沸石覆盖层控制水库底泥氮磷释放的影响因素

用模拟实验方法研究了天然沸石活性覆盖层控制底泥氮磷释放的影响因素（如温度、天然沸石厚度以及pH值等）,结果表明：1）厌氧状态下,天然沸石覆盖层可以有效地控制总氮和总磷的释放;2）温度越高,底泥总磷的释放量越大,沸石层抑制底泥总磷释放的效果越差;3）天然沸石层厚度与底泥总磷释放相关性不明显;4）温度的高低及沸石层的厚度对沸石层抑制底泥总氮释放的影响不大;5）对上覆水进行酸碱性的调节,有利于提高沸石层对总磷、总氮的控制效果,酸性条件下吸附效果更佳.     

施用秦淮河底泥对田间土壤及小麦生长的影响

[目的]合理利用秦淮河河底淤泥。[方法]将秦淮河底泥与农田土按照4∶03、∶12、∶21、∶3、0∶4混匀进行发芽率试验和盆栽试验,研究施用秦淮河底泥对田间土壤及小麦生长的影响。[结果]加入少量的底泥能够提高小麦种子的发芽率;随着底泥用量的增加,发芽率呈下降趋势,芽高呈增长的趋势。当农田土与底泥比例为3∶1时,小麦的各项生长指标最好,但随着底泥用量的增加,小麦长势随之下降。秦淮河疏浚底泥中的有机质、全磷、有效磷和氮含量明显高于农田土。随着底泥用量的增加,盆栽后土壤中的总氮、全磷和有效磷含量增加。[结论]在农田土中适当地添加秦淮河疏浚底泥,可在一定程度上促进小麦的生长。     

西溪湿地底泥重金属竖向分布规律

利用特制的底泥取样器从杭州西溪湿地钻取通长的底泥试样,对不同深度底泥中重金属Cu、Pb、Zn进行测试,并分析重金属在表层底泥、底泥孔隙水及上覆水中的含量及相关性,用地累积指数法对底泥的污染程度进行评价.结果表明:该湿地0.6 m深度内的底泥为轻度-中度污染,埋深大于0.6 m的底泥没有被污染或者污染程度较轻;重金属在表层底泥孔隙水中的含量显著大于其在上覆水中的含量,由于浓度梯度,底泥孔隙水中的重金属会释放到上覆水中,因此如只实施换水处理难以根除水体污染问题,疏浚受污染的底泥是更有效的治理措施.根据测试结果,0.6 m深度可作为湿地底泥疏浚的参考依据.     

Multiple microtektite horizons in upper eocene marine sediments: no evidence for mass extinctions

Microtektites have been recovered from three horizons in eight middle Eocene to middle Oligocene marine sediment sequences. Five of these occurrences are coeval and of latest Eocene age (37.5 to 38.0 million years ago); three are coeval and of early late Eocene age (38.5 to 39.5 million years ago); and three are of middle Oligocene age (31 to 32 million years ago). In addition, rare probable microtektites have been found in sediments with ages of about 36.0 to 36.5 million years. The microtektite horizon at 37.5 to 38.0 million years can be correlated with the North American tektite-strewn field, which has a fission track age (minimum) of 34 to 35 million years and a paleomagnetic age of 37.5 to 38.0 million years. There is no evidence for mass faunal extinctions at any of the microtektite horizons. Many of the distinct faunal changes that occurred in the middle Eocene to middle Oligocene can be related to the formation of the Antarctic ice sheet and the associated cooling phenomena and intensification of bottom currents that led to large-scale dissolution of calcium carbonate and erosion, which created areally extensive hiatuses in the deep-sea sediment records. The occurrence of microtektite horizons of several ages and the lack of evidence for faunal extinctions suggest that the effects of extraterrestrial bolide impacts may be unimportant in the biologic realm during middle Eocene to middle Oligocene time.     

Spatial and temporal offsets between proxy records in a sediment drift

Chronologies for Late Quaternary marine sediment records are usually based on radiocarbon ages of planktonic foraminifera. Signals carried by other sedimentary components measured in parallel can provide complementary paleoclimate information. A key premise is that microfossils and other indicators within a given sediment horizon are of equal age. We show here that haptophyte-derived alkenones isolated from Bermuda Rise drift sediments are up to 7000 years older than coexisting planktonic foraminifera. This temporal offset, which is apparently due to lateral transport of alkenones on fine-grained particles from the Nova Scotian margin, markedly influences molecular estimates of sea surface temperatures. More broadly, the observation raises questions about both the temporal and the geographic fidelity of paleoenvironmental records encoded by readily transported components of sediments.     

