Grazing suppression of dimethylsulphoniopropionate (DMSP) accumulation in iron-fertilised, sub-Antarctic waters

The impact of in situ iron fertilisation on the production of particulate dimethylsulphoniopropionate (DMSPp) and its breakdown product dimethyl sulphide (DMS) was monitored during the SOLAS air-sea gas exchange experiment (SAGE). The experiment was conducted in the high nitrate, low chlorophyll (HNLC) waters of the sub-Antarctic Southern Ocean (46.7°S 172.5°E) to the south-east of New Zealand, during March-April, 2004. In addition to monitoring net changes in the standing stocks of DMSPp and DMS, a series of dilution experiments were used to determine the DMSPp production and consumption rates in relation to increased iron availability. In contrast to previous experiments in the Southern Ocean, DMS concentrations decreased over the course of the 15-d iron-fertilisation experiment, from an integrated volume-specific concentration in the mixed layer on day 0 of 0.78 nM (measured values 0.65-0.91 nM) to 0.46 nM (measured values 0.42-0.47 nM) by day 15, in parallel with the surrounding waters. DMSPp, chlorophyll a and the abundance of photosynthetic picoeukaryotes exhibited indiscernible or only moderate increases in response to the raised iron availability, despite an obvious physiological response by the phytoplankton. High specific growth rates of DMSPp, equivalent to 0.8-1.2 doublings d⁻¹, occurred at the simulated 60% light level of the dilution experiments. Despite the high production rates, DMSPp accumulation was suppressed in part by microzooplankton grazers who consumed between 61% d⁻¹ and 126% d⁻¹ of the DMSPp production. Temporal trends in the rates of production and consumption illustrated a close coupling between the DMSP-producing phytoplankton and their microzooplankton grazers. Similar grazing and production rates were observed for the eukaryotic picophytoplankton that dominated the phytoplankton biomass, partial evidence that picoeukaryotes contributed a substantial proportion of the DMSP synthesis. These rates for DMSPp and picoeukaryotes were considerably higher than for chlorophyll a, indicating higher cycling rates of the DMSP-producing taxa than for the bulk phytoplankton community. When compared to the total phytoplankton community, there was no evidence of selection against the DMSP-containing phytoplankton by the microzooplankton grazers; the opposite appeared to be the case. SAGE demonstrated that increased iron availability in the HNLC waters of the Southern Ocean does not invariably lead to enhanced DMS sea-air flux. The potential suppression of DMSPp accumulation by grazers needs to be taken into account in future attempts to elevate DMS emission through in situ iron fertilisation and in understanding the hypothesised link between levels of Aeolian iron deposition in the Southern Ocean, DMS emission and global albedo.     

Shallow geothermal regime in the Perth Metropolitan Area

Exploration of Perth's geothermal potential has been performed by the Western Australian Geothermal Centre of Excellence (WAGCoE). Detailed vertical temperature and gamma ray logging of 17 Western Australia Department of Water's (DoW) Artesian Monitoring (AM) wells was completed throughout the Perth Metropolitan Area (PMA). In addition, temperature logs from 53 DoW AM wells measured in the 1980s were digitised into LAS format. The logged data are available in the WAGCoE Data Catalogue.

Analysis of the gamma ray logs yielded the first estimates of radiogenic heat production in Perth Basin formations. Values by formation ranged between 0.24 and 1.065 μW m^?3. The temperature logs provide a picture of true formation temperatures within shallow sediments in the Perth Basin. A three-dimensional model of the temperature distribution was used to produce maps of temperature at depth and on the top of the Yarragadee aquifer.

The temperature data were interpreted with a one-dimensional conductive heat model. Significant differences between the model and the observations was indicative of heat moving via non-conductive mechanisms, such as advection or convection. Evidence of non-conductive or advective heat flow is demonstrated in most formations in the region, with significant effects in the aquifers. Average conductive geothermal gradients range from 13°C km^?1 to 39°C km^?1, with sandstone formations exhibiting average gradients of approximately 25°C km^?1, while insulating silt/shale formations show higher average gradients of over 30°C km^?1.

