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Research on the Upper Campanian (Upper Cretaceous) Negev phosphorites (Mishash Formation), based on microprobe analyses, Fourier Transform Infrared spectroscopy, wet chemistry, microtextural (Scanning Electron Microscopy) studies and mineralogical analyses, together with quantified rates of sedimentation and P accumulation, enables the chemistry of these rocks to be better constrained across the Negev area and allows their suitability for the manufacture of P fertilizers to be better determined. Two phosphorite facies are differentiated: (i) a pristine phosphorite facies of low P content, more typical of basinal sections and (ii) a reworked, granular phosphorite facies commonly enriched in P, found predominantly near palaeo‐highs and forming most of the economic phosphates. The distribution of F/P2O5, CO2/F, U(IV), Cd, Zn and other trace metals (Mo, Ni, Cr, Cu, V and Y), rare‐earth elements concentration, Ce and Eu anomalies and heavy rare earth elements enrichment, are controlled by these two facies. F/P2O5 in carbonate‐fluorapatite is much lower (0·090 to 0·107) in the pristine than in the reworked facies (0·107 to 0·120); in addition, the lower F/P2O5 in the pristine facies is coupled with: (i) higher Cd, Zn, Mo, Ni, Cr, Cu and V concentrations; (ii) a considerably reduced (< 10%) U(IV) fraction of total U; (iii) lower rare earth elements/P2O5 and Y/P2O5 ratios; (iv) less negative Ce and Eu anomalies and lower heavy rare earth elements (Lu/La) enrichment; (v) an increase in Fe‐rich smectites in the clay fraction; and (vi) presence of OH in the carbonate‐fluorapatite structure. Sedimentary reworking of previously formed pristine phosphate, together with its redeposition near structural highs in more oxic bottom conditions, results in considerable diagenetic changes in the chemistry of the phosphorites, making them more suitable for economic exploitation. The results presented here provide geochemical criteria for identifying pristine phosphate in other phosphorite sequences and may help to better locate phosphate strata chemically suitable for the phosphate industry elsewhere. 相似文献
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长江和长江口高含量无机氮的主要控制因素 总被引:41,自引:6,他引:41
根据1998-1998年长江和长江口河水和雨水的现场调查、历史资料以及相关文献,定量分析长江流域无机氮的主要来源和输送调查。估算表明,降水无机氮、农业非点源氮(化肥和土壤流失的氮)和点源污水氮的输入分别占长江口无机氮输出通量的62.3%、18.5%和14.4%。氮的降水输入是长江口高含量无机氮的主要来源,进入长江的降水氮仅仅大约占长江流域全部降水氮的36.8%。降水米要受控于化肥气态损失、化石燃料及动植物过程中释放的物质等。实际上,化肥N的气态损失和农业非点源流失大约占长江流域年化肥N使用量的60%,这是控制长江口高含量无机氮的关键因素。 相似文献
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1981年以来对察尔汗盐湖三次渗漏试验结果表明,盐田渗漏是盐田土层与外界条件综合作用的结果,在盐田建设和生产管理过程中,应结合不同地点的土层特性、工程地质条件和其它有关条件,采取不同的处理措施。 相似文献
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The petrochemicals industry (mainly plastics and fertilizer production) is expanding, despite increasing attention to the environmental impact of petrochemicals. In our paper, we explore the role public finance plays in the petrochemicals industry. We do so by mapping the public and private financial flows into large-scale petrochemical projects for the decade 2010–20 and discuss the role of public financial institutions for the development of the industry globally. Secondly, we provide a detailed analysis of the roles international and national public finance has played in enabling two prominent petrochemical projects: namely the Sadara plant in Saudi Arabia and the Surgil plant in Uzbekistan. The cases are illustrative of the dynamics of state interest and involvement in fossil fuel producing countries as well as of lending and guarantees from foreign export credit agencies (ECAs) and development finance institutions, and how such public finance plays an important role in leveraging private finance. Our findings show how public finance for petrochemicals is highly globalized and to a large degree originates in developed countries. As petrochemical industrial infrastructures are designed to last decades, the public finance thus strongly contributes to the carbon lock-in of the sector and limits the possibilities for low-carbon investments needed to comply with the UN Paris Agreement. 相似文献
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化肥是提高作物产量的物质基础, 在过去的几十年中, 它在世界农业建设中起过巨大作用。近百年的肥料试验表明, 化学肥料具有和有机质一样的持续增产效果, 在提高作物产量、品质的同时, 还可培肥土壤。随着化肥工业的发展, 化肥的负作用会逐渐减小。 相似文献
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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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James G. Cooke 《水文研究》1988,2(2):123-133
The management of the riparian zone has been suggested as a technique for controlling the amounts of phosphorus (P) entering watercourses draining pasture catchments. A study was therefore made of P entering a stream from various sources (rainfall, surface and subsurface derived runoff, direct fallout from aerial topdressing), with the object of providing a rational basis for the design of effective riparian management schemes. P entrained in surface runoff could account for virtually all of the P entering the stream during storms. Approximately 20 per cent of the annual P export from the catchment could be accounted for by direct aerial input of P to the stream during autumn fertilizer topdressing. More than 85 per cent of the P was exported from the catchment as particulate P. Stream sediment had higher P sorption capacities, and were enriched with P relative to the soils from which they were derived. There was a pronounced seasonal variation in sediment enrichment which could be predicted (r2 = 0.92) by the logarithm of the rainfall since fertilizer topdressing (LNFERT) and flood intensity. The amount of P lost in streamflow during any flood event was predicted (r2 = 0.94) by peak flow, seven day antecedent peak flow and LNFERT. Approximately 40 per cent of the 1.3 kg P ha?1 exported during 1981 occurred in four storms with recurrence intervals of more than three months. From a P budget compiled from nine events it was hypothesized that the stream acted as a net sink for P at baseflow and low-medium intensity floods but was a source of P at higher flood intensities. It was concluded that P losses from hill pasture catchments could be reduced by avoidance of direct application of P fertilizer to the stream channel, and by fencing out stock from seasonally saturated areas during periods of saturation. The ultimate success of the latter technique would depend on whether buffer vegetation could retain accumulated P during extreme storm events. 相似文献