基于植被恢复的黄土高原典型流域次洪水沙特征分析

研究大规模植被恢复条件下岔巴沟流域次洪水沙变化,对揭示黄土高原土壤侵蚀演变规律和黄河水沙调控具有重要作用。基于101场洪水事件,结合NDVI和降雨数据,通过分析不同生态建设时期岔巴沟流域次洪水沙变化特征,选取2场典型洪水事件进行对比,揭示次洪输沙与径流侵蚀能量的关系。结果表明:时期Ⅱ的次洪平均径流量是时期I的1.86倍,但平均输沙量仅为0.52倍。在4个洪峰流量分级中,时期I的次洪平均输沙模数明显高于时期Ⅱ。与NO.2洪水事件相比,NO.100洪水事件的径流过程和输沙过程具有良好的同步性,洪水历时更长,洪峰流量、输沙峰值明显较低。时期I和Ⅱ的次洪输沙模数均随径流侵蚀功率的增加而增加,但时期Ⅱ的输沙模数整体低于时期I。研究结果表明大规模植被恢复对黄土高原典型流域次洪输沙的调控作用较径流更为显著。     

黄河河龙区间输沙变化特征及归因分析

黄河中游河口镇—龙门区间(河龙区间)是黄河泥沙的主要来源区。近年来黄河输沙量急剧变化,为了识别黄河输沙量变化的原因,基于河龙区间15个流域1961—2017年的输沙和降雨数据,分析了研究时段内输沙模数的变化趋势和突变时间,定量区分气候变化和人类活动对输沙减少的贡献率。结果表明:研究区内15个流域的输沙模数均呈现显著的下降趋势,突变时间集中在80,90年代。降雨减少和水土保持措施的增加共同导致了输沙模数的下降,在多数流域,人类活动是导致输沙模数减少的主要因素,80年代后急剧增加的水土保持措施有效减缓了流域产沙。研究成果可为黄河流域生态恢复及水沙调控提供决策支持。     

不同时间尺度下流域径流侵蚀功率输沙模型模拟精度

流域不同时间尺度下的水沙关系及其模拟预测是国内外水土流失研究的热点问题,基于水蚀动力过程的径流侵蚀功率理论,建立了径流侵蚀功率输沙模型,选取黄河一级支流无定河流域的实测径流泥沙资料,系统研究了年、月和次暴雨3种不同时间尺度下的径流侵蚀功率和输沙量之间的相关关系,对比分析了径流侵蚀功率输沙模型与径流—输沙模型在表征流域径流侵蚀输沙上的优劣。结果表明:1975—2010年,无定河流域径流、输沙和径流侵蚀功率在不同时间尺度下均呈下降趋势;不同时间尺度下的径流侵蚀功率输沙模型的R~2相对于径流—输沙均较高,表明基于径流侵蚀功率的流域径流侵蚀功率输沙模型在不同时间尺度上均能够更准确地表征径流侵蚀输沙关系。     

松花江流域侵蚀产沙演变特征分析

利用松花江流域116个站点的降水资料和14个典型流域水文站的径流泥沙资料,在分析降水、径流和输沙时间变化特征的基础上,研究了该区侵蚀产沙演变特征及其主要影响因素.研究结果表明,1961-1990年松花江流域降水和径流无显著增长趋势,但输沙量增长显著,每10 a平均增长幅度为34.7%,丘陵漫岗区输沙量增长幅度较山区更为显著.流域输沙量自1979年开始显著增加,降水量变化不是输沙量快速增长的主要原因,人类活动导致的下垫面变化可能是输沙量增加的重要原因.     

无定河流域径流侵蚀功率时空变化特征

不同尺度的径流侵蚀输沙关系尚未明确,亟待深入研究。为了探究流域径流侵蚀输沙的时空变化特征,基于水蚀动力过程的径流侵蚀功率理论,运用Mann-Kendall法和线性回归法分析了无定河流域1956—2010年年径流侵蚀功率和年径流量的时空变化;利用Mann-Kendall突变点检验,识别出径流的突变年份,对比分析突变年份前后的年径流侵蚀功率和年径流量变化,分析建立了年径流侵蚀功率—输沙相关模型。结果表明:1956—2010年,无定河流域年径流量与年径流侵蚀功率有显著减小趋势,径流突变年份在1971—1985年。突变年份之前流域年径流侵蚀功率平均标准差高于突变年份后;突变年份之后年平均径流侵蚀功率比突变年份前平均减少1.05×10~(-4 )m~4/(s·km~2);年径流侵蚀功率随流域面积的增大而减小。流域径流侵蚀功率—输沙相关模型相关性显著(p0.01)。研究阐明了无定河流域年径流侵蚀功率具有减少趋势,在空间上随流域面积增大而减少,在流域年尺度上径流侵蚀功率理论能够较好的表征径流侵蚀输沙关系。     

