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861.
课证融合模式下实训教学改革研究   总被引:3,自引:0,他引:3  
课证融合模式就是将课程与职业资格证书相结合的教学模式,是对职业教学改革的探索。但当前存在的实训教学标准模糊、校企合作实训教学条件不足、教师队伍转型滞后、教材开发混乱等现象严重阻碍了课证融合模式的推行,职业院校应当从明确考核评价标准、改进培养方案、加大双师教师的引进和培养、科学开发实训教材等途径进行尝试,推进课证融合。  相似文献   
862.
Generalized additive models were used to synthesize the data from 52 publications on the gonad growth and spawning seasonality of Paracentrotus lividus and identify spatial and temporal patterns in the reproductive processes. According to our results, Atlantic populations spawn in spring and develop large gonads (6.4 ± 0.2% of fresh body weight (mean ± SE)), which increase in size toward higher latitudes. While in the Mediterranean, the gonads are smaller (3.1 ± 0.1%), possibly as the result of successive spawnings which impede nutrients accumulating in the gonads. Differences were also observed between habitats: gonad production was higher in seagrass meadows in the Mediterranean and in subtidal rocky substrates in the Atlantic. Food availability might cause these variations as well as the negative correlation observed between depth and the gonad index for rocky substrates. Sex and body size do not seem to influence greatly gonad growth.  相似文献   
863.
Bioavailability is defined as the fraction of a soil contaminant readily available for microbial degradation and for naphthalene it could be estimated by conventional exhaustive extraction methods. In this study, a novel method that employed persulfate oxidation in combination with ultrasonic extraction (POUSE) was developed. Three parameters, temperature, duration of persulfate oxidation, and the ratio of persulfate to soil organic matter (2S,082 /SOM; g g-1), were investigated to obtain an optimum operating conditions. Under the condition, naphthalene bioavailability estimated by the POUSE method was verified and compared with other three exhaustive methods i.e. sonicator, supercritical fluid extraction (SFE), and soxhlet extraction (SE). When the S2,O(8)2-/SOM ratio was controlled at 11.6 g g-1, the optimum operating conditions of the POUSE method were 70 degreesC and 3 hr, for the temperature and duration. Under these conditions, the residual naphthalene concentrations were correlated well with the residual naphthalene concentrations for both the cases of freshly spiked and aged soils. By contrast, the sonicator, SFE, and the SE overestimated the naphthalene bioavailability since these three methods extracted naphthalene much more than that of biodegradation test. These results demonstrated that the POUSE could estimate more precisely the naphthalene bioavailability.  相似文献   
864.
2009年5月和10月对椒江口(121.35°E~121.85°E,28.50°N~28.80°N)浮游动物进行调查,分析其群落结构、生物量和丰度的时空分布特征及与主要环境因子的关系.结果表明,该海域浮游动物有明显的季节变化,春季鉴定到14大类50种,卡玛拉水母(Malagazzia carolinae)为绝对优势种,秋季鉴定到14大类73种,优势种分别为百陶箭虫(Sagitta bedoti)、双生水母(Diphyes chamissonis)、亚强真哲水蚤(Eucalanus subcrassus)、微刺哲水蚤(Canthocalanus pauper)、中华胸刺水蚤(Centropages sinensis)和肥胖箭虫(Sagitta enflata);多样性指数为秋季(2.59)高于春季(1.82),生物量和丰度为春季(972.66 mg/m3和1 743.54 ind/m3)远高于秋季(65.30 mg/m3和31.94 ind/m3).总生物量和丰度的空间分布由优势种决定,春季高值区出现在咸淡水交汇的出海口处;秋季有沿河口向外递增的趋势.典范对应分析(CCA)表明,营养盐、盐度和溶解氧为影响春秋季椒江口浮游动物分布的环境因子;浮游动物群落存在明显的季节和空间异质性;各物种适宜的生态环境不同.与类似河口的现状相比,椒江口的浮游动物种类丰富,可能与影响该河口的水团多样有关;与历史资料相比,椒江口4、10月份浮游动物的生物量、丰度及优势类群保持相对稳定.图9表6参44  相似文献   
865.
