Modelling of nitrate leaching from arable land into unsaturated soil and chalk 1. Development of a management model for applications of sewage sludge and fertilizer

A mathematical model has been produced to examine the impact of sewage sludge and fertilizer application to arable land and the effect of different crop regimes on the amount of nitrate leached to chalk groundwater. Previous work on nitrate leaching has concentrated on either a soil science or a hydrogeological approach with little overlap between the two. This study considered both fields to obtain an overall picture of the nitrate leaching process. IMPACT is a layered deterministic N-leaching model which predicts the nitrogen loads entering groundwater daily from arable land, and can be used as a management tool in development of sludge application and agricultural policy. The model relates nitrogen species movement resulting from the application of sewage sludge and fertilizer to differing vegetation-soil-hydrogeological conditions. Field data collected at three sites on the unconfined chalk aquifer of East Anglia, England over a two and a half year period was used to produce an initial conceptual model and to constrain the mathematical model during development. IMPACT simulates nitrogen and transport processes in the soil and unsaturated zone of the chalk. The nitrogen processes include: mineralisation of soil organic-N and sewage sludge organic-N, nitrification; crop uptake; volatilization; denitrification; and N inputs from fertilizers and precipitation. A mixing cell method is used to model solute transport in both the soil and chalk. Matrix flow and combined fissure-matrix flow are considered for the chalk. The model enables examination of the relationship between the arable/hydrogeological systems and the environmental implications of sludge application and of different arable regimes. Results are of use in developing strategies for arable farming and sludge application in areas sensitive to nitrate leaching. This Part 1 paper describes the model development approach. Results of associated modelling scenarios are presented separately in the associated Part 2 paper.     

Modelling of nitrate leaching from arable land into unsaturated soil and chalk 2. Model confirmation and application to agricultural and sewage sludge management

A layered deterministic N-leaching model, IMPACT, has been calibrated using data from two study sites on the unconfined Chalk aquilfer of East Anglia, UK. The model predicts nitrogen species movement resulting from the application of sewage sludges and fertilizers to arable land for different vegetation-soil-hydrogeological conditions. One site received sludge in the form of digested sewage cake (DSC) for the first time during the study period, whilst the other site had over 15 years history of liquid undigested sludge (LUS) applications at 3 year intervals. Site data included: 3-monthly concentration profiles at 0.3 m intervals to depths of up to 6 m for N-species and chloride; unsaturated potential measurements; water level and saturated groundwater solute concentrations, fertilizer and sludge input; daily recharge, and soil/chalk type and moisture content. The observed average movement rate for nitrate peaks in the Lower Chalk, measured at one site, was 0.2 m year⁻². Leachate peaks were not observed annually but approximately every third year, being associated with large sludge applications and ploughing of grass crops. Significant correlation between observed and modelled nitrate profiles in soil and chalk were obtained which demonstrated applications. The relationship between crop demand, application times of fertilizers and sludge, nitrate availability and recharge was shown strongly to control the shape of nitrate profiles in the soil and chalk and the quantity of nitrate leached tochalk. The change in hydrogeological conditions at the soil-chalk contact and associated potential for denitrification was also shown to exert a significant control on the shape of the nitrate profile. Following calibration, different arable crop and sludge application regimes were examined for a 6 year period and ranked according to their nitrate leaching risk. Of the modelled cereal farming scenarios, the crop/sludge regime giving the least nitrate leaching was a late autumn surface spread application of DSC followed by winter cereals, while highest nitrate leaching was generated by an autumn injection of LUS followed by spring cereals. Field and modelled results may be used in the development of sludge disposal policies to arable land particularly with regard to sludge types, application times, and following crop types and fertilizer requirements. Overall, observed and model data demonstrate the importance of examining nitrate leaching as a continuum from the soil through the chalk to the water table.     

