Dynamics of soil organic carbon following land-use change: insights from stable C-isotope analysis in black soil of Northeast China

Intensive soil tillage is a significant factor in soil organic matter decline in cultivated soils. Both cultivation abandonment and foregoing tillage have been encouraged in the past 30 years to reduce greenhouse gas emissions and soil erosion. However, the dynamic processes of soil organic carbon (SOC) in areas of either continuous cultivation or abandonment remain unclear and inconsistent. Our aims were to assess and model the dynamic processes of SOC under continuous tillage and after cultivation abandonment in the black soil of Northeast China. Soil profiles were collected of cultivated or abandoned land with cultivation history of 0–100 years. An isotope mass balance equation was used to calculate the proportion of SOC derived from corn debris (C₄) and from natural vegetation (C₃) to deduce the dynamic process. Approximately 40% of SOC in the natural surface soil (0–10 cm) was eroded in the first 5 years of cultivation, increasing to about 75% within 40 years, before a slow recovery. C₄ above 30 cm soil depth increased by 4.5%–5% or 0.11–0.12 g·kg^?1 on average per year under continuous cultivation, while it decreased by approximately 0.34% annually in the surface soil after cultivation abandonment. The increase in the percentage of C₄ was fitted to a linear equation with given intercepts in the upper 30 cm of soil in cultivated land. A significant relationship between the change of C₄ and time was found only in the surface soil after abandonment of cultivation. These results demonstrate the loss and accumulation of corn-derived SOC in surface black soil of Northeast China under continuous tillage or cultivation abandonment.     

庐山“星子变质核杂岩”中海会花岗岩的锆石UPb年龄及大地构造意义

单颗锆石ＵＰｂ 年龄测定结果显示,星子变质核杂岩中的海会花岗岩岩体的形成年龄为１２２ Ｍａ～１３０ Ｍａ,表明星子变质核杂岩形成于中生代,这与当时华南岩石圈的伸展构造环境一致。花岗岩中１ ７２３±３４８ Ｍａ的残留锆石年代信息显示,海会花岗岩是由古元古代地壳重熔形成的。扬子古陆南缘确实存在古元古代的基底     

皖东黄栗树—破凉亭断裂带北段构造岩显微—超显微变形特征及地质意义

本文就郯庐断裂带南段东部的黄栗树—破凉亭断裂带内构造岩,特别是中深层次的韧性剪切带中的糜棱岩进行了细致的野外考察、采样,在室内显微构造研究的基础上,选择有代表性的样品和视域进行透射电镜制样观察,在对各超显微构造特征分析归纳的基础上,讨论了构造岩的塑性变形特征,并对构造岩的应变参数(最大差异应力和应变速率)进行了计算,从显微—超显微构造角度仔细研究该断裂带内典型的构造岩的变形特征,初步判明断裂带的性质和运动发展历史,证实了该断裂带是形成在较深构造层次的一条以韧性变形为主的脆—韧性剪切带,应变形式为简单剪切。应变参数的计算结果表明,自东向西从前陆褶皱冲断带根部到后缘带,构造岩中石英的位错密度逐渐减小,最大差异应力逐渐降低。     

Permeability and sedimentation characteristics of pleistocene fluvio-glacial deposits in the Dadu river valley, Southwest China

There exist many fluvio-glacial deposits in the valley of Dadu River,Southwest China,which dates back to the Pleistocene.As some of the deposits are located within the seasonal water fluctuation zone of reservoirs,the seepage of groundwater acts as one of the key factors influencing their stability.Investigation into the sediment properties and permeability is,therefore,crucial for evaluating the sediment stability.In this study,in-situ permeability and sieving tests have been carried out to determine grain size distribution,correlations of permeability and hydraulic gradients,and relations between permeability and sedimentation properties.Test results indicate that the deposits are composed mostly of sands,gravels,cobbles and boulders,and the percentage of fines is less than 5%.The sediments have high densities,low porosities and natural moisture contents.At low hydraulic gradients,the seepage velocity obeys the Darcy’s law,while a nonDarcy permeability is observed with hydraulic gradient exceeding a certain value(about 0.5-0.7).The linear permeability coefficient ranges from 0.003 to 0.009 cm/s.Seepage failure occurs above a threshold between 1.1 and 1.5.The test data fit well with the non-linear permeability equations suggested by Forchheimer and Izbash.The non-Darcy permeability proves to be in accordance with the seepage equation suggested by Izbash with the power ’m’ of about 0.6-0.7.The characteristic grain sizes of the studied deposits are found in a narrow range between 0.024 and 0.031 mm,which is much lower than the effective grain size(d 10).     

