China possesses vast grassland resources that include alpine meadow, tundra, steppe and desert. It is, therefore, desirable to establish a grassland classification system that involves the formative factors contributing to this diversity. This paper reports a grassland classification system called the Integrated Orderly Classification System of Grassland (IOCSG), which was formulated through grouping or clustering units with similar properties. The IOCSG involves a hierarchy of three classification levels. At the first level, grasslands are grouped into classes according to an index of moisture and temperature. At the second level, grasslands are differentiated as subclasses by the edaphic conditions. At the third level, grassland types within a subclass are distinguished by vegetation types. Under the IOCSG, seven thermal zones and six humidity zones have been identified and used to differentiate grassland classes. The IOCSG recognises 42 grassland Classes, of which 41 are present in China.
Trinitrotoluene, usually known as TNT, is a kind of chemical explosive with hazardous and toxic effects on the environment and human health. National and societal security concerns have dictated an increasing need for the analytical detection of TNT with rapidity, high sensitivity and low cost. This work demonstrates a novel method using L-cysteine-capped CdTe quantum dots (QDs) to assay TNT, based on the formation of a Meisenheimer complex between TNT and cysteine. The fluorescence (FL) of quantum dots quench because electrons of the QDs transfer to the TNT molecules via the formation of a Meisenheimer complex. TNT can be detected with a low detection limit of 1.1 nM. Studies on the selectivity of this method show that only TNT can generate an intense signal response. The synthesized QDs are excellent nanomaterials for TNT detection. In addition, TNT in soil samples is also analyzed by the proposed method.
Highly ordered TiO(2) nanotube arrays are with unique photoelectrical properties due to their highly ordered nanostructure and the resulted short charge transportation path. We report, for the first time, on the application of Ag nanoparticle-modified TiO(2) nanotubes (Ag/TiO(2) NTs) in the electrochemiluminescence detection of polycyclic aromatic hydrocarbons (PAHs) using the Ag/TiO(2) NT film as working electrode and S(2)O(8)(2-) as coreactant, with benzo(a)pyrene (BaP) as the model compound. The hydrophobic BaP absorbs onto the TiO(2) NTs surface, and oxidized with consumption of the excited TiO(2) (TiO(2)(*+)) resulting in a decrease in ECL. Under the optimal conditions, a detection limit of 1.0 x 10(-12) M is achieved with a linear range of 3.0 x 10(-12) approximately 1.0 x 10(-9) M. Compounds which can not be oxidized by the excited TiO(2) (TiO(2)(*+)), such as benzene, naphthalene (NAP), anthracene (ANT), and tris-2,3-dibrominepropyl isocyanurate (TBC) show little interference on the detection, whereas PAHs with more than four rings can be detected by the proposed method.
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