Evaluation of multiple regression models using spatial variables to predict nitrate concentrations in volcanic aquifers

Multiple linear regression of spatial variables including land use, soil type, and topography was applied to predict nitrate concentration and evaluate major factors affecting nitrate occurrence in springs and wells in the southern and northern areas of Jeju volcanic island, Korea. Three types of contributing area surrogates (CAS), namely circle, semicircle, and wedge, were employed to calculate the spatial variables. The regression results showed R² of 0.81–0.84 for springs and 0.74–0.77 for wells; R² values for wedge and semicircular CAS were more than 10% higher than those for circular CAS. The R² of spring models was significantly affected by both the shape and size of CAS, with optimal radii of 150–250 m and 300–400 m in the southern and northern areas, respectively, corresponding to thinner upper basaltic aquifers, and implying shorter flow paths in the southern area. The most influential variables in springs were orchards and soil types related to agriculture including silty loam and silty clay loam, indicating that nitrate levels are strongly affected by N fertilization in cultivated areas. In contrast, wells showed much less sensitivity to both shapes and sizes of CAS, with less contribution of land use and soil type to the regression, which could be attributed to a mix of multiple aquifer zones and widely different factors in the installation and operation of wells. Field parameters of electrical conductivity (EC) and pH increased the R² up to 10%, suggesting that these can be useful when regression with spatial variables yields a lower R². The optimal spatial scales for prediction of nitrate concentration and spatial variables that significantly contribute to nitrate contamination can provide relevant criteria for establishing groundwater management policies, considering the increasing anthropogenic land‐use trends on the island, where groundwater is highly sensitive to changes in spatial variables. Copyright © 2015 John Wiley & Sons, Ltd.     

华北平原灌溉需水量时空分布及驱动因素

采用华北平原14个气象站点2002年-2007年的降水资料、76个站点的0-80 cm厚度的土壤参数以及ETWatch系统计算的蒸散发量数据,运用水分平衡原理计算了灌溉需水量的空间分布;利用相关及多元逐步回归分析方法,定量分析了研究区灌溉需水量的主要驱动因素.结果表明:从山前平原到滨海平原,多年平均灌溉需水量分别为28...     

一种多重水印嵌入的解决方案研究

由于矢量地图数据易于复制、分发等特点,同时矢量地图的制作成本高、安全性要求高等,使得用近年来新兴的数字水印技术对矢量地图数据进行保护,成为一个新的重要的研究方向.本文针对矢量地图数据的多重水印嵌入这一难题,提出了一种通过水印嵌入时生成附加信息的方式来进行水印多重嵌入的解决方案,并通过使用作者提出的抗道格拉斯压缩算法进行...     

一种基于SPA的多数据流同异反分析法

提出了一种分析多数据流变化趋势的新方法。该方法引入集对分析思想,使用峰值数据进行分析,计算简单、数据量小。实验表明,峰值的变化趋势较能真实地反映数据流的变化趋势;同时,本方法对解决样本点个数不一致的问题是有效的。     

地理信息工程的多指标利用设计研究

多指标利用设计,为地理信息工程实施过程提供更科学、更合理的设计方案和设计方法,并略述了多指标利用设计与综合评价的关系.     

引入低纬高原复杂地形因子的气象要素精细化估算模型

低纬高原地区的气象要素变化除了受大气环流因子的影响外,高程、坡度、坡向等地理因子的作用不可忽视.以云南省为例,应用云南省125个气象站的降水、温度、露点温度等气象资料,与各站点的经度、纬度、高程、坡向、坡度等地理因子建立关系模型,运用多元回归方法,求得回归系数,代入随机抽取的检验站点的地理因子回归方程式中,得出拟合量,...     

地震动参数与地震烈度的多元回归研究

建立合理的地震烈度与地震动参数之间的对应关系,在工程抗震及烈度速报中有着十分重要的作用,文中以美国加州3次破坏性地震和我国今年来6次地震中所获得的强震记录作为数据源,应用最小二乘法进行线性回归,得到了不同地震动参数与烈度间的相关性.经统计发现,在地面加速度峰值、标准累计绝对速度等12种描述地震动强度的参数中,各种参数在...     

海洋资料多次波组合衰减技术及应用

多次波的压制是海洋地震资料处理中的重要步骤。海洋地震勘探中的多次波一般都异常发育且较难压制,压制多次波的好坏直接决定了处理结果的质量。目前压制多次波的方法有很多种,但不同的方法基于不同的理论,具有不同的针对性。单一的方法压制多次波往往不能针对所有多次波,达不到理想的效果。笔者使用组合衰减多次波技术,综合了SRME、拉东变换、LIFT去噪对海洋实际地震数据的多次波进行压制,取得了较好的效果。     

塔里木盆地巴楚隆起低信噪比地震资料处理方法研究

塔里木盆地巴楚隆起勘探程度较低,是开展油气勘探的主要潜力区之一。受近地表激发条件差、低降速带结构变化大、目的层埋藏较深等地表和深层地质条件的影响,研究区地震资料信噪比低、品质较差,严重地制约了地震资料解决地质问题的能力。本文在分析研究区新采集的原始地震资料基础上,建立了精确的近地表模型,采用层析静校正、交互迭代静校正方法求准静校正量;利用多域多阶段联合去除噪声,采取近道内切除等多种方法串联综合应用消除多次波干扰;采用全面统计、逐点处理的地表一致性处理技术进行振幅能量补偿;精细速度分析,优选提高深层弱信号成像质量的偏移方法等一系列的关键技术,使本区低信噪比资料的信噪比、同相轴连续性和构造成像质量得到了较大的改善和提高,取得了较好的应用效果。     

Comprehensive Chemical and Isotopic Analyses of Basalt and Sediment Reference Materials

Geochemical studies of geological samples require the precise determination of their major and trace element contents and, when measured, of their isotopic compositions. It is now commonly accepted that the accuracy and precision of geochemical analyses are best estimated by the concomitant analysis of international reference materials run as unknown samples. Although the composition of a wide selection of basalts is relatively well constrained, this is far from being the case for sedimentary materials. We present here a comprehensive set of major and trace element data as well as Nd, Hf, Sr and Pb isotopic compositions for thirteen commonly used international reference materials – eight magmatic rocks (BHVO‐2, BR, BE‐N, BR 24, AGV‐1, BIR‐1, UB‐N, RGM‐1) and five sediments (JLk‐1, JSd‐1, JSd‐2, JSd‐3, LKSD‐1). We determined the concentrations of over forty elements in the magmatic rocks together with Sr, Nd, Hf and Pb isotopic compositions. Our trace element results were both accurate (difference ≤ 3%) and precise (reproducibility at 1s ≤ 3%) and the isotopic results were very similar to other published values. In contrast, we observed a significant chemical and isotopic variability in the sedimentary materials, which we attribute to mineral heterogeneities in the powders. Despite the limitation imposed by this heterogeneity, our work presents a complete set of data determined with a precision not yet achieved in the literature for sedimentary material. We also provide the first Nd, Hf and Pb isotopic measurements for the five sediments, which are commonly used by the geochemical community. Our study of both basalt and sediment reference materials represents a comprehensive and self‐consistent set of geochemical data and can therefore be considered as a reference database for the community.