Remotely sensed assessment of water quality levels in the Pearl River Estuary, China

In this paper, a method of assessing water quality from satellite data is introduced. The composite pollution index (CPI) was calculated from measured chemical oxygen demand (COD) and nutrient concentration. The relationships between CPI and 240 band combinations of SeaWiFS water-leaving radiance were analyzed and the optimal band combination for estimating CPI was chosen from the 240 band combinations. An algorithm for retrieval of CPI was developed using the optimal band combination, (L₄₄₃ × L₅₁₀)/(L₄₁₂ + L₄₉₀). The CPI was estimated from atmospherically corrected SeaWiFS data by employing the algorithm. Furthermore, the CPI value range for each water quality level was determined based on data obtained from 850 samples taken in the Pearl River Estuary. The remotely sensed CPIs were then transferred to water quality levels and appropriate maps were derived. The remotely sensed water quality level maps displayed a similar distribution of levels based on in situ investigation issued by the State Ocean Administration, China. This study demonstrates that remote sensing can play an important role in water quality assessment.     

新疆北部镁铁-超镁铁质岩的PGE成矿问题

铂族元素(PGE)矿化主要与镁铁-超镁铁杂岩有关,成矿类型主要为岩浆型矿床,这类PGE矿床的形成主要依赖两个条件:一是岩浆中富含PGE;二是具备PGE从岩浆中分离和富集的机制,主要是在岩浆演化过程中硫达到饱和。新疆北部镁铁-超镁铁质杂岩发育,并产有喀拉通克、黄山、黄山东、图拉尔根4个大型铜镍矿床和香山、土墩、葫芦、白石泉等中、小型铜镍矿,以及香山西、尾亚等中型钒钛磁铁矿矿床,但迄今尚未发现成型的PGE矿床。文中通过对PGE矿床的形成机制与镁铁-超镁铁杂岩源区特征研究,探讨了北疆地区PGE矿床的成矿问题。综合分析认为,新疆北部后碰撞镁铁-超镁铁质岩的岩石类型为经过了分离结晶形成的铁质岩石系列,是PGE矿床的有利容矿岩石;矿床的Sr、Nd、Pb、O、Os和S同位素和含矿岩石地球化学特征表明,铜镍硫化物矿床含矿岩浆在岩浆演化和成矿过程中有地壳物质加入并可导致硫化物熔离作用,说明在成矿机制上也存在形成岩浆型PGE矿化的条件。新疆北部PGE矿化微弱的原因可能在于该区广泛发育的亏损型地幔源(具正的εNd值特征),这一亏损型地幔可能部分源于洋壳熔融,与产于后碰撞造山带环境、发育于"洋壳"或"不成熟"陆壳基底之上有关,由此决定了原始岩浆为贫PGE的源区,因此不利于PGE的富集成矿。     

干湿交替条件下包气带土柱中氮素迁移转化规律实验

干湿交替的回灌方法常被用于解决地面回灌补给地下水的堵塞问题。研究干湿交替条件下地面回灌对地下水的影响对于指导再生水回灌地下水具有重要实际意义。通过室内土柱模拟实验,在入渗强度为10.5 mm/h的条件下,日均进水量3 888 mL;用干湿交替的地面回灌模式持续运行136 d,累计灌入氨氮含量为5 mg/L的模拟再生水23 894 L,研究包气带土柱对氨氮的去除效果及氮素在包气带中的迁移转化规律。研究表明,充分利用包气带的好氧、兼氧和厌氧环境,生物脱氮是地下水回灌过程中脱氮的主要途径。包气带对氨氮的去除机理主要为土壤对氨氮的吸附作用和微生物的降解作用。回灌过程中累积在土颗粒表面的氨氮在干期发生硝化作用,干湿交替会加强氮素在包气带的迁移转化,导致干期后的回灌初期大量硝态氮迁移到饱和带地下水中。     

Investigating the effect of soil models on deformations caused by braced excavations through an inverse-analysis technique

In this study, a series of inverse-analysis numerical experiments was performed to investigate the effect of soil models on the deformations caused by excavation by using the finite element method. The nonlinear optimization technique that was incorporated into the finite element code was used for the inverse-analysis numerical experiments. Three soil models (the hyperbolic model, pseudo-plasticity model, and modified pseudo-plasticity model) were employed in the intended numerical experiments on a well-documented excavation case history. The results indicate that wall deflection due to excavation can be accurately back-figured by each of the three soil models, while the ground surface settlement can be reasonably optimized only by the pseudo-plasticity model and the modified pseudo-plasticity model. Importantly, the modified pseudo-plasticity model can yield more reasonable simulations when the wall deflection and the ground surface settlement are simultaneously back-figured. The results show that selection of an adequate soil model that is capable of adequately describing the stress–strain-strength characteristics of the soils is essentially crucial when predicting the excavation-induced ground response.     