To produce preliminary heat flow estimates, temperature gradients were combined with thermal conductivities measured elsewhere. The geometric mean heat flow estimates range between 64 mW m^?2 to 91 mW m^?2, with the standard deviation of the arithmetic mean heat flow ranging between 15 and 23 mW m^?2.

The study characterises the shallow temperature regime in the Perth Metropolitan Area, which is of direct relevance towards developing commercial geothermal projects.     

柿庄南区块煤层气井早期生产特征及开采建议

从水文地质的角度揭示了不同情况下单井的排水采气机理。在此基础上结合柿庄南区块59口井的实际排采数据,综合分析了气水产量,井底流压,套压及动液面随时间的变化曲线;并将早期生产特征归纳为3种类型：①低产水-高产气型,见气早,产气量高（>1000 m3/d）、产量递减缓慢、峰值产量高,日产水量小（<2m3/d）,套压高;②低产水-中低产气型,日产气小于1000 m3,产量衰减明显且波动大,排水期较长;③高产水型,产气极少或无,日产水量大（>10m3/d）,动液面下降缓慢,套压很低或为零。最后针对不同类型的低产井,提出相应的开采建议：低产水-低产气型井可采用二次压裂措施,改善煤层渗透率;高产水井可通过无机堵水或加大排采强度等方式排采;煤层气井排采要勇于实践,探索适合该区不同煤层的成功排采方法。     

矿权的生产与经营--论地勘单位的改革与发展

矿权及矿权市场的建立,为地勘行业的找矿成果进入市场搭建了平台,矿权的生产与经营是国有地勘单位最具优势和竞争力的产业发展方向,商业性地质工作是地勘单位获取利润的重点,按市场经济的要求,以企业为主体,以局为单元,以效益为目的,地勘行业在社会经济发展中大有作为。     

热流─生热率线性关系研究综述

热流－生热率线性关系的发现被视为理论地热学上的一次重大突破，目前在全球范围内已定义了数十个热流省。但是，这一线性关系至今仍缺乏可信的理论基础。本文概述了热流－生热率线性关系的发展历史，综合介绍了２０多年来在地质、地球化学和地球物理等方面为正确理解这一经验线性关系的内在涵义而展开的研究，并对现有大陆热流省的资料进行了分析。     

跨国公司对区域经济发展影响的理论研究

(1)根据相邻学科的理论并基于前人研究成果,提出跨国公司对区域经济影响、跨国公司与区域关系以及两者关系的决定因素三层次研究思路;(2)以生产链、组织链和所有权关系三个关联系统和区域等级关系作为跨国投资的理论背景,导出跨国公司──区域综合分析方法;(3)跨国投资对区域发展影响具广泛性、层次性、区域性、多面性、差异性和时间性特点,跨国公司与投资地关系具互补性、竞争性和变化性特点,影响两者关系的主要因素为社会政治背景、结构状况和相对地位。     

Impact of Climate Warming in the Past 20 Years on Agriculture in Different Regions of China

 Based on the China Rural Statistical Yearbook of 1984-2003 published by State Statistics Bureau, and the annual temperature in the same period, impacts of temperature change, agricultural input, and planting area on grain production were analyzed for different regions of China during the last 20 years. The results show that the main characteristic of climate warming has obviously promoted the increase of grain yield in Northeast China, but to some extent suppressed it in North China, Northwest China and Southwest China, and shown no obvious effect on it in East China and Central-South China. The increase in agricultural input facilitated the grain production obviously in various regions in the early stage of the past 20 years, but showed no obvious effect in the late stage. The continuous reduction in sown area had a significant negative effect on the grain production in East China and Central-South China.     

