土壤中氧化铁的有机还原溶解动力学

研究了土壤中的氧化铁被两种酚化合物还原而溶解的动力学，结果表明，在ｐＨ恒定和有机还原剂过量的情况下，氧化铁的还原溶解符合一级反应动力学方程，还原溶解速率大小与土壤中氧化铁的结晶形态有关．氧化锰的存在影响着氧化铁的还原溶解，在存在足够的还原剂的条件下，两者可同时还原．实验中求得黄壤和赤红壤中氧化铁的还原溶解反应对［Ｈ＋］的反应级数分别为０．１２６和０．１７４。土壤中氧化铁的还原溶解是一个受表面反应控制的过程，反应的速率控制步骤是表面的电子转移反应，磷酸根在土壤中的吸附占据了氧化铁表面的反应位，因而明显抑制还原溶解反应．     

The representation of cyanobacteria life cycle processes in aquatic ecosystem models

Two simplified versions of a numerical life cycle model for diazotrophic cyanobacteria (of the order Nostocales) are developed and evaluated. Both consider two-life cycle stages, one growing, nitrogen-fixing stage and one stage that combines the resting, germinating and vegetative stages. The versions differ in the vertical resolution of the non-diazotrophic stage: version 1 collects the biomass in one layer at the bottom, version 2 considers sinking and rising of biomass explicitly. The results of the two versions are compared with a complex cyanobacteria life cycle model which describes four different life cycle stages each with two internal quotas for energy and nitrogen. The two simplified approaches show a good agreement with respect to the main characteristics of cyanobacteria dynamics (timing and duration of blooms, magnitude of nitrogen fixation, interannual variability). Our model study shows that both simplified approaches are suitable to be implemented into three-dimensional coastal or lake models.     

Uranium and other trace elements’ distribution in Korean granite: implications for the influence of iron oxides on uranium migration

To understand trace radionuclide (uranium) migration occurring in rocks, a granitic batholith located at the Korea Atomic Energy Research Institute (KAERI) site was selected and investigated. The rock samples obtained from this site were examined using mineralogical methods, including scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). The changes in the distribution pattern of uranium (U) and small amounts of trace elements, and the mineralogical textures affected by weathering, were examined. Based on the element distribution analyses, it was found that Fe²⁺ released from fresh biotite is oxidized in short geological time, forming amorphous iron oxides, such as ferrihydrite, around silicate minerals. In that case, the amorphous ferrihydrite does not show distinct adsorption for U. However, as it gradually crystallizes to goethite or hematite, the most U-rich phases were found to be associated with the secondary iron oxides having granular forms. This evidence suggests that the geological subsurface environment is favorable for the crystallized iron oxides to keep their structures more stable for a long time as compared with the amorphous phases. There is a possibility that the long residence of U which is in contact with the stable crystalline phases of iron may finally lead to the partial sequestration of U in their structure. Consequently, it seems that Fe-oxide crystallization can be a dominating mechanism for U uptake and controls long-term U transport in granites with low U contents.     

Ecological modelling of nitrate pollution in small river basins by spreadsheets and GIS

With the increasing importance and awareness of water quality in the small basins, the modelling system is developed for monitoring and predictions of surface water pollution. The compartment model deals with basin characteristics extended by land cover attributes. The parameters of the model are estimated by experimental data of water quality together with land cover types that serve as nutrient detention media or transformers. The study examines methodology to determine the potential areas of nitrate pollution from point and non-point sources by remote sensing techniques. Classification of water, agricultural, forest and urban areas is processed with satellite images (LANDSAT 7). Whereas the agricultural and urban areas act as sources of pollution, forest zones operate as sinks. The nitrate levels are decreased downstream, if the proportion of the forest inside contribution zones increases. The modelling system is used to simulate amounts of nitrates in each compartment of the stream during the monitored period of one year. The number of compartments and their lengths are estimated on the basis of morphology of the basin. Simulation of the dynamic model is carried out with the TabSim. Geographic information system (GIS) and remote sensing tools are used to manage and estimate nitrate inflows from point and non-point sources of pollution. The article presents the spatial and time variation of the nitrate (NO₃⁻) within the basin of the stream Rakovnický (the west part of Bohemia, the whole area of 368 km²). It is shown that the model approach extended by the GIS and remote sensing can support decision-making process for better management practices in the basins.     

Nitrogen availability in relation to vegetation changes resulting from grass encroachment in Dutch dry dunes

The encroachment of some tall grass species in open dune vegetation, as observed in a Dutch dry dune area, is considered unfavourable from a conservation viewpoint. This paper investigates differences in vegetation and soil properties between grass-dominated and still existing open dune grassland plots at four locations along the coast. Soil properties studied include nitrogen and phosphorus pools and nitrogen availability by mineralization. Vegetation properties included are above and below-ground biomass and nitrogen and phosphorus concentrations in above-ground biomass. Systematic differences in N-pools between grass-dominated and open dune grassland plots were not observed. However, N-availability by mineralization and its turnover rates are higher in grass-dominated plots than in open dune grassland plots, as well as above and below-ground biomass. In open dune grassland plots, atmospheric N-input is an important source of N, whereas in grass-dominated plots mineralization largely exceeds atmospheric N-input. However, these observations do not explain the mosaic-like vegetation pattern. Grazing intensity is most likely the determinant factor in the dry dune system. It is concluded, that grass encroachment is probably triggered by atmospheric deposition and is enhanced by positive feedbacks in the N-cycle. The relevance of these results for restoration management is briefly discussed.     