洮河流域径流输沙演变与降雨及降雨侵蚀力的关系

[目的]揭示气候变化、人类活动耦合作用下复杂的水沙变化、水沙关系,探明降雨侵蚀力的影响及径流输沙变化的响应机理,为流域水土流失防治和生态建设提供科学参考依据。[方法]基于洮河流域及周边6个气象站点逐日降水和下游控制站逐月径流输沙数据,采用多元统计分析法、水沙曲线、相关系数、灰色关联度、弹性分析法等方法分析研究了径流、输沙、降雨(P)、降雨侵蚀力(R)演变规律,及其相互作用关系。[结果]洮河流域1956—2019年径流整体呈显著下降趋势,线性变化率-2.8×10⁷m³/a, 1987年发生突变,输沙整体呈显著下降趋势,线性变化率-4.61×10⁵t/a, 2003年发生突变,降雨、降雨侵蚀力均呈不显著上升趋势,且未出现明显突变。洮河流域R上中游小于下游,夏季(626.33)>秋季(125.31)>春季(122.22)>冬季(0),夏季降雨侵蚀力占比71.67%,夏季对泥沙侵蚀影响最大。P与R分布相反,P相对较小的下游流域R较大,P相对较大的上中游R较小,流域水沙异源,上中游产水,下游产沙。对输沙量影响最大...     

嘉陵江流域输沙时空变化及归因分析

河流输沙过程变化对河流系统的功能发挥具有重要意义,因此探究嘉陵江流域输沙时空变化及其驱动因素,对嘉陵江流域进一步治理具有重要指导作用。基于嘉陵江流域实测降雨输沙资料,采用Mann-Kendall趋势检验、Pettitt突变检验分析输沙时空变化特征,采用双累积曲线法定量分析了典型区间内水文站点气候变化与人类活动对输沙变化贡献率。结果表明：嘉陵江流域各子流域年代输沙模数整体呈减少趋势,2007—2015年,仅武都—碧口区间输沙模数高达3 323.48 t/(km²·a)。典型区间内北碚、武胜、罗渡溪、小河坝4站1960—2015年输沙量呈极显著下降趋势,分别以3.40×10⁶,1.80×10⁶,4.0×10⁵,3.40×10⁵t/a的速率下降,以水土保持与水利工程措施为主的人类活动减沙贡献率为75.93%～96.43%,其输沙序列分别于1990年、1990年、1988年、1984年发生极显著突变。嘉陵江流域各子流域年代输沙模数整体呈减少趋势,干流修建多座大型控制性水库对河道输沙的影...     

黄土高原泾河流域1960—2000年的年输沙量时空变化

为制订合理有效的水土流失治理政策,需定量了解流域的泥沙输移总量及其时空变化。以黄土高原多泥沙的典型流域泾河为例,按有连续水文观测数据的11个水文站的控制范围,把流域划分为11个河段,统计分析1960—2000年间的年均输沙量和输沙模数在不同年代的变化和空间上的差异。结果表明:1)20世纪60年代泾河流域年均输沙量为3.024 9亿t/a,年均输沙模数为6 672 t/(km2.a);输沙等级为强度,但空间分布不均匀,其中输沙等级为极强度和强度的河段面积占流域面积的72.6%,其年均输沙量占流域总量的86.0%;输沙等级为中度和轻度的河段面积占流域面积的27.4%,其年均输沙量占流域的14.0%。2)20世纪70年代以来,泾河流域年均输沙量开始减少,90年代已减至2.657 8亿t/a,较60年代下降了12.1%,减沙主要发生在输沙等级为极强度的河段,其减沙量占流域总减沙量的93.5%,尤其以降水较高、植被较好的西部地区为主要贡献区,而其他输沙等级河段的年输沙量基本保持不变。因此,在侵蚀性暴雨增加的气候变化背景下,植被稀疏、抵抗暴雨侵蚀能力差的半干旱地区应列为水土保持重点地区。     

