黄河平渡关段全新世古洪水滞流沉积物研究

通过对黄河中游晋陕峡谷段的深入调查研究,在山西省大宁县平渡关基岩峡谷河段左岸沟口岩棚内发现了全新世古洪水滞流沉积层剖面。根据野外宏观特征及沉积环境,鉴别出平渡关(PDG)剖面夹有4层古洪水滞流沉积物。结合粒度成分、磁化率、烧失量、CaCO³含量等室内分析测定结果,确定为河流悬移质和跃移质在高水位滞流环境当中的沉积物,是典型的古洪水滞流沉积物。不同层次沉积物是不同古洪水事件的客观记录,既有细沙质粉沙,也有细沙或者中沙,反映出其物质来源的不同或者水动力大小的差异。粒度自然分布频率曲线为正偏和极正偏,主峰高且尖锐,表明其分选良好,其粒度概率累积分布曲线为典型的两段式。沉积物磁化率和烧失量均低于全新世风成黄土和古土壤,CaCO³含量介于古土壤和黄土之间,说明在黄河晋陕峡谷段,洪水所携带的悬移质泥沙是流域内黄土区和风沙区水土流失物质的混合物。     

黄河柳林段全新世特大洪水水文学研究

通过野外对黄河晋陕峡谷段的调查研究,在柳林段两河口村三川河支流沟口内发现了疑似全新世古洪水滞流沉积物剖面。将采集的沉积学样品在实验室进行磁化率、烧失量、碳酸钙和粒度成分的测试分析可知,它们是黄河悬移质泥沙在高水位滞流环境下的沉积物。本文采用古水文学方法恢复了洪峰水位,采用比降-面积法水文模型推算出其洪峰流量介于48190~52259 m3s-1之间,通过与晋陕峡谷其他地点的结果对比,证明采用古洪水SWD厚度与含沙量关系法恢复洪峰水位、推求出的洪峰流量数据比较可靠。并且根据2012年大洪水洪痕指示的洪峰水位,采用同样的水文参数和方法,恢复其洪峰流量,其结果与实测数据误差较小,也表明该断面古洪水洪峰流量的恢复结果是可靠的。该研究成果丰富了黄河流域古洪水水文学研究的资料,对于黄河晋陕峡谷水资源开发、防洪减灾具有重要的科学意义。     

黄河柳林滩段全新世古洪水滞流沉积物物源研究

通过对黄河中游进行古洪水沉积学研究和水文学研究,为超长尺度水文学提供数据基础。对黄河中游晋陕峡谷段进行详细的考察,在黄河窟野河口右侧柳林滩附近发现3层全新世古洪水滞流沉积物(SWD)。光释光(OSL)测年结果表明,这一期3次古洪水事件分别发生在11 800~11 000aB.P.,10 800~10 200a B.P.,10 600~9 600aB.P.。通过对样品进行磁化率、烧失量、粒度成分、化学元素和扫描电镜的试验分析,确定其为河流悬移质泥沙在高水位滞流环境下的产物,是典型的古洪水滞流沉积物。其中,古洪水SWD的磁化率和烧失量较古土壤低,说明其是新鲜的滞流沉积物,未受到风化成壤作用的影响。3层古洪水SWD的自然分布频率曲线都呈现单峰,峰态尖锐,为极正偏态,说明其分选性好。扫描电镜的分析表明,3层SWD属于河流沙,偏关县L0属于典型的黄土—风积粉砂。不同层次的沉积物记录了不同期次的古洪水事件,反映出其水动力大小的不同或物质来源的差异。结合粒度分析和化学元素的结果,确定古洪水SWD2、SWD3与现代洪水SWD均为细沙质粉沙,化学成分相同,表明是黄河主流大洪水悬移质沉积形成。古洪水SWD1为中沙,与SWD2、SWD3在常量元素和重金属元素含量上有显著差异,而与前人在毛乌素沙漠地区所进行的粒度和元素分析结果接近,说明本层古洪水SWD是支流窟野河流域暴雨洪水从毛乌素沙漠地区侵蚀搬运而沉积下来的物质。该研究成果为今后准确鉴别古洪水SWD及来源判断提供参考借鉴。     

