Testing GLEAMS for Nitrate Leaching Modeling in an Agricultural Catchment of Southeast China

利用我国东南亚热带地区农业小流域不同土地利用方式的硝氮渗漏淋失实测数据检验了GLEAMS(Groundwater Loading Effects of Agricultural Management Systems)模型在该地区的适用性。通过现场试验和实地调查并结合模型手册,获取模型所需的水文和营养盐参数,参考模型参数的敏感性分析结果对模型进行调试。结果表明模型对水稻田除外的其它土地利用方式的硝氮渗漏淋失模拟效果较好。水稻田渗漏模拟效果差的主要原因在于模型的水分平衡方程不能反应水稻田长期淹水的实际情况。模型模拟结果的精度可以接受,从而验证了GLEAMS模型在该流域的适用性。GLEAMS(Groundwater Loading Effects of Agricultural Management Systems)model was introduced to test and validate nitrate leaching in an agricultural catchment in southeast China.Field experiments were performed under different landuses such as paddy,bananas and vegetables,in Wuchuan catchment of Fujian Province with the area of 9.6 km2.Eight boreholes were drilled and monitoring pipes were installed for continuous monitoring of nitrate leaching from April to December in 2002.The hydrologic and nutrient parameters of GLEAMS model were extracted based on measurements and experiments during the main crop growing season.Model parameters were tuned to achieve desired agreements between measurements and model simulations based on sensitivity analysis.After calibration and validation,the model generally had acceptable performances in simulating nitrate leaching throughout the landuses with an exception in paddy field.The model simulations can be used to specifically establish best management practices for nutrient management and pollution mitigation in the catchment.国家自然科学基金(40671116;40301045

Denitrification Determination in soil of Wu Chuan Agricultural Catchment and the Control Measure

反硝化作用是土壤氮素转化的一个重要过程,为探明五川流域内的农业土壤的反硝化作用强度及其影响因素,利用乙炔抑制-原状土柱培养法对其进行测定。通过3次试验测定,发现五川流域农业土壤具有较强的反硝化作用强度,在种植季节,土壤平均反硝化作用强度为0.1kgN·hm-2·d-1,最高达到0.6kgN·hm-2·d-1,其中蔬菜地反硝化作用强于其他土地利用类型。反硝化作用同土壤的NO3-含量、含水量、温度以及pH都存在正相关关系,它们是流域土壤反硝化作用的主要影响因子。五川流域农业土壤经由反硝化作用氮损失量占流域平均施肥量的16%,高于国内其他地区。针对五川流域的环境和农业经济特点,提出了控制反硝化作用的措施:在温度较低的夜间进行施肥灌溉宜以防止氮肥损失,用农村富余的厩肥代替化肥以减轻反硝化作用的发生,同时加大节水灌溉力度。Denitrification in soil is the main pathway of gaseous nitrogen loss in the catchments.In order to find out the denitrification flux in top-soil and the affecting factors in Wu Chuan catchment,the denitrification rate of top-soil was determined using the acetylene inhibition-intact soil core technique for 5 months.Three times of the denitrification experiment were carried out from Dec.15th 2005 to Apr.18th 2006,at the same time,the chemical and physical properties of the soils were also measured during every experiment.The soils in Wu Chuan catchment belong to typical Haplic red soil,with the chemical and physical properties suitable for denitrification and the organic matter,total N,NO3-N and pH of the soils being 9～25 g·kg-1,0.4%～7.9%,1.5～6.8 mg·kg-1 and 4.9～5.7,respectively.The results indicated that denitrification of the soil showed temporal and spatial variations.The denitrification rate in uplands of the catchment was higher than that in any other places,and was enhanced when there were many rains and when the soil temperature was high.The flux of denitrification was mostly related with fertilization,soil moisture,air temperature and pH.Air temperature affected denitrification significantly.The gaseous N loss rate through denitrification represented about 16% of the fertilizer applied in the catchment scale.Also,the denitrification flux of the top-soil in Wu Chuan catchment was much higher than that in other places of China,and the denitrification rate of soils in south was higher than that in north.The soils in Wu Chuan catchment may be the source of atmospheric nitrous oxide gas.Since the high level of agricultural economic development in Wu Chuan catchment and the frequently used fertilizers,the flux of fertilizers is much higher than other agricultural region in China.Based on the environmental characteristics and agricultural economy in Wu Chuan catchment,the following control measures should be adopted:(1) fertilization and irrigation in the low-temperature night to prevent fertilizer loss;(2) utilization of livestock waste instead of fertilizer to inhibit denitrification;(3) popularizing economical irrigation to avoid reductive situation in the soil.国家自然科学基金(40301045和40671116

