Summer pattern of phytoplankton distribution at a station in jangmok bay

Daily changes in phytoplankton abundance and species composition were monitored from July to September 2003 (n=47) to understand which factors control the abundance at a station in Jangmok Bay. During the study, the phytoplankton community was mainly composed of small cell diatoms and dinoflagellates, and the dominant genera wereChaetoceros,Nitzschia, Skeletonema andThalassionema. Phytoplankton abundance varied significantly from 6.40x10⁴ to 1.22x10⁷ cells/l. The initially high level of phytoplankton abundance was dominated by diatoms, but replacement by dinoflagellates started when the N/P ratio decreased to < 5.0. On the basis of the N/P and Si/N ratios, the sampling period could be divided into two: an inorganic silicate limitation period (ISLP, 14^th July-12^th of August) and an inorganic nitrogen limitation period (INLP, 13^th of August - the end of the study). Phosphate might not limit the growth of phytoplankton assemblages in the bay during the study period. This study suggests that phytoplankton abundance and species composition might be affected by the concentrations of inorganic nutrients (N and Si), and provides baseline information for further studies on plankton dynamics in Jangmok Bay.     

Biogeochemical Character of Dissolved Inorganic Nitrogen and Phosphate at Plume Front in the Changjiang River

Biogeochemical character of dissolved inorganic nitrogen and phosphate at plume front is studied based on the data, which were observed in the Changjiang River Estuary in 1988. The results are as follows: The concentrations of nitrate and phosphate change abruptly at plume front and halocline. The concentrations of NO-2 and NH 4 are very high at 10～25m depth. The vertical circumfluence transports NO-3 and PO3-4 , which are released from organisms at the bottom to phytoplankton.     

黄土丘陵沟壑区不同退耕年限刺槐林地土壤氮素动态特征

土壤无机氮的可利用性是影响植物生长发育和植被演替进程的关键因子之一,尤其在生态系统十分脆弱的黄土丘陵沟壑区更为重要。因此,采用时空代换法,通过选取不同退耕年限（10 a、20 a、30 a、40 a）的刺槐林地及相邻对照草地为研究对象,系统研究刺槐林在生长季（4~9月）土壤无机氮净转化速率的变化情况。结果表明：（1）刺槐林地土壤NO₃^--N平均含量约是对照草地的4.57倍,而NH₄⁺-N在两个样地之间没有显著差异。（2）刺槐林地及对照草地土壤在7~8月以硝化作用为主,在4~5月和8~9月以氨化过程为主,且刺槐林地氮素净转化速率大于对照样地。（3）刺槐林地土壤NO₃^--N在前30 a处于积累状态,随后呈现消耗趋势。总而言之,退耕地刺槐林营造可以减少土壤NO₃^--N的淋失,提高NO₃^--N净转化速率,但刺槐林NO₃^--N的累积状态在30 a后变为消耗状态。所以要采取应对30 a以上林龄的刺槐林采取间伐措施,以促进刺槐林的健康发展。     

胶州湾典型河口湿地土壤无机碳分布及影响因素

选择胶州湾大沽河与洋河河口湿地作为研究区,按平行于海岸带方向的光滩和垂直于海岸带方向的河漫滩分层采集土壤样品,测定土壤无机碳（Soil inorganic carbon,SIC）含量、相关离子含量及土壤理化性质,应用Duncan方法及Pearson方法对SIC含量进行组间数据差异显著性分析和相关性分析。结果表明：光滩SIC含量总体呈现距入海口越远,SIC含量越高的趋势,水体的冲刷作用是导致该现象的主要原因。随距海距离增加,河漫滩SIC含量总体呈现先降低后升高的趋势,主要受人类活动等综合因素的影响。互花米草（Spartina alterniflora）入侵使SIC含量明显降低,这是入侵物种根系的转化作用所导致的。养殖活动改变了养殖池塘自身环境因子,进而改变了SIC分布规律,表现为其总体SIC含量高于光滩。相关性分析表明,SIC含量与土壤含盐量、土壤溶解性无机碳含量及土壤pH呈显著正相关。     

合肥市不同天气条件下大气气溶胶粒子理化特征分析

为探讨合肥市霾天气大气气溶胶粒子的组成及来源,在2012-2013年代表性月份用安德森分级采样器在合肥市区进行大气气溶胶粒子采样,并分析各样本中水溶性无机离子成分(NH4+、Mg2+、Ca2+、Na+、 K+、NO2-、NO3-、Cl-、SO42-)。根据同期气象资料把采样背景天气分为晴空、雾、霾、轻雾等4类,详细分析了这4种天气下大气细粒子(指PM2.1)和粗粒子(粒径大于2.1 μm部分)的浓度、组成以及主要离子组分的异同。结果表明:(1)观测期间晴空天多对应空气质量优良,雾、霾天对应轻度到重度污染,从晴空天到雾、霾天,PM2.1浓度大幅度上升,且其占总悬浮颗粒物(TSP)的比例显著上升。(2)从晴空天到雾、霾天,水溶性无机离子质量占PM2.1质量浓度的比例上升,分别为46%(晴空)、67%(霾)、61%(雾)、80%(轻雾)。PM2.1中水溶性无机离子浓度居前3位的雾、霾天是SO42-、NO3-和NH4+,晴空天为SO42-、Ca2+、NO3-。(3)与晴空天相比,霾天PM2.1中水溶性无机离子浓度变化倍数最大的是NO3-(为晴空的6.1倍,下同)、其次是NH4+(3.6倍)和SO42-(3.0倍);雾和轻雾天PM2.1中水溶性无机离子浓度变化最大的是NO3-(>10倍)、其次是NH4+(>5倍)和Cl-(>4.0倍)。(4)4种天气下,与人为污染有关的离子(SO42-、NO3-、Cl-、NH4+)尺度谱存在显著差异,呈双峰型、单峰型、三峰型等;而Ca2+的尺度谱无明显变化,基本上都呈双峰型。(5)在粒径3.3 μm以下,阳、阴离子平衡较好,随着尺度增大变差,且晴空天比雾、霾天差。主要阴离子浓度间、Cl-和Na+间的比值和相关性,在晴空天和雾、霾天差异较大。      

