Assessing wave climate trends in the Bay of Biscay through an intercomparison of wave hindcasts and reanalyses

The Bay of Biscay, located in the Northeast Atlantic Ocean, is exposed to energetic waves coming from the open ocean that have crucial effects on the coast. Knowledge of the wave climate and trends in this region are critical to better understand the last decade’s evolution of coastal hazards and morphology and to anticipate their potential future changes. This study aims to characterize the long-term trends of the present wave climate over the second half of the twentieth century in the Bay of Biscay through a robust and homogeneous intercomparison of five-wave datasets (Corrected ERA-40 (C-ERA-40), ECMWF Reanalysis Interim (ERA-Interim), Bay Of Biscay Wave Atlas (BOBWA-10kH), ANEMOC, and Bertin and Dodet 2010)). The comparison of the quality of the datasets against offshore and nearshore measurements reveals that at offshore locations, global reanalyses slightly underestimate wave heights, while regional hindcasts overestimate wave heights, especially for the highest quantiles. At coastal locations, BOBWA-10kH is the dataset that compares the best with observations. Concerning long time-scale features, the comparison highlights that the main significant trends are similarly present in the five datasets, especially during summer for which there is an increase of significant wave heights and mean wave periods (up to +15 cm and +0.6 s over the period 1970–2001) as well as a southerly shift of wave directions (around ?0.4° year^?1). Over the same period, an increase of high quantiles of wave heights during the autumn season (around 3 cm year^?1 for 90th quantile of significant wave heights (SWH₉₀)) is also apparent. During winter, significant trends are much lower than during summer and autumn despite a slight increase of wave heights and periods during 1958–2001. These trends can be related to modifications in the wave-type occurrence. Finally, the trends common to the five datasets are discussed by analyzing the similarities with centennial trends issued from longer time-scale studies and exploring the various factors that could explain them.     

Plastic ingestion by planktivorous fishes in the North Pacific Central Gyre

A significant amount of marine debris has accumulated in the North Pacific Central Gyre (NPCG). The effects on larger marine organisms have been documented through cases of entanglement and ingestion; however, little is known about the effects on lower trophic level marine organisms. This study is the first to document ingestion and quantify the amount of plastic found in the gut of common planktivorous fish in the NPCG. From February 11 to 14, 2008, 11 neuston samples were collected by manta trawl in the NPCG. Plastic from each trawl and fish stomach was counted and weighed and categorized by type, size class and color. Approximately 35% of the fish studied had ingested plastic, averaging 2.1 pieces per fish. Additional studies are needed to determine the residence time of ingested plastics and their effects on fish health and the food chain implications.     

Assimilation of sea surface temperature into CECOM by flux correction

Sea surface temperature (SST) from a near real-time data set produced from satellites data has been assimilated into a coupled ice–ocean forecasting model (Canadian East Coast Ocean Model) using an efficient data assimilation method. The method is based on an optimal interpolation scheme by which SST is melded into the model through the adjustment of surface heat flux. The magnitude and space–time variation of the adjustment depend on the depth of heat diffusion into the water column in response to changes in surface flux, the correlation time scale of the data, and model and data errors. The diffusion depth is scaled by the eddy diffusivity for temperature. The ratio of the model and data errors is treated as an adjustable parameter. To evaluate the quality of the assimilation, the results from the model with and without assimilation are compared to independent ship data from the Atlantic Zone Monitoring Program and the World Ocean Circulation Experiment. It is shown that the assimilation has a significant impact on the modeled SST, reducing the root mean square difference (RMSD) between the model SST and the ship SST by 0.63°C or 37%. The RMSD of the assimilated SST is smaller than that of the satellite SST by 0.23°C. This suggests that model simulations or predictions with data assimilation can provide the best estimate of the true SST. A sensitivity study is performed to examine the change of the model RMSD with the adjustable parameter in the assimilation equation. The results show that there is an optimal value of the parameter and the model SST is not very sensitive to the parameter.     

MAROS: a decision support system for optimizing monitoring plans

The Monitoring and Remediation Optimization System (MAROS), a decision-support software, was developed to assist in formulating cost-effective ground water long-term monitoring plans. MAROS optimizes an existing ground water monitoring program using both temporal and spatial data analyses to determine the general monitoring system category and the locations and frequency of sampling for future compliance monitoring at the site. The objective of the MAROS optimization is to minimize monitoring locations in the sampling network and reduce sampling frequency without significant loss of information, ensuring adequate future characterization of the contaminant plume. The interpretive trend analysis approach recommends the general monitoring system category for a site based on plume stability and site-specific hydrogeologic information. Plume stability is characterized using primary lines of evidence (i.e., Mann-Kendall analysis and linear regression analysis) based on concentration trends, and secondary lines of evidence based on modeling results and empirical data. The sampling optimization approach, consisting of a two-dimensional spatial sampling reduction method (Delaunay method) and a temporal sampling analysis method (Modified CES method), provides detailed sampling location and frequency results. The Delaunay method is designed to identify and eliminate redundant sampling locations without causing significant information loss in characterizing the plume. The Modified CES method determines the optimal sampling frequency for a sampling location based on the direction, magnitude, and uncertainty in its concentration trend. MAROS addresses a variety of ground water contaminants (fuels, solvents, and metals), allows import of various data formats, and is designed for continual modification of long-term monitoring plans as the plume or site conditions change over time.     

