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Humic substances exposed to solar light play the role of photosensitizers in aquatic photochemical processes, generating free
radicals during UV and visible light irradiation. During irradiation, high molecular weight structures are destroyed and low
molecular weight constituents are formed. Alterations of the humic acids metal binding capacity due to their photochemical
alterations occur. The present work reports controlled laboratory experimental results on the binding of copper by a certified
purified peat humic acid (PPHA) before and after irradiation in a laboratory scale photoreactor. A reference curve of copper
binding by photochemically unaltered humic acid was experimentally determined as a function of solution pH by potentiometric
titrations. The experimental data series correspond to a pH range from 3 to 8.5, necessary for the simultaneous consideration
of complexation and metal species solubility contribution in the obtained results. From the experimental results, it was apparent
that copper is strongly bound by humic acid even at the acidic range of pH where the percentage of copper bound reached 60
and 95% at pH values of 3.5 and 5.5, respectively. During 12 and 20 days of irradiation experiments, humic acid photoalteration
was experimentally monitored by a size exclusion chromatography system (HPLC-SEC). From the potentiometric titrations of the
irradiated humic acid solutions by a copper selective electrode, it was apparent that the copper binding capacity of photoaltered
humic acid solutions was significantly reduced for pH values up to 6. 相似文献
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新疆煤炭资源赋存规律与资源潜力预测 总被引：2，自引：0，他引：2
新疆预测煤炭资源量虽居全国首位,但探明程度很低,仅为12%,煤炭资源分布极不均衡。依据构造控制、成煤时代及聚煤规律等因素,将新疆含煤地层划分为三大含煤地层区,即：准噶尔含煤地层、塔里木含煤地层及昆仑山―喀喇昆仑山含煤地层区。依据早―中侏罗世的聚煤作用与古地理环境、古构造的关系,可将三大含煤地层区再划分为13个赋煤带,进而细分出60个煤田（煤产地、煤矿点）。通过对13个赋煤带含煤地层与构造的研究,对新疆煤炭资源勘查开发潜力作出评价,认为新疆煤炭资源量潜力巨大,有很好的勘查开发利用前景。 相似文献
3.
Bioavailability and toxicity of antimony 总被引：1，自引：0，他引：1
Antimony (Sb) is a toxic trace element widely distributed in the lithosphere and mainly associated with arsenic. Sb compounds are considered to be pollutants of high interest, however, the biogeochemical behaviour of Sb is still largely unknown, especially compared to other well-known toxic elements. In particular, questions remain about the availability of Sb to vascular plants. In this work, we focused on the following problems: (i) Sb uptake by plants; (ii) the availability of Sb to plants and (iii) variations in uptake and distribution of essential plant nutrients and trace elements resulting from bioaccumulation of Sb in Triticum aestivum (wheat) seedlings. The seedlings were either germinated or grown in media enriched with Sb. By the end of germination, concentrations of Sb in the seedlings germinated in Sb-amended media increased significantly. Sb content was highest in the roots and lowest in the leaves of the seedlings. After transfer of the seedlings germinated in an Sb-free medium to Sb-enriched media, Sb concentration in the seedlings increased with time, especially in the roots. Bioaccumulation of Sb influenced concentrations of different macro- and trace elements in all parts of the plants. The least variations were observed in the leaves, probably because the increase of Sb concentration in leaves was not as significant as in the seeds and roots. 相似文献
4.
Tjahyo Nugroho Adji Eko Haryono Hendy Fatchurohman Roza Oktama 《Environmental Earth Sciences》2017,76(20):709
A hydrogeochemical study was conducted in the Gunung Sewu Karst, Java Island, Indonesia. The main objective of this study is to describe the spatial and temporal variations of hydrochemistry that occur in the central and western parts of Gunung Sewu. Discharge measurements for a one-year period are taken in some karst springs or underground rivers to define their discharge hydrograph. Furthermore, baseflow separation analysis was conducted to determine the base flow percentage throughout the year. Water sampling for hydrogeochemical analysis was taken every month to represent the dry and rainy season conditions. To describe the hydrogeochemical processes, a scatter plot analysis with a small sample size was conducted. The results showed that the hydrochemistry of karst water in the study area has different characteristics spatially and temporally. Within the dry season, the dominant hydrogeochemical process is water–rock interaction (precipitation of calcite mineral), indicated by achieving the maximum level of Ca2+, HCO3 ?, electrical conductivity, base flow percentage, and SI calcite, with the lowest level of log \(P_{{{\text{CO}}_{2} }}\) in the water. In addition, the dry season hydrochemistry is characterized by a strong relationship between electrical conductivity–calcium/bicarbonate, base flow percentage-discharge, base flow percentage-SI calcite, and SI calcite-log \(P_{{{\text{CO}}_{2} }}\). Spatially, the different level of correlations between these parameters depended on the sampling location, flow recharge, and the conduit development. Conversely, in the rainy season, the hydrogeochemical process shifted from water–rock interaction to dilution of rainwater as a result of rain water supply through a conduit system channel, which is characterized by declining Ca2+, HCO3 ?, electrical conductivity, base flow percentage, and SI calcite, with the highest level of log \(P_{{{\text{CO}}_{2} }}\) in the water. The dilution of rainwater process also caused a decline in the correlation of some hydrogeochemical parameters. 相似文献
5.
Roza Tchoukaleyska 《Urban geography》2018,39(6):944-962
This article examines the dislocations produced when competing understandings of public space come into contact. Focusing on Montpellier, France, where an urban renewal program has seen portions of the city-centre renovated, the article considers the breaking apart of a North African commercial cluster under the guide of French heritage protection. Arguing that such action is tiedto municipal urban politics and wider trajectories that place diverse identities in a separate category, I trace the process through which a plaza encompassed in the urban renewal program has been labelled as “empty” and “dead” space. Suggesting that the relocation of a well-used outdoor food market is an instance of public space being deliberately emptied of its social and civic function, I argue that such sites are better defined as “municipal spaces”, entities that are firmly in the realm of the state, rather than ones within the purview of diverse publics. 相似文献
6.
Site survey and assessment for the planned seismogeodynamic monitoring network in the Republic of Armenia 
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下载免费PDF全文 We present results of a detailed analysis of data obtained from seismic geodynamic field studies conducted at proposed sites for the development of advanced seismic monitoring stations in the Republic of Armenia. These studies aim to determine the background seismic and geodynamic noise level around such sites. Finally, based on the received data and international standards, nine survey points were classified into respective classes according to their noise level. We also calculated minimum significant earthquake magnitude detectable by the proposed seismic network in different regions of Armenia and mapped it based on recorded regional earthquakes. The resulting map indicates that the proposed seismic monitoring network will provide homogenous initial data for the various seismically active regions of the territory of the Republic of Armenia. 相似文献
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