Physicochemical conditions in coastal waters off Syndney, central NSW, Australia

The continental shelf off Sydney is narrow and characterized by extensive areas of rocky reef and sandy sediment. The overlying coastal waters are dynamic with a complex current structure. Important oceanographic processes include East Australian Current (EAC) activity, northward propagating coastal trapped waves, local wind driven currents and relatively high frequency internal tides and waves. These produce influences on a wide range of temporal and spatial scales. The activity of the EAC and its eddies has been associated with episodic incursions of waters which can quickly replace large parts of the shelf waters off Sydney. Thermal stratification and the episodic presence of cold, nutrient rich waters intruded from the continental slope are important features of the water column. Thermal stratification of up to 6°C generally exists for all but a few months of the year. Nutrient concentrations are generally low in surface waters but are higher and more variable at depth because of irregular intrusions of slope waters from depths greater than 150–200 m. The trace element levels in surface seawater entering the Sydney area are expected to be extremely low.     

Australia''s first deepwater sewage outfalls: Design considerations and environmental performance monitoring

The discharge of sewage to the ocean can be an issue of public and scientific concern. Such has been the case in Sydney over at least the past 25 years. In this paper, the history of Sydney's sewage discharge is outlined, and the decisions taken to address concerns about the environmental effects of shoreline discharge of large volumes of primary treated sewage effluent are described. Design criteria are described for deepwater outfall systems that, since 1990–1991, have discharged 80% of Sydney's sewage after primary treatment at North Head, Bondi and Malabar Sewage Treatment Plants (STP). The integrated elements of a comprehensive five year Environmental Monitoring Programme (EMP) are set out. Other papers in this volume describe the result of EMP component studies. The five year EMP was designed to provide the basis to assess the environmental performance of the new deepwater outfall systems during the first two years of their operation and to provide a baseline against which further change may be measured.     

Color centers,associated rare-earth ions and the origin of coloration in natural fluorites

Natural colored fluorites were studied by means of optical absorption and electron paramagnetic resonance (EPR). Complex centers involving rare-earth ions and/or oxygen give rise to the various colors observed. These include yttrium-associated F centers (blue), coexisting yttrium and cerium-associated F centers (yellowish-green), the (YO₂) center (rose) and the O ₃ ^? molecule ion (yellow). Divalent rare-earth ions also contribute to the colorations, as for instance Sm³⁺ (green fluorites), or they are at the origin of strong fluorescence observed (Eu²⁺). Strong irradiation of the crystals with ionizing radiation leads to coagulation of color centers, and to precipitation of metallic calcium colloids. There is probably no simple relation connecting the coloration and the growth process of the crystal. Thermal stability studies, however, have allowed to partially classify the colors as being of primary or secondary origin.     

How Much Warming are We Committed to and How Much can be Avoided?

This paper examines different concepts of a ‘warming commitment’ which is often used in various ways to describe or imply that a certain level of warming is irrevocably committed to over time frames such as the next 50 to 100 years, or longer. We review and quantify four different concepts, namely (1) a ‘constant emission warming commitment’, (2) a ‘present forcing warming commitment’, (3) a‘zero emission (geophysical) warming commitment’ and (4) a ‘feasible scenario warming commitment’. While a ‘feasible scenario warming commitment’ is probably the most relevant one for policy making, it depends centrally on key assumptions as to the technical, economic and political feasibility of future greenhouse gas emission reductions. This issue is of direct policy relevance when one considers that the 2002 global mean temperatures were 0.8± 0.2 ^°C above the pre-industrial (1861–1890) mean and the European Union has a stated goal of limiting warming to 2 ^°C above the pre-industrial mean: What is the risk that we are committed to overshoot 2 ^°C? Using a simple climate model (MAGICC) for probabilistic computations based on the conventional IPCC uncertainty range for climate sensitivity (1.5 to 4.5 ^°C), we found that (1) a constant emission scenario is virtually certain to overshoot 2 ^°C with a central estimate of 2.0 ^°C by 2100 (4.2 ^°C by 2400). (2) For the present radiative forcing levels it seems unlikely that 2 ^°C are overshoot. (central warming estimate 1.1 ^°C by 2100 and 1.2 ^°C by 2400 with ～10% probability of overshooting 2 ^°C). However, the risk of overshooting is increasing rapidly if radiative forcing is stabilized much above 400 ppm CO₂ equivalence (1.95 W/m²) in the long-term. (3) From a geophysical point of view, if all human-induced emissions were ceased tomorrow, it seems ‘exceptionally unlikely’ that 2 ^°C will be overshoot (central estimate: 0.7 ^°C by 2100; 0.4 ^°C by 2400). (4) Assuming future emissions according to the lower end of published mitigation scenarios (350 ppm CO₂eq to 450 ppm CO₂eq) provides the central temperature projections are 1.5 to 2.1 ^°C by 2100 (1.5 to 2.0 ^°C by 2400) with a risk of overshooting 2 ^°C between 10 and 50% by 2100 and 1–32% in equilibrium. Furthermore, we quantify the ‘avoidable warming’ to be 0.16–0.26 ^°C for every 100 GtC of avoided CO₂ emissions – based on a range of published mitigation scenarios.     