新疆砂岩型氧化铜矿溶剂萃取工艺研究

溶剂萃取技术是目前常用的处理低浓度铜溶液的方法。根据新疆砂岩型铜矿资源和自然条件等特点，对不同浸出工艺条件、不同浸出溶液进行了溶剂萃取的工艺基础研究，提出了基于低浓度氨堆浸出－萃取－电积工艺，以达到成功开发新疆砂岩型氧化铜矿之目的。     

高岭石与碱性驱替剂间作用的实验研究

用Ｔｅｆｌｏｎ惰性反应器在２５℃、５０℃、和７５℃的条件下，以１ｇ／２０ｍｌ的固／液比，研究了高岭石与各三个浓度的两种碱性驱替剂间（Ｎａ２ＣＯ３和ＮａＯＨ）的作用，反应时间为０～６００ｈ，对反应后液相中的硅、铝元素浓度参数和固相物质分别进行了分光光度法和Ｘ－射线衍射（ＸＲＤ）检测，弄清了实验研究参数与液相参数和高岭石相变的关系，得出了高岭石在ＮａＯＨ溶液中存在非一致性的溶蚀趋势。高岭石在碱液中会发生溶蚀，进而可生成方钠石。此研究增加了对碱驱的认识，对提高原油采收率是一项有意义的研究工作。     

海水中碱性磷酸酶活力的测定及其在磷的循环中的作用初探

建立了海水介质中浮游植物、细菌及游离态三种碱性磷酸酶活力的分光测定法。在厦门西港海域及实验生态中分别测定了这三种碱性磷酸酶的活力;同时采用~(32)P示踪法探讨了碱性磷酸酶对小球藻直接利用溶解有机磷(DOP)的影响。结果表明,浮游植物体的碱性磷酸酶活力占主导地位;当水体溶解无机磷降低到一定浓度时,浮游植物体碱性磷酸酶活力可突增,它提供了浮游植物直接利用DOP的条件。     

Effect of dissolved phosphorus on alkaline phosphatase activity in marine microalgae

I~IOXThe alkaline phOSPhataSe (AP) has been more and more studied following the study of thephosphorus limitation (Suttle and Harrision, 1988; Hu et al., 1989; Huang et al., 1996). PeOple used to take dissolved inorganic phOSphorus (DIP) level and uptake rate by algae as phosphOrus limitation indicators (Vera and Petterson 1992; Huang and HOng, 1994). But recent resultsindicate that diSSOlved organic phosphorus (DOP) and particulate organic phOSphorus (PP) couldalso be utilized b…     

不同类型含磷营养物质对微小亚历山大藻(Alexandrium minutum)生长和毒素产生的影响

采用显微镜细胞计数和麻痹性贝毒的高效液相色谱分析方法,通过对比磷酸二氢钾、磷酸甘油和三磷酸腺苷（ATP）等含磷营养物质对微小亚历山大藻生长和毒素产生的影响,研究了微小亚历山大藻对不同类型含磷营养物质的利用情况.结果表明,在磷限制条件下,加入磷酸二氢钾、磷酸甘油和ATP均能促进微小亚历山大藻的生长,所获得的最大藻细胞密度分别为22700、28400和27800藻细胞/ml,对数期生长速率分别为0.12/d、0.14/d和0.15/d,溶解态有机磷对藻生长的促进作用稍好于溶解态无机磷.三种含磷营养物质对毒素产生的效应没有明显差别,稳定期藻细胞毒素含量分别为22.87、23.98和21.80fmol/cell.磷限制对毒素组成的影响很大,磷限制条件下膝沟藻毒素GTX1/4的含量占绝对优势,GTX2/3含量很少.在添加含磷营养物质后,GTX1/4所占比例降低,GTX2/3比例增加,说明磷限制显著改变了微小亚历山大藻的毒素组成.对藻体碱性磷酸酶活性分析的结果显示,磷限制组具有最高的碱性磷酸酶活性,添加有机磷化合物实验组的碱性磷酸酶活性显著高于添加无机磷化合物的实验组.研究结果表明,微小亚历山大藻可以利用实验中采用的无机磷化合物和有机磷化合物,但其利用溶解态有机磷化合物的机制尚不清楚,可能是通过诱导合成碱性磷酸酶来水解培养基中的溶解态含磷有机物,从而释放无机磷酸盐用于藻细胞的生长.     

