河道型水库干支流交汇段水力特性数值分析     

陆建宇  毛劲乔  龚轶青  蔡海滨  曹青  戴会超  闫杰 《排灌机械工程学报》2019,37(9):776-781

以典型河道型水库库区主流与支流交汇段几何尺寸与来流条件为参照,建立了三维概化数学模型并开展多情景数值分析,以揭示不同交汇角对干支流交汇段关键水力特性变化的影响.重点研究了交汇角α分别为30°,60°,90°,120°,150°的5种工况,计算结果表明:在不同交汇角条件下均存在紊动能高值集中区域,且紊动能与交汇角大小存在正相关关系,即随着交汇角增大,紊动能峰值区域的面积及峰值大小显著增大;不同交汇角条件下床面切应力最大值均由交汇口向支流上游沿程递减,而当α<90°时断面流速变异系数沿程先增大后减小,当α≥90°时断面流速变异系数沿程减小;另外,当α<90°时,床面切应力和断面流速变异系数与交汇角大小存在负相关关系,而当α≥90°时,这2个特性指标随着交汇角增大而递增.  相似文献   

农田土壤重金属淋洗剂筛选与效应分析   总被引：2，自引：0，他引：2  

杨文俊  辜娇峰  周航  黄芳  王诗龙  张竞颐  龙坚  袁腾跃  廖柏寒 《水土保持学报》2019,33(4):321-328

为分析不同淋洗剂在不同淋洗条件下对重金属淋洗效果的影响,采用振荡淋洗法对比研究4种淋洗剂(柠檬酸(CA)、酒石酸(TA)、乙二胺四乙酸二钠盐(EDTA)和氨三乙酸三钠盐(NTA))不同浓度、淋洗时间、pH和固液比对重金属复合污染农田土壤中Pb、Cd、Cu和Zn的淋洗效果及单因素最佳淋洗条件下土壤淋洗前后重金属不同形态含量的变化。结果表明,CA和TA的最佳淋洗浓度为0.3mol/L,EDTA和NTA为0.05mol/L;CA和NTA的最佳淋洗时间为480min,EDTA和TA为720min;4种淋洗剂的最佳淋洗pH均为3,最佳固液比均为1∶20。单因素最佳淋洗条件下,EDTA对土壤重金属去除效果最佳,对Pb、Cd、Zn和Cu的去除率分别为67.4%,61.0%,13.8%和76.0%;NTA效果次之,去除率分别为41.6%,42.4%,9.9%和54.3%。土壤重金属去除率随淋洗剂pH的降低而升高,随固液比的增加而增加,随淋洗剂CA与TA浓度增大而增大。淋洗剂对土壤重金属的解吸动力学曲线符合准二级动力学模型,解吸过程为化学解吸,且解吸反应速率受土壤重金属含量与淋洗剂浓度控制。土壤重金属在淋洗剂作用下的解吸速率为Cd>Pb≈Zn≈Cu。EDTA和NTA淋洗显著降低土壤中Pb、Cd、Zn和Cu铁锰氧化态和有机结合态的含量,CA和TA显著降低Pb、Cd、Zn和Cu铁锰氧化态的含量。淋洗剂对重金属的去除效率为EDTA>NTA>CA>TA。  相似文献   

Glyphosate Dissipation in Different Soils Under No-Till and Conventional Tillage   总被引：1，自引：0，他引：1  

Elena OKADA  José Luis COSTA  Francisco BEDMAR 《土壤圈》2019,29(6):773-783

Glyphosate is the most used herbicide in Argentina, accounting for 62% of the commercialized pesticides on the market. It is used as a weed controller in no-till systems, and it is also applied to various genetically modified crops (e.g., soybean, corn, and cotton). Although it has a high solubility in water, it tends to adsorb and accumulate in agricultural soils. The main objectives of this work were to compare the dissipation of glyphosate and the accumulation of its metabolite aminomethylphosphonic acid (AMPA) over time in three soils from agricultural areas of Argentina under long-term management with no-till (NT) and conventional tillage (CT) practices. There were no differences in dissipation between NT and CT, indicating that the glyphosate-degrading microflora was not modified by the different tillage managements. Moreover, tillage practices did not alter the general soil properties; therefore, glyphosate bioavailability was not affected by NT or CT practice. Forty percent of the applied glyphosate was degraded within the first three days in all soils, indicating a fast initial dissipation rate. However, the dissipation rate considerably decreased over time, and the degradation kinetics followed a bi-exponential (or two-compartment) kinetic model. No differences were found between tillage practices. Dissipation was not related to the microbial activity measured as soil respiration. The fast decrease in the concentration of glyphosate at the beginning of the dissipation study was not reflected in an increase in the concentration of AMPA. The estimated half-lives for glyphosate ranged between 9 and 38 d. However, glyphosate bioavailability decreases over time, as it is strongly adsorbed to the soil matrix. This increases its residence time, which may lead to its accumulation in agricultural soils.  相似文献   

Formation of mineral–mineral and organo–mineral composite building units from microaggregate‐forming materials including microbially produced extracellular polymeric substances     

Tom Guhra  Thomas Ritschel  Kai Uwe Totsche 《European Journal of Soil Science》2019,70(3):604-615

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沈阳市天然降雨雨滴特征研究   总被引：3，自引：1，他引：2  

尚佰晓  王瑄  陶伟  任秉枢  王莉  李洪丽 《水土保持研究》2008,(6)

