Occurrence of severe floods in the Salado River Basin,Buenos Aires province,Argentina

Floods in the Salado Riverbasin, Argentina, seriously affect bothhuman activities and the environment.Inadequate and improper water managementaggravates the effects of natural extremeevents. The damage caused by the extremeflood in 1993 cost US$507 million,affected 14,500 farmers and flooded6,500,000 ha within the basin. This paperanalyses natural trends within the rainfalland riverflow records, and considers thepossible effects of human interference. Theriver basin is mainly underlain byimpermeable soils with a high water table.The soil factor and the low topographicgradients often produce surface run-off withslow lateral drainage. Very often, heavyrainfall associated with high soil moisturecontent leads to flooding of the basin.Three major flood events that have occurredsince 1960 have been analysed. Floodoccurrences have been placed in the contextof precipitation variability and soil waterstorage. The precipitation records of twolong-term stations in the basin (Junin andDolores) show an increasing trend and thisis due to rainfall increases in the warmseason. However, none of the rain eventsreached the probable maximum precipitationof 100 year return period. The dischargerecords of the Salado River are comparedwith the pattern of the ElNiño/Southern Oscillation and it isfound that only the May discharge anomaliesare weakly related to the El Niñodriven climate variability. Results fromthis study are useful for the formulationof flood mitigation measures. The paperconcludes with a consideration of the floodmitigation policy developed in PlanMaestro.     

Risk perception, risk management and vulnerability to landslides in the hill slopes in the city of La Paz, Bolivia. A preliminary statement

The article begins by describing the difficult living conditions of many people in the hill slopes (laderas) of La Paz, Bolivia, demonstrating that they are exposed to a combination of natural and social hazards. ¹ It shows that residents, community leaders and city planners tend to underestimate or deny risk, with important consequences for risk management, such as a failure to raise risk awareness. The article then proposes some hypotheses to explain risk perceptions in La Paz, discarding the usual single-approach interpretations and suggesting instead more nuanced theoretical explanations to account for why people build their homes in such hazardous environments.     

Study on preparation and microwave absorption property of the core-nanoshell composite materials doped with La

Microwave absorbing material plays a great role in electromagnetic pollution controlling, electromagnetic interference shielding and stealth technology, etc. The core-nanoshell composite materials doped with La were prepared by a solid-state reaction method, which is applied to the electromagnetic wave absorption. The core is magnetic fly-ash hollow cenosphere, and the shell is the nanosized ferrite doped with La. The thermal decomposition process of the sample was investigated by thermogravimetry and differential thermal analysis. The morphology and components of the composite materials were investigated by the X-ray diffraction analysis, the microstructure was observed by scanning electron microscope and transmission electron microscope. The results of vibrating sample magnetometer analysis indicated that the exchange-coupling interaction happens between ferrite of magnetic fly-ash hollow cenosphere and nanosized ferrite coating, which caused outstanding magnetic properties. The microwave absorbing property of the sample was measured by reflectivity far field radar cross section of radar microwave absorbing material with vector network analyzer. The results indicated that the exchange-coupling interaction enhanced magnetic loss of composite materials. Therefore, in the frequency of 5 GHz, the reflection coefficient can achieve -24 dB. It is better than single material and is consistent with requirements of the microwave absorbing material at the low-frequency absorption.     

La0.8Ce0.2CoO3/Al2O3对油烟的催化净化

将稀土金属La、Ce和过渡金属Co按照一定的比例采用浸渍法负载在γ-Al2O3载体上制备成La0.8Ce0.2CoO3/Al2O3催化剂,用X-射线衍射仪和扫描电镜对催化剂负载层的表面形态、晶相结构和粒径大小进行了表征,并用正交实验法考察了其对油烟的催化净化效果。结果表明,当负载量30%、焙烧温度800℃、催化温度300℃、烟气流量10L/min时催化剂对油烟的净化效果最佳,净化效果可达88%,催化剂对油烟的催化具有较好的低温高活性。     

厄尔尼诺-拉尼娜事件对新疆环境气候的影响研究

基于近54年发生的厄尔尼诺/拉尼娜事件和新疆气候资料,分析新疆环境气候变化特点表明:1961年以来新疆降水量和气温均呈现明显增加的趋势.厄尔尼诺/拉尼娜事件呈现出起伏波动的特点,且1980年以后波动趋势更为剧烈,厄尔尼诺事件发生强度要大于拉尼娜事件.强厄尔尼诺年极端降水事件增多.厄尔尼诺/拉尼娜事件年对新疆各地区降水、气温影响不同,厄尔尼诺年塔城、阿勒泰北部、巴州北部、南疆西部喀什至和田一带增湿明显,阿勒泰东部、哈密北部升温作用显著.     

