Recent changes of Shandong sandy coast and in fluence of human activities

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Effects of Meteorological Factors on Toxic Red Tide Events in Sabah, Malaysia

Abstract. Red tides of the toxic dinoflagellate Pyrodinium bahamense var. compressum have occurred almost annually since 1976 in the coastal waters of the west coast of Sabah, Malaysia. Field obSérvations have indicated that the timings of these outbreaks could be linked to meteorological forcings. All the red tides have occurred during either the northeast or southwest monsoon periods. Matching of red tide outbreaks with total monthly rainfall, monthly-averaged index of wind-induced surface water mixing, and monthly-averaged upwelling index for the period from 1975 to 1989 failed to show any definite pattern. However, more red tide events occurred in months with high mixing index values. The absence of definable patterns could be due to the use of monthly, rather than daily, values in the calculations.     

Spartina anglica eradication experiment and in situ monitoring assess structuring strength of habitat complexity on marine macrofauna at high tidal level

The cordgrass Spartina anglica is an introduced species that tends to invade sheltered sand and mudflats, at the upper low marsh level. In Arcachon Bay, a lagoon in South West of France, the cordgrass can also replace Zostera noltii beds. The consequence of cordgrass presence on macrobenthic fauna was estimated and compared to adjacent habitats (bare sands, Z. noltii sea grass beds) during one year. The communities of the three habitats were characterised by low species richness, low abundance and biomass (when Hydrobia ulvae, 90% of abundance, is not considered) and high seasonal stability. The infaunal assemblages were particularly homogeneous between habitats without any characteristic species.Cordgrass eradication experiments were performed and zoobenthic recolonisation was observed the following year. Modifications in benthic fauna were observed on epifauna only.These results highlight the limited structuring effect of habitat heterogeneity at high tidal levels and in soft-bottom sediments where desiccation becomes the dominant factor determining infauna community structure.     

大亚湾海域沉积物中的硝化与反硝化作用

2004年1、4、8、10月在大亚湾海域的4个站点采用自行设计和制作的无扰动沉积物采样器采集沉积物样品,通过使用AIT技术(乙炔同时抑制硝化与反硝化作用),进行实验室同步恒温受控模拟培养实验,并同时测定沉积物上覆水的温度、盐度、DO和pH值,沉积物的Eh值和有机质含量,间隙水的NO3-、NO2-和NH4 浓度,研究沉积物中的硝化与反硝化速率及其影响因素。结果显示大亚湾沉积物的硝化速率范围为[(0.00—4.68)±0.87]μmol/(m2·h);反硝化速率范围[(0.00—2.88)±0.41]μmol/(m2·h);硝化与反硝化作用之间存在耦合,比例范围为0%—100%。沉积物的硝化、反硝化速率和耦合比例与上覆水的温度、DO含量,及沉积物中的有机质含量和Eh值密切相关,人类活动对沉积物的硝化与反硝化作用有明显的影响。     

加强海洋灾害地质学研究,减少海洋工程灾害

随着我国近海油气资源的开发及海洋工程的需要,海洋灾害地质学这一边缘学科正在我国兴起和迅速发展。本文对这一学科的研究对象、研究领域以及灾害地质因素分类进行了概述,并对海洋灾害地质学的特点与应用前景,进行了初步总结,最后对该学科的发展方向提出了积极建议。     

Spatio-temporal variability of surface soil water content and its influencing factors in a desert area,China

Abstract

Knowledge of the variability of soil water content (SWC) in space and time plays a key role in hydrological and climatic modelling. However, limited attention has been given to arid regions. The focus of this study was to investigate the spatio-temporal variability of surface soil (0–6 cm) water content and to identify its controlling factors in a region of the Gobi Desert (40 km²). The standard deviation of SWC decreased logarithmically as mean water content decreased, and the coefficient of variation of SWC exhibited a convex upward pattern. The spatial variability of SWC also increased with the size of the investigated area. The spatial dependence of SWC changed over time, with stronger patterns of spatial organization in drier and wetter conditions of soil wetness and stochastic patterns in moderate soil water conditions. The dominant factors regulating the variability of SWC changed from combinations of soil and topographical properties (bulk density, clay content and relative elevation) in wet conditions to combinations of soil and vegetation properties (bulk density, clay content and shrub coverage) in dry conditions. This study has important implications for the assessment of soil quality and the sustainability of land management in arid regions.     

