Spatial and temporal variation of nitrogen exported by runo from sandy agricultural soils

The eutrophication problem has drawn attention to nutrient leaching from agricultural soils, and an understanding of spatial and temporal variability is needed to develop decision-making tools. Thus, eleven sites were selected to monitor, over a two-year period, spatial and temporal variation of runoff discharge and various forms of N in surface runoff in sandy agricultural soils. Factors influencing the variation of runoff discharge and various forms of N in surface runoff were analyzed. Variation of annual rainfall was small among 11 sites, especially between 2001 and 2002. However, variation of annual discharge was significant among the sites. The results suggest that rainfall patterns and land use had significant effect on discharge. The concentrations of total N, total kjeldahl N （TKN）, organic matter-associated N （OM-N）, NO3- -N, and NHn＋-N in the runoff ranged widely from 0.25 to 54.1, 0.15 to 20.3, 0.00 to 14.6, 0.00 to 45.3, and 0.00 to 19.7 mg/L, respectively. Spatial and temporal variations in the N concentration and runoff discharge were noted among the different sites. Annual loads of N in the runoff varied widely among monitoring sites and depend mainly on runoff discharge. High loads of total N, OM-N, NO3--N, and NHn＋-N in the runoff either in citrus groves or on vegetable farms occurred from June to October for each year, which coincided with the rainy season in the region. This study found that N in surface runoff was related to rainfall intensity, soil N level, and fertilizer use.     

山区乡村山洪灾害分析与防洪减灾措施

山区乡村建筑防洪与减灾技术研发课题一行5人组成调研组,于2009年8月20日赴江西省黎川县厚村乡焦陂村进行了山区洪水灾害调研工作.厚村乡地处武夷山脉西麓,山区面积约占乡域的67%,境内山峦叠峰,溪流交错.焦陂村与厚村乡比邻,位于山脚下大源河河岸.大源河是山间的一条小河,河床宽20多米,平时河床中有水,清澈见底.     

黑龙江省气候变化对粮食生产的影响

收集1986~2000年黑龙江省79个县市农业生产资料和30个气象台站逐日气温、降水资料,应用柯布-道格拉斯生产函数方法将粮食产量分解为气候产量和经济产量,然后用EOF方法分析了粮食产量、气候影响程度指数、≥10℃积温、生长季降水的时空变化特征及其关系。结果表明:15年间全省粮食产量稳步增加,气候变暖趋势明显但降水变化不显著,变暖对粮食生产有利,降水的变化未对粮食产量产生实质影响。15年间气候影响程度总体增大,但气候变化及其影响具有时空差异性:1986~1993年北部和西南部积温增加明显,粮食产量增加大于东北部和东南部;1993~2000年东北部和东南部积温增加明显,粮食产量增加超过北部和西南部。     

Physical Land Suitability Assessment for the Large Cardamom Amomum subulatum Roxb. Cultivation in Hills of Kathmandu Valley

Nepal is one of the top three exporters of larger cardamom （Amomum subulatum Roxb.） in the world market contributing largely to the Nepalese economy. Sub-Himalayan range of hilly area of eastern Nepal is popular for large cardamom cultivation. Being similar phytogeographical and ecological setting, cultivation has begun in hills of Kathmandu Valley however land suitability needs to be evaluated with reference to specific need of the crop. Kathmandu is a valley with alluvial bottom and altitudinal range between 1200 and 2730m above sea level having cool to warm temperate climatic range. Varieties of aspects and slope gradient have potentiality for the large cardamom cultivation. Aim of the study was set to categorize available land area in the range of suitability for large cardamon cultivation on the basis of physical characteristics of the land and ecological need of crop. Land evaluation methodology has been designed along with site specific amendment in FAO framework （1976）. Land use map in scale of 1：25 000 was used in geographic information system environment. Suitability was done through map overlaying methods. Aim of the study was set to categorize available land area in the range of suitability categories for large cardamom cultivation based on physical characteristics of the land matching with ecological need of crop. Analysis of data shows that altitudinal range at uplands of Kathmandu Valley and annual average rainfall and temperature are found to be within suitability range for Amomum subulaturn cultivation. Sandy loam soil, slightly acidic in nature with gentle sloping land of about 5-8° provides highly suitable condition. Result showed that more than one-third of total land area above 1800 m of altitude is suitable. Selectively, of the total area, 5% are north facing slope, 13% gentle slopes are highly suitable. 16% lands with north east orientation are moderately suitable. Most of the land areas which are marginaly suitabile for vegetable and cereal crops are highly suitable for large cardamom. Hills of northern boundary hills found to be suitable due to more rainfall distribution pattern compared to southern boundary hills. Therefore, land evaluation also identifies limitations and input requirements for sustainable production.     