海南岛三叠纪中基性岩的年代学、地球化学及其地质意义

辉长岩大多为地幔岩石部分熔融的产物,辉绿岩脉及碱性正长岩的形成通常与伸展构造有关,本文对海南岛万宁辉长岩及辉绿岩脉和分界洲正长岩进行了系统的年代学和岩石地球化学研究,并以此来讨论其构造意义。LA-ICP-MS锆石U-Pb定年结果表明,万宁辉长岩及辉绿岩脉形成约在240 Ma,分界洲正长岩形成约在231 Ma,主量元素特征表明万宁辉长岩和辉绿岩分别属碱性系列和亚碱性系列,分界洲正长岩属于典型的碱性岩浆岩。万宁辉长岩及辉绿岩脉的稀土元素具有轻稀土富集的特点(LREE/HREE=7.22～8.50和8.11～11.10),微量元素具有岛弧型火山岩的特征,富集大离子亲石元素K、Rb、Ba、Th,贫高场强元素Nb、Ta和Zr、Hf;分界洲正长岩的微量元素特征显示出与A型花岗岩类似的特征。海南岛三叠纪中基性岩如分界洲正长岩和万宁辉长岩及辉绿岩脉形成的构造背景为陆内伸展环境,指示海南岛在240～230 Ma处于印支造山运动的应力松弛阶段。     

东天山伊吾二叠纪花岗质杂岩体的锆石定年、地球化学及其构造意义

伊吾花岗质杂岩体主要由二长花岗岩和碱长花岗岩构成。锆石LA-ICP-MS U-Pb定年分析得到二长花岗岩和碱长花岗岩的侵位年龄分别为284.6±1.4Ma和284.0±1.1Ma。结合地质证据,此年龄表明该杂岩体形成于碰撞之后的二叠纪早期挤压-伸展转折阶段。岩石学、地球化学和同位素等方面的对比研究表明这两种岩石为同一岩浆演化的产物。与二长花岗岩相比,碱长花岗岩表现为硅、碱的含量较高,而铝的含量较低;富Th、U、Nb、Ta,贫Sr、P、Ti、Sm;DI和Rb/Sr升高,Nb/Ta和Zr/Hf下降,从二长花岗岩到碱长花岗岩表现出连续分异演化的趋势。计算得到二长花岗岩和碱长花岗岩的模式年龄(t_(DM))分别为693Ma和763Ma,ε_(Nd)(t)分别为+4.53和+4.64,(~(87)Sr/~(86)Sr)_i分别为0.703858和0.703855,表现出高ε_(Nd)(t)低(~(87)Sr/~(86)Sr)_i的特征。这些特征表明,伊吾岩体的岩浆来自新元古代时从亏损地幔分离出来的初生地壳源区。二长花岗岩岩浆是这种初生地壳岩浆演化的产物,而碱长花岗岩形成于二长花岗岩母岩浆经斜长石、磷灰石、钛铁氧化物、榍石、独居石、褐帘石和锆石等矿物分离结晶后的残留岩浆。     

泰安市矿产开发监督管理工作的思考

根据泰安市区域矿产开发特点,及时掌握矿山企业开采情况,通过加强采矿登记现场预审查、开展矿山开采督察和采矿权人矿产资源开发利用年查等措施,强化了矿产资源开发过程中的监督管理,维护了正常开采秩序及采矿权人的合法权益。     

Subtropical montane evergreen broad-leaved forests of Yunnan, China: diversity, succession dynamics, human influence

This paper integrates studies on the natural subtropical montane evergreen broad-leaved forests (EBLFs) and secondary succession of the forests and plantations in Yunnan, to provide a basis for evaluating the sustainability of the forests in the mountain ecosystems of Yunnan, China. The EBLFs include mid-montane moist, monsoon, and semi-humid categories. The monsoon EBLF yielded the highest indices of the Shannon-Wiener H, Equitability J, Simpson D and Fisher’s alpha, followed by the mid-montane moist EBLF, then by the semi-humid forest. Since human uses have varied widely, the plant communities ranged from pioneer deciduous broad-leaved and/or pioneer coniferous stands to late-successional evergreen broad-leaved stands. The secondary succession pathways were from pioneer deciduous stands of Alnus accompanied by stands of pioneer coniferous Pinus and Keteleeria, through broad-leaved and coniferous mixed stands, to late-successional evergreen broad-leaved forests of Cyclobalanopsis and Castanopsis. In Yunnan, the EBLF is commonly replaced by plantations of exotic fast-growing Eucalyptus to produce industrial wood, oil, pulp and fuel. The result has been reduced plant diversity, and great loss of soil nutrients by erosion and runoff, as compared to the EBLF. Seventy-six plant species in the area have been ranked as critically endangered, endangered, or vulnerable. Their condition is seen as largely attributable to habitat loss or degradation. A clear understanding of ecological features and succession pathways of the EBLF can lead to more effective conservation and management of these fragile forests and the mountain ecosystems.     

Characteristics and influencing factors of frontal upwelling in the Yellow Sea in summer

Frontal upwelling is an important phenomenon in summer in the Yellow Sea (YS) and plays an essential role in the distribution of nutrients and biological species. In this paper, a three-dimensional hydrodynamic model is applied to investigate the characteristics and influencing factors of frontal upwelling in the YS. The results show that the strength and distribution of frontal upwelling are largely dependent on the topography and bottom temperature fronts. The frontal upwelling in the YS is stronger and narrower near the eastern coast than near the western coast due to the steeper shelf slope. Moreover, external forcings, such as the meridional wind speed and air temperature in summer and the air temperature in the preceding winter and spring, have certain influences on the strength of frontal upwelling. An increase in air temperature in the previous winter and spring weakens the frontal upwelling in summer; in contrast, an increase in air temperature in summer strengthens the frontal upwelling. When the southerly wind in summer increases, the upwelling intensifies in the western YS and weakens in the eastern YS. The air temperature influences the strength of upwelling by changing the baroclinicity in the frontal region. Furthermore, the meridional wind speed in summer affects frontal upwelling via Ekman pumping.