Anthropogenic influences on estuarine sedimentation and ecology: examples from the varved sediments of the Pettaquamscutt River Estuary,Rhode Island

Estuaries and lakes are undergoing anthropogenic alterations as development and industry intensify in the modern world. Assessing the ecological health of such water bodies is difficult because accurate accounts of pre-anthropogenic estuarine/lacustrine conditions do not exist. Sediments preserved in water bodies provide archives of environmental changes that can be used to understand both natural and anthropogenic forcings. Here, a high-resolution, multi-proxy approach is used to reconstruct environmental conditions of the Pettaquamscutt River Estuary, Rhode Island, over the last millennium. Two specific time periods reveal anthropogenic alterations to sediment supply and water-column productivity. First, European land clearance at the end of the seventeenth century caused two decades of increased sediment transport through the watershed and increased primary productivity in the water column. Turbidity increases associated with increased water column biomass likely limited green sulfur bacteria that reside below the oxycline. The second anthropogenic effect began in the 1950s with increased residential development in the watershed. Evidence of resulting cultural eutrophication is apparent in both stable nitrogen isotope values as well as in productivity proxies. This effect is likely related to residential development in the watershed and the use of septic systems to treat human waste. These results demonstrate that true base-line conditions of the estuary have not occurred for over three centuries, and that anthropogenic effects can last on the order of decades. The Pettaquamscutt River record serves as a model for using high-resolution sediment records to better understand anthropogenic forcing to natural estuarine/lacustrine systems.     

The use of statistical methods to separate natural background and anthropogenic concentrations of trace elements in radio-chronologically selected surface sediments of the Venice Lagoon

A new method has been developed that predicts the natural background concentrations of microelements of interest in sediments using the concentrations of various components present in the sample. This is done by developing multiple linear regressions using a dataset which has been selected, using radiochronological dating and statistical methods, to reflect the concentration distributions of natural levels of a large number of sediment constituents. This method is demonstrated in Venice Lagoon, using data generated in a lagoon-wide sampling effort. A quantitative assessment is carried out of the variability of natural background levels at the lagoon scale for the main inorganic microelements, and distribution maps of the background and anthropogenic concentrations of a selected metal (Ni) in sediments at the lagoon scale are presented. With sufficient data, this method can be applied in other areas, allowing for a site-specific separation of natural background and anthropogenic levels of microconstituents in sediments, providing insights into regional geochemistry and aiding in the risk-based management of coastal sediments.     

乐山市盐气资源开发中应重视的一些问题

总结乐山市开发利用威西岩盐矿和犍为县麻柳场天然气出现诱发地震活动的特点,分析其形成原因,提出在威西岩盐矿和天然气开发区建立高质量的地震监测台网,为科学研究提供更多系统可靠的基础观测资料,深入开展盐气资源开发与诱发地震活动关系的研究,为制定科学合理的开发规划提供依据;开展跨行业科学研究,搞好盐气资源综合开发利用;切实抓好重大建设项目的抗震设防管理和各类设备的抗震安全,提高抗震防灾能力,加强领导与协调,共同做好盐气资源的开发利用。     

Measuring natural phytoplankton fluorescence and biomass: a case study of algal bloom in the Pearl River estuary

A moored optical buoy was deployed in the Pearl River estuarine waters for a 15-day period. A four-day algal bloom event occurred during this study period. Both chlorophyll a concentration and algal cell density (a proxy for biomass) changed dramatically before and after the event. The chlorophyll concentration at a 2.3 m depth rose from 5.15 mg/m⁻³ at 15:00 h on August 19 to 23.62 mg/m⁻³ at 9:00 h on August 21, and then decreased to 3.24 mg/m⁻³ at 15:00 h on August 24. The corresponding cell density ranged from 1.57 × 10⁵ to 1.76 × 10⁶ cells/L. We used normalized fluorescence line height (NFLH) and normalized fluorescence intensity (NFI) in order to determine fluorescence activity. Combined with the in situ sampling dataset, we were able to correlate natural fluorescence (NFLH and NFI) with chlorophyll a concentrations, and found correlation coefficients of 0.72 and 0.75, respectively. We also found correlations between natural fluorescence and cell density, with correlation coefficients of 0.71 and 0.65, respectively. These results indicate that applying continuous time series of natural fluorescence can reflect changes in biomass. This technique will prove extremely useful for in situ and real-time observations using an optical buoy. Although there are still problems to solve in the real-time observation of natural fluorescence in algal bloom events, we discuss the primary factors affecting fluorescence signals and suggest possible methods for mitigating these issues.     