Study on multi-scale seepage calculation model

新世纪以来非常规油气获战略突破，致密油气作为典型代表，是常规油气资源的重要接替能源。致密油气主要赋存于致密砂岩和致密碳酸盐岩储层中。然而，致密砂岩和致密碳酸盐岩中的多尺度-多维度渗流通道（孔、洞、缝）、多种类型流体（油、水、气）以及多类渗流特征（滑移、扩散、吸附），使得致密油气运移不再是单一尺度、线性理论所能描述的。因此建立一套描述致密油气运移的多尺度渗流模型是致密油气研究的关键。本文针对致密砂岩和致密碳酸盐岩，建立了三个多尺度渗流计算模型，搭建了致密油气渗流计算平台。具体研究工作从以下三个方面开展。 识别孔隙孔喉。首先，基于数学形态学理论提出了划分孔隙-孔喉的方法。根据孔隙和孔喉的特征，运用形态学方法将岩石三维图像中不规则的孔隙空间划分为新型孔隙-孔喉系统。该系统的优势在于孔隙和孔喉的识别计算无参数调试，可完备表征岩石的孔隙孔喉空间结构。其次，提出了该系统的并行算法，研究分析了算法的可靠性和计算效率，为后续多尺度渗流计算模型奠定了基础。 致密砂岩的油气渗流模型。针对致密油，引入微链接表征纳米尺度微孔，在实测渗透率约束下，建立了多尺度油水两相渗流模型。该模型考虑了致密砂岩的多尺度孔隙结构，以及微纳孔喉引起的液体滑移效应。通过他人的实验结果验证了模型的可靠性；与现行计算模型比较，在相同计算精度下，该模型计算效率提高了一个量级。针对致密气，引入孔隙簇等效模型表征纳米孔的气体传输，提出了三维的变径微通道，有机地串联起岩石的微-纳结构，形成了致密气的多尺度渗流计算模型，并通过实验数据证明了模型的可靠性。初步形成了致密砂岩的渗流计算平台。 致密碳酸盐岩的油渗流模型。针对致密碳酸盐岩中微-纳孔、洞、缝共存的特点，提出中轴线-最大球（AB）算法和中轴面算法相结合抽提孔-缝混合网络，并在图像基质内引入小尺度随机孔隙网络表征纳米孔。进一步在实测渗透率的约束下，有机地串联起纳米孔-微米孔以及纳米孔-裂缝，形成了多尺度混合油水两相渗流模型。和现有模型相比，该模型完备考虑了致密碳酸盐岩的微-纳孔、洞、缝的空间结构，以及微纳孔喉引起的液体滑移效应和裂缝内液体的流动效应。通过实验结果验证了模型的可靠性，研究分析了裂缝对油水两相渗流的影响。本文建立的三个致密油气多尺度渗流计算模型计算效率高，计算结果准确，形成了致密油气渗流计算平台，为致密油气研究提供一种新的方法。</p

一种从三维图像确定孔隙结构关键参数的方法

本发明提供了一种从三维图像确定孔隙结构关键参数的方法，包括如下步骤：先将测试岩心转化后得到由固体体素和空隙体素形成的三维二值图像，再分别建立一个对应半径的固体圆球结构元素和空隙圆球结构元素；对对应的空隙空间进行转换，由此得到每个空隙空间及其连通空间块，进行孔隙和孔喉的识别后即可得到当前测试岩心中空隙空间的孔隙和孔喉特征。本发明整个识别过程中孔隙孔喉边界明确，无人为因素，一方面能有效表征多孔介质孔隙结构微观特征，另一方面可以得到的孔隙结构关键参数为约束条件建立孔隙网络模型，在不进行系数调整的情况下能够有效预测绝对渗透率和相对渗透率等流动性质，对揭示孔隙尺度流动机制有重要意义

