An Effective and Inexpensive Gas-Drive Ground Water Sampler

Ground water scientists engaged in assessment of contaminant occurrence and migration are faced with a number of practical problems. These problems include, but are not limited to, escalating drilling costs, labor costs for proper sampling of monitoring wells, collection of ground water samples that are representative of aquifer conditions and accurate delineation of hydrogeologic regimes and the areal and vertical distribution of ground water contaminants.
In response to these problems, a number of ground water sampling devices have been developed. One device is a gas-driven ground water sampler developed for multilevel installation. Use of these samplers have been shown to decrease project costs and allow easy collection of high quality samples. However, the currently available samplers are relatively expensive, some of them operate on a closed check valve system, which does not allow determination of piezometric heads in aquifers with fluctuating water tables and they are not adaptable to design changes in the field necessitated by site-specific hydrogeologic conditions.
GHR Engineering Associates Inc. has designed an effective gas-driven sampler, which accomplishes the same objectives as the commercially available models, but is on the average, one-tenth the cost of currently available samplers. It offers the advantages of being more cost-effective than commercially available models, has an open check valve system to allow measurements of water table fluctuation and is easily adaptable in the field to meet site-specific hydrogeologic conditions.     

Gulf of Mexico hydrocarbon seep communities: VI. Patterns in community structure and habitat

Communities of chemosynthetic fauna that depend on seeping oil and gas have been found in the Gulf of Mexico at approximately 45 sites between 88°W and 95°W and between the 350 and 2,200 m isobaths. Investigations suggest that the number of sites and the range of occurrence will increase with additional exploration. The dominant fauna consist of species within four groups: tube worms, seep mussels, epibenthic clams, and infaunal clams. These species co-occur to some degree, but tend to form assemblages dominated by a single group. Community development is closely coupled to the geological and geochemical processes of seepage.     

无机水化学离子在实验流域降雨径流过程中的响应及其示踪意义

为研究无机水化学离子在降雨径流示踪中的可能性,在实验流域实测降雨、地面径流、壤中流、地下水径流过程和流域内17个测孔的地下水过程中,施测了Na+,K+,Ca2+,Mg2+,Cl-,SO₄2-,HCO₃-+CO₃2-,NO₃-,F-,NH₄-,PO₄2-,SiO₂和pH,EC,18O的同步过程,还施测了少数土壤水水样。结果是:①在Ca2+与Cl-/SO₄2-和EC与Na+/(Na++Ca2+)的关系中以及除NO₃-,NH₄-,PO₄2-外的所有离子,都可识别出上述各种径流组分;②径流离子过程均与降雨离子过程相仿,随径流组分从地面到地下而渐趋坦化;③除个例外,离子浓度过程均以降雨为最小并从地面径流到地下水径流渐次增大;④降雨和地下水离子过程表现为径流离子过程的两端元;⑤在降雨和各径流组分中,18O过程与大部分离子过程有一定的同步性。从以上结果认为,降雨并不是流域径流离子输出的主要来源,然而却是形成它的主要控制因素。此外,有关试验结果还对应用Cl-进行地下水补给的估算方法提出了问题。     

Polysynthetic feldspar twin-width distributions: Models for inversion twinning

The lamella-width distribution of the transformation polysynthetic twins produced in volcanic anorthoclases during cooling reflects certain aspects of twin nucleation and growth kinetics. An analysis of simple hypothetical statistical models for the kinetics of the transformation process outlines the range and type of twin-width distributions possible. The general characteristics of these distributions, particularly at small twin widths, are sensitive to whether twin boundaries or twin centers nucleate. The rates of twin nucleation and growth during transformation also influence the general form, particularly the skewness, of the final twin-width distribution. The generally exponential nature of the upper tails to the distributions studied is apparently quite insensitive to kinetic details.     

