Intra-annual variability in nutrients in the Godavari estuary,India

Daily variations in nutrients were monitored for 15 months (September 2007–November 2008) in the Godavari estuary, Andhra Pradesh, India, at two fixed locations. River discharge has significant influence on nutrients loading to the estuary, which peaks during June–August (peak discharge period; monsoon) whereas exchanges at the sediment–water interface, groundwater and rainwater contribute significantly during other period. Despite significant amount of nutrients brought by discharge to the study region, phytoplankton biomass, in terms of chlorophyll-a (Chl a), did not increase significantly due to high suspended load and shallow photic depth. Nutrients showed downward gradient towards downstream of the estuary from upstream due to dilution by nutrient poor seawater and biological uptake. The N:P ratios were higher than Redfield ratio in both upstream and downstream of the estuary during no discharge period suggesting PO₄ to be a limiting nutrient for phytoplankton production, at levels <0.10 μmol L⁻¹. On the other hand, Si:N ratios were always more than unity during entire study period at both the stations indicating that Si(OH)₄ is not a limiting nutrient. Our results suggest that suspended matter limits phytoplankton biomass during peak discharge period whereas PO₄ during no discharge period.     

石油初次运移动力学模型研究及其应用

烃源岩中生成的油气经过初次运移, 进入到储集层, 其本质应该是一个动力学过程。前人对于油气初次运移动力学有一定的研究, 但是定量研究较少。本文以烃源岩中石油初次运移为研究对象, 建立下生、上储型排烃地质模型, 从微观动力学的角度对即将进入储集层的游离相石油进行力学分析, 认为烃源岩中的石油发生初次运移进入储集层是一个动力和阻力的力学非平衡过程, 运移动力包括烃源岩地层压力和烃源岩层毛细管力, 运移阻力包括储集层地层压力、储集层毛细管力和内摩擦力。当动力大于阻力时, 石油发生初次运移; 当动力与阻力相等时, 对应着石油初次运移的临界状态; 当动力小于阻力时, 石油不能发生初次运移。因此, 可以通过对比石油初次运移动力和阻力的大小定量地预测石油初次运移充注窗口。本文将建立的石油初次运移力学模型应用到安塞油田长6段油藏, 定量地预测了石油初次运移充注窗口, 为进一步的油气勘探提供依据。     

寿阳区块马首区段煤层气地质特征及储量估算

通过对寿阳区块马首区段地质条件、煤层赋存特征、煤层气含气性、渗透性、解吸/吸附特征等研究,认为该区段构造简单,岩层覆盖条件较好;水文地质条件简单,地下水缓流或滞流有利于煤层气富集;主采煤层发育基本稳定,埋藏深度适中;煤层气含量较高,主要在6~16m3/t;煤层割理裂隙发育,整体渗透率较高,非均质性较明显;煤储层处于欠压状态、实测含气饱和度较低、原地应力较低,整体上适合进行煤层气开采。在此基础上估算了煤层气资源储量,并优选区段的中、北部为煤层气开发的有利区。     

中心城市信息来源、加工和扩散研究──以《广州日报》为例

本支以信息服务业中的报纸业为研究对象，描述《广州日报》信息来源、加工和扩散的过程，分析其时空变化特征．《广州日报》信息来源的渠道，各渠道的相对重要性，信息的收集和加工的技术效率，信息产品的质量，信息扩散的规模、方式和过程都发生了很大变化，呈现出整体提高的趋势．文章还分析了《广州日报》信息扩散的空间变化特征，并对这些特征的形成因素进行了确定。文章最后还对本案例研究的理论意义进行了讨论，指出；在多个微观案例研究的基础上进行宏观概括将更接近事情的真相。     

Submarine groundwater discharge enhances primary productivity in the Yellow Sea,China:Insight from the separation of fresh and recirculated components

