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Jean de la Paix Mupenzi Lanhai Li Jiwen Ge Achal Varenyam Gabriel Habiyaremye Nzayisenga Theoneste Kamanzi Emmanuel 《地学前缘(英文版)》2011,2(4):599-607
This study has focused on the processes of soil degradation and chemical element concentration
in tea-growing regions of Rwanda, Africa. Soil degradation accelerated by erosion is caused not only
by topography but also by human activities. This soil degradation involves both the physical loss and
reduction in the amount of topsoil associated with nutrient decline. Soil samples were collected from
eleven tropical zones in Rwanda and from variable depth within each collecting site. Of these, Samples
from three locations in each zone were analyzed in the laboratory, with the result that the pH of all soil
samples is shown to be less than 5 (pH < 5) with a general average of 4.4. The elements such as iron (Fe),
copper (Cu), manganese (Mn), and zinc (Zn) are present in high concentration levels. In contrast calcium
(Ca) and sodium (Na) are present at low-level concentrations and carbon (C) was found in minimal concentrations. In addition, elements derived from fertilizers, such as nitrogen (N), phosphorous (P), and
potassium (K) which is also from minerals such as feldspar, are also present in low-level concentrations.
The results indicate that the soil in certain Rwandan tea plantations is acidic and that this level of pH may
help explain, in addition to natural factors, the deficiency of some elements such as Ca, Mg, P and N. The
use of chemical fertilizers, land use system and the location of fields relative to household plots are also
considered to help explain why tea plantation soils are typically degraded. 相似文献
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长江口水下三角洲沉积物记录的古环境演化 总被引:4,自引:0,他引:4
长江口水下三角洲60 m的HYZK5钻孔,揭示了末次冰期以来河流相、滨海湖沼相、河口湾-浅海相(前三角洲相)和水下汉道相的沉积环境演化.泥炭层形成于末次冰期的冷湿气候环境;有孔虫丰度的变化反映了12 000 cal.aBP以来海平面迅速上升,但在11 200~10 000 cal.aBP出现短暂的停顿.沉积物的粒度、磁... 相似文献
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海南岛三亚小东海岸礁礁坪沉积物的稀土元素分布特征 总被引:1,自引:0,他引:1
对海南岛三亚小东海东北岸礁礁坪表面沉积物的稀土元素进行了分析,结果表明,沉积物的∑REE为80.22mg/kg,稀土元素含量球粒陨石标准化分布模式呈现轻稀土富集、重稀土亏损,Eu明显负异常(0.58),Ce无异常,Y/Ho低(27.60)的陆相模式特征.根据小东海礁坪沉积样品稀土元素的空间分布情况可以推测出礁坪珊瑚表面... 相似文献
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R. ShynuV. Purnachandra Rao Pratima M. KessarkarT.G. Rao 《Estuarine, Coastal and Shelf Science》2011,94(4):355-368
Rare earth elements (REEs) in the suspended particulate matter (SPM) of the Mandovi estuary indicated that the mean total-REEs (∑REE) and light REE to heavy REE ratios are lower than that of the average suspended sediment in World Rivers and Post-Archean average Australian shale. High ∑REE were associated with high SPM/low salinity and also with high SPM/high salinity. Although the ∑REE broadly agree with SPM levels at each station, their seasonal distributions along transect are different. SPM increased seaward in the estuary both during the monsoon and pre-monsoon, but consistently low at all stations during the post-monsoon. The mean ∑REE decreased marginally seaward and was <25% at sea-end station than at river-end station. Spatial variations in ∑REE are maximum (64%) during the pre-monsoon. Strong to moderate correlation of ∑REE with Al, Fe and Mn in all seasons indicates adsorption and co-precipitation of REEs with aluminosilicate phases and Fe, Mn-oxyhydroxides. The ratio of mean ∑REE in sediment/SPM is low during the monsoon (1.27), followed by pre-monsoon (1.5) and post-monsoon (1.62). The middle REE- and heavy REE-enriched patterns with positive Ce and Eu anomalies are characteristic at every station and season, both in SPM and sediment. They also exhibit tetrad effect with distinct third and fourth tetrads. Fe-Mn ore dust is the most dominant source for REEs. However, the seasonal changes in the supply of detrital silicates, Fe-Mn ore dust and particulates resuspended from bottom sediments diluted the overall effect of salinity on fractionation and distribution of REEs in the estuary. 相似文献
107.
The concentrations of Cu, Zn, Cr, Ni, Pb, As, Mn and Co were determined by Inductively Coupled Plasma–Mass Spectrometry both in recent sediments from different locations of the Huelva littoral (SW Iberian Peninsula) and in their humic acid (HA) fractions in order to evaluate distribution and binding capacity of those trace elements to HAs. In addition, elemental composition (C, N, S) and δ13C values were determined to appraise the sources of organic matter in the area. This study involved the comparison of selected samples taken from different environments including the estuary of the Guadiana River, the main fluvial system of the region, the Tinto and Odiel estuary system and the proximal shelf. Significant positive correlations were found among Cu, Zn, As and Pb in bulk sediments, suggesting a common origin of all of those elements: the mining activities and pyrite deposits located hinterland. On the other hand, results for Cr, Co and Ni pointed to the basic rocks from the low basin of the Guadiana River as their main source. Elemental (C, N) and isotopic (δ13C) composition of sediments indicated a significant contribution of autochthonous plankton in coastal shelf sediments, whereas estuarine and riverine sediments showed a major contribution of terrestrial biomass. Geochemical values for their corresponding HAs suggested a greater terrestrial contribution in the sedimentary OM of the coastal shelf sediments than in bulk sediments, which evidenced the influence of coastal currents and sediment fluxes. Humic acids sequester considerable amounts of Cu and Zn contributing to reduce the bioavailability of these contaminants. 相似文献
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电感耦合等离子体质谱法测定灌木枝叶中微量元素的样品预处理方法研究 总被引:1,自引:1,他引:0
利用电感耦合等离子体质谱法(ICP-MS)测定植物样品中微量元素的关键技术是消除植物样品的有机基体效应,本文通过预处理方法中的酸消解体系、称样量和消解方式消除其影响。以国家标准物质灌木枝叶组合样(GBW07603)为材料进行研究,对比分析了硝酸-过氧化氢、硝酸-氢氟酸、硝酸-氢氟酸-过氧化氢3种酸溶体系的消解效果,以确定最佳酸溶体系,进而定量研究2种称样量(50 mg和100 mg)和3种消解方式(密封高压二次消解、密封高压一次消解、微波消解)的消解效果,并以In作为内标采用ICP-MS测定微量元素含量。结果表明:硝酸-氢氟酸-过氧化氢酸溶体系的消解效果最好;50 mg的测定值更接近于参考值;微波消解法的测定值明显偏低,而密封高压二次消解法是灌木枝叶样品预处理的有效方法。 相似文献