Numerical analysis of projectile penetration and perforation of plain and fiber reinforced concrete slabs

The research presented in this paper deals with the numerical analysis of projectile impact on regular strength concrete (RSC), high‐strength concrete (HSC), and engineered cementitious composites (ECC) using the Lattice Discrete Particle Model (LDPM). The LDPM is chosen in this study as it naturally captures the failure mechanisms at the length scale of coarse aggregate of concrete, and its capabilities include the accurate depiction of both intrinsic and apparent rate effects in concrete, as well as fiber reinforcement effects. The model is used to predict the experimental impact response performed by four independent testing laboratories, and for each data set the model parameters are calibrated and validated using a combination of uniaxial compression, triaxial compression, uniaxial strain compression, and dogbone tests. In the first study, perforation experiments on RSC and HSC for varied impact velocities are carried out, and the exit velocity is compared with the available experimental data. The second study focuses on ECC, where multiple impact of steel and plastic fiber reinforced concrete panels are explored. A third investigation is performed on four RSC panels with varied thicknesses and subjected to the same impact velocity. In this instance, the model is used to predict the penetration depths for the different cases. Finally, in the last study, the response of large‐thickness infinite panels of sizes ranging from 300 mm to 700 mm under projectile impact is considered. Copyright © 2016 John Wiley & Sons, Ltd.     

江苏黄桥无机油气的地球化学演化模式与富集规律

江苏黄桥CO2气田中的CO2,历来被认为是幔源CO2。但最近的研究结果表明,这种CO2并非幔源CO2。而是幔源CH4上升至地表（－3000m-0m)被氧化的结果。黄桥CO2气田犹如一床棉被覆盖在无机油气上方,形成气被,其下就是储量巨大的凝析油和CH4气田。黄桥地区无机油气藏的找矿方向在其CO2气田的下面深部,勘探重点放在地下5000－10000m之间的构造富集的有利部位,研究提出了一种在未知区既较为经济,又能较大提高钻井成功率的无机油气藏立体勘查模型。     

Contrasting carbon export dynamics of human impacted and pristine tropical catchments in response to a short‐lived discharge event

Utilising newly available instrumentation, the carbon balance in two small tropical catchments was measured during two discharge events at high temporal resolution. Catchments share similar climatic conditions, but differ in land use with one draining a pristine rainforest catchment, the other a fully cleared and cultivated catchment. The necessity of high resolution sampling in small catchments was illustrated in each catchment, where significant chemical changes occurred in the space of a few hours or less. Dissolved and particulate carbon transport dominated carbon export from the rainforest catchment during high flow, but was surpassed by degassing of CO₂ less than 4 h after the discharge peak. In contrast, particulate organic carbon dominated export from the cleared catchment, in all flow conditions with CO₂ evasion accounting for 5–23% of total carbon flux. Stable isotopes of dissolved inorganic carbon (DIC) in the ephemeral rainforest catchment decreased quickly from ~1.5 ‰ to ~ ?16 ‰ in 5 h from the flood beginning. A two‐point mixing model revealed that in the initial pulse, over 90% of the DIC was of rainwater origin, decreasing to below 30% in low flow. In the cultivated catchment, δ¹³C_DIC values varied significantly less (?11.0 to ?12.2 ‰) but revealed a complex interaction between surface runoff and groundwater sources, with groundwater DIC becoming proportionally more important in high flow, due to activation of macropores downstream. This work adds to an increasing body of work that recognises the importance of rapid, short‐lived hydrological events in low‐order catchments to global carbon dynamics. Copyright © 2013 John Wiley & Sons, Ltd.     

Responses of water yield and dissolved inorganic carbon export to forest recovery in the Houzhai karst basin,southwest China

Karst terrain (carbonate rocks) covers a vast land of 0.446 million km² in southwest China. Water yield and carbonate rocks weathering in this region have been receiving increased attention due to a large‐scale forest recovery. Using both hydrological measurements and forest inventories from 1986 to 2007 in the Houzhai karst basin (HKB), we analyzed the responses of water yield and dissolved inorganic carbon (DIC) export to forest recovery in southwest China. With implementation of both the Natural Forest Conservation Program (NFCP) and the Conversion of Farmland to Forests Program (CFFP), the fraction of forest area in HKB was increased from near zero to 18.9% during the study period, but the ratio of total water yield (surface and underground) to precipitation varied very little over the annual period, neither in wet season nor in dry season. By contrast, the concentration of DIC in water, especially in the surface water had a pronounced increase during the study period, with an increase of 0.53 and 0.25 g C m^?3 yr^?1 for surface water and underground water, respectively. As a result, total annual DIC export at mean annual rainfall significantly increased from the low to high forest area stage. This increase was largely driven by surface water during the wet season, presumably being related to biological activity. It was concluded that forest recovery in HKB had no significant effect on water yield, but resulted in more carbon dioxide (CO₂) dissolved in karst water accompanying with carbon uptake by forests. Our results suggested that implementations of both NFCP and CFFP had no shifted water yield regimes in southwest China; instead, they might have alleviated global climate change by increasing carbon uptake through combined biological processes and carbonate rocks weathering. Copyright © 2013 John Wiley & Sons, Ltd.