人为热对城市边界层结构影响研究

为研究不同人为热源引入方案对城市边界层结构模拟性能的影响，以杭州地区为例，在区域边界层模式（RBLM）中引入一种新人为热源处理方案，即对城市中的人为热排放分层考虑，将低层的人为热源加入地表能量平衡方程，将高层人为热源分布与建筑物高度和密度联系起来，加入热量方程中，同时考虑了人为热源强度的日变化。数值试验结果表明，这是一种比较合理的处理方案。人为热源引入方案对城市边界层结构的影响表现在:气温、湍流动能增加，并通过湍流交换输送到较高层大气；大气不稳定度增加，混合层高度最高抬升了400 m；城市地区上升速度增加，热岛环流加强；白天人为热源一般为太阳辐射的10%～20%，对地气交换的影响较小。夜间没有了太阳辐射能量，对地气交换的影响比日间更明显；冬季低层湍流活动加强，湍能约增加40%，大气层结稳定度降低。     

A comparison between natural and anthropogenic emissions of the reduced sulfur compounds H2S, COS, and CS2 in a tropical industrialized region

Extensive ambient concentration and flux measurements have been performed in the heavily polluted region of Cubatão/Brazil. Substantial contribution of anthropogenic sources to the local reduced sulfur burden has been observed. As a result of this atmospheric sulfur burden average gas exchange between vegetated soils and the atmosphere shows net deposition. Based mainly on own field measurements a local budget for H₂S, COS, and CS₂ has been made up in order to calculate anthropogenic emissions. All major sources and sinks in the chosen atmospheric reservoir (24×20×1 km) have been taken into account. Due to the small reservoir size fluxes across its boundaries are dominant sources and sinks. The differences between outflux and influx therefore account for the unknown anthropogenic emissions which have been determined to be 80±10 (H₂S), 66±15 (COS), and 29±6 Mmol year^-1 (CS₂). Other sources and sinks like natural emissions, chemical conversion, and dry deposition turned out to be of minor importance on a local scale. In fact, inside the investigated reservoir natural emissions were below 0.5% of anthropogenic emissions. Anthropogenic emissions of H₂S, COS, and CS₂ quantified in this work have been compared with global emission estimates for these compounds made by other authors. We conclude that global anthropogenic emissions of reduced sulfur compounds especially of COS and CS₂ are currently under-estimated.     

Methodological Development of the Conditional Sampling Method. Part I: Sensitivity to Statistical and Technical Characteristics

The relaxed eddy accumulation (REA), method based on the conditional sampling concept, has received increasing attention over the past few years as it can be used to measure surface fluxes of a wide variety of trace gases for which fast response analysers are not available. In the REA method, a turbulent flux is simply expressed as the product of the standard deviation of vertical wind velocity, the difference between mean scalar concentration in the updrafts and downdrafts and an empirical coefficient, (about 0.63 as based on simulations with a Gaussian distribution, and 0.58 as derived from experimental data). A simulation technique is developed here to evaluate the performance of a ground-based REA system. This analysis uses generated series whose internal structure can be controlled to a large extent. They are stationary and their characteristics are similar to those of physical turbulence. In a first step the influence of some statistical characteristics of vertical velocity and scalar concentration series is investigated. The effect of the third- and fourth-order moments can explain to some degree the difference between calculated and measured values. The impact of a threshold on the vertical velocity is then considered, and its effect on is quantified. The influence of the time lag between and the effective scalar sampling, and the consequences of lowpass filtering of the signal are also investigated. The simulation technique presented in this study can be used to develop elaborate algorithms for near real-time conditional sampling, based on the statistical characteristics of the previous sample.     

大气对流层平流层交换(STE)研究进展

大气平流层对流层交换(Stratosphere-Troposphere Exchange,STE)包括平流层向对流层的输送(Stratosphere-Troposphere Transport,STT)和对流层向平流层的输送(Troposphere-to-Stratosphere Transport,TST)2个过程,通常统称为STE交换过程.其对大气的辐射平衡、化学成分具有重要影响.研究STE对于大气化学、气候变化、平流层对流层耦合模式的发展等领域意义重大.对国内外不同尺度STE的观测、模拟与诊断做了评述,讨论了各种尺度STE的机制,比较了不同诊断方法和模式的性能和特点.着重指出目前天气尺度STE的研究虽然比较充分,但在STE过程中,中小尺度混合、湍流混合等物理过程的机制、诊断以及模拟方法的研究还有待提高.中小尺度强对流引起的TST对对流层污染物向平流层的输送作用和影响越来越受到关注.在全球快速城市化的背景下,研究城市群高污染区域强对流天气引起的TST过程及其影响具有重要的科学意义.     

