Oxygen-enhanced biodegradation of phenoxy acids in ground water at contaminated sites

The effects of adding oxygen to anaerobic aquifer materials on biodegradation of phenoxy acid herbicides were studied by laboratory experiments with aquifer material from two contaminated sites (a former agricultural machinery service and an old landfill). At both sites, the primary pollutants were phenoxy acids and related chlorophenols. It was found that addition of oxygen enhanced degradation of the six original phenoxy acids and six original chlorophenols. Inverse modeling on 14C 4-chloro-2-methylphenoxypropanoic acid (MCPP) degradation curves revealed that increasing the oxygen concentrations from <0.3 mg/L up to 7 to 8 mg/L shortened the lag phases (from approximately 150 d to 5 to 25 d) and increased first-order degradation rate constants by 1 order of magnitude (from approximately 5 x 10(-2) d(-1) to up to 30 x 10(-2) d(-1)). Additionally, the degree of MCPP mineralization was increased (30% to 50% mineralized at low oxygen concentrations and 50% to 70% mineralized at high oxygen concentrations, based on 14CO2 recovery). These positive effects on degradation were observed even at relatively low oxygen concentrations (2 mg/L). Furthermore, effects related to the addition of oxygen on the general geochemistry were studied. An oxygen consumption of 2.2 to 2.6 mg O2/g dw was observed due to oxidation of solid organic matter and, to some extent (0.5% to 11% of the total oxygen consumption), water-soluble compounds such as Fe2+, dissolved Mn, nonvolatile organic carbon, and NH4+. Overall, the results suggest that stimulated biodegradation by addition of oxygen might be a feasible remediation technology at herbicide-contaminated sites, although oxygen consumption by the sediment could limit the applicability.     

Polycyclic aromatic hydrocarbons in surface sediments of the East China Sea and their relationship with carbonaceous materials

This study measured concentrations of polycyclic aromatic hydrocarbons (PAHs) in surface sediments in the East China Sea (ECS) to investigate possible sources and fate of PAHs. Total concentration of PAHs in the sediments of the ECS ranged from 22 to 244 ng g(-1), with the highest levels in the coastal area and outer shelf. The observed PAH results showed elevated levels in both inner and outer shelf areas, a finding that is different from predictions by an ocean circulation model, suggesting that terrestrial sources are important for PAH contaminations in the ECS, while sediment resuspension, tidal changes and lateral transport may be important in affecting the distribution of PAHs in the outer shelf. The distribution of PAHs in the surface sediments of the ECS is similar to the distribution of carbonaceous materials (e.g., particulate organic carbon and black carbon), suggesting that carbonaceous materials may strongly affect the distribution of PAHs.     

全球地学断面计划：成就与未来目标

国际岩石圈委员会的全球地学断面计划在过去的五年中取得了重大进展,区域性的合作及学术交流鼓励各国的编图者编制一些跨越固界的断面,首批7条断面将于1991年8月出版。这种编图需要全球及交叉学科的研究与探索,并依赖于国际间的合作。断面计划现在已向着一个新的方向发展,即通过使用小型计算机和大量可获得的软件使断面资料数字化。阿巴拉契亚及安底斯断面所做的这方面的工作将指导数字化断面的编制,因此,未来的断面将以数字化格式和普通两种形式出版。通过这一过程,世界范围的地质,地球物理和地球化学信息的相互影响的操作将成为新一代地质学家的一种工具,并且成为沟通现今地质学不同学科的桥梁。     

Clay-mineral suites,sources, and inferred dispersal routes: Southern California continental shelf

Clay mineralogy is useful in determining the distribution, sources, and dispersal routes of fine-grained sediments. In addition, clay minerals, especially smectite, may control the degree to which contaminants are adsorbed by the sediment. We analyzed 250 shelf sediment samples, 24 river-suspended-sediment samples, and 12 river-bed samples for clay-mineral contents in the Southern California Borderland from Point Conception to the Mexico border. In addition, six samples were analyzed from the Palos Verdes Headland in order to characterize the clay minerals contributed to the offshore from that point source. The <2 microm-size fraction was isolated, Mg-saturated, and glycolated before analysis by X-ray diffraction. Semi-quantitative percentages of smectite, illite, and kaolinite plus chlorite were calculated using peak areas and standard weighting factors. Most fine-grained sediment is supplied to the shelf by rivers during major winter storms, especially during El Ni?o years. The largest sediment fluxes to the region are from the Santa Ynez and Santa Clara Rivers, which drain the Transverse Ranges. The mean clay-mineral suite for the entire shelf sediment data set (26% smectite, 50% illite, 24% kaolinite+chlorite) is closely comparable to that for the mean of all the rivers (31% smectite, 49% illite, 20% kaolinite+chlorite), indicating that the main source of shelf fine-grained sediments is the adjacent rivers. However, regional variations do exist and the shelf is divided into four provinces with characteristic clay-mineral suites. The means of the clay-mineral suites of the two southernmost provinces are within analytical error of the mineral suites of adjacent rivers. The next province to the north includes Santa Monica Bay and has a suite of clay minerals derived from mixing of fine-grained sediments from several sources, both from the north and south. The northernmost province clay-mineral suite matches moderately well that of the adjacent rivers, but does indicate some mixing from sources in adjacent provinces.     

Potential benefits to fisheries and biodiversity of the Chagos Archipelago/British Indian Ocean Territory as a no-take marine reserve

On 1st April 2010, the British Government announced designation of the British Indian Ocean Territory - or Chagos Archipelago - as the world’s largest marine protected area (MPA). This near pristine ocean ecosystem now represents 16% of the worlds fully protected coral reef, 60% of the world’s no-take protected areas and an uncontaminated reference site for ecological studies. In addition these gains for biodiversity conservation, the Chagos/BIOT MPA also offers subsidiary opportunities to act as a fisheries management tool for the western Indian Ocean, considering its size and location. While the benefits of MPAs for coral-reef dwelling species are established, there is uncertainty about their effects on pelagic migratory species. This paper reviews the increasing body of evidence to demonstrate that positive, measurable reserve effects exist for pelagic populations and that migratory species can benefit from no-take marine reserves.