采用滤纸色斑法对沈阳市天然降雨雨滴进行观测,通过计算并运用回归分析对沈阳地区天然降雨雨滴特性进行研究。结果表明:沈阳地区天然降雨雨滴的大小分布遵守Best函数分布式;雨滴中数直径及降雨动能同降雨强度关系显著,呈幂函数关系。  相似文献   

超声波辅助提取荷叶多酚工艺及其动力学分析     

王占一  孙晓梅  徐妍玉  王维青  王森  向兰 《北方园艺》2020,(5):95-103

以微山湖荷叶为试材,用超声波辅助提取荷叶多酚,在单因素试验基础上,采用Box-Behnken响应面法优化提取工艺,并建立4种数学模型对提取过程的动力学进行研究,采用决定系数(R2)、精准因子(Af)、偏差因子(Bf)和根平均方差(RMSE)4种模型评价参数对模型的适用性进行分析。结果表明:当乙醇体积分数68%、料液比1∶25 g·mL-1、提取温度40℃、提取时间38 min时,荷叶多酚得率为3.231%;2种非线性增长函数模型,即Sgompertz模型和Slogistic1模型能很好地拟合荷叶多酚提取的动力学过程。超声波辅助提取的工艺参数及所建立的动力学数学模型,均可用于荷叶多酚提取过程的工程放大和优化控制。  相似文献   

Effects of different forage combinations in total mixed rations on in vitro gas production kinetics,ruminal and milk fatty acid profiles of lactating cows          下载免费PDF全文

Sarvvl Bai  Zhi‐Jun Cao  Bin‐Bin Cao  Hong‐Jian Yang  Sheng‐Li Li  Jian‐Xin Liu 《Animal Science Journal》2018,89(9):1261-1270

This study aimed to determine the effects of different forage combinations on in vitro gas production (GP) kinetics, ruminal and milk fatty acid profiles. Forty‐five lactating cows were randomly arranged into three groups and fed three total mixed rations (TMRs) with different forage combinations: TMR1, 23% alfalfa hay, 7% Chinese wild ryegrass hay and 15% whole corn silage; TMR2, 30% corn stover plus 15% whole corn silage; TMR3, 30% rice straw plus 15% whole corn silage. In vitro dry matter disappearance ranked: TMR1 > TMR2 > TMR3, and highest cumulative GP and asymptotic GP occurred in TMR1 while no difference occurred between TMR2 and TMR3. The average GP rate ranked: TMR1 > TMR2 > TMR3. TMR1 in comparison with TMR2 and TMR3 presented lower rumen contents of acetate and butyrate and greater rumen contents of propionate, valerate, C13:0, C14:0, C15:0, C18:1cis‐9, C18:2n‐6, C18:3n‐3, C20:0 and C22:0 as well as milk C18:2n‐6 and C18:3n‐3 proportions. Transfer efficiencies of C18:2n‐6 and C18:3n‐3 from diet to milk ranked: TMR1 > TMR2 > TMR3. The findings suggest TMRs containing alfalfa hay and Chinese wild ryegrass hay in comparison with corn stover or rice straw improve rumen fermentation and transfer efficiency of C18:2n‐6 and C18:3n‐3.  相似文献   

温度对管囊酵母乙醇产量及动力学参数的影响     

杨文  孙福来  孟晓峰 《扬州大学学报(农业与生命科学版)》1998,(4)

在２０～４０℃条件下对管囊酵母进行了培养,研究其生物量、乙醇产量、残糖量等指标随温度变化的消长趋势,以及在不同温度下在对数生长期各项动力学参数的变化。该菌株的最适培养温度为２８～３２℃,在这一范围内,比生长速率、比乙醇产率和木糖比消耗速率分别达到最高值：０．１９／ｈ、４．３ｇ／（ｇ·ｈ）和２８．０ｇ／（ｇ·ｈ）。  相似文献   

我国南方地区典型土壤有机硫矿化速率及供硫潜力研究   总被引：3，自引：0，他引：3  

胡正义  曹志洪 《中国农业科学》1999,32(6):69-74

利用开放培养技术研究了21个中国南方代表性土壤有机硫矿化动力学。结果表明,182d培养土壤有机硫矿化量（S）为61.86～145.1mg/kg(均值88.56mg/kg),其中22.45%～48.03%(均值32.74%)来自前14d的矿化。14d和182d土壤有机硫矿化量分别占土壤总有机硫1.5%～8.2%(均值3.6%)和6.73%～19.8%(均值10.6%)。实测数据拟合方程发现,土壤有机硫矿化符合一级动力学方程S#-t=S#-0[1-e#+（-kt）]。21个土壤有机硫矿化势（S#-0）为62.76～133mg/kg(均值84.94mg/kg)。试验还发现第四纪红土母质发育的土壤有机硫供硫潜力及速率明显大于花岗岩、砂页岩和紫砂岩母质。  相似文献   

粳稻光敏核不育系93—926s的育性转换研究   总被引：3，自引：0，他引：3  

牛芝霞  邹美智 《天津农业科学》1999,5(4):1-4

讨论了粳型水稻光敏核不育系93—926s的育性转换特点及育性转换期,证明93—926s是以光敏为主的不育系,育性转换明显,在天津地区,其不育期在8月初到8月底,育性转换期在8月30日左右,其育性转换临界日照长度为13～14h,临界日平均温度为23.0～24.0℃。  相似文献