稀土元素La对油菜某些生理指标的影响及其临界浓度

通过水培试验 ,研究了稀土元素La对油菜生物量和叶绿素含量、硝酸还原酶活性、根系活力、POD活性等一系列生理指标的影响。结果表明 :喷施或根施 0 0 3～ 3mg/kg的La3+对油菜的生长起了一定的促进作用 ,表现为生物量、叶绿素含量、硝酸还原酶活性和根系活力增加 ;而高于 3 0mg/kg浓度的La3+对油菜的生长产生了抑制作用 ,油菜生物量、叶绿素含量、硝酸还原酶活性和根系活力降低 ,POD活性增高。La对油菜的临界浓度为 3 0mg/kg。     

镉对大豆苗期素质的影响与镧的防护作用

以盆栽实验研究了镉对大豆苗期素质的影响及镧的防护作用。实验结果表明,每钵根施１００ｍｇ氯化镉会严重抑制大豆幼苗生长;而先期一次性叶片喷布３０ｍｇ／ＬＬａＣｌ３能明显减轻镉造成的伤害。     

La对Pb伤害大豆幼苗的影响

以盆载法研究了Ｐｂ对大豆幼苗的伤害及Ｌａ对Ｐｂ伤害的生态生理效应．结果显示,１０００ｍｇＬ－１ＰｂＡｃ２能严重抑制大豆幼苗代谢与生长,叶面喷布３０ｍｇＬ－１ＬａＣｌ３１次,能减轻Ｐｂ造成的毒害．实验证明,此与Ｌａ能增加大豆幼苗光合速率,提高叶绿素含量与硝酸还原酶活性,降低细胞质膜透性与体内Ｐｂ含量,维持ＴＴＣ还原力等多种作用相关     

稀土元素(La3+)对厨余垃圾暗发酵产氢性能影响研究

通过在厨余垃圾暗发酵产氢过程中添加不同质量浓度的稀土元素La3+,考察稀土元素对产氢性能的影响。结果表明,添加一定质量浓度的La3+能促进厨余垃圾产氢效率,而高质量浓度则有抑制效应。添加La3+质量浓度为0.5 mg/L时效果最佳,产氢量和总有机酸量达到最大,分别为43.11 mL/gVS和11 871.7 mg/L,分别是对照组的1.45倍和1.24倍。添加一定量的稀土元素也能同时促进产氢污泥的胞外多聚物的生成。     

浙江三门湾沉积记录:U k37表层海水温度和浮游植物群落变化与El Ni?o/La Ni?a的关联

应用三门湾沉积柱样中长链烯酮不饱和指数(U k37)与表层海水温度SST的关系重建历史上的El Ni?o/La Ni?a事件;利用3种浮游植物标志物菜子甾醇(brassicasterol)、甲藻甾醇(dinosterol)和长链烯酮C37(alkenones)来恢复单一种硅藻Diatom、甲藻Dinoflagellates和颗石藻Emiliania huxleyi变化.研究结果表明:(1)U k37估算温度在15.19~17.61℃波动,与当地秋季海水实测温度接近.U k37估算的温度清晰地再现了全球变暖的趋势,且其波动可能与El Ni?o/La Ni?a震荡有关.(2)浮游植物标志物总含量变化范围为710.7~6998.5 ng·g-1,180年以来呈总体上升趋势.沉积记录中硅藻相对比例最高、甲藻次之,硅藻/甲藻比值在2.1~7.2波动,表现出近岸浮游植物对海洋环境变化的敏感性.(3)El Ni?o/La Ni?a事件可影响到浮游植物细胞丰度以及群落结构变化,在El Ni?o盛期,浮游植物细胞丰度剧增,而浮游植物种类数及群集多样性程度明显减少.另外,浮游植物细胞丰度的季节性规律不明显,El Ni?o事件可能是影响三门湾海域浮游植物生产力的主要因素.