汉江与渭河大洪水滞流沉积物性质对比分析

通过广泛野外考察,在汉江上游和渭河干支流发现多次现代大洪水滞流沉积物(SWD),进行样品采集和粒度成分、磁化率特征对比分析。结果表明:汉江上游与渭河大洪水SWD的磁化率都很低,在(20～60)×10-8 m3/kg之间。这与渭河流域马兰黄土L1的磁化率相当。这也正是那些未受到风化成壤作用影响的新鲜沉积物的基本特征。汉江上游与渭河大洪水SWD粒度成分均以粉沙为主,沙级颗粒含量次之,粘土成分含量最少。它们主要是河流洪水悬移质和跃移质成分在高水位滞流环境当中的沉积物。与渭河相比,汉江上游大洪水SWD粒度成分更粗,沙级颗粒成分含量略多。汉江上游大洪水SWD性质主要是粉沙质亚沙土和沙质粉沙土。渭河大洪水SWD性质则主要是粉沙土、沙质粉沙土和粘土质粉沙土。这是因为汉江上游穿行于秦岭和巴山基岩山地之间,羽毛状分布的支流水系比降大,河流搬运动力强,在暴雨洪水期间,不断地向干流输入粗颗粒泥沙。而渭河流域为黄土高原,河流泥沙主要来源于粉沙质的黄土层和地表土壤。该研究成果对汉江上游和渭河流域防洪减灾和水土流失防治具有重要的科学意义。     

渭河下游全新世古洪水滞流沉积物研究

通过广泛的野外考察,在渭河下游发现了全新世古洪水滞流沉积物,对其进行了深入观察、地层划分和系统采样。在实验室内进行磁化率、烧失量、碳酸钙和粒度成分等多指标的分析测试。结果表明,这些古洪水沉积物以细粉沙为主,性质为粉沙质亚黏土,致密坚硬,具有水平或波状层理,与覆盖在河流阶地面的风成黄土和古土壤有着显著的区别。通过OSL测年断代,发现它们与渭河上游固川镇剖面的古洪水SWD为同一期特大洪水的沉积物。这表明渭河流域在3200—3000aBP发生了一组3次特大洪水事件。这个时期正是全新世大暖期结束之际,也就是中国历史上商代末期。渭河流域特大洪水事件的发生与全球性气候恶化转折密切相关。     

泾河下游全新世古洪水滞流沉积物研究

通过对泾河流域广泛的野外考察,在泾河下游高陵县段发现了典型的全新世古洪水滞流沉积剖面,系统地进行采集样品和粒度成分、磁化率、烧失量、吸湿水含量等多指标分析。从沉积学角度将古洪水滞流沉积物与全新世风成黄土和土壤进行对比,证明了该剖面所夹古洪水滞流沉积物的性质为细砂质粉砂,属于河流洪水悬移质泥砂沉积物。根据地层结构及与流域内其它剖面的对比,结合OSL测年数据,确定泾河在全新世中期4200~4000 a B.P.发生了第1期古洪水事件,在全新世晚期3200~2800 a B.P.发生了第2期洪水事件。这些古洪水事件都发生在全球性气候突变转折时期,表明在这些时期气候极端恶化,变率增大,洪水和干旱事件皆有发生。该研究对于泾河防洪减灾、水资源开发利用,对于揭示水文系统对于全球变化的响应规律,具有重要的科学意义。     

长江宜都段全新世古洪水滞流沉积物研究

对长江中游地区进行详细的野外调查,在长江宜都段剖面发现3层古洪水滞流沉积物(SWD).综合全新世地层关系对比、文化遗物和光释光(OSL)技术测年结果,确定这三期古洪水事件分别发生在950～850 a B.P.,750～650 a B.P.,550～350 a B.P..结合野外宏观特征和粒度成分以及地球化学元素的测定分析,结果表明:现代土壤、近代黄土和古土壤的沉积物性质是粘土质粉沙,而古洪水SWD是沙质粉沙.古洪水SWD的峰值集中,分选性好,中值粒径和平均粒径偏粗且沙级颗粒含量偏大.古洪水SWD的Fe2O3、MnO、Rb/Sr和残积指数明显偏低,这与其粘粒含量少有关;而Na2O、CaO、Sr含量和残积指数偏高,这与其很少受到风化成壤影响,且沙粒含量高有关.     

