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Sunil K. Jha 《洁净——土壤、空气、水》2012,40(12):1392-1400
The geochemical characteristics and the spatial distribution of the fluoride were studied in the soils of Indo‐Gangetic plains using multivariate analysis. The fluoride (F) distribution in soil profiles and surface soil (0–15 cm) samples were studied. It was found that total fluoride (TF) in the profiles ranged from 248 to 786 mg kg?1 with a mean of 515.1 mg kg?1 whereas CaCl2 extractable soluble fluoride (FCa) was found to be in the range of 1.68 to 99.1 mg F kg?1 soil. On the other hand, in surface soils, the TF and FCa ranged from 118 to 436 mg kg?1 with a mean of 251.2 mg kg?1 and 1.01 to 5.05 mg kg?1 with a mean of 2.12 mg kg?1, respectively, in the study area. The principal component analysis revealed that the natural weathering of fluoride bearing rock and minerals, various ion‐exchange and dissolution processes in the soil, alkalinity, sodium adsorption ratio, calcium (Ca), magnesium (Mg), and clay contents of the soil are responsible for high fluoride occurrence in the area. The fluoride contamination index developed by using these factors could explain more than 76% variance of F contamination due to FCa in soils. The interpolated kriged map of FCa in surface soil indicated a distinct loop of 1.0–2.0, 2.0–3.0, 3.0–4.0, and >4.0 mg kg?1. 相似文献
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碱度增加对蛋白核小球藻光合活性与胞外多糖的影响 总被引：1，自引：0，他引：1
本文研究了不同重碳酸盐(HCO3)碱度2.3mmol/L(ALK2.3)和12.4mmoFL(ALK12.4)条件对蛋白核小球藻光合活性、色素组成、丙二醛(MDA)含量与胞外多糖的影响.实验结果表明,碱度增加对蛋白核小球藻光合活性呈促进一抑制一促进效应,ALK2.3对光合活性影响的强度.高于ALK12.4.碱度增加提高叶绿素b/叶绿素a(Chl.b/Chl.a)的值,降低类胡萝卜素/叶绿素(Caro/TChl)的值,并且ALKl24条件下对藻细胞的作用程度强于ALK2.3.此外碱度增加刺激蛋白核小球藻胞外多糖分泌,ALK2.3在培养初期提高MDA含量,ALK12.4下细胞MDA含量显著降低.说明碱度增加会促进蛋白核小球藻光合活性,促进光合产物的积累与分泌.暗示胞外多糖的分泌可能是细胞适应高碱度的一种自我保护机制. 相似文献
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High fluoride in groundwater has been reported from many parts of India. However, a systematic study is required to understand
the behaviour of fluoride in natural water in terms of local hydrogeological setting, climatic conditions and agricultural
practices. Present study is an attempt to assess hydrogeochemistry of groundwater in Ajmer district in Rajasthan to understand
the fluoride abundance in groundwater and to deduce the chemical parameters responsible for the dissolution activity of fluoride.
Ajmer district falls in the semi-arid tract of central Rajasthan and is geologically occupied by Precambrian rocks (granites,
pegmatites, gneisses, schists etc) where groundwater occurs under unconfined condition. A total of 153 well-water samples,
representing an area of 8481 km2 (further subdivided into eight blocks), were collected and chemically analyzed. The results of chemical analyses (pre-monsoon
2004) show fluoride abundance in the range of 0.12 to 16.9 mg/l with 66% of the samples in excess of permissible limit of
1.5 mg/l.
