Flooding patterns of the Okavango Wetland in Botswana between 1972 and 2000

The inundated area of the Okavango Delta changes annually and interannually. The variability relates to regional precipitation over the catchment area in the Angolan highlands, and to local rainfall. The patterns of the wetland were captured using more than 3000 satellite images for the period 1972 to 2000, near daily NOAA AVHRR data for 1985-2000, and less frequent images of the Landsat sensors from 1972 onwards. One AVHRR image for every 10-day period was classified into land and water using an unsupervised classification method. Evaluation against Landsat TM and ERS2-ATSR data indicate an agreement of 89% for the size of estimated inundation area. Results show that the wetland area has varied between approximately 2450 km2 and 11400 km2 during the last 30 years.     

An Investigation of Environmental Racism Claims: Testing Environmental Management Approaches with a Geographic Information System

The purpose of this research was to explore the concept of an environmental racism claim through the use of several environmental management tools. The EPAs Toxics Release Inventory, Cumulative Exposure Project, and the Los Angeles County Department of Health Services' Hot Zone Census Tract Assessment were combined with racial and socioeconomic data to test claims that minorities in South Central Los Angeles are disproportionately exposed to environmental lead. Multivariate analysis indicated that race is strongly associated with the number of cases of elevated blood lead levels in South Central, irrespective of poverty status. Proximity to point sources, a common focal point for studies of environmental racism, was not a contributing factor to health outcomes. Proximity to transportation corridors was consistently the strongest indicator of environmental lead exposure, while median home values were significantly and positively related to elevated blood lead levels. Implications for environmental justice advocates and social and environmental scientists are discussed.     

Aerial measurements on uranium ore mining, milling and processing areas in Germany

The paper describes aerial measurements at several sites containing residues from uranium mines, waste rock dumps and tailings ponds of the Wismut company in Saxony and Thuringia. For the measurements, a computerized gamma-ray spectrometer equipped with a HPGe-detector and a NaI(Tl)-detector array with a volume of 121 was used. Radioactive anomalies from natural radionuclides have been detected and mapped. The activity concentrations of 226Ra, 228Th and 40K in areas with elevated radioactivity from natural radionuclides were determined from aerial measurements. Ground-based measurements--as far as available--confirmed these results. The mean 226Ra activity concentrations in the different waste rock dumps were found to be in the range 370 to 1600 Bq kg-1. The highest mean 226Ra activity concentrations were measured for the tailings ponds with values up to 1300 Bq kg-1. For 40K and 208Tl, activity concentrations of 860 and 40 Bq kg-1, respectively, were obtained as averages of all measurements. These values are commonly found in the environment. In general, there is reasonable agreement between the results measured with different detectors and measuring methods.     

Specific Conductance and pH as Indicators of Watershed Disturbance in Streams of the New Jersey Pinelands, USA

/ We used linear regression to independently and jointly relate specific conductance and pH measured at New Jersey Pinelands stream sites to the percentage of altered land in a watershed. Percentage altered land included developed and agricultural land uses and represented watershed disturbance for a given site. Median values calculated for a 2-year period (September 1992 through August 1994) characterized pH and specific conductance at the study sites. We found the relationships between the median values for both water-quality measures and percentage altered land for a site to be consistent across subregion and dominant altered-land use. Our results also demonstrated that the water-quality/altered-land relationships developed using median values were similar to relationships developed using data from any single-sample period within the entire study period. Individually, pH and specific conductance explained 48% and 56%, respectively, of the variability in watershed disturbance among study sites. The joint use of pH and specific conductance explained 79% of the watershed disturbance variability among sites. The joint use of these easily obtained water-quality measures can provide a quick assessment of instream water-quality impacts from upstream watershed disturbance at any Pinelands stream site. Additionally, a range in pH and specific conductance, and hence a range in ambient water quality, can be predicted for a given altered-land percentage or a change in existing altered-land conditions.     

The Information Cycle as a Framework for Defining Information Goals for Water-Quality Monitoring

/ The necessity to tailor information becomes increasingly urgent as the information revolution continues to generate ever-increasing flows of data and so-called information. From European experiences, a new approach for monitoring system design is suggested in this paper. In this approach, careful and detailed specification of information needs is a major contributing factor to the effectiveness of information products. To develop better specifications for information products, the process of collecting and transforming data into useful information requires careful thought and guidance. A dialogue between information users on one hand and information producers on the other is essential. This dialogue can be based on the information cycle, describing the continuous process from specifying information needs for water management and a strategy to collect information through data collection and data analysis up to utilization of information by water management. By following the respective steps in the information cycle, the process of information gathering can be completed. The cyclic character provides a quantitative means of connecting monitoring system design and operations with the information expectations and/or products required by management.     