汉江上游黄坪村段古洪水滞流沉积物研究及意义

古洪水滞流沉积物是古洪水事件的直接产物,蕴含古洪水的重要信息。以汉江上游郧县黄坪村剖面为研究对象,对其粒度、磁化率、烧失量及碳酸钙等进行了分析。结果表明:古洪水滞流沉积物的粒度具有粉砂含量砂级颗粒黏粒含量的特征;磁化率值在78×10-8~81.2×10-8m3kg-1之间;烧失量值较低为23.9~27.7 g kg-1,碳酸钙为2.72%~3.20%。其宏观特征和上述参数与黄土和古土壤有明显的区别。沉积物的粒度组成特征及粒度参数、磁化率、烧失量、碳酸钙等对于鉴别古洪水滞流沉积层有重要的参考价值。     

渭河流域全新世古洪水滞流沉积物地球化学特征

对渭河流域野外实地详细调查,在渭河中游发现了具有典型古洪水滞流沉积物(SWD)的全新世黄土-古土壤沉积剖面。根据地层学对比和OSL测年,确定渭河流域在3200-2800aB.P.发生了特大古洪水事件。对沉积物地球化学特征分析表明,SWD为典型的古洪水滞流沉积物,各化学元素和氧化物的变异系数大,元素数据分布较为分散;Fe2O3、Al2O3、Ba、Cr、Cu、V、Rb含量高于S0和L0,SiO2、Zr含量低于S0和L0;化学元素粒度效应表明,SWD粒径小、粘粒强,是在滞流环境的水动力条件下沉积而成;通过气候指标Rb/Sr和Ba/Sr分析,认为古洪水滞流沉积物(SWD)记录的3200-2800aB.P.的特大古洪水事件,是在全新世大暖期结束之际,因夏季风减弱、气候系统不稳定、降水变率较大所导致的。     

淮河上游全新世黄土-古土壤序列元素地球化学特性研究

在野外考察研究的基础上,对河南禹州全新世风成黄土-古土壤剖面系统采样,利用X-荧光光谱仪测定了常量元素和微量元素的含量及其变化,并与磁化率曲线、粒度变化曲线对比分析发现:常量元素氧化物比值钾钠比、残积系数和以Rb为代表的微量元素含量等随剖面层次呈规律性变化,即在古土壤层(S0)中含量最高,表土层(MS)中次之,在黄土层(L1、Lt、L0)中最低。硅铝率和Sr的含量表现出相反的变化规律。表明在全新世古土壤层和表土层形成时期,气候温暖湿润,成壤作用和次生粘化作用较强;在黄土堆积时期,气候比较干旱,沙尘暴频繁,成壤作用微弱。这些化学参数与磁化率曲线可以进行对比,表明成土过程中元素的迁移变化受全新世以来气候变化和成壤环境变化的控制。与黄土高原腹地的洛川剖面相比,淮河上游禹州剖面中绝大多数常量元素的含量较高,而绝大多数微量元素的含量偏低,磁化率也显著偏低,绝对值差别很大,粒度组成当中细沙成分含量很高,这说明淮河上游黄土物质来源与黄土高原地区明显不同。联系全新世时期黄河频繁泛滥、改道、沉积与黄淮平原盛行东北风形成流沙地的事实,认为淮河上游的黄土是黄河泛滥沉积物质经过风沙活动改造,由东北风力系统搬运而来的近源粉尘堆积,再经过就地风化或者成土改造而形成。     

汉江上游郧县庹家洲河段全新世古洪水研究

通过对汉江上游的实地调查,在湖北省郧县庹家洲段发现了含有4期古洪水滞流沉积层的典型全新世黄土-古土壤剖面。结合野外观察和室内粒度、磁化率和烧失量等指标的测定,判定为典型的古洪水滞流沉积物(SWD),记录了汉江上游4期古洪水事件。通过地层对比、OSL断代等方法,确定这4期古洪水事件分别发生在12 600-12 400aB.P.,4 200-4 000aB.P.,3 200-2 800aB.P.和东汉时期1 900-1 800aB.P.。然后利用沉积学和水文学原理恢复了洪峰水位,并选择合适的水文参数,采用比降法水文模型推算出了这4期特大古洪水洪峰流量。同时,根据相同的方法,推算了剖面附近1983,2005和2010年洪痕对应的洪峰流量,与实测流量相比,误差在1.99%~4.21%,说明计算古洪水洪峰流量的水文参数选择与计算结果是合理的,而且古洪水洪峰流量计算结果也符合洪峰流量与流域面积关系。     

