降水随机模拟中的超离差现象

简单的随机模式拟合的日降水量时间序列具有过低估计月（或季）总降水观察（或年际）变化的显著趋势。研究发展一种称为链相关过程的特殊类型的随机模式，估计了“超离差（ｏｖｅｒｄｉｓｐｅｒｓｉｏｎ）”现象的程度，这种现象可归因子模式对降水的高频变化考虑不充分。对加利福尼亚奇科（Ｃｈｉｃｏ，Ｃａｌｉｆｏｒｎｉａ）１月份日降水量，拟合更复杂的随机模式，大大地减少月总降水方差的过程估计，通过利用日降水出现的高阶马     

美国海水养殖业的机会

世界人口对蛋白质来源的需求日益增长,而全球野生鱼类和贝类供应目前尚满足不了人们日益增长的需求。因此,海水养殖的发展具有广阔的前景。 人类养殖(农牧)鱼类和贝类已有数百年的历史。尽管大多数人认识到海水养殖是一个全球增长潜力很强,并可持续发展的行业,但是最佳的机遇在何处、何时出现敏感问题则是很难证明的。美国是否可能以海水养殖生产者大国的地位出现在国际舞台上,在这个时候也是很     

Field validation, in Scotland and Iceland, of the artificial mussel for monitoring trace metals in temperate seas

The artificial mussel (AM), a novel chemical sampling device, has been developed for monitoring dissolved trace metals in marine environments. The AM consists of Chelex-100 suspended in artificial seawater within Perspex tubing and enclosed with semi-permeable polyacrylamide gel at both ends. To validate the field performance of the AM in temperate waters, we deployed AMs alongside transplanted blue mussels Mytilus edulis in coastal environments in Scotland (Holy Loch, Loch Fyne, Loch Striven and Millport) and Iceland (Reykjavikurh?fn, Gufunes, South of thornerney, Hofsvik, Hvalfj?rethur and Sandgerethi) for monitoring trace metals. While uptake patterns of Cd between the AM and M. edulis were highly comparable, discrepancies were found in the accumulation profiles of the other metals (Cu, Cr, Pb and Zn), in particular Zn. Nonetheless, the AMs gave a better resolution to accurately reveal the spatial difference in dissolved metal contamination when compared with M. edulis. AMs complement the use of mussels since AMs indicate dissolved metals in seawater, whereas uptake by mussels indicates a mixture of dissolved and particulate metals. Our results also indicated that historical metal exposure of the transplanted M. edulis could significantly confound their metal concentrations especially when the deployment period was short (i.e. <34d). This study suggested that the AM can overcome problems associated with variable biological attributes and pre-exposure history in the mussel, and provides a standardized and representative time-integrated estimate of dissolved metal concentrations in different marine environments.     

Large and growing environmental reservoirs of Deca-BDE present an emerging health risk for fish and marine mammals

Polybrominated diphenyl ethers (PBDEs) have been the subject of intense scientific and regulatory scrutiny during recent years. Of the three commercial forms (Penta, Octa and Deca) of PBDEs that have been widely used as flame retardants in textiles, furniture upholstery, plastics, and electronics, only Deca-BDE remains on the general market in North America, while a recent ruling of the European Court spells an impending end to its use in Europe. We review here highlights of aquatic research documenting the rapid emergence of PBDEs as a high priority environmental concern in Canada. PBDEs are being introduced in large quantities to the aquatic environment through sewage discharge and atmospheric deposition. In certain environmental compartments, the single congener BDE-209, the main ingredient in the Deca-BDE formulation, has surpassed the legacy PCBs and DDT as the top contaminant by concentration. Limited biomagnification of BDE-209 in aquatic food webs reflects its high log K_ow and preferential partitioning into the particle phase. As a result, large environmental reservoirs of BDE-209 are being created in sediments, and these may present a long-term threat to biota: BDE-209 breaks down into more persistent, more bioaccumulative, more toxic, and more mobile PBDE congeners in the environment.     

Effects of gas generation and precipitates on performance of Fe0 PRBs

Long-term reactivity and permeability are critical factors in the performance of granular iron permeable reactive barriers (PRBs). Thus it is a topic of great practical importance, as well as scientific interest. In this study, four types of source solutions (distilled H2O, 10 mg/L TCE, 300 mg/L CaCO3, and 10 mg/L TCE + 300 mg/L CaCO3) were supplied to four columns containing a commercial granular iron material. In all four columns, gases accumulated to approximately 10% of the initial porosity and resulted in declines in permeability of approximately 50% to 80%. In the columns receiving CaCO3, carbonate precipitates accumulated to approximately 7% of the initial porosity, with no apparent decline in permeability. The data indicate that precipitates formed initially at the influent ends of the columns, reducing the reactivity of the iron in this region. As a consequence of the reduced reactivity, calcium and bicarbonate migrated further into the column, to precipitate in a region where the reactivity remained high. Thus precipitation occurred as a moving front through the columns. The results suggest improved methods for PRB design and rehabilitation, and also suggest improvements that are needed in the mathematical models developed for predicting long-term performance.