Modelling ion composition in seepage water from a column experiment with an open cut coal mine sediment

Secondary reactions occurring in pyrite-containing sediments from open cut coal mines are complex and not fully understood. In this study, the changes in seepage water composition in a column experiment with a sediment containing pyrite (5.6 g kg⁻¹) were evaluated using a chemical equilibrium model. A column experiment with artificial irrigation (730 mm water yr⁻¹) was carried out for 2 yr with a sediment from the open pit mine Garzweiler, Germany, at the Institute of Applied Geology. Tracer (LiCl) was added to the sediment. Seepage water composition at 52 cm depth was sampled weekly. Redox potential and the water potential were also recorded weekly. Sulphate and Fe(II) were the dominant ions in the seepage water with concentration maxima of 500 and 350 mmol l⁻¹ after 50 days (0.7 pore volumes (PV)). Minimum pH values were around 0.8 after 100 days (1.4 PV), but increased subsequently and reached 2.4 after 700 days (9.5 PV). Ion activity product calculations indicated the intermediate formation of gypsum (19th–480th day of the experiment). Solutions were undersaturated with respect to alunite, jarosite, jurbanite, schwertmannite, melanterite, gibbsite and goethite during the whole experiment. The model of coupled equilibria which included inorganic complexation, precipitation/dissolution of gypsum and multiple cation exchange was tested. Pyrite oxidation and pH-dependent silicate weathering were considered using simple input functions. Transport was modelled using a field capacity cascade submodel. Model results showed satisfactory agreement with measured values for pH and concentrations of SO₄, Fe, Mg, Ca and Al. Correlation coefficients lay between 0.7 and 0.9 and linear regression coefficients (modelled against measured) were 1.5 (Ca), 1.0 (Fe, SO₄), 0.8 (Mg), 0.7 (pH) and 0.6 (Al). The results showed that the protons produced during pyrite oxidation (94 mmol_c H⁺ kg⁻¹) were mainly released into seepage water (as HSO₄⁻ and H⁺). Cation exchange reactions buffered 20 mmol_c of H⁺ kg⁻¹ sediment, and Al released by silicate weathering accounted for 3.6 mmol_c H⁺ kg⁻¹. Modelling was useful to further understand the significance of different pH buffer reactions.     

地下水埋深及水质对塔克拉玛干沙拐枣气体交换特性的影响

塔克拉玛干沙漠地下水储量丰富,但因埋深和水质的限制,植物可有效利用的水资源十分有限。通过分析沙漠特有灌木塔克拉玛干沙拐枣(Calligonum taklimakanensis B.R.Pan & G.M.Shen）气体交换特性对地下水埋深和水质变化的响应,探讨了地下水对天然植物分布及生长的影响。结果显示,有天然植被分布的区域地下水埋深一般较浅,土壤水分供应充足;但受地下水矿化度、总硬度、总碱度、全盐含量及各离子含量比例的区域间差异影响,不同区域的塔克拉玛干沙拐枣气体交换特性各不相同。地下水总碱度大小是影响塔克拉玛干沙拐枣光合特性最主要的因素,总碱度增加时,净光合速率（Pn）、蒸腾速率（Tr）、气孔导度（Gs）及潜在最大净光合速率（Pmax）、光补偿点（LCP）和光饱和点（LSP）分别从14.9±0.39 μmolCO2·m-2·s-1、6.79±0.21 mmol·m-2·s-1、0.192±0.013 mmol·m-2·s-1、21.4±1.1 μmolCO2·m-2·s-1、175.5±3.5 μmol·m-2·s-1、1 805±31.2 μmol·m-2·s-1降为11.7±0.5 μmolCO2·m-2·s-1、5.79±0.18 mmol·m-2·s-1、0.130±0.009 mmol·m-2·s-1、16.3±2.5 μmolCO2·m-2·s-1、78.1±15.8 μmol·m-2·s-1、1 564±55.6 μmol·m-2·s-1。研究结果还表明,较浅的地下水埋深是沙漠腹地天然生植物生存繁衍的必要条件,塔克拉玛干沙拐枣天然分布区的适宜地下水埋深应在1.5~2.5 m的范围内;塔克拉玛干沙拐枣也具有很强的盐碱耐受能力,在矿化度高达16 g·L-1的环境中依然能正常存活生长。     