汉江上游郧县辽瓦店全新世古洪水研究

以汉江上游谷地郧县辽瓦店全新世古洪水滞流沉积剖面为研究对象,对其进行了洪水沉积学和水文学研究,并对其粒度组成、磁化率、烧矢量等理化性质进行了测量。结果证明,辽瓦店(LWD)剖面中夹有典型的古洪水滞流沉积物(SWD),它记录了一次特大洪水事件。利用地层学方法确定该次洪水事件发生在AD100-300之间(东汉-魏晋时代之间)。根据沉积学和水文学原理恢复了古洪水的洪峰水位在159.80m,以此计算出洪峰流量为65 420m3/s。根据2011年9月19日汉江洪水洪峰水位痕迹高程并利用相同方法反推洪水流量,所获流量数据与实测数据误差小于1%。     

Effects of combined sewer overflows and storm water drains on metal bioavailability in small urban streams (Prague metropolitan area,Czech Republic)

Purpose

The aims of the study were to evaluate the effect of combined sewer overflows (CSO) and storm water drains (SWD) on metal bioavailability in small urban streams in Prague and to evaluate levels of metals in water, sediment, and macroinvertebrates. The following working hypotheses were adopted: (a) sites dominantly affected by SWD are less polluted by metals, and (b) sites dominantly affected by SWD have higher bioavailability of metals.

Materials and methods

Physical and chemical parameters (pH, conductivity, NO₃-N, NH₄-N, COD, alkalinity, and water hardness) and concentrations of the metals Cu, Zn, Pb, Ni, and Cr were determined in samples of water and sediment at five to six sites on four target streams—Záti?ský Creek, Ko?íkovský Creek, Boti? Creek, and Rokytka Creek—three to five times per year during the period 2002–2004. The sites from all studied creeks were categorized into five groups according to the prevailing type of urban drainage impact. Macroinvertebrates were sampled and analyzed for metals at each site for a period of 1 month. The concentration patterns of metals were interpreted by partition coefficient (Kd), hazard quotient (HQ), cumulative criterion unit (CCU), and biota sediment accumulation factor (BSAF).

Results and discussion

Concentrations of metals in water as well as in sediment at sites receiving water from SWD were lower than at sites where creeks receive water from CSO, except for Pb. Concentrations of Cu, Zn, and Pb in sediment were higher at sites affected by CSO. Concentrations of metals in aquatic macroinvertebrates, expressed as BSAF, indicated higher values at sites affected by SWD. Frequencies of high BSAF (>1) were lower in CSO compared to SWD. This finding was explained by (a) a decrease of pH on SWD sites compared to the increase of pH on CSO sites during rain events, (b) a greater resuspension of sediment at SWD sites during rain events, and (c) an abundance of organic matter in CSO available for sorption of metals and a corresponding reduction of their bioavailability.

Conclusions

In the study area, the type of urban drainage affects the bioavailability of metals—while SWD increase metal bioavailability, CSO cause its decrease. The sediments in SWD sites do not indicate risk to the benthic community according to the applied environmental quality standards. Water and sediment in creeks affected by SWD are less polluted by metals. Both working hypotheses were therefore supported.

