Fast-track remediation for redevelopment of a former integrated steel mill site

Remedial action was initiated and completed on an approximately 500-acre brownfield site in southern California within a period of five months during the summer of 1995. Remedial actions included design and construction of an approximately 14-acre cap, including a synthetic membrane; design, construction, and testing of an in-situ soil vapor extraction system; excavation, on-site treatment, and off-site disposal of approximately 7,000 cubic yards of residual waste and affected soil; and verification sampling, analysis, and health risk screening in 20 units of a former integrated steel mill. Completion of remedial action on this portion of the mill site within this time frame was required due to site redevelopment plans which included construction of an auto raceway with scheduled races in early 1997. Rapid remedial action was possible only through simultaneous completion of multiple remediation tasks. This could be done only with continuous communication and close coordination among the site owner, lead regulatory agency, and contractors.     

Pulmonary function testing of animals chronically exposed to diluted diesel exhaust for 267 days

Thw purpose of this work was to assess the potential effect that chronic inhalation of diesel exhaust may have on lung mechanics and lung volumes. Noninvasive pulmonary function tests have been conducted repeatedly on 25 rats exposed to diesel exhaust at a particulate concentration of 1500 μg/m³, for 20 h/day, days/week for 267 days. The same tests were conducted on 25 clean air control animals. When the data is normalized, there are no apparent functionally significant changes occurring in the lungs that may be attributed to the chronic inhalation of diesel exhaust.     

Water quality in rice-growing watersheds in a Mediterranean climate

Rice (Oryza sativa L.) agriculture is estimated to cover 161 million ha of land on Earth, with 10% grown in temperate regions. Currently there are strong concerns about surface water nutrient pollution, and the purpose of this study was to determine the impacts of temperate rice cultivation on nutrient dynamics at the small watershed scale. Over the course of the 2008 growing season (May through September), bi-weekly grab samples were collected from outlets of 11 agricultural subwatersheds in California. Samples were analyzed for NO₃-N, NH₄-N, PO₄-P, K, and dissolved organic nitrogen (DON) concentrations, and the average values across all subwatersheds and sampling dates were 0.22, 0.031, 0.047, 1.36, and 0.32 mg L⁻¹, respectively. Linear mixed effects analysis was used to evaluate the magnitude of relationships between nutrient concentration and flux and subwatershed characteristics (i.e. percent soil clay and organic matter, percent rice area, irrigation water reuse, subwatershed discharge, irrigated area, and time, measured as the day in the growing season). For all nutrients, flux decreased over time and increased with discharge. Concentrations of K and DON were highest at the start and end of the growing season. Concentrations of NH₄-N were near non-detect levels, with the exception of a peak in mid-July, which corresponds to when many growers top-dress rice fields with N fertilizer. Nitrate-N concentration and flux decreased with percent rice area, whereas PO₄-P concentrations increased with percent rice area, indicating that rice area should be considered in future watershed-scale studies of nutrient discharge. In all subwatersheds, the discharge loads of K were smaller than surface water input loads, while NO₃-N, NH₄-N, PO₄-P, and DON discharge loads exceeded input loads when total growing season discharge was greater than 3500-6600 m³ ha⁻¹. This implies that the management of subwatershed discharge can be used to control nutrient export from rice-growing areas.     

The Reduction of Stranded Oil by In Situ Shoreline Treatment Options

The Svalbard Shoreline Field Trials quantified the effectiveness of sediment relocation, mixing, bioremediation, bioremediation combined with mixing, and natural attenuation as options for the in situ treatment of oiled mixed-sediment (sand and pebble) shorelines. These treatments were applied to oiled plots located in the upper beach at three experimental sites, each with different sediment character and wave-energy exposure. Systematic monitoring was carried out over a 400-day period to quantify oil removal and to document changes in the physical character of the beach, oil penetration, oil loading, movements of oil to the subtidal environment, biodegradation, toxicity, and to validate oil-mineral aggregate formation.The results of the monitoring confirmed that sediment relocation significantly accelerated the rate of oil removal and reduced oil persistence where oil was stranded on the beach face above the level of normal wave activity. Where the stranded oil was in the zone of wave action, sediment relocation accelerated the short-term (weeks) rate of oil loss from the intertidal sediments.Oil removal rates on a beach treated by mechanical mixing or tilling were not significantly higher than those associated with natural recovery. However there is evidence that mixing/tilling may have enhanced microbial activity for a limited period by increasing the permeability of the sediment.Changes in the chemical composition of the oil demonstrated that biodegradation was significant in this arctic environment and a bioremediation treatment protocol based on nutrient enrichment effectively doubled the rate of biodegradation. However, on an operational scale, the success of this treatment strategy was limited as physical processes were more important in causing oil loss from the beaches than biodegradation, even where this oil loss was stimulated by the bioremediation protocols.     

Statistical Evaluation of Variables Affecting Occurrence of Hydrocarbons in Aquifers Used for Public Supply,California

The variables affecting the occurrence of hydrocarbons in aquifers used for public supply in California were assessed based on statistical evaluation of three large statewide datasets; gasoline oxygenates also were analyzed for comparison with hydrocarbons. Benzene is the most frequently detected (1.7%) compound among 17 hydrocarbons analyzed at generally low concentrations (median detected concentration 0.024 μg/l) in groundwater used for public supply in California; methyl tert‐butyl ether (MTBE) is the most frequently detected (5.8%) compound among seven oxygenates analyzed (median detected concentration 0.1 μg/l). At aquifer depths used for public supply, hydrocarbons and MTBE rarely co‐occur and are generally related to different variables; in shallower groundwater, co‐occurrence is more frequent and there are similar relations to the density or proximity of potential sources. Benzene concentrations are most strongly correlated with reducing conditions, regardless of groundwater age and depth. Multiple lines of evidence indicate that benzene and other hydrocarbons detected in old, deep, and/or brackish groundwater result from geogenic sources of oil and gas. However, in recently recharged (since ~1950), generally shallower groundwater, higher concentrations and detection frequencies of benzene and hydrocarbons were associated with a greater proportion of commercial land use surrounding the well, likely reflecting effects of anthropogenic sources, particularly in combination with reducing conditions.