Sediment distribution on the mid-ocean ridges with respect to spreading of the sea floor

An abrupt change in sediment thickness between the crests and flanks of the mid-ocean ridges can be interpreted as a major discontinuity in the rates either of spreading of the sea floor or of accumulation of sediment. The preferable interpretation of the data is that the process of spreadig of the sea floor is intermittent and that the present cycle of spreading commenced around 10 million years ago. following a long period Of quiescence during which most of the observed sediments were deposited.     

太湖沉积物中重金属的垂向分布特征及迁移转化

为了解太湖沉积物中重金属污染的变化特征和迁移规律,选取太湖柱状沉积物为研究对象,测定Cd、Pb、Cu、Cr 4种重金属的总量及赋存形态,分析重金属在垂向上的分布状况及污染程度。结果表明,金属Cd、Pb、Cu、Cr的含量随着深度的增加而降低,并在1950年和1980年出现拐点,其中1980年污染最为严重;湖区分布特征表现为西北部梅梁湾、竺山湾和贡湖湾的重金属污染最为严重,湖心次之;重金属的赋存形态均以残渣态为主,Cd、Pb、Cu、Cr的残渣态分别占59.74%、81.67%、77.81%、97.56%,除残渣态外,Cd和Cu的可交换态含量较高,分别占15.81%、13.62%,而Pb的铁锰化物结合态所占比例较高,平均为11.36%。通过计算淋失比可知,重金属在上层沉积物中的迁移率较高,而下层沉积物中的重金属较稳定,迁移性较弱;分析重金属的形态迁移可知,表层沉积物中重金属的可交换态较多,由细颗粒物质等吸附直接沉淀在表层沉积物中,随着泥沙的运动逐渐向下迁移;随着沉积物中铁锰化物的积累、AVS(酸可挥发性硫化物)积累等环境条件的变化,可交换态向铁锰化物结合态、有机物及硫化物结合态转化。     

Mummified pleistocene ostracods in alaska

Preserved soft parts of ostracod specimens were recovered from beach and lagoon sediments from the Gubik Formation, of Quaternary age, at Barrow, Alaska.     

河流底泥中六价铬释放规律初步研究

[目的]研究河流底泥中Cr^6＋的释放规律。[方法]以北江底泥为研究对象,通过模拟环境备件的改变,研究了水体中各因素的改变对河流底泥样品中Cr^6＋释放量的影响。[结果]随着温度的提高,底泥样品中Cr^6＋的析出量逐渐增加。随着pH值的增大,Cr^6＋的析出量逐渐减少,当pH值大于8时,Cr^6＋的析出量有较小幅度的增加。随着NaCl溶液浓度的增加,Cr^6＋的析出量有较大幅度增加,当NaCl的浓度大于2g／L时。Cr^6＋的析出量出现下滑现象。Cr^6＋的释放量随着酸雨成分中阳离子浓度的升高而逐渐增加,随着阴离子浓度的升高,Cr^6＋的释放量达到一个峰值后逐渐减少。[结论]该研究为探讨河流底泥中Cr^6＋的二次污染问题提供了依据。     

东平湖表层沉积物中磷的吸附容量及潜在释放风险分析

利用沉积物磷吸附指数(PSI)和磷吸附饱和度(DPS)研究了东平湖表层沉积物的磷吸附容量,并讨论了沉积物中磷的潜在释放风险。结果表明,表层沉积物的磷吸附指数变化范围为30.3～45.2[mgP·(100g)-1]·(μmol·L-1)-1,表现出从湖心、湖东向湖北、湖南逐渐增大的扇形特征;而磷吸附饱和度变化范围为6.5%～24.1%,与磷吸附指数变化趋势恰好相反。磷吸附指数与沉积物中草酸铵提取的铁(FeOX)含量呈极显著正相关,与草酸铵提取的铁铝总量呈显著正相关,磷吸附饱和度与沉积物中草酸铵提取的磷(POX)含量呈显著正相关。此外,磷释放风险指数(ERI)变化范围为14.9%～67.5%,表明东平湖表层沉积物中磷释放诱发富营养化的风险处于高度风险范围。     