Numerical Simulation Study on the Effect of Horizontal Well Reservoir Stimulation for Gas Hydrate Production

A new gas hydrate reservoir stimulation method of in-situ fracturing with transient heating is proposed, in line with analysis of the technological bottlenecks faced by marine gas hydrate production. This method injects the developed chemical reagents into a hydrate reservoir through hydraulic fracturing, releasing heat during the chemical reaction to increase the hydrate decomposition rate. The chemical reaction product furthermore has a honeycomb structure to support fractures and increase reservoir permeability. Based on the geological model of natural gas hydrate in the South China Sea, three development methods are simulated to evaluate hydrate production capacity, consisting of horizontal well, fractured horizontal well and in-situ fracturing with transient heating well. Compared with the horizontal well, the simulation results show that the cumulative gas production of the fractured horizontal well in one year is 7 times that of the horizontal well, while the cumulative gas production of in-situ fracturing with transient heating well is 12 times that of the horizontal well, which significantly improves daily efficiency and cumulative gas production. In addition, the variation patterns of hydrate saturation and temperature-pressure fields with production time for the three exploitation plans are presented, it being found that three sensitive parameters of fracture conductivity, fracture half-length and fracture number are positively correlated with hydrate production enhancement. Through the simulations, basic data and theoretical support for the optimization of gas hydrate reservoir stimulation scheme has been provided.     

Seasonal variation of microzooplankton (20–200 μm) and its possible implications on the vertical carbon flux in the western Bay of Bengal

Stratification (throughout the year) and low solar radiation (during monsoon periods) have caused low chlorophyll a and primary production (seasonal average 13–18 mg m⁻² and 242–265 mg C m⁻² d⁻¹, respectively) in the western Bay of Bengal (BoB). The microzooplankton (MZP) community of BoB was numerically dominated by heterotrophic dinoflagellates (HDS) followed by ciliates (CTS). The highest MZP abundance (average 665±226×10⁴ m⁻²), biomass (average 260±145 mg C m⁻²) and species diversity (Shannon weaver index 2.8±0.42 for CTS and 2.6±0.35 for HDS) have occurred during the spring intermonsoon (SIM). This might be due to high abundance of smaller phytoplankton in the western BoB during SIM as a consequence of intense stratification and nitrate limitation (nitracline at 60 m depth). The strong stratification during SIM was biologically evidenced by intense blooms of Trichodesmium erythraeum and frequent Synechococcus–HDS associations. The high abundance of smaller phytoplankton favors microbial food webs where photosynthetic carbon is channeled to higher trophic levels through MZP. This causes less efficient transfer of primary organic carbon to higher trophic levels than through the traditional food web. The microbial food web dominant in the western BoB during SIM might be responsible for the lowest mesozooplankton biomass observed (average 223 mg C m⁻²). The long residence time of the organic carbon in the surface waters due to the active herbivorous pathways of the microbial food web could be a causative factor for the low vertical flux of biogenic carbon during SIM.     

Potential of in situ-produced cosmogenic nuclides for quantifying strength reduction of bedrock in soil-mantled hillslopes

This study presents a semi-empirical model for quantifying the reduction in the mechanical strength of bedrock beneath actively eroding soil-mantled hillslopes. The strength reduction of bedrock controls the rate of physical disintegration of saprolite, which supplies fresh minerals that are then exposed to intense chemical weathering in soil sections. To determine the values of parameters employed in the model requires knowledge of the denudation rate of the hillslope, the thickness of the soil and saprolite layers, the strength of fresh bedrock, and the threshold strength for physical erosion at the uppermost face of the saprolite. These parameters can be obtained from cosmogenic nuclide analyses for quartz samples from the soil–saprolite boundary and basic field- and laboratory-based investigations. Further testing of the model within a diverse range of climatic, tectonic, and lithologic environments is likely to provide clues to the mechanisms responsible for local and regional variations in the rates of soil production and chemical weathering upon hillslopes.