Effects of natural gas condensate - water accommodated fraction on coral larvae

The toxic effects of the water accommodated fraction (WAF) of a natural gas condensate on the larvae of five brooding coral species of the Family Pocilloporidae were examined in short term (96 h) bioassays. Lethality was observed in some larvae of Seriatopora hystrix and Seriatopora guttatus upon exposure to high concentrations of the condensate WAF, while those of Stylophora pistillata, Pocillopora damicornis and Pocillopora verrucosa did not experience mortality. Furthermore, increasing concentrations of WAF produced either delayed or impeded metamorphosis for all species except P. damicornis. Growth of juveniles, exposed to different WAF treatments for 96 h during their larval/early juvenile stages, was measured after 30 d. Marked decrease in subsequent growth rate (polyp count) was observed for S. hystrix, S. guttatus and S. pistillata with increasing WAF concentration. The results showed differential susceptibility of larvae of closely related coral species to oil stress, with the following sensitivity ranking: S. guttatus>S. hystrix>S. pistillata>P. verrucosa>P. damicornis. Oil exposure during the planktonic, larval stage of susceptible corals can adversely affect survivorship, recruitment and/or subsequent colony growth, thereby having profound consequences for the abundance of these corals in space and time.     

The influence of hazardous liquid waste on the permeability of earthen liners

 Permeability and its susceptibility to changes with time or exposure to chemicals are major factors in selection of earthen liners for use in hazardous liquid-waste containment systems. Earthen liners often consist of mixtures including both granular soil and fine matrix. Six different solid mixtures were tested to investigate the influence of hazardous liquid waste on their permeability. The granular part of the mixtures included sand and crushed natural zeolite, whereas the matrix was composed of bentonite and microcement. Highly acidic solutions, bases, leather industry leachate and municipal waste leachate were used as permeants. Of the mixtures tested, only two mixtures performed well against the attack of chemicals. The testing method was the falling head system with the compaction mold permeameter. The period of experiments varied from two to eight weeks. Received: 24 September 1998 · Accepted: 5 January 1999     

Gaseous hydrocarbons generated during pyrolysis of petroleum source rocks using unconventional grain-size: implications for natural gas composition

Open-system pyrolysis experiments were performed on a suite of immature to marginally mature source rocks to investigate the influence of kerogen type on primary gas composition and the effect of grain size on gas expulsion characteristics. The pyrolysis of rock powders confirmed that hydrogen-rich kerogens yielded wetter gases than did hydrogen-poor kerogens. Gases detected from the pyrolysis of rock chips were drier than those from powders of equivalent samples. This was due to two processes: the retention and secondary cracking of higher molecular weight pyrolysis products and the preferential expulsion of methane from the rock matrix. These two effects, one chemical the other physical, could be distinguished using a novel approach involving multi-step pyrolysis of rock chips followed by on-line crushing of the residues. The enrichment of methane in natural gas attributed, by earlier workers, to be a consequence of fractionation during secondary migration (post-expulsion) has been proven to be real also during expulsion from source rocks at least for pyrolysis conditions.     

Recognising biodegradation in gas/oil accumulations through the δC compositions of gas components

A large suite of natural gases (93) from the North West Shelf and Gippsland and Otway Basins in Australia have been characterised chemically and isotopically resulting in the elucidation of two types of gases. About 26% of these gases have anomalous stable carbon isotope compositions in the C₁–C₄ hydrocarbons and CO₂ components, and are interpreted to have a secondary biogenic history. The characteristics include unusually large isotopic separations between successive n-alkane homologues (up to +29‰ PDB) and isotopically heavy CO₂ (up to +19.5‰ PDB). Irrespective of geographic location, these anomalous gases are from the shallower accumulations (600–1700 m) where temperatures are lower than 75°C. The secondary biogenic gases are readily distinguishable from thermogenic gases (74% of this sample suite), which should assist in the appraisal of hydrocarbons during exploration where hydrocarbon accumulations are under 2000 m. While dissolution effects may have contributed to the high ¹³C enrichment of the CO₂ component in the secondary biogenic gases, the primary signature of this CO₂ is attributed to biochemical fractionation associated with anaerobic degradation and methanogenesis. Correlation between biodegraded oils and biodegraded “dry” gas supports the concept that gas is formed from the bacterial destruction of oil, resulting in “secondary biogenic gas”. Furthermore, the prominence of methanogenic CO₂ in these types of accumulations along with some isotopically-depleted methane provides evidence that the processes of methanogenesis and oil biodegradation are linked. It is further proposed that biodegradation of oil proceeds via a complex anaerobic coupling that is integral to and supports methanogenesis.     

铀矿床的天然类似物研究

本文叙述连山关铀矿床内的地下水和铀矿体中的12 9I和2 39Pu的测量结果。研究表明 ,铀矿床内的地下水把12 9I从铀矿石中淋滤出来 ,12 9I在地质环境中具有活泼的地球化学特征 ;铀矿体中积累的2 39Pu自该矿床形成 190 0Ma以来未发生迁移。     

Natural Heritage value of Xinjiang Tianshan and global comparative analysis

Xinjiang Tianshan is a serial natural property that has been nominated for World Heritage status.This paper presents a systematically comprehensive and comparative analysis of the heritage resources of Xinjiang Tianshan according to the World Heritage criteria.Its biological,ecological and aesthetic values,which are of global importance, are documented.It is concluded that Xinjiang Tianshan meets the world heritage criteria(vii)and (ix).Xinjiang Tianshan is compared with other mountain world heritage sites,mountains in Central Asia,the Tianshan Mountains outside China,and with the protected areas of the Tianshan Mountains on the Tentative List for World Heritage Sites,so as to provide objective data for the world heritage application.