通过对生态地球化学调查评价形态分析实验室间比对试验结果的统计分析和技术分析,进一步验证和统一生态地球化学评价样品形态分析方法,提高实验室间形态分析数据的可比性,了解参加实验室形态分析的技术能力,为制定生态地球化学评价样品形态分析相关规范提供基础数据依据。  相似文献   
866.
Atmospheric oxidizing capacity (AOC) is an essential driving force of troposphere chemistry and self-cleaning, but the definition of AOC and its quantitative representation remain uncertain. Driven by national demand for air pollution control in recent years, Chinese scholars have carried out studies on theories of atmospheric chemistry and have made considerable progress in AOC research. This paper will give a brief review of these developments. First, AOC indexes were established that represent apparent atmospheric oxidizing ability (AOIe) and potential atmospheric oxidizing ability (AOIp) based on aspects of macrothermodynamics and microdynamics, respectively. A closed study refined the quantitative contributions of heterogeneous chemistry to AOC in Beijing, and these AOC methods were further applied in Beijing-Tianjin-Hebei and key areas across the country. In addition, the detection of ground or vertical profiles for atmospheric OH·, HO2·, NO3· radicals and reservoir molecules can now be obtained with domestic instruments in diverse environments. Moreover, laboratory smoke chamber simulations revealed heterogeneous processes involving reactions of O3 and NO2, which are typical oxidants in the surface/interface atmosphere, and the evolutionary and budgetary implications of atmospheric oxidants reacting under multispecies, multiphase and multi-interface conditions were obtained. Finally, based on the GRAPES-CUACE adjoint model improved by Chinese scholars, simulations of key substances affecting atmospheric oxidation and secondary organic and inorganic aerosol formation have been optimized. Normalized numerical simulations of AOIe and AOIp were performed, and regional coordination of AOC was adjusted. An optimized plan for controlling O3 and PM2.5 was analyzed by scenario simulation.  相似文献   
867.
The atmospheric chemical mechanism is an essential component of airshed models used for investigating the chemical behaviors and impacts of species. Since the first tropospheric chemical mechanism was proposed in the 1960s, various mechanisms including Master Chemical Mechanism (MCM), Carbon Bond Mechanism (CBM), Statewide Air Pollution Research Center (SAPRC) and Regional Atmospheric Chemistry Mechanism (RACM) have been developed for different research purposes. This work summarizes the development and applications of these mechanisms, introduces their compositions and lumping methods, and compares the ways the mechanisms treat radicals with box model simulations. CBM can reproduce urban pollution events with relatively low cost compared to SAPRC and RACM, whereas the chemical behaviors of radicals and the photochemical production of ozone are described in detail in RACM. The photolysis rates of some oxygenated compounds are low in SAPRC07, which may result in underestimation of radical levels. As an explicit chemical mechanism, MCM describes the chemical processes of primary pollutants and their oxidation products in detail. MCM can be used to investigate certain chemical processes; however, due to its large size, it is rarely used in regional model simulations. A box model case study showed that the chemical behavior of OH and HO2 radicals and the production of ozone were well described by all mechanisms. CBM and SAPRC underestimated the radical levels for different chemical treatments, leading to low ozone production values in both cases. MCM and RACM are widely used in box model studies, while CBM and SAPRC are often selected in regional simulations.  相似文献   
868.
运用三维荧光光谱(EEMs)技术结合平行因子分析法(PARAFAC)以及紫外-可见光谱技术(UV-vis),对雄安新区-白洋淀冬季冰封期不同特征区域水体溶解性有机物(DOM)的空间分布、光谱特征以及来源进行解析.结果表明,冬季冰封期白洋淀水体DOM吸收系数无特征峰,不同特征区域的差异显著;表层水体DOM与底层水体DOM的吸收系数差异不明显;冰封期白洋淀水体的E3/E4均大于3. 5,说明DOM以低腐殖质成分为主,E2/E3为6. 35±0. 72,表明DOM中小分子量的居多,而且SR为1. 33±0. 14均大于1,显示DOM主要为生物源;三维荧光通过PARAFAC解析出3种组分,分别为类酪氨酸(C1)、类色氨酸(C2)和陆源腐殖质(C3);对3个组分进行相关性分析,结果显示C1与C2之间具有显著的相关性(P 0. 001);白洋淀各个特征区域间的DOM总荧光强度和各荧光组分荧光强度呈现显著的差异(P 0. 01); DOM的总荧光强度以及各组分的荧光强度均呈现出唐河入淀口高、烧车淀低的特征,C1+C2是DOM的主要成分;冰封期白洋淀水体的DOM生物源指数(BIX)为1. 23±0. 18,荧光指数FI为2. 30±0. 16 ( 1. 8),表明白洋淀DOM来源于生物活动并且以自生源为主,与腐殖程度指标(HIX)的结果相吻合; PCA结合Adonis分析显示,白洋淀不同区域水体DOM的光谱特征差异明显(P 0. 05),表层与底层的DOM光谱特征相近(P 0. 05);并且组分C1、C2、C3与DOM特征参数(HIX、BIX、Fn280、Fn355)以及水质参数(总氮、高锰酸盐指数、溶解性总磷)构建的多元线性回归方程显著相关性(P 0. 001).综上,通过对冬季冰封期白洋淀各个典型淀区水体DOM光谱特征进行研究,可以为分析白洋淀水体有机物污染特征和白洋淀的水质管理提供技术支持.  相似文献   
869.