达里诺尔湖生物有效态重金属的形态分布及生态风险评价

以内蒙古赤峰市达里诺尔湖为研究对象,利用Tessier连续提取法,对表层沉积物及柱芯中Cu、Zn、Pb、Cd 4种重金属的形态进行了研究.基于形态及上覆水、过滤水和孔隙水中重金属的浓度,探讨了重金属在水-沉积物界面间的迁移转化规律,评价了湖泊沉积物重金属的污染状况.结果表明:达里诺尔湖的水体环境污染是以Cu、Pb和Zn为主的多金属复合污染,Pb有从上覆水向沉积物迁移的显著趋势,Cu有从孔隙水向上覆水迁移的微弱趋势;沉积物中4种重金属生物有效态主导形态因其元素地球化学性质的差异性而存在差异,表层沉积物中Cu、Pb、Zn和Cd生物有效态的主导形态分别为有机硫化物结合态、碳酸盐结合态、铁锰氧化物结合态和碳酸盐结合态,分别占总生物有效态的61.64％、60.72％、71.50％和53.59％;水平方向上,总生物有效态重金属含量表现出从南西向北东逐渐减小的趋势;沉积柱芯中4种金属有效态之和波动变化,但在40 cm以下均随深度的增大呈现增加趋势.沉积物中4种金属的综合污染指数(RI)为41.18～155.64,空间分布上表现从南西向北东逐渐减小的趋势.达里诺尔湖尚处于轻微生态危害,但南部湖区重金属污染应引起重视.     

改性沸石改良底泥对土壤中微生物生物量碳及酶活性的影响

为了减小底泥中重金属的活性,实现底泥回田再利用,以洞庭湖重金属污染底泥为实验对象,探究以Na Cl和壳聚糖改性沸石改良的底泥对土壤中微生物生物量碳和生物酶(脲酶和脱氢酶)活性的影响。实验结果表明,两种沸石改良底泥添加后,土壤中水溶态金属浓度减小。Na Cl改性沸石处理组(沸石/底泥质量比3/7)和壳聚糖改性沸石处理组(沸石/底泥质量比1/9、3/7和6/4)中微生物量碳含量增加,微生物量C/N比最大提高至原来的2.8倍。壳聚糖改性沸石添加底泥对土壤生物酶影响较Na Cl改性沸石明显,土壤脲酶和脱氢酶活性随壳聚糖改性沸石投加量的增加而明显提升,壳聚糖改性沸石最大投加量组中(6/4)脲酶和脱氢酶活性较对照组分别增大1.1、1.6倍。     

包头南海湖沉积物中AVS-SEM的分布规律研究

酸可挥发性硫化物（AVS）与同步提取的重金属（SEM）之间的比例关系是控制缺氧性沉积物中重金属生物有效性及毒性的主要因素。采用野外采样及室内测定方法，对包头市南海湖表层沉积物和柱状沉积物的AVS、SEM、[SEM]/[AVS]进行了作图和分析比较。结果表明，黄河补水的污染、历史及现有生活污水排放、城市径流以及游船排放均提高了南海湖的重金属含量，并形成重金属含量高值区。水深的增加和现有生活污水的排放以及挺水植物的影响形成南海湖下游区域AVS明显高于上游。南海湖AVS垂向分布出现极大值下移和多个极大值的现象，不同于一般淡水湖泊。南海湖表层和垂向沉积物中AVS含量均远高于SEM含量，初步评价得出南海湖沉积物重金属是安全的。     

Purines and pyrimidines in sediments from lake erie

Quantitative analyses of purines and pyrimidines in sequential sections of cores from the central and eastern basins of Lake Erie show steeply increasing concentrations in the youngest sediments. This may be related to increased loading of nutrients and recent cultural eutrophication of the lake. The purine and pyrimidine distributions suggest the operation of a specific degradative process for uracil at an extremely early stage in, or prior to, sediment formation.     

Ancient ice islands in salt lakes of the central andes

Massive blocks of freshwater ice and frozen sediments protrude from shallow, saline lakes in the Andes of southwestern Bolivia and northeastern Chile. These ice islands range up to 1.5 kilometers long, stand up to 7 meters above the water surface, and may extend out tens of meters and more beneath the unfrozen lake sediments. The upper surfaces of the islands are covered with dry white sediments, mostly aragonite or calcite. The ice blocks may have formed by freezing of the fresh pore water of lake sediments during the "little ice age." The largest blocks are melting rapidly because of possibly recent increases in geothermal heat flux through the lake bottom and undercutting by warm saline lake water during the summer.     

