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551.
有机磺酸类化合物的络合萃取研究 总被引:15,自引:0,他引:15
本文以三烷基胺为络合剂,正辛醇,煤油,氯仿,四氯化碳等为稀释剂,测定了络合萃取剂对于对甲基苯磺酸,磺基水杨酸稀溶液的相平衡分配系数,讨论了稀释剂,体系PH值和7301络合剂含量对萃取相平衡分配系数D值的影响,确定了形成的萃合物的组成。 相似文献
552.
天然水体中有机酸当量浓度的确定方法 总被引:3,自引:0,他引:3
本文根据天然水体中溶解有机在碳与化学需氧量和生化需氧量之间的相关性,以及有机酸当量和水体溶解有机碳之间的近似定量关系,提出了由化学需氧量或生化需氧量得到溶解有机碳或总有机碳浓度,最终得到有机酸和有机酸根当量浓度的转换方法,为大区域天然水体有机酸碱缓冲作用的评估提供了一个实用的转换途径。 相似文献
553.
554.
Acidification of groundwater in water-filled gravel pits -- a new environmental and geomedical threat 总被引:1,自引:0,他引:1
Swimmers and users of motor boats frequenting old, water-filled gravel pits in Kiiminki, Northern Finland, found in August 1993 that they were suffering from painful irritation of the eyes and that their boats had developed a finely polished surface on their aluminium hulls, evidently due to the corrosive action of the water. Subsequent measurements carried out by the water authority showed that the pH of the water in some of the pits was extremely low, reaching a value of 3.4 at its lowest. To find out the causes of the abnormally low pH values, the present authors began systematic measurements of the pH and determination of the chemical composition (Si, Al, Ca, Mg, K, Na, Fe, Mn, Cu, Pb, Ni, Cd, Cl-, NO3
-, SO4
2-) of the water in 23 gravel pits. In addition, a series of laboratory experiments was carried out to examine the interaction of water with samples of the soil and bedrock of the area to evaluate the role of this process as a possible cause of the acidification. The results show that the reaction of water with the moderately to intensively weathered sulphide and jarosite-bearing black schists, typical of the bedrock of the area, can bring about aqueous solutions similar in pH and sulphate--nitrate ratios to those found naturally in the gravel pits. The contribution of other possible mechanisms, e.g. acidic precipitation as such or combined with enhanced evaporation, the possible use of the pits as dumping sites for acidic waste or the flow or seepage of acidic peat-bog waters into the pits from the surrounding wetlands, cannot be ruled out entirely, but their contribution seems to be of minor importance. Since the concentrations of several heavy metals (notably Pb, Cd, Ni, Fe and Mn) and of sulphate and aluminium has increased in the pit water as a result of the acidification process and exceed the norms laid down in the EU Drinking Water Directive, acidification of water in gravel pits due to the oxidation of sulphides must be regarded as a new, serious environmental and geomedical threat which has so far remained poorly known or unrecognised. 相似文献
555.
溶液中金属离子和pH对红壤吸附SO4^2—的影响 总被引:2,自引:2,他引:2
本文研究了溶液中金属离子和pH对红壤吸附SO_4~(2-)的影响。实验结果表明,溶液pH降低,红壤吸附SO_4~(2-)的量增加;溶液中金属离子种类不同,红壤吸附SO_4~(2-)的量差异很大。其次序为Al~(3+)>Zn~(2+)>Na~+。实验结果也表明,当溶液中有Al~(3+)Zn~(2+)离子存在时吸附的SO_4~(2-)较有Na~+离子存在时吸附SO_4~(2-)难被水解吸下来。 相似文献
556.
557.
This study delineated the mathematical forms for the reactions involved in the mass balance of As in cropland soils. Even
mathematically simplified, many model parameters are required to define the reactive processes involved. Example simulations
were conducted based on the range of parameter values and initial conditions derived from published literature. The outcomes
showed that the As inputs due to fertilizers and irrigation water caused total As content of the root zone to gradually increase
over time. The plant uptake and leaching were equally important as pathways for removal of the added As. In turn, the dissolution
kinetics of the mineral phase and the distribution coefficient of the adsorbed phase affected the availability of the As for
plant uptake and leaching. Parameters based on laboratory-derived data on the dissolution of As mineral phase, mineralization
and oxidation of As(III), and the As plant uptake however appeared to overestimate the As transformations in soils. While
the development of mathematical model was a straightforward process, its application to realistic situations was hindered
by difficulties of defining model parameter values with confidence. Current knowledge on the processes and reactions of As
transformation in the soil–plant system is inadequate to calibrate or validate the model. Studies are needed to understand
the kinetics of soil As mineral dissolution and precipitation and the dynamics of root growth and As uptake by plant in soils. 相似文献
558.
Uranium Accumulation of Crop Plants Enhanced by Citric Acid 总被引:6,自引:0,他引:6
Citric acid was applied to soil to enhance U accumulation in four crop plants. While the highest enhanced U accumulation of
aboveground tissues (a.c. 2000 mg kg−1 dry weight) occurred in the leaves of Indian mustard (Brassica juncea), the highest enhanced U accumulation of roots (a.c. 3500 mg kg−1 dry weight) occurred in canola (Brassica napus var. napus). Uranium translocation among tissues of test plants is in the relation of roots>shoots ≅ leaves. The flowers of sunflower
(Helianthus annuus) contained similar or higher U concentrations than those found in shoots, but concentrations in seeds are close to zero.
In conclusion, Indian mustard is recommended as a potential species for phytoextraction for U-contaminated soil due to its
high U accumulation of aboveground biomass (a.c. 2200 μg per plant). There is no evidence that two types of soils cause a
significant difference of the enhanced U accumulation (p<0.05). Results, however, indicate that additional citric acid may result in downward U migration that may contaminate groundwater.
Speciation of U that is taken up by plants is also discussed in the end. 相似文献
559.
根据浙江省丽水市 1 986— 2 0 0 2年酸雨监测数据 ,对该市酸雨污染的现状特征及成因进行了分析。结果表明 ,丽水市酸雨污染严重 ,并呈逐年加重的趋势。冬、春季酸雨率高 ,降水 pH值低 ;降水的主要离子SO42 -与NO-3比值逐年下降 ,说明大气污染有从煤烟型转为煤烟型与机动车尾气混合型的趋势 ;煤耗量、地型地貌特点、低空逆温层频率、地面弱风频率对酸雨率和降水 pH值有明显的影响。 相似文献
560.
几种化感物质对杉木幼苗生长的影响 总被引:25,自引:1,他引:25
采用培养皿滤纸法 ,研究了不同浓度的肉桂酸、苯甲酸、对羟基苯甲酸对杉木 (Cunninghamialanceolata)幼苗生长的影响 .结果表明肉桂酸、苯甲酸、对羟基苯甲酸分别在 1× 10 -5molL-1、1× 10 -3molL-1、1× 10 -4 molL-1浓度时降低了叶绿素含量 (P =0 .0 5 ) ,而在 1× 10 -6molL-1、1× 10 -4 molL-1、1× 10 -5molL-1浓度时抑制了杉木幼苗胚根和胚芽的生长 (P =0 .0 1) .3种酚类物质对胚根生长的抑制作用明显高于对胚芽生长的抑制作用 .在 3种酚类物质中 ,肉桂酸对杉木幼苗生长的抑制作用最强 ,对羟基苯甲酸次之 ,苯甲酸最弱 .这表明酚类物质能在不同程度上抑制杉木幼苗的生长 ,降低其生产力 ,可能是连栽杉木人工林生产力降低的因素之一 .图 2表 1参 14 相似文献