Qualitative and quantitative characterization of a transitional shale reservoir: A case study from the Upper Carboniferous Taiyuan shale in the eastern uplift of Liaohe Depression,China

The paper takes the Upper Carboniferous Taiyuan shale in eastern uplift of Liaohe depression as an example to qualitatively and quantitatively characterize the transitional (coal-associated coastal swamp) shale reservoir. Focused Ion Beam Scanning Electron Microscope (FIB-SEM), nano-CT, helium pycnometry, high-pressure mercury intrusion and low-pressure gas (N₂ & CO₂) adsorption for eight shale samples were taken to investigate the pore structures. Four types of pores, i.e., organic matter (OM) pores, interparticle (InterP) pores, intraparticle (IntraP) pores and micro-fractures are identified in the shale reservoir. Among them, intraP pores and micro-fractures are the major pore types. Slit-shaped pores are the major shape in the pore system, and the connectivity of the pore-throat system is interpreted to be moderate, which is subordinate to marine shale. The porosity from three dimension (3D) reconstruction of SEM images is lower than the porosity of helium pycnometry, while the porosity trend of the above two methods is the same. Combination of mercury intrusion and gas absorption reveals that nanometer-scale pores provide the main storage space, accounting for 87.16% of the pore volume and 99.85% of the surface area. Micropores contribute 34.74% of the total pore volume and 74.92% of the total pore surface area; and mesopores account for 48.27% of the total pore volume and 24.93% of the total pore surface area; and macropores contribute 16.99% of the total pore volume and 0.15% of the total pore surface area. Pores with a diameter of less than 10 nm contribute the most to the pore volume and the surface area, accounting for 70.29% and 97.70%, respectively. Based on single factor analysis, clay minerals are positively related to the volume and surface area of micropores, mesopores and macropores, which finally control the free gas in pores and adsorbed gas content on surface area. Unlike marine shale, TOC contributes little to the development of micropores. Brittle minerals inhibit pore development of Taiyuan shale, which proves the influence of clay minerals in the pore system.     

Spatial and temporal variations of overland flow during rainfall events and in relation to catchment conditions

Improved knowledge on overland flow (OF) generation and its dynamics (i.e. spatial and temporal variations) is essential to understand catchment hydrology, a prerequisite for better water resources and soil management. In this study, our main objective was to quantify the dynamics of OF during rainfall events and to assess its main factors of control. The research study was undertaken in an agricultural 23‐ha catchment of a communal pasture in KwaZulu‐Natal (South Africa) experiencing Mediterranean climate and with variations of soil, topography and vegetation conditions. The dynamics of OF was evaluated during three rainfall seasons (2007 to 2010) by using 1 × 1‐m² microplots (n = 15) located at five landscape positions. At each location, a microplot was equipped with an automatic tipping bucket linked to a logger to estimate the delay between the start of the rain and the start of OF [i.e. the time to runoff initiation (TRI)]. Multivariate analysis was applied to the total OF and TRI data and the information on selected environmental factors (rainfall characteristics; soil type; soil clay content, Clay; proportion of the soil surface covered by vegetation, Cov; proportion of the soil surface covered by crusting, Crust; mean slope gradient, S; soil bulk density, ρ_b; soil water tension at different depths, SWT). The average OF rate over the 3‐year study period varied 2.3‐fold across the catchment (from 15% footslope to 35% backslope), whereas the average TRI varied by a 10.6‐fold factor (between 0.6 min at bottomland and 6.4 min at footslope). TRI temporal variations correlated the most with event duration (r = 0.8) and cumulative amount of rainfall since the onset of the rainy season (r = ?0.47), whereas TRI spatial variations were controlled the most by Crust (?0.97 < r < ?0.77). Ultimately, TRI spatial variations were modelled and mapped in an attempt to model OF dynamics over the entire microcatchment. Copyright © 2012 John Wiley & Sons, Ltd.     