Submarine groundwater discharge(SGD)is being increasingly recognized as a significant source of nutri-ent into coastal waters,and generally comprises two components:submarine fresh groundwater dis-charge(SFGD)and recirculated saline groundwater discharge(RSGD).The separate evaluation of SFGD and RSGD is extremely limited as compared to the conventional estimation of total SGD and associated nutrient fluxes,especially in marginal-scale regions.In this study,new high-resolution radium isotopes data in seawater and coastal groundwater enabled an estimation of SGD flux in a typical marginal sea of the Yellow Sea.By establishing 226Ra and 228Ra mass balance models,we obtained the SGD-derived radium fluxes,and then estimated the SFGD and RSGD fluxes through a two end-member model.The results showed that the total SGD flux into the Yellow Sea was equivalent to approximately 6.6 times the total freshwater discharge of surrounding rivers,and the SFGD flux accounted for only 5.2％-8.8％of the total SGD.Considering the nutrient concentrations in coastal fresh and saline groundwater,we obtained the dissolved inorganic nutrient fluxes(mmol m-2 yr-1)to be 52-353 for nitrogen(DIN),0.21-1.4 for phosphorus(DIP),34-226 for silicon(DSi)via SFGD,and 69-262 for DIN,1.0-3.9 for DIP,70-368 for DSi via RSGD,with the sum of nutrient fluxes equaling to(1.8-9.3)-fold,(1.3-5.6)-fold and(2.0-9.5)-fold of the riverine inputs.Compared to the conventional estimation of the total SGD flux,the nutrient fluxes derived from the separation of SFGD and RSGD were(1.6-2.1),(1.6-1.8)and(4.0-4.9)times lower for DIN,DIP and DSi,respectively,indicating that the estimates by separating SFGD and RSGD could be conservative and representative results of the Yellow Sea.Furthermore,we suggested that SGD played an important role in nutrient sources among all the traditional nutrient inputs sources,providing 15％-48％,33％-68％and 14％-43％of the total DIN,DIP and DSi input fluxes into the Yellow Sea,and the high nutrient stoichiometric ratios(i.e.,DIN/DIP)in SGD probably contributed to the increasing ratios in the Yellow Sea.In addition delivering large amounts of nutrient into the Yellow Sea,SGD would create primary productivity of 10-49,1.6-6.8 and 8.8-42 g C m-2 yr-1 based on N,P and Si,which were equivalent to 5.2％-27％,0.9％-3.7％and 4.7％-23％of the total primary productivity,respectively.In par-ticular,the SFGD-derived DIN flux can be converted to primary productivity of 4.2-28 g C m-2 yr-1 thus demonstrating the disproportionately large role of SFGD in ecological environment of the Yellow Sea rel-ative to its flux.Therefore,we conclude that SGD,particularly SFGD,plays an important role as a nutrient source for the Yellow Sea,and not only affects nutrient budgets and structures but also enhances the pri-mary productivity.     

黑河流域植被净初级生产力的遥感估算

利用光能利用率模型C-FIX,高时空分辨率的SPOT/VEGETATION遥感数据,全球格网化气象再分析资料以及黑河流域土地利用图,估算了1998—2002年黑河流域不同生态系统净初级生产力(NPP)的年总量和平均生产力,输出了黑河流域NPP年累积量空间分布格局图、NPP季节动态图,分析了近5a来黑河流域NPP时空变化特征,评价了不同土地利用类型下的生态系统生产力水平差异。其结果表明,黑河流域陆地生态系统NPP空间分布及其季相变化特征是流域自然环境、地貌、气候以及人类生产活动长期共同作用和影响的结果,其中水分条件是控制黑河流域陆地生态系统NPP空间格局的决定因子。1998—2002年黑河流域山区高覆盖度草地和下游荒漠区净初级生产力持续下降,反映出这些地区生态环境恶化严重。这些研究结果可以为黑河流域的水-生态-经济系统的合理设计与有效实施提供科学数据集。     

