Freshwater inflow: Science, policy, management

The papers in this special issue were presented in a special session during the 2001 biennial conference of the Estuarine Research Federation held in St. Pete Beach, Florida. The session, “Freshwater inflow: Science, policy and management,” was focused on issues related to reduced freshwater inflow to estuaries. The session brought together scientists, managers, and regulators, and included presentations on the estimation of freshwater input to estuaries, development of ecological indicators to assess changes in inflow, management strategies used to set freshwater requirements, and experiences with the reintroduction of freshwater to restore inflow.     

The organochlorine contamination history of the Mersey estuary, UK, revealed by analysis of sediment cores from salt marshes

Sediment profiles in the Banks, Ince and Widnes Warth salt marshes in Northwest England contain a mappable record of historic pollution. For persistent organochlorine compounds this stretches back over 90 years. The PCB and HCH profiles can be successfully rationalised by dating methods, and they can be related to the dates of initial production and subsequent withdrawal from use of these chemicals as a result of restrictive environmental legislation. HCB has a more complex pollution profile as it has been manufactured in Northwest England, both deliberately as a pesticide and accidentally as a by-product of several chlorination processes, dating back to the start of the 20th century. The concentrations of degradation products of DDT are relatively constant through the sediment profile and are dominated by op'- and pp'-DDD with only minor contributions from the most toxic species, pp'-DDT. The quantities of these compounds resident in the reservoir of pollutants under these marshes have been calculated, and have fallen progressively in the last 30-50 years.     

Ocean dumping of seafood wastes in the United States

In the United States fish wastes can be ocean dumped without an Ocean Dumping Permit if the wastes contain no additives (flocculating or preserving agents, etc.). Fish wastes are currently ocean dumped off American Samoa, Louisiana and Puerto Rico. Fish wastes are characteristically high in proteins, fats, dissolved and suspended organic materials. Water quality parameters affected by these wastes are biochemical oxygen demand, total dissolved solids, chemical oxygen demand, oil and grease, pH, and turbidity. Other key factors include organic and nutrient enrichment, the attractant of undesirable predator species (i.e. sharks) and the natural oxygen regeneration processes.     

Long Island Sound: Distributions,trends, and effects of chemical contamination

Trace metals and organic contaminants concentrations are monitored annually in surface sediments, blue mussel tissue, and winter flounder livers at multiple sites in Long Island Sound by National Oceanic and Atmospheric Administration’s National Status and Trends (NS&T) program for Marine Environmental Quality. The NS&T program is also conducting various studies on the bioeffects of contaminants in the sound. Three years of monitoring results indicate organic and elemental contaminants concentrations in sediments and biota at sites in the western portion of the sound are high on a national scale. Possible decreasing trends in cadmium and chlordane in the sound are suggested by the 1986–1988 data for their concentrations in mussels. A comparison between NS&T Mussel Watch results and those of the Environmental Protection Agency’s Mussel Watch, conducted from 1976 through 1978, indicated a decadal increase in copper concentrations and a decrease in lead in the sound. Bioeffects studies in the sound have revealed responses to contamination only in localized zones where contaminant levels are very high.     

Ceboruco hazard map: part II—modeling volcanic phenomena and construction of the general hazard map

Natural Hazards - Ceboruco volcano in the western Trans-Mexican Volcanic Belt is one of the eleven most active stratovolcanoes in Mexico. Due to its recent eruptive history including a large...     

Progress in Remediation of Groundwater at Petroleum Sites in California

Quantifying the overall progress in remediation of contaminated groundwater has been a significant challenge. We utilized the GeoTracker database to evaluate the progress in groundwater remediation from 2001 to 2011 at over 12,000 sites in California with contaminated groundwater. This paper presents an analysis of analytical results from over 2.1 million groundwater samples representing at least $100 million in laboratory analytical costs. Overall, the evaluation of monitoring data shows a large decrease in groundwater concentrations of gasoline constituents. For benzene, half of the sites showed a decrease in concentration of 85% or more. For methyl tert‐butyl ether (MTBE), this decrease was 96% and for TBE, 87%. At remediation sites in California, the median source attenuation rate was 0.18/year for benzene and 0.36/year for MTBE, corresponding to half‐lives of 3.9 and 1.9 years, respectively. Attenuation rates were positive (i.e., decreasing concentration) for benzene at 76% of sites and for MTBE at 85% of sites. An evaluation of sites with active remediation technologies suggests differences in technology effectiveness. The median attenuation rates for benzene and MTBE are higher at sites with soil vapor extraction or air sparging compared with sites without these technologies. In contrast, there was little difference in attenuation rates at sites with or without soil excavation, dual phase extraction, or in situ enhanced biodegradation. The evaluation of remediation technologies, however, did not evaluate whether specific systems were well designed or implemented and did not control for potential differences in other site factors, such as soil type.     