Spatial correlations of ground motion for non-ergodic seismic hazard analysis

Traditional probabilistic seismic hazard analysis (PSHA) uses ground-motion models that are based on the ergodic assumption, which means that the distribution of ground motions over time at a given site is the same as their spatial distribution over different sites. Evaluations of ground-motion data sets with multiple measurements at a given site and multiple earthquakes in a given region have shown that the ergodic assumption is not appropriate as there are strong systematic region-specific source terms and site-specific path and site terms that are spatially correlated. We model these correlations using a spatial Gaussian process model. Different correlations functions are employed, both stationary and non-stationary, and the results are compared in terms of their predictive power. Spatial correlations of residuals are investigated on a Taiwanese strong-motion data set, and ground motions are collected at the ANZA, CA array. Source effects are spatially correlated, but provide a much stronger benefit in terms of prediction for the ANZA data set than for the Taiwanese data set. We find that systematic path effects are best modeled by a non-stationary covariance function that is dependent on source-to-site distance and magnitude. The correlation structure estimated from Californian data can be transferred to Taiwan if one carefully accounts for differences in magnitudes. About 50% of aleatory variance can be explained by accounting for spatial correlation.     

Significance of sedimentological studies to man's use of transitory coastal areas

A beach-ridge complex is a migrating sediment body constructed and kept in motion by high-energy processes, and the same processes that construct these features will, in time, partially or completely destroy them. The beach-ridge complex along the shore of southwestern Lake Michigan serves as an example. This body of sediment, approximately 17 by 3 km has undergone considerable change in the last 3,000 years, moving about 13 km along the shore as a result of forces generated by the Lake Michigan system — erosion at the northern end, deposition of the displaced sediment at the southern end of the complex. Sedimentological analysis of the beach-ridge complex demonstrates that each major modern environment can be characterized by a unique range in grain sizes, which make it possible to determine the environment in which the subsurface sediments were deposited. Lateral and thickness distribution of textural types can then be predicted. Erosion has been an important natural geologic process in the development of the beach-ridge complex, but it has become a problem only since man has occupied the nearshore areas. It will continue to be a problem, particularly at times of high lake level. Man's attempts to protect these areas by trying to alter the natural processes frequently have upset the delicate natural balance, unintentionally accelerating destruction in other areas. Beach replenishment is one method that would adapt well to this coast because there is an adequate supply of sand in the subsurface of the beach ridge complex whose grain size matches that of the modern beach sand.     

An overview of the mink study

Highlights of the previous papers in this series are reviewed. Methodology developed for the MINK study has improved the ability of impacts analysis to deal with questions of (1) spatial and temporal variability in climate change; (2) CO₂-enrichment effects; (3) the reactions of complex enterprises (farms and forests) to climate change and their ability to adjust and adapt; and (4) integrated effects on current and, more particularly, on future regional economies. The methodology also provides for systematic study of adjustment and adaptation opportunities and of the inter-industry linkages that determine what the overall impacts on the regional economy might be. The analysis shows that with a 1930s dust bowl climate the region-wide economic impacts would be small, after adjustments in affected sectors. In this final paper we consider whether synergistic effects among sectoral impacts and more severe climate change scenarios might alter this conclusion. The MINK analysis, as is, leads to the conclusion that a strong research capacity will be required to ensure that technologies facilitating adaptation to climate change will be available when needed. The capacity to deal with climate change also requires an open economy allowing for free trade and movement of people and for institutions that protect unpriced environmental values. More severe climate scenarios and negative synergisms can only strengthen these conclusions.     

Population Belongs on the Johannesburg Agenda

The forthcoming World Summit on Sustainable Development (WSSD) in Johannesburg (August 26-September 4, 2002) has been set by the United Nations to consider strategies toward sustainable development in all its dimensions. Hence, its mandate is broader than that of the Rio 1992 United Nations Conference on Environment and Development (UNCED). Population issues have so far been discussed in a separate series of World Population Conferences (Bucharest 1974, Mexico City 1984, Cairo 1994). With no new World Population Conference scheduled for 2004 and Johannesburg having a mandate that is stated to explicitly include social and economic aspects, population as a key component of sustainable development should figure prominently on the Johannesburg agenda. Yet, after the third of four preparatory meetings for Johannesburg (which ended in New York on April 5th), consideration of population is completely absent. The reasons for this are not entirely clear. We assume that they have to do with the fear of entering into political controversies over abortion. We are concerned that, despite its broader mandate, in most countries inputs to Johannesburg are being prepared mainly by environment ministries who have little experience in dealing with population questions. This revised version was published online in July 2006 with corrections to the Cover Date.