滴定分析中终点的判断

本文根据分析测定原理和实际工作经验，提出了环境监测工作中几个滴定分析项目的滴定终点判断问题。同时，结合实际，阐述了分析过程中需要注意的有关事宜，对提高分析结果的准确度和精密度有一定指导意义。     

自动电位滴定法测定含硼卤水中的CO_3~=、HCO_3~-

利用自动电位仪进行电位滴定、测定含硼卤水中的CO_3~=、HCO_3~-,判断清楚,速度快,同时解决了以往滴定过程中出现的负值,比单独用指示剂指示终点,结果准确,可靠。     

蒸馏法测定污水中脂肪酸方法的改进

通过用蒸馏法对西北地区城市污水中脂肪酸（ＶＡＦ）的测定，结果表明，该方法在滴定终点的判断和温度的选择，样品量的量取等方面予以改进之后对ＶＡＦ的测定取得了较理想的结果。     

仪器法测定水环境高锰酸盐指数的应用

高锰酸盐指数是表征水质污染程度的重要指标之一,按照GB 11892—1989《水质高锰酸盐指数的测定》中的水浴温度、水浴时间、滴定终点颜色判断、滴定条件的要求,人为因素和实验环境因素对高锰酸盐指数检测数据的准确性影响较大,传统手工容量法检测的弊端日益显现,因此按照环境监测标准设计自动化检验分析设备,提高实验室检测水平尤为重要。文章对水质高锰酸盐指数全自动分析仪方法的准确度和精密度进行了测定分析,并与国标容量法的操作过程和数据进行对比探讨,仪器法测定下限为0.05 mg/L,而国标容量法规定的测定下限为0.5 mg/L,仪器法在实际样品测定中的应用范围更广,数据更可靠。     

碘量法测定硫化物实验研究

用碘量法测定了污水中的硫化物,实验探讨了加药次序、空白滤纸、滴定终点的判断问题。由实验结果可知:必须严格按照先加入碘标准溶液、再加入硫酸溶液的次序进行处理。空白实验中是否使用滤纸,其结果差异显著。在反应过程中,随着放置时间延长,硫化物测量值会增大。     

高锰酸盐氧化-碘量法测定高锰酸盐指数

在高锰酸盐指数的测定方法中,标准碱性法具有较强的抗氯离子干扰能力,但对于高氯离子浓度水样,在酸化后的滴定过程中高锰酸盐可使氯离子氧化导致滴定终点难于辨认。采用高锰酸盐氧化－碘量法（以下简称碘量法）可以较好地解决这一问题。试验得出：碘化钾加入量为４～５ｍＬ（０．５ｍｏｌ／Ｌ）,氯离子浓度在１２０００ｍｇ／Ｌ以下对测定结果基本无影响;Ｆｅ３＋对结果有负干扰,当用氟离子掩蔽后,Ｆｅ３＋浓度对测定结果基本上无影响;碘量法的回收率在９６％～１０２％之间。     

水中氯离子测定时干扰物的消除

用硝酸银滴定法测定水中氯离子时，存在S~2-、SO_3~2-、S_2_O_3~2-的干扰，原用H_2O_2消除干扰，但滴定到达终点后，颜色不太稳定，为此，我们采用过硫酸钾氧化法进行消除干扰的试验。实践证明,该方法对消除上述干扰物是可行的，对测定石油勘探开发废水中氯离子时消除干扰是适用的。     

我国制定首个天然气领域国际标准

<正>9月15日,中国石油西南油气田制定的我国首个天然气领域国际标准《用氧化微库仑法测定总硫含量》,经国际标准化组织天然气技术委员会21个成员国全票通过,正式成为国际标准。天然气总硫含量,指天然气中硫化氢等所有硫化合物的总和。硫化氢是一种无色、易燃、低浓度时有臭鸡蛋味的剧毒气体。含硫天然气必须经过脱硫净化,总硫含量控制在国家安全环保强制标准内,才能投入使用。氧化微库仑法依据化学燃烧和电化学滴定理论测定天然气中总硫含量,是我国检测天然气中总硫含量的标准方法之     

水样的代表性和滴定剂浓度对重铬酸钾法测定化学需氧量的影响

化学需氧量测定中,样品的代表性和滴定的误差直接影响结果的准确性。采用水浴超声器均化水样,可提高样品的代表性,通过调整滴定液硫酸亚铁铵标准溶液的浓度,可以减小滴定的误差,从而提高结果的准确性。     

甘肃省红色文化景观空间分布特征研究

红色文化景观是红色文化的有机组成部分,是开展红色文化旅游的重要载体。通过对《甘肃省志》数据的分析和革命史的梳理,整理得出甘肃省现存红色文化景观资源相关资料,并依托空间分布模型和ArcGIS10.6平台对样本数据的空间分布类型特征、集中性特征、均衡性特征和密度特征进行分析,梳理其空间分布的影响因素。结果表明:①甘肃省红色文化景观属于凝聚型分布,区域空间分布均衡性较低,市州差异大。②高密度分布区域为陇中城市群凝聚区和陇东凝聚区。③影响其空间分布的因素主要是历史背景和地形地势。     

源分离黄水氮磷资源化利用研究进展

黄水(尿液)中含有较高的氮磷钾组分,具有较高的资源化回收潜力。对黄水在源头分离并资源化利用,能够提高氮磷的回收效率,同时降低污水厂的运行压力。对氮磷减排和资源化回收现状、源分离排水系统以及源分离黄水的处理技术发展现状等进行综述,为源分离黄水资源化提供技术支持,为"厕所改革"在农村地区的推广提供参考。     