New advancements for in situ treatment using electrical resistance heating

Electrical resistance heating (ERH) is proving to be an effective technology to rapidly heat the subsurface and, in doing so, removing volatile organic compounds. Practitioners of this technology have observed that other processes (biodegradation, abiotic degradation, hydrolysis, and possibly others) occur to break down the chemicals of concern, and remediation is not solely accomplished through vaporization. Few sites treated using ERH have been monitored during and after treatment to identify and evaluate the processes occurring and assess the contribution of these other biological and chemical processes in the remediation effort so that they may be incorporated in the remediation design. At Fort Lewis, Washington, a landfill has been undergoing ERH treatment in three phases, where chlorinated volatile organic compounds represent the primary chemicals of concern in soil and groundwater. Other chemicals of concern include petroleum products, oils, and lubricants. The Fort Lewis remediation projects provided an opportunity to observe the reactions occurring in the subsurface during ERH and fine‐tune the study with each phase of operation. This study is still under way. However, the data gathered to date, which focuses on biodegradation, provides insights into the processes that have been observed. For the Fort Lewis site, biotic and abiotic degradation processes have been observed throughout the range of operating temperatures. At the lower temperature ranges (up to 70°C), biological processes appear to predominate. Above 70°C, abiotic processes become much more active. The goal of this work is to eventually optimize the use of these intrinsic processes in ERH remediation to reduce energy requirements and costs. © 2007 Wiley Periodicals, Inc.     

Remediation with cyclodextrin: Recovery of the remedial agent by membrane filtration

Cyclodextrin‐enhanced flushing of contaminants from the subsurface is a promising innovative remediation technology. It will become more economically viable at more sites if methods can be developed to recover and reconcentrate the cyclodextrin solution after it has been flushed through an aquifer. The goal of this study was to determine if membrane technology is capable of meeting that need. Five membranes with different material properties were tested for this purpose in the laboratory. The results of these tests indicate that there are large differences both in the efficiency of these membranes to extract hydroxpropyl‐β‐cyclodextrin (HPCD) and their stability when exposed to trichloroethylene (TCE) at concentrations near aqueous solubility. Not only does the molecular weigh cutoff (MWCO) of a membrane determine if HPCD can be retained, but crucial selection criteria are the membrane's resistance and compatibility with TCE. Of the five membrane materials tested, only two (polymer composite membrane and polysulfone) met both these requirements. The polymer composite membrane (MPF‐44) showed reliable and stable HPCD recoveries (>95 percent) even when exposed to high TCE concentrations. The polysulfone membrane showed high HPCD recoveries, 88.5 ± 0.4 percent to 97 percent ±1 percent for ultrafiltration and nanofiltration membranes, respectively. However, membrane swelling and deterioration became a problem at high TCE concentrations (>1,000 mg/L). These problems diminished when the TCE concentration was less than 1 mg/L. Field tests demonstrated that batch mode treatment by ultrafiltration doubled the cyclodextrin concentration from 5 to 10 percent within three hours at a constant operating pressure of 13 psi. Under continuous single‐pass treatment conditions, cyclodextrin concentration also increased, although the rate of increase was much smaller than in batch mode. Overall, these tests showed that cyclodextrin recovery is possible under field conditions. © 2007 Wiley Periodicals, Inc.     

Considerations for the design of organic mulch permeable reactive barriers

Organic mulch consists of insoluble carbon biopolymers that are enzymatically hydrolyzed during decomposition to release aqueous total organic carbon (TOC). The released TOC is utilized by microorganisms as an electron donor to transform electrophilic contaminants via reductive pathways. Over the last decade, organic mulch permeable reactive barriers (PRBs), or biowalls, have received increased interest as a relatively inexpensive slow‐release electron donor technology for addressing contaminated groundwater. To date, biowalls have been installed to enhance the passive bioremediation of groundwater contaminated with a variety of electrophilic compounds, including chlorinated solvents, explosives, and perchlorate. In addition, several mulch biowall projects are currently under way at several U.S. Department of Defense facilities. However, at the present time, the guidelines available for the design of mulch PRBs are limited to a few case studies published in the technical literature. A biowall design, construction, and operation protocol document is expected to be issued by the Air Force Center for Environmental Excellence in 2007. In this publication, three technical considerations that can have a significant impact on the design and performance of mulch PRBs are presented and discussed. These technical considerations are: (1) hydraulic characteristics of the mulch bed; (2) biochemical characteristics of different types of organic amendments used as mulch PRB fill materials; and (3) a transport model that can be used to estimate the required PRB thickness to attain cleanup standards. © 2007 Wiley Periodicals, Inc.