金盆水库沉积物磷的来源及分布特征   总被引:2,自引:2,他引:0  
为探究分层型水源水库沉积物中磷的来源与分布特征,以西安金盆水库为对象,针对2017年3~11月金盆水库水体、沉降颗粒及沉积物柱状样品总磷(TP)含量及形态分布特征进行研究.结果表明,金盆水库主库区表层沉积物总磷含量及形态分布受水体颗粒磷(PP)沉降作用明显,相关系数r~2=0. 877 5;同时表层沉积物总磷含量还受到沉积物内部生物地球化学的共同作用. 6~8月金盆水库水体藻类剧烈繁殖演替,繁殖过程中大量失去活性、死亡的藻类不断向底部水体沉积,形成以藻类等颗粒磷为主导的内源污染,沉降颗粒总磷含量达(753. 51±17. 11) mg·kg~(-1),表层沉积物总磷含量随之增加,以铁铝结合态非活性磷(NaOH-nrP)为主; 9~11月进入汛期,径流水体携带大量泥沙等负荷较大的污染物汇入水库,使得水体颗粒磷浓度相应增大,然而由于单位质量泥沙中总磷含量占比较小,导致径流过程中表层沉积物总磷含量逐渐降低,泥沙径流过程中颗粒磷以无机态的钙磷(Ca-P)和残渣态磷(rest-P)为主,二者约占沉积物总磷(TP) 55. 8%~66. 2%,受颗粒沉降影响相对较大.活性磷(SRP)、铁锰螯合态磷(BD-P)和铁铝结合态活性磷(NaOH-srP)这3种形态磷较活跃,在环境条件的变化(主要是氧化还原条件)下发生一系列迁移转化,受沉积物内部生物地球生物化学过程作用明显.  相似文献   
870.
程萌  马俊杰  刘丹  薛璐  吴宁  胡芊 《环境科学学报》2021,41(6):2390-2401
为研究CO2地质封存过程中CO2泄漏对水稻及稻田土壤的风险影响,利用CO2模拟泄漏平台,研究了不同CO2泄漏速率下水稻生长、稻田土壤性质与土壤细菌组成及多样性的变化特征.结果表明:随着CO2泄漏速率的增加,稻田土壤pH显著降低,电导率显著增加,水稻生长受到明显抑制;稻田土壤细菌的丰富度指数和多样性指数均有增加,均匀度指数有所降低.CO2泄漏显著改变了稻田土壤细菌组成,稻田土壤的优势菌门中变形菌门、拟杆菌门与绿弯菌门的相对丰度总体降低,而酸杆菌门与放线菌门的相对丰度总体升高;稻田土壤优势菌属中RB41、MND1、厌氧粘菌属及鞘脂单胞菌属的丰度总体升高,而硝化螺旋菌属的丰度总体降低;稀有细菌中CO2泄漏下全部出现的有粘胶球形菌门、柔膜菌门及双头菌属、硫杆菌属,CO2泄漏后全部消亡的为假单胞菌属.建议将变形菌门的减少和酸杆菌门的增加,以及RB41、MND1及厌氧粘菌属的增加作为稻田土壤CO2泄漏监测的推荐指标.  相似文献   
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