     

Water-deficit impact on fatty acid and essential oil composition and antioxidant activities of cumin (Cuminum cyminum L.) aerial parts

This study is designed to examine the effect of water deficit on growth, fatty acid and essential oil composition, and antioxidant activities of Cuminum cyminum aerial part extracts. Plants were treated with different levels of water deficit: control (C), moderate water deficit (MWD), and severe water deficit (SWD). Plant growth (height, fresh and dry matter weights) as well as yield components were significantly increased under moderate water deficit and conversely reduced at severe level. Total fatty acid content decreased significantly with severity of constraint. Drought reduced considerably the proportions of major fatty acids and the unsaturated to saturated fatty acid ratio. The essential oil yield was 0.14% (based on the dry weight); it increased by 2.21-fold at MWD but decreased by 42.8% under SWD in comparison to the control. Drought results in the modification of the essential oil chemotype from 1-phenyl-1-butanol to 1-phenyl-1,2-ethanediol. Antioxidant activities of the acetone extracts were determined by two complementary test systems, namely, DPPH and β-carotene/linoleic acid. The highest activity was exhibited by moderately stressed plants and was reduced significantly under SWD. In control plants, the total phenolic amount was 10.23 mg GAE/g DW, which increased by 1.5-fold under MWD and decreased by 42% under SWD.     

华北平原灌溉农田的土壤水量平衡和水分利用效率

华北平原农业面临的主要问题是水资源短缺,地下水位持续下降。通过一维土壤水量平衡模型模拟了华北平原不同灌溉方式下农田耗水量和土壤水分深层渗漏的变化,并分析了作物的产量和水分利用效率。结果显示在正常的灌溉条件下,冬小麦季地下水的采补差额超过了200mm,某生育期一定程度的水分亏缺(返青期、拔节期或灌浆期)能明显减少冬小麦的耗水量,但没有明显减少作物的产量。因此,在一定程度上减少灌溉是可行的,但仍不能达到地下水资源的采补平衡。从长远来看,华北平原维持可持续的地下水灌溉开采,应减少冬小麦的种植面积、增加低耗水经济作物的比例。     

双季稻减排增收的水氮优化管理模式筛选

为筛选出"低投入-低排放-高收益"的稻田水氮管理模式，该研究以汉江平原双季稻为研究对象，设计4种氮肥管理方式：1）普通尿素；2）树脂包膜控释尿素；3）普通尿素减氮20%；4）控释尿素减氮20%，和2种水分管理方式：1）常规灌溉；2）薄浅湿晒节水灌溉。采用静态箱-气相色谱法测定甲烷（CH4）和氧化亚氮（N2O）的排放量，应用生命周期法（life cycle assessment, LCA）计算水稻生产碳足迹，基于成本收益核算分析单位水稻产量和单位净收益的碳排放强度。结果表明，控释尿素能有效提高双季稻产量，节水灌溉和减氮20%能节约投入成本，对双季稻产量存在一定负效应，但差异不显著。相比普通尿素和常规灌溉，不同水氮优化处理可不同程度降低水稻生产的碳足迹和排放强度，并有助于提高收益。其中节水灌溉搭配控释尿素减氮的综合减排效果最好，早、晚稻总减排量分别为45.8%和42.5%（P<0.05），同时全年净利润最高，达14 340元/hm2。因此，节水灌溉、控释尿素同时减氮20%的组合技术可实现稻田节本减排增收。     

A mid–late Holocene flood record from the alluvial reach of the Mahi River, Western India

Flooding of rivers in India is linked with the peak monsoons. Investigating the linkage between monsoonal patterns and flood history of various rivers is therefore of fundamental importance in the Indian context. In the present study, the slackwater deposits in the alluvial reaches of the Mahi river basin, western India have been documented. These occur in the ravines incised during the early Holocene on an alluvial surface comprising sediments of Late Pleistocene age. The slackwater deposits occur at elevations up to 20 m from the present river level and extend to about 500 m inland. The carbonate rich sediments forming the ravine cliffs have provided bank stability and the dissections in the ravines have helped in the accumulation of slackwater deposits due to backflooding of the floodwater from the main channel. Recent gullies have incised the sediments and exposed deposits related to major flood events. The best exposures of slackwater deposits have been observed at Dodka. The sediment succession of the slackwater deposits is dominated by bedsets and laminasets of silt and sand separated by colluvial sediments. Four events of flood deposition occurred during the mid to late Holocene. Two units of slackwater deposits, SWD 2 and 4 have been dated by IRSL at 4.6 ± 1 ka and 1.7 ± 0.5 ka. The stratigraphy of these deposits indicates that the first two slackwater units (SWD1 and SWD2) have resulted due to flooding in a regime of intense monsoon. The other two units, however, represent extreme high magnitude floods in a period of low average precipitation.