黄河流域产流侵蚀及其分布特性的变异

随着人类活动的加剧和气候变化,黄河流域水沙特性也发生了变化。为了解黄河流域产流和产沙的变化过程,通过引入区域径流深和区域输沙模数等参数,根据黄河流域主要水文站1950—2015年以来的实测水沙资料,利用Mann-Kendall统计检验法和水文量累积曲线法,深入研究黄河流域产流侵蚀过程和空间分布的变异特点。结果显示:黄河流域除唐乃亥站无明显趋势变化外,其他干流水文站和11条支流水文站的径流深和输沙模数大都以指数形式呈显著减少趋势,表明黄河流域产流产沙能力减弱。黄河上游水文站多年平均径流深和区域径流深较大,为主要产流区;中游水文站多年平均输沙模数和区域输沙模数较大,为主要产沙区;下游多年平均区域径流深和输沙模数均为负值,为水沙主要消耗区。黄河流域水沙异源现象仍然存在,但有减弱趋势。     

金沙江流域水沙变化及其驱动机制

为了探究金沙江流域控制水文站屏山站水沙序列的趋势及突变特性,量化不同驱动因素对水沙变化的贡献。基于金沙江流域1954—2016年径流和输沙数据,从长时期及场次事件两个角度揭示了水沙关系的动态变化特征。结果表明：(1) 63年间,径流量年均变化速率为-1.16×10⁸m³/a;输沙量年均变化速率为-2.0×10⁶t/a; 1998年长江流域发生特大洪水,水沙序列在该年发生突变;(2)水沙关系的特征参数a值在1998年前后由上升改为下降趋势,退耕等坡面水保措施在1998年后发挥了重要作用;b值始终下降,河道影响因素始终发挥减沙作用;在场次降雨尺度上,流域径流-悬移质泥沙环路(C-Q环路)以顺时针形环路为主,表明坡面泥沙物源充足,是影响流域产沙的重要因素;(3)流域内降水、温度及NDVI与径流和输沙之间有明显的相关性,人类活动与降水因素对径流量的贡献比为-1∶2,而输沙量主要受人类活动影响,对应的贡献比为-6∶1。综上,金沙江流域63年间的径流输沙受多种因素综合影响,径流量的变化主要由于降水的变化,输沙量受人类活动影响更大。     

Comparisons of soil test phosphorus by Olsen,Bray P1, Mehlich I and Mehlich III methods

Abstract

A study was undertaken to evaluate the agreement among different university laboratories performing the Olsen, Bray P1, and Mehlich I tests for P on a diverse group of noncalcareous agricultural soils and to develop relationships among the Olsen, Bray P1, Mehlich I, and Mehlich III soil tests. For each test, the results from the individual laboratories were highly correlated (r² ≥ 0.90) and in almost all instances the slopes of the equations describing the relationships among laboratories approached one, The results indicate that the Olsen, Bray P1 and Mehlich I soil tests may be performed with a high degree of precision when standard soil test procedures are followed.

Of the three most commonly performed tests in the U.S. (Olsen, Bray P1, and Mehlich I), the Olsen and Mehlich I tests were the most highly correlated (r² = 0.87) although the Mehlich I test removed approximately one and one half times more P than did the Olsen test. Bray P1 and Olsen and Mehlich I P were less highly correlated (r² ≤ 0.72) and the relationships between these variables were influenced by the texture of the soils. The quantity of P removed by the Bray P1 test was on the order of two and three times greater than that removed by the Olsen and Mehlich I tests, respectively. The Bray P1 and Mehlich III soil tests were highly correlated (r² = 0.97) and similar quantities of P were extracted from the soil by the two tests.     

基于Web的在线考试系统设计与实现

从基于Web的在线考试系统的体系结构、系统结构设计和系统主要功能实现的三方面,对基于Web的在线考试系统进行了简要的介绍,并提出了系统进一步完善的方向。     

Relationship between Soil Test Boron and Pea Yields in the Inland Pacific Northwest

Critical soil test boron (B) levels and consequent fertilizer recommendations for spring peas have been traditionally based on values developed for alfalfa, sweet clover, and other legumes commonly grown in other regions of the USA. The purpose of this study was to define the relationship between soil test B values and spring pea yields. Seventy‐eight field studies using B were conducted between 1981 and 2001 on Mollisols and Alfisols in northern Idaho and eastern Washington. Soil sampling to the effective rooting depth of 0.6 m for spring peas results in the best relationship between soil test B and spring pea yield; however, samples taken to the depth of 0.3 m result in the same B critical value (0.5 µg/g). Based on these field studies, the data clearly demonstrate that the 0.5 µg/g critical soil test value of B is important for spring pea yield optimization.     