Field study on denitrification in soil of south Fujian agricultural catchment

土壤反硝化是流域土壤氮损失的重要途径之一。利用乙炔抑制培养法对五川流域内表层土壤的反硝化进行测定,研究发现,闽南农业小流域土壤具有较强的反硝化作用强度,在种植季节土壤平均反硝化作用强度为N 0.1 kg/(hm2.d),最高达到N 0.6 kg/(hm2.d),其中蔬菜地反硝化作用强于其他土地利用类型。反硝化作用同土壤的含水量、温度以及NO3-含量都存在有正相关关系,温度是流域土壤反硝化作用的最主要影响因子。五川流域土壤经由反硝化作用氮损失量占流域施肥量的16%,稍高于国内其他地区。Denitrification from soils is the main pathway of gaseous loss for nitrogen in the catchments.We measured the denitrification rate from the top-soil in Wuchuan catchment by using the acetylene inhibition technique.The result of this experiment indicated that denitrification of the soil had the temporal and spatial variance.The rate of denitrification that occurred in uplands of the catchment was higher than any other places,and denitrification was enhanced when there were many rains and when the soil temperature was high.The flux of denitrification was mostly related with fertilization,soil moisture and air temperature.Air temperature was top-dressed affected denitrification significantly.The gaseous N loss rate through denitrification represent about 16% of the fertilizer applied in the catchment scale.国家自然科学基金(40301045

Field Study on Nitrogen Mineralization in Soil of South Fujian Agricultural Catchment

用原位培养法对五川流域内的香蕉地、菜地、香蕉地与菜地间作地、林地、甘蔗地土壤的氮矿化作用进行了研究,结果发现不同土地利用方式下土壤氮矿化速率平均为N0.11mgkg-1d-1,其中香蕉地土壤氮矿化最高可达N1.47mgkg-1d-1;土壤硝化速率平均为N0.27mgkg-1d-1,其中菜地下土壤硝化作用强度最高可达N0.69mgkg-1d-1。土壤矿化作用同土壤湿度、温度、C/N、土壤肥力存在明显的相关关系。不同土地利用方式下温度是土壤氮矿化最主要的影响因子。闽南流域土壤年矿化量平均为N240kghm-2,部分样地最高可达N850kghm-2,而年施肥量平均N650kghm-2。相比较而言,说明了土壤矿化是我国南方流域农业土壤氮素的重要来源。Nitrogen (N) mineralization determines soil N availability, which limits plant growth and productivity. In this study, a field experiment was conducted to study soil nitrogen mineralization function of five different land use patterns in the Wuchuan catchment of Nanjing county of Zhangzhou city. The results showed that the average net nitrogen mineralization rate was 0.11mg N kg-1 d-1, and the highest of five different land use patterns was in the banana (about 1.47mg N kg-1 d-1). The soil average nitrification rate was 0.27mg N kg-1 d-1, and the highest of five different land use patterns was in the vegetable (about 0.69mg N kg-1 d-1). The soil nitrogen rate has obvious correlated relation. And the temperature was major factor in the five different land use patterns. The annual mineralization rate in the catchment was about 240kg N hm-2, the highest rate was about 850kg N hm-2 in some land use patterns, but the annual average fertilization was 650kg N hm-2. It could explain the soil nitrogen mineralization as a major N source in the agricultural soil in the catchment of south of China.国家自然科学基金项目40671116和40301045资

Identifying the comprehensive pore structure characteristics of a rock from 3D images

Characterization of pore structure in reservoirs plays a significant role in predicting properties of rocks and classifying the reservoirs. The focus is on determining comprehensive geometric and topological parameters of pore structure. X-ray computerized tomography scanning provides a 3D image of the pore structure. However, these images cannot directly generate pore structure parameters without numerical characterization of the images. A new method is developed to determine comprehensive geometric and topological parameters of pore structure from images. These parameters were determined by utilizing common mathematical morphology operations to segment the entire pore space into a series of space blocks of different radii, subsequently identifying these blocks as pores and throats based on the proposed morphological features of pore and throat. The parallel scheme was also studied to obtain the highest efficiency. Thereafter, the characteristics of pore structures and the performance of the method were assessed for various samples. The results were compared to the results calculated by other methods. Results showed that the method produced reliable pore structure characteristics for a wide variety of rocks. Additionally, in order to discuss whether our results can be used as the basic input data for other researches, an example about two-phase flow simulation was made and a comparison of simulation results and experimental data was made. Our results were a competent choice for other studies. Also, after proposing the detection criteria of pore and throat, the subsequent detecting procedure is without artificial adjustable parameters, making the method convenient to use. This method can comprehensively, efficiently, accurately, and conveniently characterize the pore structure based only on images

二维同步OCDMA系统的性能分析

构造了一种用于二维同步光码分多址（OCDMA）系统的修正素数跳频码（MPC/PC）,分析了码字的自相关和互相关性能,研究了二维同步OCDMA系统的误码率和吞吐量性能。结果表明,与一维同步OCDMA系统相比,二维同步OCDMA系统的可接入用户数大大增加,误码率大大降低,吞吐量明显提高