly for biotechnology. But regardless of the grounds for preserving biodiversity, writers are generally in agreement that it should be preserved. But, in examining the various references biodiversity, such as species diversity, genetic diversity, and habitat diversity, it is apparent that we cannot aim to preserve biodiversityas such, since there are a number of conflicts in any such undertaking. In preserving one aspect of biodiversity, we damage another aspect. Five arguments which attempt to ground our moral concern for biodiversity are reviewed and critiqued, not only for their consistency but also for their power to move us to action. The final section of the paper shows how conflicts in the values of personal and environmental health can impair ethical action and especially policy formation.An earlier version of this paper was read at the conference on Agriculture, Food, and Human Values: Tradition and Change, Orlando, Florida, October 7–9, 1987.