山西吕梁袁家村条带状铁建造沉积相与沉积环境分析

山西吕梁作为华北克拉通上条带状铁建造(BIF)的重要产区之一,位于华北中央构造带中。袁家村BIF分布于吕梁岚县袁家村一带,极有可能是华北克拉通内最为典型的Superior型BIF。与华北克拉通其他大多数BIF相比,袁家村BIF具有明显的差异性,其中包括它的形成时代(2.3~2.1Ga)、铁建造类型和低级变质程度(低绿片岩相)等。因此,研究袁家村BIF具有特殊的研究意义,可为探讨大氧化事件之后古海洋氧化还原状态以及国内Superior型BIF的成因提供研究基础。袁家村BIF产于吕梁群袁家村组变沉积岩系的下部,前人根据上覆和下伏含火山岩地层的时代,推测袁家村组的形成时代为2.3~2.1Ga。BIF整体产状陡倾,沿北北东-北东东向呈L形带状分布。依据原生矿物的共生组合及产出特征,可将BIF沉积相划分为氧化物相(60%)、硅酸盐相(30%)和碳酸盐相(10%)。氧化物相是本区BIF最主要的沉积相,主要矿物为赤铁矿、磁铁矿和石英,从而可进一步划分为赤铁矿(24%)和磁铁矿(36%)亚相;硅酸盐相BIF以大量硅酸盐矿物出现为特征,散布于研究区,主要矿物组成除了石英和磁铁矿之外,还有铁黑硬绿泥石、绿泥石、铁滑石、镁铁闪石和阳起石等。在与碳酸盐相BIF构成过渡相的BIF中,还可发现大量的铁白云石。而碳酸盐相主要矿物为菱铁矿、铁白云石和石英等,主要发育于研究区的南部。依据含铁岩系构造格局特点复原获得了原始沉积相分布略图,沉积相主要呈南北向延展,自东向西显示出相变规律,西边为碳酸盐相,东边为氧化物相,其间是过渡的硅酸盐相。通过袁家村BIF的岩相学和含铁矿物化学成分的研究,可大致推测原始沉积的矿物组成为无定形硅胶、水铁矿、与铁蛇纹石和黑硬绿泥石组成类似的铁硅酸盐凝胶、富Al的粘土碎屑和含铁、镁、钙的碳酸盐软泥。这些沉积物在随后的成岩期和绿片岩相的区域变质作用下发生矿物之间的相互转变。BIF中主要含铁矿物的PO-P-Eh 2CO2和pH相关图解说明除了赤铁矿之外,其他矿物均是在较低氧逸度环境中形成的,且所有矿物共存的水体系为中性到弱碱性。袁家村BIF氧化物相中发育豆粒、内碎屑结构和板状交错层理等原始沉积构造,指示氧化相部分是在相对高能的浅水环境下沉积的。但BIF大部分应该形成于浪基面以下(200m)较为深水的环境中,沉淀可能同时发生于上部氧化和下部还原的水体之中,由于还原弱酸性的深部富铁海水在海侵的过程中上升到浅部相对氧化和弱碱性的浅水环境中,因为Eh、pH及氧逸度等物化条件的骤然变化,最终导致铁质的沉淀和沉积相自上而下的变化。     

石河子市空气质量特征及其气象影响因素的研究

运用石河子市2015—2020年6种污染物浓度，研究了石河子市近6年空气质量及污染物浓度时间变化特征。结果显示：石河子市近6年空气质量有所改善，首要污染物主要以可吸入颗粒物和臭氧为主，并有明显的采暖期和非采暖期之分。冬季空气质量对全年空气质量优良天数占比为负贡献，各污染物浓度的峰值多出现在白天。分析石河子市相对湿度、气压、温度等气象要素和空气质量指数的相关性，并建立拟合方程，结果显示石河子市除冬季外其他时间最小相对湿度、最低气温和空气质量指数相关性较好，在预报空气质量过程中可重点考虑。