福建省新生代火山岩岩石化学特征及与构造地质关系的讨论

Cenozoic volcanic rocks in Fujian are of Pliocene and Pleistocene ages and can be divided into three zones: the east volcanic rock zone consists mainly of tholeiite,file west zone is limburgite and the intermediate zone is transitional in character between the former two zones with a little prevalance of olivine basalt. Two rock types can be distinguished, i.e., the limburgites containing no feldspars and the basalts including olivine basalt and .tholeiitic basalt In terms of petrochemistry, the volcanic rocks can be classified as strong alkaline, alkaline and sub-alkaline suites.Most of the strong alkaline rocks are distributed in the west zone, while the alkaline is in the intermediate zone and the subalkaline occurs predominantly in the east zone.With increasing distance from the coastline, the rocks become progressively alkaline and the potassium content and K/Si ratio increase. Significant amount of mantle material, including garnet lherzolite xenoliths and pyrope xenocrysts, has been noticed in the above-mentioned volcanic rocks. The garnet lherzolite bears strong resemblance to “mantle rocks”, especially with respect to the high values of Mg and Fe. Garnets in these rocks are Cr-bearing pyrope, with pyrope component in excess of 60 percent.It is suggested that the original basaltic melt might have been resulted from partial melting of garnet lherzolite in the upper mantle and then extruded onto the surface along the ultra-deep fault in the Pacific plate.     

Containment criterion for contaminant isolation by cutoff walls

A rigorous solution is developed from first principles to guide the preliminary design of cutoff walls installed to contain the migration of contaminants from source zones. The full analytic solution is used to develop a criterion for determining the configuration and hydraulics of optimal wall designs. The solution is used to demonstrate the interaction between the properties of the wall, the Darcy flux, and the concentration of contaminants at the outside face of the well. For a particular wall design, the containment criterion can be used to estimate the long-term concentration that will develop at the outside face of the wall. Alternatively, for a given concentration on the outside face of the cutoff wall, the containment criterion can be used to estimate the Darcy flux required to balance the outward diffusion of contaminants. The results of numerical simulations are presented to evaluate the analytic approach. The numerical results confirm that for a wall with known transport properties, a specified Darcy flux is associated with a unique outside contaminant concentration.     

化学定时炸弹:中国陆地环境面临的新问题

根据中国环境地球化学监控网络第一次采样的结果,发现中国东部,尤其是华南地区,是Ｎａ２Ｏ,ＭｇＯ,ＣａＯ的低背景地球化学区,Ａｌ的高背景地球化学区,这个独特的地球化学区,恰好也是我国酸性沉降物的分布区,由于持续的酸性物质沉降,使这一地区成为对酸性物质沉降最脆弱的地区,有可能导致土壤中Ａｌ的突然释放,出现森林大面积突然死亡的环境危害。研究还发现,该地区也是Ｔｈ、Ｃｕ、Ｃｄ、Ｔｉ、Ａｕ、Ｂ、Ｔｌ、Ｗ、Ｚｎ、Ｓｂ、Ａｇ、Ｉ、Ｕ、Ａｓ、Ｓｅ、Ｍｏ、Ｂｉ、Ｒｂ、Ｇａ、Ｌａ、Ｃｅ、Ｙ、Ｐｂ、Ｇｅ、Ｚｒ、Ｂｅ、Ｎｂ、Ｓｎ等２８种元素的地球化学高背景分布区。随着土壤的ｐＨ值不断降低,最终将导致这些金属中的一种或数种元素同时从土壤中释放,有可能在不同的时间阶段及不同地区的大面积范围内出现不同元素的化学定时炸弹。     

Future use of tritium in mapping pre-bomb groundwater volumes

The tritium input to groundwater, represented as volume-weighted mean tritium concentrations in precipitation, has been close to constant in Tucson and Albuquerque since 1992, and the decrease in tritium concentrations at the tail end of the bomb tritium pulse has ceased. To determine the future usefulness of tritium measurements in southwestern North America, volume-weighted mean tritium levels in seasonal aggregate precipitation samples have been gathered from 26 sites. The averages range from 2 to 9 tritium units (TU). Tritium concentrations increase with site latitude, and possibly with distance from the coast and with site altitude, reflecting local ratios of combination of low-tritium moisture advected from the oceans with high-tritium moisture originating near the tropopause. Tritium used alone as a tool for mapping aquifer volumes containing only pre-bomb recharge to groundwater will become ambiguous when the tritium in precipitation at the end of the bomb tritium pulse decays to levels close to the analytical detection limit. At such a time, tritium in precipitation from the last one to two decades of the bomb pulse will become indistinguishable from pre-bomb recharge. The threshold of ambiguity has already arrived in coastal areas with a mean of 2 TU in precipitation and will follow in the next three decades throughout the study region. Where the mean tritium level is near 5 TU, the threshold will occur between 2025 and 2030, given a detection limit of 0.6 TU. Similar thresholds of ambiguity, with different local timing possible, apply globally.     

Plastic ingestion by planktivorous fishes in the North Pacific Central Gyre

A significant amount of marine debris has accumulated in the North Pacific Central Gyre (NPCG). The effects on larger marine organisms have been documented through cases of entanglement and ingestion; however, little is known about the effects on lower trophic level marine organisms. This study is the first to document ingestion and quantify the amount of plastic found in the gut of common planktivorous fish in the NPCG. From February 11 to 14, 2008, 11 neuston samples were collected by manta trawl in the NPCG. Plastic from each trawl and fish stomach was counted and weighed and categorized by type, size class and color. Approximately 35% of the fish studied had ingested plastic, averaging 2.1 pieces per fish. Additional studies are needed to determine the residence time of ingested plastics and their effects on fish health and the food chain implications.     

荒漠化,干旱与植被—以西非萨赫勒为例

关于西非荒漠化的本质和特征存在着许多看法。该文将追溯其历史，回顾荒漠化对气候影响的研究现状，并介绍一些有关研究结果。对荒漠化的认识通常为“沙漠”的扩张，是一个总体上不可逆转的人为过程。其过程与地表反照率增强，风沙加大以及土地生产力下降相联系。研究表明，在最近１６年里撒哈拉沙漠的边界和萨赫勒植被均变化不大，从植被水分有效利用率来看，“生产力”没有系统性降低，地表反照率也没有多少改变。自２０世纪５０年