Polychlorinated biphenyl (PCB) concentrations and congener composition in masu salmon from Japan: A study of all 209 PCB congeners by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS)

We collected two subspecies of masu salmon: Oncorhynchus masou masou from four localities (southern Sea of Japan northward to Hokkaido) and O. masou ishikawae from upstream from Ise Bay close to a heavy industrial area. All 209 PCB congeners were analyzed using HRGC/HRMS. PCA ordination of congener concentrations divided data into three groups: (i) ssp. masou from Hokkaido, (ii) ssp. masou from the other regions and (iii) ssp. ishikawae. The highest ∑ PCB concentration (40.39 ng/wet wt) was in ssp. ishikawae followed by ssp. masou from southern waters; however the TEQ_{dioxin-like PCBs} was highest in ssp. masou from southern water (1.96 pg-TEQ_{dioxin-like PCBs}/g wet wt.) due to the high proportion of congener #126 in its complement (#126 has the highest toxic equivalency factor among congeners). There is likely a contamination source offshore in the southern Sea of Japan and/or along the migratory route of ssp. masou.     

Trace element concentrations in barramundi (Lates calcarifer) collected along the coast of Vietnam

We determined concentrations of 23 trace elements (TEs), and stable carbon and nitrogen isotope (δ¹³C and δ¹⁵N) signatures in barramundi (Lates calcarifer) specimens collected along the coast of Vietnam in the Northern (NCZ), Central (CCZ) and Southern (SCZ) zones in the period 2007–2010. A combination of δ¹³C and δ¹⁵N signatures provided insight into ontogenetic shifts in barramundi foraging choices. There were clear zone-dependent differences in Mn, As, Sr and Tl concentrations; levels of Tl were highest in the NCZ, As in the CCZ, and Mn and Sr in the SCZ. Lowest concentrations of Rb occurred in the NCZ, Bi was lowest in the CCZ, and Cd and Cs were lowest in the SCZ. δ¹⁵N values significantly increased with increasing Zn, Se, Sn and Cs. Concentrations of TEs in barramundi from Vietnam were below worldwide guidelines for human consumption.     

青海省玛沁县5.0级地震的烈度分布及其构造环境

在玛沁县５．０级地震的宏观调查的基础上,分析了烈度和断层与震害间的相互依存关系,阐述了发震构造（库玛断裂带）的新活动特征,并对地震形成的区域构造环境及地震发展趋势进行探讨。     

开拓矿业、发展地学的一位先知先觉先行者——缅怀侯德封先生

时值侯德封先生百年华诞之际,仅以此文缅怀他老人家在中国开拓矿业及发展地学两个方面所做出的重大贡献。     

南方涛动极端位相对北半球降水的影响及其周期性讨论

采用一种对应于南方涛动的矢量合成分析方法,描述了对应于南方涛动（高、低位相）事件的区域降水的特征。并就南方涛动对于北半球陆面降水影响的周期性进行了检测。结果发现：南方涛动对区域降水的影响有明显的谐波形态,谐波周期在２ａ以上。这解释了南方涛动高低位相降水出现极端异常较少,而降水极端异常出现在南方涛动的高低位相年附近的几率却相当大的统计事实,３６月波是描述这种降水变化周期的较合理的型态。由于本方法是     

基于多元数据的地基GNSS水汽观测对比分析

在“超大城市垂直综合气象观测技术研究及实验”中,利用欧洲中期天气预报中心（ECMWF）的ERA Interim再分析数据集,对2018年北京观象台的地基导航卫星气象观测（GNSS/MET）、探空和微波辐射计观测的水汽总量（PWV）进行了对比分析,结果表明,3种观测和ECMWF模式分析具有较好的相关性,可以较好地监测北京水汽的变化。与ECMWF模式对比,GNSS/MET、探空和微波辐射计的偏差分别为0.54mm、1.94mm、-0.65mm,均方根误差分别为3.55mm、3.60mm、6.08mm;若以探空作为参考,GNSS/MET、ECMWF和微波辐射计的偏差分别为-1.39mm、-1.94mm、-2.58mm,均方根误差为2.85mm、3.59mm、6.79mm。由此可见GNSS/MET、探空和ECMWF模式分析的水汽具有较好的质量。从对比结果看,GNSS/MET在相关性、偏差和均方根误差方面均表现突出,和探空、ECMWF相当,而微波辐射计差别明显,均方根误差最大,但剔除雨日后,资料质量得到提高,表明微波辐射计资料的应用需要注意降水条件,反演算法需在今后进行改进。