大气高CO2浓度对油菜氮素同化累积与植株生长的影响

为了指导高CO2浓度条件下甘蓝型油菜Brassica napus L.合理施氮、创建油菜高产高效以及进一步探明油菜氮代谢的调节机制提供理论依据,本研究采用微区试验,研究2个油菜品种（沪油15-33号和742-2）在2个CO2浓度水平（自然CO2摩尔分数400μmol·mol-1和高CO2摩尔分数（800±20）μmol·mol-1）和2个氮素水平（施氮与不施氮）条件下,氮素同化酶（NR和GS）活性和可溶性蛋白含量的变化,以及油菜地上部干物质量和氮素累积量的响应。试验结果表明,高CO2浓度会提高NR和GS活性;在氮素处理的影响方面,NR活性的变化与油菜的品种和生育时期不同有关：在高CO2浓度条件下,品种A在各时期的施氮处理的酶活性高于不施氮处理;品种B只在抽薹期的施氮处理低于不施氮处理,其他时期则升高;对于GS酶活性,在自然CO2浓度条件下施氮会提高GS酶活性,高CO2浓度条件下施氮则降低其活性（苗期除外）。CO2浓度升高会降低叶片中可溶性蛋白含量（盛花期除外）;在正常CO2浓度下,增施氮肥会提高叶片中可溶性蛋白含量,而在高CO2浓度下,增施氮肥会降低叶片中可溶性蛋白含量。CO2浓度升高和增施氮肥都会提高油菜地上部干物质量与氮素累积量,油菜干物质量与氮素累积量总体上与上述测定指标呈极显著相关。     

铁、铝氧化物和土壤对苄嘧磺隆的吸附

用平衡吸附法研究了苄嘧磺隆在两种土壤(广州赤红壤、湖南红壤)和两种人工合成氧化物(针铁矿、铝氧化物)中的吸附,以及pH对吸附的影响.结果表明:(1)用Langmuir,Freundlich和Temkin等温方程描述供试样品对苄嘧磺隆的吸附,其中Freundlich吸附等温方程拟合的结果较佳.在苄嘧磺隆的实验浓度范围内和一定的pH条件下,吸附苄嘧磺隆的量随其浓度的升高而增加,其顺序为:铝氧化物>湖南红壤>针铁矿>广州赤红壤.(2)苄嘧磺隆在供试样品中的吸附量随溶液pH值的升高而减小.     

液相络合-铁屑还原-酸吸收回收法脱除烟气中的NOx

用\"Fe2+螯合剂吸收-铁屑还原-酸吸收\"回收法脱除烟气中的NOx,研究了铁屑脱硝过程的影响因素,确定了脱硝过程的合适工艺条件,并对络合脱硝溶液的再生和循环利用进行了研究.结果表明:最佳工艺参数为:络合脱硝溶液中Fe2+EDTA浓度20mmol·l-1,pH值6.0,温度65℃;在此条件下,用两个反应器串联,对O2含量为10.5%的模拟烟气可取得90%以上的脱硝效率.     

洱海沉积物有机质、铁、锰对磷的赋存特征和释放影响

利用SMT磷连续提取分级方法研究了洱海表层沉积物中磷的赋存特征,探讨有机质(OM),Fe和Mn对磷赋存形态及释放的影响,同时评估了洱海沉积物磷的释放风险. 结果表明:洱海表层沉积物w(TP)为710.3～1 961.2 mg/kg,其中w(Ca-P)最高(占36.9%～59.2%),w(OP)次之(占24.6%～36.9%),w(Fe/Al-P)最低(占9.8%～20.7%);w(OM)为25.0～119.6 mg/g,与w(TP)和w(Ca-P)呈显著负相关;w(总锰)为0.8～3.8 mg/g,w(总铁)为34.3～127.2 mg/g,均与w(TP)及其各形态磷含量呈显著正相关. 沉积物中w(Fe/Al-P)/w(Ca-P)比低于0.5,且w(总铁)/w(TP)远大于20,表明磷释放强度小,但w(TOC)/w(OP)<200,说明有机磷的潜在释放风险较大. w(TP)及其各形态磷含量均与无定形铁氧化物(Feo-Fep)含量呈显著正相关,而与结晶态铁氧化物(Fed-Feo)含量的相关性不显著,且全湖沉积物中的铁氧化物以Feo-Fep为主,表明洱海沉积物磷释放主要受Feo-Fep控制.