Exceptionally Long MTBE Plumes of the Past Have Greatly Diminished

Studies published in the late 1990s and early 2000s identified the presence of exceptionally long methyl tert‐butyl ether (MTBE) plumes (more than 600 m or 2000 feet) in groundwater and have been cited in technical literature as characteristic of MTBE plumes. However, the scientific literature is incomplete in regard to the subsequent behavior and fate of these MTBE plumes over the past decade. To address this gap, this issue paper compiles recent groundwater monitoring records for nine exceptional plumes that were identified in prior studies. These nine sites exhibited maximum historical MTBE groundwater plume lengths ranging from 820 m (2700 feet) to 3200 m (10,500 feet) in length, exceeding the lengths of 99% of MTBE plumes, as characterized in multiple surveys at underground storage tank sites across the United States. Groundwater monitoring data compiled in our review demonstrate that these MTBE plumes have decreased in length over the past decade, with five of the nine plumes exhibiting decreases of 75% or more compared to their historical maximum lengths. MTBE concentrations within these plumes have decreased by 93% to 100%, with two of the nine sites showing significant decreases (98% and 99%) such that the regulatory authority has subsequently designated the site as requiring no further action.     

Effect of Different Sampling Methodologies on Measured Methane Concentrations in Groundwater Samples

Analysis of dissolved light hydrocarbon gas concentrations (primarily methane and ethane) in water supply wells is commonly used to establish conditions before and after drilling in areas of shale gas and oil extraction. Several methods are currently used to collect samples for dissolved gas analysis from water supply wells; however, the reliability of results obtained from these methods has not been quantified. This study compares dissolved methane and ethane concentrations measured in groundwater samples collected using three sampling methods employed in pre‐ and post‐drill sampling programs in the Appalachian Basin. These include an open‐system collection method where 40 mL volatile organic analysis (VOA) vials are filled directly while in contact with the atmosphere (Direct‐Fill VOA) and two alternative methods: (1) a semi‐closed system method whereby 40 mL VOA vials are filled while inverted under a head of water (Inverted VOA) and (2) a relatively new (2013) closed system method in which the sample is collected without direct contact with purge water or the atmosphere (IsoFlask^®). This study reveals that, in the absence of effervescence, the difference in methane concentrations between the three sampling methods was relatively small. However, when methane concentrations equaled or exceeded 20 mg/L (the approximate concentration at which effervescence occurs in the study area), IsoFlask^® (closed system) samples yielded significantly higher methane concentrations than Direct‐Fill VOA (open system) samples, and Inverted VOA (semi‐closed system) samples yielded lower concentrations. These results suggest that open and semi‐closed system sample collection methods are adequate for non‐effervescing samples. However, the use of a closed system collection method provides the most accurate means for the measurement of dissolved hydrocarbon gases under all conditions.     

The Poynting-Robertson effect in the Newtonian potential with a Yukawa correction

We consider a Yukawa-type gravitational potential combined with the Poynting-Robertson effect. Dust particles originating within the asteroid belt and moving on circular and elliptic trajectories are studied and expressions for the time rate of change of their orbital radii and semimajor axes, respectively, are obtained. These expressions are written in terms of basic particle parameters, namely their density and diameter. Then, they are applied to produce expressions for the time required by the dust particles to reach the orbit of Earth. For the Yukawa gravitational potential, dust particles of diameter \(10^{ - 3}\) m in circular orbits require times of the order of \(8.557 \times 10^{6}\) yr and for elliptic orbits of eccentricities \(e =0.1, 0.5\) require times of \(9.396 \times 10^{6}\) and \(2.129 \times 10^{6}\) yr respectively to reach Earth’s orbit. Finally, various cases of the Yukawa potential are studied and the corresponding particle times to reach Earth’s are derived per case along with numerical results for circular and various elliptical orbits.