Point and Diffuse Nutrient Emissions and Transports in the Odra Basin and its Main Tributaries     

H. Behrendt  M. Kornmilch  R. Korol  M. Stronska  W.-G. Pagenkopf 《洁净——土壤、空气、水》1999,27(5):274-281

The river Odra is one of the biggest transboundary rivers in Central Europe. The basin is characterized by an area of 110 074 km?sk (upstream Krajnik Dolny) and a population of about 15.5 million inhabitants. Compared with the Westeuropean river basins the specific runoff of the Odra basin is low and amounts only 4.5 L km?sk s–1. The long term changes of the average annual nutrient transport of the Odra at Krajnik Dolny show for the period 1991 to 1994 a low reduction for phosphorus but no changes for nitrogen. For the period of 1991 to 1994 an inventory of the point sources produces emissions of 10.7 kt a–1 P and 54.4 kt a–1 N upstream of the station Krajnik Dolny/Schwedt. Emissions from agricultural land and urban areas represent the main diffuse sources. A range of 68 to 96 kt a–1 N and 3.3 to 3.9 kt a–1 P were estimated for the total diffuse emissions depending on the database and the method of modeling. The emission situation of the river is characterized by a high dominance of point sources in the case of phosphorus (about 73%). For nitrogen the diffuse emissions dominate the total emissions to an amount between 59 and 67%. Compared to the emissions the nutrient transport is low. An average load of 5.1 kt a–1 P and 70.1 kt a–1 N was observed at the station Krajnik Dolny for the period 1991 to 1994. The emission and load situation within the main tributaries of the river Odra is comparable to the whole basin. The big difference between the total emissions and the observed load refers to intensive retention and loss processes within the river system of the Odra.  相似文献   

Mass fluxes in the Canary Basin   总被引：1，自引：1，他引：0  

F. Machín  A. Hernndez-Guerra  J.L. Pelegrí 《Progress in Oceanography》2006,70(2-4):416

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泉州湾赤潮藻类优势种演替影响因子探讨   总被引：4，自引：1，他引：3       下载免费PDF全文

江兴龙  宋立荣 《海洋与湖沼》2009,40(6):761-767

于2006年5—11月对东海泉州湾赤潮监控区设定4个采样站位,进行赤潮常规监测。结果表明,泉州湾藻类优势种由中肋骨条藻(Skeletonema costatum)、太平洋海链藻(Thalassiosira pacifica)、微小原甲藻(Prorocentrum minimum)、尖刺拟菱形藻(Pseudo-nitzschia pungens)、丹麦细柱藻(Leptocylindrus danicus)及旋链角毛藻(Chaetoceros curvisetus)等赤潮生物组成,虽然中肋骨条藻为最主要的优势种,但有3个站位出现了上述优势种的演替。通过深入分析该海域水质营养盐含量及组成结构的动态变化对赤潮藻类优势种演替的影响,发现由于不同的赤潮藻类种群具有各自的生态习性及适应环境的生长增殖策略,海域水质营养盐含量和组成结构的变化,会引起赤潮藻类种群增殖竞争力间强弱的相对变化,而种群增殖竞争力强的种类有可能迅速增殖取代原有的优势种而演替为新的优势种,这是一个动态的过程。  相似文献   

基于机器学习的两个代表城市上呼吸道感染与气象要素关系及其发病风险预测研究          下载免费PDF全文

郑甲炜  王式功  尹立  吴千鹏  张祥健 《沙漠与绿洲气象(新疆气象)》2023,17(4):160-168

选取华南地区深圳市、西南地区攀枝花市两个不同气候区的当地医院上呼吸道感染发病逐日就诊病例数据和同期气象数据，采用随机森林方法和RNN（Recurrent neural network）深度学习方法，通过对两地上呼吸道感染发病特征及其与气象条件关系进行细致研究，分别构建了两地上呼吸道感染发病风险预测模型。研究结果表明：(1)深圳市上呼吸道感染就诊人数峰值每年出现在6-8月期间，谷值出现在1-2月期间，呈现以热不舒适的效应为主；而攀枝花市上呼吸道感染就诊人数峰值则出现在每年11月到次年的1月期间，谷值出现在每年3-7月期间，呈现以冷不舒适效应为主。(2)逐日平均气温的变化对两地上呼吸道感染发病的影响最明显，当日平均气温高于25℃或者低于10℃时，两地上呼吸道感染发病风险明显上升。(3)日平均风速影响次之，它与日平均相对湿度和日平均气温一起，通过对气候舒适度产生影响，进而影响上人群上呼吸道感染发病情况。(4)在对上呼吸道感染与气象要素关联性分析及预测方法优选的基础上，基于RNN深度学习方法构建的两城市上呼吸道感染发病风险预测模型，可为当地相关疾病风险预测及防控提供重要科技支持。  相似文献