Constraints on a plume in the mid-mantle beneath the Iceland region from seismic array data

Teleseismic P waves passing through low-wave-speed bodies in the mantle are refracted, causing anomalies in their propagation directions that can be measured by seismometer arrays. Waves from earthquakes in the eastern Pacific and western North America arriving at the NORSAR array in Norway and at seismic stations in Scotland pass beneath the Iceland region at depths of ∼ 1000–2000 km. Waves arriving at NORSAR have anomalous arrival azimuths consistent with a low-wave-speed body at a depth of ∼ 1500 km beneath the Iceland–Faeroe ridge with a maximum diameter of ∼250 km and a maximum wave-speed contrast of ∼ 1.5 per cent. This agrees well with whole-mantle tomography results, which image a low-wave-speed body at this location with a diameter of ∼ 500 km and a wave-speed anomaly of ∼ 0.5 per cent, bearing in mind that whole-mantle tomography, because of its limited resolution, broadens and weakens small anomalies. The observations cannot resolve the location of the body, and the anomaly could be caused in whole or in part by larger bodies farther away, for example by a body imaged beneath Greenland by whole-mantle tomography.     

Evaluating equilibrium and non‐equilibrium transport of ammonium in a loam soil column

Release of nitrogen compounds into groundwater, particularly those compounds from excessive agricultural fertilization, is a major concern in an aquifer recharge. Among the nitrogen compounds, ammonium ( ) is a common one. In order to assess the risk of agricultural fertilizer contamination to an aquifer through infiltration, adsorption onto a loamy agricultural soil profile (0–0.60 m depth) was studied using a soil column experiment and modelling simulation. The soil used in the experiment was drawn from an agricultural field in Xinzhen, Fangshan district, Beijing, China, and reconstituted in laboratory soil columns. Column experiments were conducted using bromide (conservative tracer) and ‐bearing aqueous solutions. The ammonium concentrations in the soil water samples were measured, and their values were plotted as the breakthrough curves. The chemical's soil–water distribution coefficients (K_d) were calculated using breakthrough curves. Then the retardation factor (R) in saturated soil was calculated. For the ‐bearing aqueous solutions, the strongest adsorption occurred at the soil depth of 0.30–0.45 m. The convection–dispersion equation model and chemical non‐equilibrium model in Hydrus‐1D were used to simulate transport in the loamy soil. The two‐site chemical non‐equilibrium model in Hydrus‐1D was best to simulate transport through the soil column. Parameter sensitivity study was conducted to investigate the influences of solute transport by K_d, the fraction of exchange sites assuming to be in equilibrium with the solution phase (f), the longitudinal dispersivity (λ), and the first‐order rate coefficients (ω). The sensitivity analysis results indicate K_d is the most critical parameter.     

云南-香港宽视场巡天新发现的一个磁活动双星系统

云南-香港宽视场巡天新发现了一个磁活动双星系统,其轨道周期为0.60286 d.利用云南天文台1 m光学望远镜附加CCD (Charge-Coupled Device)相机,观测得到了这个双星系统的V、Rc双色光变曲线,结果表明该系统食外存在明显的测光畸变.借助云南天文台丽江2.4 m望远镜附加云南暗弱天体光谱成像仪(Yunnan Faint Object Spectrograph and Camera, YFOSC)对该双星系统的分光观测,测定了该双星系统主星的视向速度曲线并发现该系统的主星表面存在着强烈的色球活动,从而证明系统的光变曲线畸变源自主星的黑子活动.使用W-D (Wilson-Devinney)程序分析上述观测得到的光变曲线和视向速度曲线,得到了该双星系统的轨道参数以及黑子参数.最后,对该系统的特性进行了讨论并对未来的工作进行了展望.