Seasonal Variation and Meteorological Control of CO2 Flux in a Hilly Plantation in the Mountain Areas of North China

The carbon cycle of terrestrial ecosystems is an important scientific issue in global climate change re- search. Plantation forest plays an important role in terrestrial carbon budget in China. In this study, eddy covariance flux data measured at Xiaolangdi forest ecosystem research station (XLD) in 2007 and 2008 are used to analyze the seasonal variation and meteorological control of CO2 flux in a 30-yr-old mixed plantation. The plantation forest mainly consists of Quercus variabilis, Platycladus orientalis, and Robinia pseudoacacia. The results show that the seasonal variations of net ecosystem exchange of CO2 (NEE), gross primary production (GPP), and ecosystem respiration (Re) display single-peak curves. The maximum of carbon sequestration appears during May and June each year. The relative contribution of carbon re- lease from ecosystem respiration to GPP varied slightly between 2007 and 2008. The relationship between NEE and photosynthetic active radiation (Qp) accords with the rectangular hyperbola model on diurnal scale, and shows a good linear correlation on monthly scale. The ecosystem photosynthetic parameters: the maximum photosynthetic rate (Pmax), the ecosystem photosynthetic photonyield (α), and the daytime ecosystem respiration (Rd) exhibit seasonal variations. Pmax reaches the maximum in August each year, with small interannual di?erence. The interannual differences of α and Rd are obvious, which is attributed to the changes of meteorological factors, such as solar radiation, vapor pressure deficit (D), precipitation, etc. Parameters Re, GPP, and NEP (net ecosystem production) have obvious exponential relations with temperature on monthly scale. There is a hysteresis in the response of GPP and NEP to temperature, i.e., the carbon sequestration is not the maximum when the temperature reaches the peak value. The Q10 values were 1.37 and 1.45 in 2007 and 2008, respectively. On monthly scale, Re, GPP, and NEE increase as D increases, but rise slowly and even decrease when D is higher than 1.5 kPa.     

How well can the subsurface storage–discharge relation be interpreted and predicted using the geometric factors in headwater areas?

Headwater storage–discharge (S–Q) remains one of the least understood processes, and there is renewed interest in the S–Q relation. How well can the S–Q relation be interpreted mechanistically using geometric factors? In this paper, the hillslope storage Boussinesq and hillslope storage kinematic wave equation were adopted to guide the theoretical derivations. Analytical solutions were derived based on the hsKW equation for nine idealized hillslope aquifers, which were subdivided into two groups, i.e. hillslope aquifers with exponential hillslope width function (C1) and hillslope aquifers with Gaussian hillslope width function (C2). We found that analytical expressions of the S–Q relation can be derived for C1 hillslope aquifers. For more compound hillslope aquifers, i.e. C2, no explicit S–Q relation can be obtained. The whole subsurface recession after a rainstorm is simulated by applying the initial saturation condition. We found that the simulated S–Q processes can be characterized by a two‐phase recession, i.e. quick and slow recession. The time (t_b) at the dividing point of the quick and slow recessions depends on the geometric factors, such as the plan and profile curvature. In the quick recession for C1, many of the S–Q curves can be described as linear or quasi‐linear functions, which indicate that linear reservoir models can be applied approximately for recession simulations. However, during the slow recession phase of C1 and during the whole recession of C2, the S–Q relations are highly non‐linear. Finally, we compared the hillslope storage kinematic wave and hillslope storage Boussinesq models for simulating subsurface water recession after a rainstorm event in a real‐world headwater catchment (G5) in China. Through comparison of the recession slope curves, we found that the simulated results of the models employing the Gaussian hillslope width function match the observed hydrograph. The results indicated that appropriate organization of the hillslope geometric factors enhances our ability to make S–Q predictions. Copyright © 2016 John Wiley & Sons, Ltd.