人参果主要病毒检测方法研究

为了给人参果病毒检验及抗病性研究提供支持,对人参果采用ELISA和RT-PCR两种检测方法对8份田间材料中的马铃薯M病毒(PVM)、番茄花叶病毒(ToMV)和烟草花叶病毒(TMV)进行检测,对比筛选病毒检测方法。结果表明,ELISA法检测PVM的阳性检出率为87.5%;ToMV为37.5%,疑似率为12.5%;TMV为37.5%。通过RT-PCR检测体系,从人参果样品中分别扩增出与试验设计大小相符的特异条带,PVM阳性检出率为100%,ToMV为 50.0%,TMV为37.5%,检测灵敏性和准确性更高,检测结果符合率在87.5%以上。对扩增阳性产物进行凝胶回收测序,确定为目标条带。     

Ecotoxicity of Alternative De-icers

Background  De-icers are essential to wintertime road maintenance in Nordic countries. The use of road salts (NaCl, CaCl₂ and MgCl₂) is having significant effects on groundwater. There has been a growing concern of environmental effects resulting from de-icing. Regulatory bodies have tried to find de-icers which have less harmful impacts on soil and groundwater. Alternative new organic de-icers are e.g. potassium formiate, potassium acetate, and calcium magnesium acetate. Objectives  At present, the decision finding for soil and water quality assessment is mainly based on the results of chemical analyses. However, ecotoxicological characterization will provide more useful information for determining environmental effects of de-icers. Methods  Six different de-icers, NaCl, CaCl₂, MgCl₂, potassium formicate KFo, potassium acetate KAc and calcium magnesium acetate CMA were studied with different bioassays. These bioassays were two plant tests (onion Allium cepa root elongation test and duckweed Lemna growth inhibition test), an enzyme inhibition test (reverse electron transport test, RET) and a microbial test (luminescent bacteria Vibrio fischeri, BioTox test). Results and Discussion  Most of the responses of the de-icers tested were toxic to test organisms. CMA was unsuitable for RET and BioTox tests because it was not possible to analyze turbid samples with these bioassays. On the whole, organic chemicals were more toxic than the inorganic salts. According to the Lemna and Allium cepa tests KFo was the most toxic and the toxicity ranking of the de-icers was KFo > KAc > CMA > CaCl₂ > NaCl > MgCl_2. The sensitivity ranking for tests in decreasing order was Lemna > Allium cepa > RET > BioTox. The plant tests proved to be relevant, easy, cost-effective and sensitive screening methods of de-icers: Lemna test was 92 times more sensitive and Allium test 70 times more sensitive than BioTox to KFo. Conclusion and Outlook  The tested de-icers had significant effects on plant growth, microbial luminescence and enzymatic activity. Toxicity could hardly be predicted from the chemical concentrations of these de-icers. In summary, these results demonstrate a need for including toxicity measurements in the evaluation of technologies used in soil treatment and illustrate the potential value of such measurements for ensuring that no or minimal environmental contamination would arise from de-icing process.     

Comparison of the effects of zinc nitrate-tetrahydrate and tributyltin-oxide on the reproduction and avoidance behavior of the earthworm Eisenia andrei in laboratory tests using nine soils

The aim of this contribution was to evaluate whether the sensitivity of the earthworm avoidance test is comparable to that of the earthworm reproduction test (standard test guidelines for both are available). The objective was to determine if relatively simple short-term tests are useful as an initial screening step for the environmental risk assessment (ERA) of potentially contaminated soils prior to performing long-term, elaborate tests. Therefore, the effects of two model substances, zinc nitrate-tetrahydrate and tributyltin-oxide (TBT-O) on the reproduction and the avoidance behavior of the earthworm Eisenia andrei were compared using Organization for Economic Co-operation and Development (OECD) artificial soil as well as eight natural soils, including LUFA St. 2.2 soil, covering a wide range of pH-values, organic matter content and texture. Almost all tests fulfilled the validity criteria defined in the two standard guidelines published by the International Organization for Standardization (ISO), despite the fact that the properties of natural soils differed clearly from those of OECD artificial soil. The median effective concentration (EC50) values estimated for zinc nitrate-tetrahydrate in 48-h avoidance tests and in 56-day reproduction tests were often similar when using the same soil (seven out of nine soils). However, in the case of TBT-O, the outcome was more complex: in two test soils the avoidance EC50 values were by a factor >3 higher than the reproduction EC50 values. In one of the test soils it was the other way around and the remaining soils showed comparable EC50 values in both tests. Summarizing the results obtained here and according to experiences reported in the available literature, the earthworm avoidance test may be recommended as an initial screening tool in the ERA of potentially contaminated soils. However, further research is needed to understand the factors that contribute to the difference in sensitivity between reproduction and avoidance tests.     