Fluid evolution in the nepheline syenites of the Ditrău Alkaline Massif, Transylvania, Romania

The Ditrău Alkaline Massif is an intrusion into the Bucovina nappe system that is part of the Mesozoic crystalline zone located in Transylvania, Romania, in the Eastern Carpathians. Nepheline syenites are the most abundant rocks in the central and eastern part of the Massif, and represent the last major intrusion of the complex. Fluid inclusions in nepheline, aegirine and albite were trapped at magmatic conditions on or below the H₂O-saturated nepheline syenite solidus at about 400–600 °C and 2.5–5 kbars. Early nepheline, and to a lesser extent albite, were altered by highly saline fluids to produce cancrinite, sodalite and analcime, during this process cancrinite also trapped fluid inclusions. The fluids, in most cases, can be modeled by the H₂O–NaCl system with varying salinity; however inclusions with more complex fluid composition (containing K, Ca, CO₃, etc., in addition to NaCl) are common. Raman spectroscopic analyses of daughter minerals confirm the presence of alkali-carbonate fluids in some of the earliest inclusions in nepheline, aegirine and albite.

During crystallization, the melts exsolved a high salinity, carbonate-rich magmatic fluid that evolved to lower salinity as crystallization progressed. Phases that occur early in the paragenesis contain high-salinity inclusions while late phases contain low-salinity inclusions. The salinity trend is consistent with experimental data for the partitioning of chlorine between silicic melt and exsolved aqueous fluid at about 2.0 kbars. The activity of water (a_H2O) in the melt increases during crystallization, resulting in the formation of hydrous phases during late-stage crystallization of the nepheline syenites.     

Neutral Leaching of Low-Grade Pyrolusite with High Silica Content

Leaching studies of low-grade pyrolusite, containing 11.84% Mn with high silicon, were carried out using sodium sulfite as a reductant in ammonium sulfate medium. Various process parameters including temperature, leaching time, solid-liquid ratio, quantity of ammonium sulfate, as well as the amount of reducing agent were studied in detail. The manganese extraction yield was the response of the process. Temperature and reagent concentration exerted the most important positive effect on the manganese extraction. The optimized conditions showed that when the amount of reducing agent was a stoichonmetric amount, over 90% manganese extraction and the lowest impurities were achieved, the amount of heavy metal impurities in the manganese leaching liquid was less than 5 mg/L, and almost no iron and aluminum were extracted in 3 mol/L ammonium sulfate concentration at 100 ℃ in 45 min.     

内蒙古哈达门沟金矿床单矿物金浸出实验研究及其地质意义

哈达门沟金矿床产于华北克拉通北缘西段，形成于伸展构造背景中，成矿流体富钾高碱且氧化性强，矿石建造中铁氧化物含量高，并且可见铁氧化物被硫化物交代的现象。文章拟揭示金在铁氧化物中的含量和赋存状态，并探讨金矿床成因。对哈达门沟金矿3种类型矿石中的黄铁矿、铁氧化物(磁铁矿和赤铁矿)单矿物进行金、铁浸取实验，结果表明：铁氧化物含金较高；黄铁矿中的金和铁的浸出曲线不同步，金浸出率与铁浸出率呈负相关，表明黄铁矿中的金主要以颗粒金形式存在；铁氧化物中金、铁同步浸出，浸出率为正相关，表明铁氧化物中的金主要以品格金和(或)胶体吸附金形式存在。哈达门沟金矿床的上述特征均表明其具铁氧化物型金矿床的特点。