MANAGING GROUND WATER QUALITY IN RELATION TO AGRICULTURAL ACTiVITIES1

ABSTRACT: Ground water quality is an environmental issue of national concern. Agricultural activities, because they involve large land areas, often are cited as a major contributor of ground water contaminants. It appears that some degree of ground water contamination from agricultural land use is inevitable, especially where precipitation exceeds evapotranspiration. For this reason, and because agriculture differs significantly from point sources of pollution, farmers, policymakers, and scientists need alternative management strategies by which to protect ground water. Mathematical models coupled to geographic information systems to form expert systems can be important management tools for both policymakers and agricultural producers. An expert system can provide farmers, researchers, and environmental managers with information by which to better manage agricultural production systems to minimize ground water contamination. Significant research is necessary to perfect such a system, necessitating interim ground water management strategies that include not only a strong research program, but educational and public policy components as well.     

Effects of elevated atmospheric CO2 on invasive plants: comparison of purple and yellow nutsedge (Cyperus rotundus L. and C. esculentus L.)

The rise in atmospheric CO(2) concentration coupled with its direct, often positive, effect on the growth of plants raises the question of the response of invasive plants to elevated atmospheric CO(2) levels. Response of two invasive weeds [purple nutsedge (Cyperus rotundus L.) and yellow nutsedge (Cyperus esculentus L.)] to CO(2) enrichment was tested. Plants were exposed to ambient (375 micromol mol(-1)) or elevated CO(2) (ambient + 200 micromol mol(-1)) for 71 d in open top chambers. Photosynthetic rate did not differ between CO(2) treatments for either species. Conductance was lower in purple nutsedge and tended to be lower in yellow nutsedge. Purple nutsedge had higher instantaneous water use efficiency; a similar trend was noted for yellow nutsedge. Purple nutsedge had greater leaf area, root length and numbers of tubers and tended to have more tillers under high CO(2). In yellow nutsedge, only tuber number increased under CO(2) enrichment. Leaf dry weight was greater for both species when grown under elevated CO(2). Only purple nutsedge made seed heads; CO(2) level did not change seed head dry weight. Root dry weight increased under the high CO(2) treatment for purple nutsedge only, but tuber dry weight increased for both. Total dry weight of both species increased at elevated CO(2). Purple nutsedge (under elevated CO(2)) tended to increase allocation belowground, which led to greater root-to-shoot ratio (R:S); R:S of yellow nutsedge was unaffected by CO(2) enrichment. Findings suggest both species, purple more than yellow nutsedge, may be more invasive in a future high-CO(2) world.     

我国非点源污染的基本特征与时空分布规律研究综述

随着点源污染控制的逐步完善,非点源污染对环境造成的危害日益突出,成为了目前我国水质环境恶化的又一重大因素。为有效控制非点源污染,本研究对非点源污染的基本特征进行了概述,分析了非点源污染的研究方法。根据国内学者对非点源污染负荷时空分布的调查、计算及研究成果,总结分析了我国非点源污染负荷时空分布规律的特征,并针对性地提出了非点源污染的控制需从源头减量、过程控制及末端治理等方面进行,从而为非点源污染的预防和治理提供相应的指导。     

Dual Objective Control of Nutrient Loading into a Lake1

ABSTRACT: The control of nutrient loading into a water body is approached from a multiobjective viewpoint. The example of phosphorus (P) loading into Lake Balaton, Hungary, is used as a case study. The element P is chosen because it appears to be the limiting factor of eutrophication in the lake considered, as in many other lakes. About one-half of P loading originates from nonpoint sources; furthermore, the mechanism is poorly known and only few observation data are available. The objective of eutrophication control is to minimize P loading, while the objective of watershed management is to maximize agricultural revenue. These two objectives often appear to be in conflict. A discrete set of alternative control methods is defined, consisting in controlling a mix of the following elements: point sources, runoff, fertilizer type and application, cropping management, erosion, and sedimentation. The system dynamics is provided by a previously developed stochastic model, whose output is an empirical prohability density function (pdf) of P-loading reflecting the control policy. A compromise solution of “satisfactum” can then be chosen as a mix of the best ranked policies.     

黄腐酸的萃取和性质研究

黄腐酸是腐植酸中最具活力的组成部分,蕴藏量丰富,萃取方法简便。研究了从红原1#泥炭中萃取黄腐酸和降解物。它的分子量较小,易溶于水,抗絮凝性能好,分子内含有较多的活性官能团,具有很高的化学活性和生物活性,用途广泛。     

OPTICAL CHARACTERISTICS OF NEW ZEALAND RIVERS IN RELATION TO FLOW1

ABSTRACT: Six years (1989–1994) of data from New Zealand's National Rivers Water Quality Network were used to characterize the optical water quality regime of river waters as regards: visual clarity (black disc visibility), turbidity, and light-absorbing aquatic humic material (referred to as ‘yellow substance,’ measured as light absorption at 440 nm). Quantitative relationships between optical water quality variables and flow in rivers are well-described by power law expressions. Visual clarity usually decreases strongly with increasing flow in individual rivers. There is a strong, inverse relationship between turbidity and visibility, but, because of differences between sites, turbidity is not a good general predictor of visual clarity (the attribute of real interest) in rivers. Yellow substance tends to increase with increasing flow, probably because during rainstorms, soil water high in yellow-colored humic material, rather than rain water or ground water, dominates discharge. Therefore, rivers are typically clear and low in humic matter at low flow, and turbid and yellow-colored at high flow.