全球陆地生态系统与大气之间碳交换的模拟研究

利用陆面物理过程和植被生理生态过程完全动态耦合的大气植被相互作用模式 (AVIM) ,对全球陆地生态系统的净初级生产力进行模拟。全球陆地生态系统植被分为 1 3类 ,土壤质地分为 7类 ,确定了各种植被和土壤的模式参数。采用全球陆地 0 .5× 0 .5网格点气候平均资料 ;以 30分钟为步长进行积分。并用全球不同地区各种植被类型的 1 9个 NPP观测样点数据校准模型。AVIM模拟全球陆地生态系统 NPP的主要模拟结果如下 :全球陆地生态系统净初级生产力 (NPP)总量约为 60 .72 Gt Cyr- 1。分析了不同植被类型的 NPP分布 ,模式较好地模拟了全球陆地生态系统净初级生产力的纬向分布和区域分布的差异 ,模拟出中国植被生产力的分布特征。陆地生态系统净初级生产力与温度、降水和辐射等气候因素在不同地区有不同程度相关性 ,北方针叶林地区气候因子与 NPP的相关性明显 ,反映出植被对环境因子的不同响应及其物候特征。赤道热带雨林地区NPP与气候因子的相关性不明显。     

金云母-蛭石间层矿物阳离子交换容量的影响因素研究

采用氯化铵交换-原子吸收光谱法和CaCl2-甲醛缩合法测定3个金云母-蛭石间层矿物样品的各阳离子交换分量和阳离子交换总量,通过分析样品粒度和溶液pH值对阳离子交换容量的影响及晶层端面水解使表面荷电的特点,确定样品的等电点.结果表明,随着粒度的增大,样品的阳离子交换容量逐渐减小;随着pH值的增大,样品的阳离子交换容量先急剧减小(pH=2～5),后趋于平缓(pH=5～9),而后再急剧减小(pH=9～11.5),这些变化主要与晶层端面的水解作用和八面体片阳离子的溶出作用有关;样品的等电点为pH值≈9.研究结果对于排除端面水解作用对阳离子交换容量的影响和进一步确定蛭石晶层的层电荷具有重要的意义.     

Porewater-derived dissolved inorganic carbon and nutrient fluxes in a saltmarsh of the Changjiang River Estuary

Saltmarshes are one of the most productive ecosystems, which contribute significantly to coastal nutrient and carbon budgets. However, limited information is available on soil nutrient and carbon losses via porewater exchange in saltmarshes. Here, porewater exchange and associated fluxes of nutrients and dissolved inorganic carbon(DIC) in the largest saltmarsh wetland(Chongming Dongtan) in the Changjiang River Estuary were quantified. Porewater exchange rate was estimated to be(37±35) cm/d during December 2017 using a radon(~(222)Rn) mass balance model. The porewater exchange delivered 67 mmol/(m~2·d), 38 mmol/(m~2·d) and 2 690 mmol/(m~2·d) of dissolved inorganic nitrogen(DIN), dissolved silicon(DSi) and DIC into the coastal waters,respectively. The dominant species of porewater DIN was NH_4~+ (99% of DIN). However, different with those in other ecosystems, the dissolved inorganic phosphorus(DIP) concentration in saltmarsh porewater was significantly lower than that in surface water, indicating that saltmarshes seem to be a DIP sink in Chongming Dongtan. The porewater-derived DIN, DSi and DIC accounted for 12%, 5% and 18% of the riverine inputs, which are important components of coastal nutrient and carbon budgets. Furthermore, porewater-drived nutrients had obviously high N/P ratios(160–3 995), indicating that the porewater exchange process may change the nutrient characteristics of the Changjiang River Estuary and further alter the coastal ecological environment.     

Influence of reclamation works on the marine environment in a semi-enclosed bay

1Introduction GamakBay,anegg shapedseasurfaceareaofap proximately112km2,isasemi enclosedshallowwaterareawithameandepthof9mandhasbotheastandsouthchannelstoreceiveseawaterfromoutside(seeFig.1).Similarscalesoftidalwavesalmostsimultane ouslyenterorexitthrough…