Presence of fluoride bearing minerals in the host rock, the chemical properties like decomposition, dissociation and dissolution
and their interaction with water is considered to be the main cause for fluoride in groundwater. Chemical weathering under
arid to semi-arid conditions with relatively high alkalinity favours high concentration of fluoride in groundwater. Dental
and skeletal fluorosis are prevalent in the study area which can be related to the usage of high fluoride groundwater for
drinking. The suggested remedial measures to reduce fluoride pollution in groundwater include dilution by blending, artificial
recharge, efficient irrigation practices and well construction. 相似文献
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Causes of recent salinization of numerous plots in the Yizre'el Valley of Israel were examined through a detailed field study of two severely affected sites. in particular, the theory of artesian influence on salt build-up in the upper cultivated soil layer was investigated. Two piezometer nests and 12 wells were installed to study the subsurface hydraulic regime. Water samples and soil extracts were taken to characterize the chemical composition down to 10m. No significant head differences were measured at the lower site, while at the upper site 96 per cent of the head that existed at the deep (7.5 m) artesian layer was dissipated within the overlying thick clay layer. Slight head differences were noted in the shallow layers. the deep-lying, coarse-textured aquifer differs markedly from the upper confining layers and constitutes an independent water body that has little relevance to surface processes. Chemical and hydrological analyses indicate that applied low-quality irrigation waters May, be the primary cause of downward-moving salinity and alkalinity which, in turn, affect soil permeability and site productivity. 相似文献
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Sustainable land management often requires redevelopment of existing and often contaminated Brownfield sites over use of Greenfield or agricultural land. Stabilisation / solidification (S/S) offer a viable remediation option with particular suitability in treating heavy metal contaminants. However, uncertainties over long-term durability and previously cheap landfill disposal costs resulted in limited use in many countries. There is a need to characterise treated material and assess components containment and release, to improve S/S confidence and inform remedial design, using the evaluation of the leaching controlling mechanisms. To improve understanding of key features that will enable improvements to such designs, this paper presents an evaluation of leaching for CEM II stabilised kaolin, using the leaching behaviour of 4 main components—aluminium, silicon, calcium and sulphur. Results show no detrimental implications on chemical durability due to kaolin degradation with hydration under induced alkalinity, with increased formation of stable cementitious minerals. Availabilities for components show that aluminium and silicon had minimal leachability compared to total content, whilst calcium and sulphur show almost total leaching availability. Decreasing calcium and silicon leachability under natural chemical conditions with increased hydration duration supports the increased formation of stable cementitious products with time, using the products of kaolin dissociation. 相似文献
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《Chemie der Erde / Geochemistry》2016,76(2):227-241
This study describes the groundwater quantity and quality conditions in the Damghan aquifer in Iran. The quantitative analysis of data obtained from observation wells indicates overexploitation of groundwater during recent years, which has resulted in deterioration of water quality. The mean water level has declined about 7.4 m between years of 1966 and 2010. The hydrochemical facies of water collected from sampling wells were investigated though Piper and Chadha diagrams, and the general dominant type of water in the study area was determined as Na-Cl. The quality assessment examined the suitability of groundwater for drinking and irrigation purposes. Compared to the World Health Organization (WHO) guidelines for drinking water, all regions were found to have unpotable groundwater. Furthermore, unsuitability of groundwater for agricultural applications due to high salinity was observed through analysis of major quality indicators. The saltwater intrusion was investigated by ionic ratio analyses and was determined to be the main factor contributing to high salinity and deterioration of the groundwater quality in the Damghan basin. 相似文献
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A quantitative estimation of the factors affecting pH changes using simple geochemical data from acid mine drainage 总被引：3，自引：0，他引：3
The behavior of heavy metals in acid mine drainage (AMD) is mainly controlled by pH values. Therefore, a quantitative estimation
of factors affecting pH values in AMD is very important in predicting the behavior of those metals. Many different factors
cause pH changes in streams affected by AMD and we quantitatively estimated those factors by making simple equations from
geochemical data collected from the Dalsung mine. In a stream from that mine, the pH values decrease as the stream flows downstream
from the AMD source, which is different from normal streams affected by AMD. The stream shows low pH ranges (4.04–5.96), high
electrical conductivity (1,407–1,664 μS/cm), and sulfate concentration (680–854 ppm). Most ion concentrations decrease or
do not show noticeable changes mainly due to dilution. The change of the iron content is most significant, even though the
concentration of iron is relatively low compared with other ions. The iron concentration (13.4 ppm) becomes almost 0 ppm due
to precipitation. Schwertmannite is the dominant precipitated phase downstream and whitish basaluminite is observed in the
upstream. From our pH estimation, precipitation is the most important process lowering pH values from 5.96 to 4.04. The dilution
factor was calculated by the concentration changes in sulfate ions. Dilution increases pH values, but compared with the precipitation
factor, the contribution of the dilution factor to pH is relatively small. Alkalinity is the main factor that buffers hydrogen,
which is released by precipitation. The redox changes, which were calculated from the pH and Eh values, also affect pH at
each sampling site. The trend of estimated pH changes is almost identical to the observed ones, but the values are slightly
different. Some errors are expected mainly due to the uncertainty in the observed Eh values and the chemistry of the added
water for dilution. 相似文献
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