Deep sea drilling: age and composition of an atlantic basaltic intrusion

The fission track age of a basalt recovered from beneath Campanian sediments on the lower western flank of the Mid-Atlantic Ridge is (15.9 +/- 1.6) x 10(6) years. The major element composition of a glassy margin of the basalt is similar to that of oceanic tholeiites except for a markedly higher potassium concentration.     

红树林表层沉积物老化过程中铅的赋存形态

采用3种不同类型的东寨港红树林表层沉积物，通过室内沉积物老化培养试验和改进的BCR提取法，分析了3种沉积物中铅的各赋存形态随不同老化时间与可溶性外源污染铅浓度变化的特征。结果表明，老化时间对红树林表层沉积物可还原态铅的影响不显著，对酸可提取态铅、可氧化态和残渣态铅的影响会因沉积物类型的不同而呈差异显著。随老化时间延长，沉积物A中酸可提取态铅含量先增加再降低（除1 000 mg·kg?1）、可氧化态铅含量在0，25，250 mg·kg?1时增加；沉积物B中酸可提取态铅含量增加、残渣态铅含量降低（除500 mg·kg?1）；沉积物C中残渣态铅含量在0，25，250，500 mg·kg?1时增加。此外，当老化时间为30，60，120 d时，添加较低外源铅浓度（25，250，500 mg·kg?1）的沉积A和B中，酸可提取态铅和可还原态铅占总量的比例增加，残渣态铅占比减少；在沉积物C中，老化30 d后，随浓度增加，酸可提取态铅含量降低，残渣态铅含量增加，老化60 d和120 d后，可氧化态铅含量的比例呈现增加趋势。可见，外源铅进入沉积物经老化后的主要赋存形态是残渣态和可还原态，外源铅初始浓度会影响铅赋存形态达到稳定的时间，并且铅的赋存形态受到沉积理化特征的影响。结果揭示了红树林沉积物中铅的环境化学行为，可为红树林湿地修复重金属污染提供参考依据。     

不同初始磷浓度下湖泊沉积物对磷吸附的动力学特征

通过选取自然湖泊梅梁湾和人工湖泊华家池2个湖泊的沉积物,研究不同初始磷浓度(C0)对沉积物磷吸附动力学的影响以及2种沉积物磷吸附动力学的类型.结果表明:1)梅梁湾沉积物对磷的吸附量大,吸附过程明显分为快、慢吸附2个阶段,华家池沉积物对磷的吸附过程较慢且吸附量小;2)梅梁湾与华家池沉积物零净吸附磷浓度(EPC0)分别为0.03和0.42mg爛L-1,当C0相似文献   

扰动强化河道底泥对磷持留能力的研究

以城市河道上覆水和底泥为材料,研究了扰动对底泥持留磷能力的强化作用,并分析了强化机理.结果表明,底泥扰动促进了上覆水中磷向底泥中迁移.与对照试验相比,溶解性磷酸盐(DIP)和总磷(TP)平衡浓度分别降低了73.02%和42.39%;与原底泥相比,扰动试验底泥中溶解性磷酸盐(DIP)的释放量降低了173.77 mg·kg-1,对照试验底泥中DIP的释放量基本保持一致.另外,底泥扰动后,钙结合态磷(Ca-P)含量显著增加,并接近总磷的增加量;而对照试验底泥中,总磷的净增加量比较均匀地分配到弱吸附态磷(NH4Cl-P)、铁结合态磷(Fe-P)、钙结合态磷(Ca-P)中.     

小城镇河流沉积物无机氮迁移循环研究

通过对河流柱状沉积物在通气下和厌气下进行避光短期静置模拟培养试验，研究了小城镇河流底泥-上覆水体系无机氮的迁移特征。结果表明，沉积物有机质降解对NH4的迁移有很大影响，通气和厌气下NH4的迁移均是向上覆水方向，NO3的迁移均是向沉积物方向，由于通气条件和静水环境引起的沉积物无机氮硝化作用和反硝化作用是影响沉积物一水界面体系氮迁移的最重要因素。