Seasonal and spatial dynamics of nutrients and phytoplankton biomass in Victoria Harbour and its vicinity before and after sewage abatement

This study investigated the seasonal and spatial dynamics of nutrients and phytoplankton biomass at 12 stations in Hong Kong (HK) waters during a three year period from 2004 to 2006 after upgraded sewage treatment and compared these results to observations before sewage treatment. Pearl River estuary (PRE) discharge significantly increased NO(3) and SiO(4) concentrations, particularly in western and southern waters when rainfall and river discharge was maximal in summer. Continuous year round discharge of sewage effluent resulted in high NH(4) and PO(4) in Victoria Harbour (VH) and its vicinity. In winter, spring and fall, the water column at all stations was moderately mixed by winds and tidal currents, and phytoplankton biomass was relatively low compared to summer. In summer, the mean surface phytoplankton chl biomass was generally > 9 microL(-1) in most areas as a result of thermohaline stratification, and high nutrients, light, and water temperature. In summer, the potential limiting nutrient is PO(4) in the most productive southern waters and it seldom decreased to limiting levels ( approximately 0.1 microM), suggesting that phytoplankton growth may be only episodically limiting. The mean bottom dissolved oxygen (DO) remained > 3.5 mg L(-1) at most stations, indicating that the eutrophication impact in HK waters was not as severe as expected for such a eutrophic area. After the implementation of chemically enhanced primary sewage treatment in 2001, water quality in VH improved as indicated by a significant decrease in NH(4) and PO(4) and an increase in bottom DO. In contrast, there were an increase in chl a and NO(3), and a significant decrease in bottom DO in southern waters in summer, suggesting that hypoxic events are most likely to occur in this region if phytoplankton biomass and oxygen consumption keep increasing and exceed the buffering capacity of HK waters maintained by monsoon winds, tidal mixing and zooplankton grazing. Therefore, future studies on the long-term changes in nutrient loading from PRE and HK sewage discharge will be crucial for developing future strategies of sewage management in HK waters.     

On the generation and decay of the long-period coda energy of large earthquakes

Seismic coda wave is the tail portion of the earthquake record after main arrivals. Studies on the coda usually focus on high-frequency data within several hours after regional events and attribute them to the scattering effect of the heterogeneities inside the earth. Here, we use records of seven large earthquakes at globally distributed seismic stations to examine the decay of long-period (100 s to 300 s) coda in the time window of 10,000 s to 140,000 s after the origin time and fit it with a statistical model. The geometric spreading effect in the estimated initial energy and a location-independent equivalent attenuation coefficient indicate that the long-period coda energy is less affected by the heterogeneity-induced scattering effect than that of shorter-period coda. The coda energy can reach the earth's inner core and can be explained by a 1D earth model, making it more effective for constraining the global attenuation model. It also has the potential to determine the magnitudes of large earthquakes and to explore the interior of planetary bodies.     

PCBs and PAHs in sea-surface microlayer and sub-surface water samples of the Venice Lagoon (Italy)

Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) are two classes of micropollutants intensively monitored and regulated due to their toxicity, persistency and wide diffusion. Their concentrations have been investigated in sea-microlayer (SML) and sub-surface water (SSW) samples collected at two sites of the Venice Lagoon, a fragile ecosystem highly influenced by industrial and anthropogenic emissions. The total sigmaPCB concentration varies from 0.45 ng/l to 2.1 ng/l in SSW while a clear enrichment is observed in the SML, where it ranges from 1.2 ng/l to 10.5 ng/l. The total sigmaPAH concentration shows marked differences between the two stations and varies from 12.4 ng/l to 266.8 ng/l in SSW; in SML it is more uniform and ranges from 19.6 ng/l to 178.9 ng/l. The enrichment factors are not larger than 1 for both pollutants in the 'dissolved' phase, while they are most significant for the 'particulate' phase (sigmaPCB: 5-9; sigmaPAH: 4-14).     

Distribution and sources of polynuclear aromatic hydrocarbons in Mangrove surficial sediments of Deep Bay, China

Twelve sediment samples collected from three transects of mangrove swamp of Deep Bay, Shenzhen, China, were determined for polynuclear aromatic hydrocarbons (PAHs). The total PAHs concentrations ranged from 237 to 726 ng g(-1) dry weight, and showed strong correlation with total organic carbon (TOC), clay content and Pb concentrations. The highest PAHs concentrations were found in the samples from mangrove sediments. Overall, PAHs in Deep Bay sediment were lower than those in other developed areas. The biological effect due to PAHs alone in Deep Bay is expected to be low, based on the comparisons of individual and total PAHs concentrations determined in the sediment with those in USEPA sediment quality guidelines. Four and five-ring compounds dominated the PAHs composition pattern profiles. Principal component analysis (PCA) was applied to further investigate the source of PAHs. The PAH sources of Deep Bay mangrove swamp were suggested to be primarily combustion of fossil fuel, especially leaded-gasoline exhaust.     