2016年湖北省梅雨期暴雨特征及灾情影响分析

通过对2016年湖北省梅雨期降雨量特征及其与灾情之间的关系进行分析,得到承灾体与雨量的关系及暴雨致灾阈值。结果表明,梅雨期6轮降水灾度均在3以上,6月30～7月6日的暴雨过程灾度高达8。不同承灾体（受灾人口、倒损房屋、受灾面积）与直接经济损失均为正相关,其中倒损房屋最高,达0.9以上。灾情发生阈值日最大降雨量和过程雨量分别为35 mm和50 mm。过程降雨量和有效降雨指数与灾情的相关性较好,大于0.5。承灾体中死亡人口集中区域与降水量大值区对应,分散区域与局地短时强降雨有关;而农作物绝收面积在降雨强度指数相当或偏低时,降雨叠加效应会促使其占比增加。 关键词： 梅雨期;暴雨;过程降雨量;灾情     

2009年广州能见度变化规律及主要影响因素分析

通过对2009年的广州大气能见度和影响因素的数据资料统计,结合定性分析、相关性计算及各时间尺度中物理量的相互作用过程研究,得出能见度的变化规律和各因素的相关性特征。结果表明,2009年整体能见度水平略有提高;24h的降雨量、气温差值较大时,该日的能见度小时均值波动较大;风速、相对湿度与中尺度(24h)能见度的相关性较强;降雨量、气温对小尺度(1h、5min)能见度影响显著;相对湿度水平能制约风速对能见度的改善作用。灰霾现象等与能见度水平密切相关。     

到城里“看海”——水淹城市的尴尬

夏天“来北京看海”,是不少人不愿再提及的回忆,也是大多数人不想再见到的场景。但气象部门预计,今年汛期降雨量预计总体比常年偏多,极端天气和局地强降雨发生概率很大。     

渭河下游洪水灾害的降水危险性评估与区划

大气降水的不规则运动是引发洪水灾害的重要因素.通过对"小洪水、大灾情"特性显著的渭河下游洪泛区的洪水特性、降水规律以及二者的关系进行分析,利用插值计算法进行降水量和降水变率空间分析,评估并区划了研究区汛期洪灾风险的降水危险性.主要结论为:①季节性的强降水过程是引发渭河下游洪水灾害的重要因素,连续暴雨或大范围暴雨往往带来洪水灾害;②汛期降雨量呈现出显著的南多北少特征,且从东南到西北依次递减,咸阳、高陵县、大荔县西北部降水量偏低,而秦岭北麓的华县、华阴及西安市区降水相对丰富;③汛期降水变率虽然呈现出相间分布的特征,但降水量变化较大的区域(西安市区、华县以及潼关县东南部)都集中于南部的秦岭北麓;④根据降水量越大,影响度越高,降水变率越大,降水量越不稳定,洪水危险性越高的原则,进行洪灾的降水危险性评估与区划,结果显示降水危险性较高与较低区域呈环状相间分布,危险性较高的区域更多地分布于渭河干流南岸.     

降雨径流面源污染年负荷预测方法的开发——以镇江古运河为例

在对镇江古运河2009~2013年的降雨量、降雨径流污染物量监测的基础上,运用回归分析建立降雨量-径流污染方程,并采用灰色理论对未来降雨量进行预测,进而得出降雨径流面源污染年负荷值。结果表明:2014~2020年间,镇江古运河降雨径流中污染物TP、NH₃-N和SS的年负荷与降雨量同向变化,2020年降雨量达到1 381.2 mm时,污染物TP、NH₃-N和SS的年负荷可分别达到217.15 t、421.4 t、5 811.87 t,数值较大;灰色理论与回归分析结合所提出的降雨径流面源污染年负荷预测方法,能够在小样本、贫信息和波动数据序列情况下,简捷有效的对降雨径流面源污染负荷进行高精度的预测,实用与推广价值较大。     

鄂南棕红壤区不同植茶年限茶园CH4通量特征

于2014年3月—2015年12月,采用静态箱-气相色谱法测定了鄂南棕红壤丘陵区茶园和樟树林地土壤CH_4通量,研究了不同植茶年限茶园及临近林地土壤CH_4通量特征.结果表明,不同植茶年限对茶园土壤CH_4通量有显著影响,中、低龄茶园土壤CH_4以排放为主,植茶20 a和植茶8 a茶园土壤CH_4累积排放量分别为0.26和0.27 kg·hm~(-2),高龄茶园和对照林地土壤CH_4以吸收为主,植茶50 a茶园和林地土壤CH_4累积吸收量分别为0.39和1.95 kg·hm~(-2).降雨促进了鄂南棕红壤丘陵区茶园和林地土壤CH_4排放,除了植茶8 a茶园外,高、中龄茶园和樟树林地土壤CH_4通量均与7 d累积降雨量呈显著的正相关关系.施肥造成了茶园土壤CH_4排放量增加,同时土壤中矿质氮类型对该地区茶园和林地土壤CH_4通量有不同影响,CH_4排放通量与土壤硝态氮含量呈显著正相关关系,而与铵态氮含量相关关系不显著.研究表明,降雨量是影响鄂南红壤丘陵区茶园和林地土壤甲烷通量的主要因素;随着茶园种植年限的延长,土壤CH_4排放通量呈降低的趋势,高龄茶园土壤为大气CH_4汇.