某沿海地区砂性软土类的试验研究

结合某工程实例，分析了沿海地区沙性软土的基本特性，总结了沙性软土的物理力学特性变化的影响因素，提出了控制室内土工实验可靠性的处理方法，为该类土的工程地质评价与基础设计提供了较为有价值的试验成果。     

Duration of the standard earthworm avoidance test: Are 48 h necessary?

Ecotoxicological tests are often recommended for the environmental risk assessment (ERA) of contaminated soils. In comparison to chemical residue analysis that focuses on individual contaminants, ecotoxicological tests are able to integrate the effects of the overall contamination, including interactions between individual contaminants, as well as between the contaminants and the various soil properties. However, their use is limited by the fact that the most sensitive tests are chronic tests such as the earthworm reproduction test which lasts 56 days. In order to promote the use of ecotoxicological tests for the routine assessment of contaminated test soils, the usage of short-term earthworm avoidance tests were investigated in the German project ERNTE. According to the International Organization for Standardization (ISO) guideline no. 17512-1, such a test has a duration of just 48 h which, although less than chronic tests, is still quite long in comparison to modern methods of chemical analysis whereby results are often available within 24 h (“on-site analysis”). Therefore, we assessed the effects of shortening the duration of the earthworm avoidance test from 48 to 24 h on the resulting ecotoxicological data. Eight uncontaminated natural soils and 22 contaminated natural soils containing a wide range of chemicals were tested concurrently for 24 and 48 h. Additionally, seven of the uncontaminated natural soils (one was excluded due to its low pH) plus Organization for Economic Co-operation and Development (OECD) artificial soil or LUFA (Landwirtschaftliche Untersuchungs- und Forschungsanstalt, Speyer, Germany) St. 2.2 soil were spiked with two model chemicals (zinc nitrate-tetrahydrate and tributyltin-oxide (TBT-O)) and tested accordingly. It was also investigated whether the results would differ when using either standard LUFA St. 2.2 or OECD artificial soil as a control when contaminated natural soils were tested. Statistical analysis of the data indicates that a decrease in test duration in general did not result in a different assessment of the test soils. In view of the fact that an ERA of contaminated soils is increasingly starting with an on-site analysis (i.e. data are available within 24 h) it is recommended to change the existing ISO guideline, i.e. to decrease the test duration from 48 to 24 h. In doing so, the use of a multi-concentration design increases the robustness of the test results. Both OECD and LUFA St. 2.2 soils are equally suitable as controls.     

Relationship between Soil‐Test Boron and Lentil Yields in the Inland Pacific Northwest

Abstract

Critical soil‐test boron (B) levels and consequent fertilizer recommendations for lentils have been traditionally based on values (0.5 µg/g) developed for alfalfa, sweet clover, and other legumes commonly grown in the inland Pacific Northwest. The purpose of this study was to define the relationship between soil‐test B values and lentil yields. Fifty‐nine field studies using B were conducted between 1980 and 2003 on Mollisols and Alfisols in northern Idaho and eastern Washington. Based on the results of these studies, the critical soil B value for optimum lentil yields is 0.4 µg/g. These studies found that the traditionally used critical soil‐test B values were higher (0.5 µg/g) than needed to achieve optimum yield. Even though this newly established critical B value is lower, about 50% of the soils in the region are too low in B to produce optimum lentil yields.     

疏浚淤泥的固化试验研究

采用一种成分可调的水泥系土壤固化剂对太湖清淤工程的3种代表性淤泥质土(HH-4、HH-10、LM-2)进行了固化试验，以研究太湖淤泥固化后用于路基填筑的可行性，确定固化剂各组分的质量分数，掺入固化剂的最佳质量分数以及固化土的强度变化特性。结果表明：当固化剂质量分数为6%时，3种固化土均能满足路堤填料的规范要求，但加固HH-10土样时，需要提高固化剂中A、D、F组分的质量分数。由于土样颗粒级配和化学成分的不同，HH-4固化土具有较高的早期强度，LM-2固化土具有较高的后期强度。疏浚淤泥固化并用于路基填筑，避免了淤泥的长期占地堆放，既减少了环境污染，又保护了土地资源，经济和社会效益显著。