Determination and load of organophosphorus and organochlorine pesticides at water from Jiulong River Estuary,China

Seventeen organic phosphorus pesticides (OPs) and 18 organic chlorine pesticides (OCs) at water from Jiulong River Estuary (JLRE) are determined by SPE–GC–(FPD and μECD). The contents of the total OPs (17) ranged from 134.8 to 354.6 ng/l (the mean is 227.2 ng/l). Total OCs concentrations varied from 115.4 to 414.7 ng/l in water (mean 237.7 ng/l). The levels of total hexachlorocyclohexane in water varied from 31.95 to 129.8 ng/l (mean 62.51 ng/l), and those of total DDTs were in the range 19.24–96.64 ng/l (mean 48.69 ng/l). The distribution and behavior characteristics of OPs indicate that five main OPs (methamidophos, dichlorvos, malathion, omethoate and dimethoate) occupied the most part of the total OPs, in addition, the sources of the OPs (mainly from current usage) are not stable. While the OCs mainly came from early application and were more stable. The OPs did not have obvious correlation with the dissoved organic carbon and suspended particulate matter at water from JLRE. It maybe due to the complicated hydrological kinetics in the estuary, and the higher water solubility and weak absorption (with organic matter) action of OPs. When compared with other areas, the OPs and OCs level in JLRE are some moderate.     

海陆过渡带中超基性岩的铂族矿物组合标型

太平洋活动带西北部海陆过渡带的优地槽铂矿床成因模式巳进行了研究。铂族元素成矿作用与较长地质时期〔里非期(z)至晚白垩纪〕内各种超基性岩有关。含铂岩体中斜方辉橄岩和纯橄榄岩(含有蛇纹岩)的暗残岩(restite)组合到处可见。熔点特别高的锇和钉锇同铱的自然金属互化物(铱锇矿、钌铱锇矿、铱钌锇矿和铱饿钌矿)对上述岩体来说是标型的。而超基性火山岩(苦橄岩和麦美奇岩等)与纯橄榄岩斜方辉橄岩建造的含铂深成岩体是同生的,而且在空间上直接相连,铱和锇的金属互化物(饿铱     

Study on the adsorption kinetics of orthophosphate anions on layer double hydroxide

A kinetic study was conducted on the adsorption of orthophosphate anions on layer double hydroxide (LDH). The adsorption has proved itself to be a spontaneous endothermic process and is large in capacity and rate. The adsorption isotherm correlates well with the Freundlich model, and a rise in temperature will lead to an increase in adsorption efficiency. Additionally, the results suggested that the adsorption is an entropy-increasing process and is in good agreement with the pseudo-second order kinetics. The free energy (ΔG) of adsorption of orthophosphate onto LDH varies within the range of −1.75–−3.34 kJ/mol, the enthalpy (ΔH) varies by 7.96 kJ/mol and the entropy (ΔS) by 33.59 kJ/mol. The adsorption activation energy is 8.3 kJ/mol, showing that the adsorption of orthophosphate onto LDH is determined to be a physical adsorption.     

岩石圈气田与利用岩石吸附气预测矿产资源的可能性

抽提岩石(沉积物)中吸附气和吸收气的方法可用于预测矿藏,这是因为这些气体会逐渐聚集和保存在岩石中。来自地幔的流体会补充热解吸附流体,运移到地表的流体则产生岩石圈气田。产生于这种方式的背景气田可能会受到物理场和来自不同矿床流体的影响。矿床的物理场可能会改变背景气田的成分。     

基于GIS的农业面源硝酸盐地下水污染动态风险评价

地下水中的硝酸盐污染具有全球性,这不仅是一个环境问题,也是一个经济和人类健康问题。DRASTIC方法可以进行地下水污染的脆弱性评价,但是却没有涵盖风险的概念,也忽视了污染物随地表水流运动的动态特性。因此,所得结果可能有碍于“欧洲水管理框架指南”在地下水水质管理中的执行。笔者基于DRASTIC方法开发了一个动态风险评价方法,并将其运用于英国北爱尔兰Upper Bann流域中的一个小流域。研究区地下水硝酸盐污染风险评价结果表明,此方法将有效地帮助决策者在流域范围内开展农业面源地下水污染预防措施。“非常高风险”和“高风险”区分别占研究区面积的5.1%和10.5%。此结果可帮助当地政府针对流域内这些“非常高风险”和“高风险”区的特点制订地下水质保护政策。此方法同样适用于任何面源可溶性污染物的地下水污染动态风险评价。