In Situ Monitoring of Vapor Phase TCE Using a Chemiresistor Microchemical Sensor

A chemiresistor microchemical sensor has been developed to detect and monitor volatile organic compounds in unsaturated and saturated subsurface environments. A controlled study was conducted at the HAZMAT Spill Center at the Nevada Test Site, where the sensor was tested under a range of temperature, moisture, and trichloroethylene (TCE) concentrations. The sensor responded rapidly when exposed to TCE placed in sand, and it also responded to decreases in TCE vapor concentration when clean air was vented through the system. Variations in temperature and water vapor concentration impacted baseline chemiresistor signals, but at high TCE concentrations the sensor response was dominated by the TCE exposure. Test results showed that the detection limit of the chemiresistor to TCE vapor in the presence of fluctuating environmental variables (i.e., temperature and water vapor concentration) was on the order of 1000 parts per million by volume, which is about an order of magnitude higher than values obtained in controlled laboratory environments. Automated temperature control and preconcentration is recommended to improve the stability and sensitivity of the chemiresistor sensor.     

Field-Scale Evaluation of Bioaugmentation Dosage for Treating Chlorinated Ethenes

A field demonstration was performed to evaluate the impacts of bioaugmentation dosage for treatment of chlorinated ethenes in a sandy-to-silty shallow aquifer. Specifically, bioaugmentation using a commercially available Dehalococcoides (DHC)-containing culture was performed in three separate groundwater recirculation loops, with one loop bioaugmented with 3.9 × 10¹¹ DHC, the second loop bioaugmented with 3.9 × 10¹² DHC, and the third loop bioaugmented with 3.9 × 10¹³ DHC. Groundwater monitoring was performed to evaluate DHC growth and migration, dechlorination rates, and aquifer geochemistry. The loop inoculated with 3.9 × 10¹² DHC showed slower dechlorination rates and DHC migration/growth compared with the other loops. This relatively poor performance was attributed to low pH conditions. Results for the loops inoculated with 3.9 × 10¹¹ and 3.9 × 10¹³ DHC showed similar timeframes for dechlorination, as evaluated at a monitoring well approximately 10 feet downgradient of the DHC injection well. Application of a recently developed one-dimensional bioaugmentation fate and transport screening model provided a reasonable prediction of the data in these two loops. Overall, these results suggest that increasing bioaugmentation dosage does not necessarily result in decreased dechlorination timeframes in the field. The ability to predict results suggests that modeling potentially can serve as an effective tool for determining bioaugmentation dosage and predicting overall remedial timeframes.     

Embedding eco-friendly and smart technology features in affordable housing for community happiness in Malaysia

GeoJournal - Two phases of study are involved in this research: first, the sales strategies for affordable houses embedded with eco-friendly and smart technology features; and second, the impact of...     

Potential toxicity of resuspended particulate matter and sediments: Environmental samples from the Bay of Banyuls-sur-Mer and Thermaikos Gulf

This contribution attempts to determine whether, and to what degree, environmental samples of resuspended particulate matter and sediments exert a toxicological impact. Further, an attempt is made also to screen the toxic level of potentially hazardous sites, based upon established sediment toxicity criteria. Therefore, a rapid, cost-effective and highly sensitive biotest (bioluminescence assay, based upon marine bacteria) has been applied on: biological fluid extracts; bottom sediments; and sediment trap samples. Samples were taken either from the Bay of Banyuls-sur-Mer (northwestern Mediterranean, France) or Thermaikos Gulf (northeastern Mediterranean, Greece). Biological fluid extracts and sediment trap samples corresponded to periods of resuspension events, or preceding and following such events.The results have revealed that the sampling strategy and biotest implemented in this study might be a useful tool for screening the toxicity of resuspended matter and sediments. Resuspension events appear to be able to exert an influence on the chemical forms of the micro-pollutants; thus on their bioavailability and toxicity. Nevertheless, based upon chemical analysis combined with the bioassay, the toxic level of the sediment samples could be determined, with the level at potentially hazardous sites being characterised.