Retrieval of mixing height and dust concentration with lidar ceilometer

The Vaisala ceilometers CT25K and CL31 are eye-safe single lens lidar systems reporting attenuated backscatter profiles; they often operate 24 h a day in fully automated, hands-off operation mode. These profiles can be used for more than just cloud-base height determination. In dry weather situations, there is a fairly good correlation between the ceilometer near-range backscatter and in situ PM10 concentration readings. The comparison of mixing height values based on soundings and on ceilometer backscattering profiles indicates that ceilometers are suitable instruments for determining the convective mixing height. Its enhanced optics and electronics enables the CL31 ceilometer to detect fine boundary-layer structures whose counterparts are seen in temperature profiles.     

岩溶区和碎屑岩区林地和农田土壤氮矿化过程对比研究

通过15N标记法和MCMC氮素转化模型,研究了岩溶区(石灰性土壤)和碎屑岩区(红壤)林地和农田土壤易分解有机氮矿化(M易)、难分解有机氮矿化(M难)和总有机氮矿化(M总)速率.结果发现,土壤矿化速率受土壤类型和土地利用方式的显著影响.林地石灰性土壤M总 (3.71 mg N/kg)显著低于林地红壤(5.57mg N/kg),石灰性土壤MNab(1.81 mg N/kg)与MNrec(1.90 mg N/kg)相近,而红壤M易 (4.60 mg N/kg)显著高于M难 (0.96 mg N/kg).林地变为农田后,石灰性土壤M总显著提高,而红壤显著降低.与林地相比,岩溶区农田土壤M易提高了72.5%,而M难下降了33.7%.碎屑岩区农田土壤M易和M难分别降低至2.47和0.46 mg N/kg.岩溶区土壤CaO和MgO含量与M易呈显著负相关,而与M难呈显著正相关,表明岩溶区土壤钙镁含量是影响氮矿化速率的重要因素.     

Formation of low-pressure reaction textures during near-isothermal exhumation of hot orogenic crust (Bohemian Massif,Austria)

Two types of aluminous paragneiss from the Loosdorf complex (Bohemian Massif, NE Austria) contain coarse-grained granulite assemblages and retrograde reaction textures that are investigated to constrain the post-peak history of the Gföhl unit in the southern Bohemian Massif. Both types have a peak assemblage garnet–biotite–sillimanite–plagioclase–K-feldspar–quartz–granitic melt ± kyanite ± ilmenite ± rutile, recording peak metamorphic conditions of $$0.9–1.1 GPa and $$780–820°C estimated by isochemical phase equilibrium modelling. The first sample type (Ysper paragneiss) developed (i) cordierite coronae around garnet and (ii) cordierite–spinel and cordierite–quartz reaction textures at former garnet–sillimanite interfaces. Calculated chemical potential relationships indicate that the textures formed in the course of a post-peak near-isothermal decompression path reaching $$0.4 GPa. Texture formation follows a two-step process. Initially, cordierite coronae grow between garnet and sillimanite. As these coronae thicken, they facilitate the development of local compositional domains, leading to the formation of cordierite–spinel and cordierite–quartz symplectites. The second sample type (Pielach paragneiss) exhibits only discontinuous cordierite coronae around garnet porphyroblasts but lacks symplectites. The formation of cordierite there also indicates near-isothermal decompression to 0.4–0.5 GPa and 750–800°C. This relatively hot decompression path is explained by the contemporaneous exhumation of a large HP–UHT granulite body now underlying the Loosdorf complex. The timing of regional metamorphism in the granulites and the southern Bohemian Massif in general is well constrained and has its peak at $$340 Ma. Monazite from Loosdorf paragneiss samples yield a slightly younger age of $$335 Ma. Although the ages overlap within error, they are interpreted to reflect near-isothermal decompression and exhumation resulting in the formation of the observed reaction textures.     

Origin and Petrogenetic Implications of Spessartine Garnet in Highly‐Fractionated Granite from the Central Eastern Desert of Egypt

A highly-fractionated garnet-bearing muscovite granite represents the marginal granitic facies of the Abu-Diab multiphase pluton in the Central Eastern Desert of Egypt. New electron microprobe analyses(EMPA) and laser ablation inductively coupled plasma mass spectrometry(LA-ICP-MS) data from garnets are reported, in order to constrain their origin and genesis. Garnet in the Abu-Diab host granite is euhedral to subhedral, generally homogeneous and, in rare cases, it shows weak zonation. The garne...