Calcasieu River Research Articles

Metal Transport in the Mixing Zone of an Estuarine River to the Northern Gulf of Mexico

To better understand the pollution potential of metals in estuaries heavily concentrated with petrochemical industries, we measured concentrations of total recoverable metals in the lower Calcasieu River in southwestern Louisiana that flows into the northern Gulf of Mexico. Water samples were collected at six sites along the last 88 km reach of the river monthly between May 2013 and November 2015, during which salinity ranged from 0.02 to 29.5 ppt from upstream to downstream. The samples were analyzed for a series of total recoverable metals, including aluminum (Al), arsenic (As), boron (B), cadmium (Cd), calcium (Ca), cobalt (Co), chromium (Cr), copper (Cu), iron (Fe), lithium (Li), magnesium (Mg), manganese (Mn), nickel (Ni), silicon (Si), titanium (Ti), vanadium (V), and zinc (Zn), of which only Al, As, B, Ca, Fe, Li, Mg, Mn, Si, Ti, and Zn had a detection rate higher than 30% over the 31-month study period. In the freshwater portion of the river, Si, Ca, Al, Fe, and Mg showed the highest concentration (8, 5, 4, 2, and 2 mg/L, respectively), while Li, As, Zn, Ti, and B had the lowest concentration (6, 16, 27, 34 and 50 µg/L, respectively). The concentrations of Al and Si declined by more than 30% from the freshwater to the river mouth, but the concentrations of Li and B increased by 61 and 66 times, respectively. None of these metals’ concentrations were found to exceed US EPA standards, but the rapid increase in Li and B concentrations may indicate a potential anthropogenic influence. On average, the Calcasieu River discharged a total of 35,484 tons of the elements each year (or 8059 kg/km2/yr), of which Si, Al, Ca, Fe, and Mg contributed 98%. Three major components of factors were extracted explaining 34, 20, and 13% (cumulative 67%) of the total variation in the metal concentrations. Salinity and pH were the major (>0.3) parameters in component 1 explaining the variability of B and Li; TSS was the major (>0.3) parameter in component 2 explaining the variation of Al, Fe, and Ti concentration; and temperature and DO% were the major (>0.3) parameters in component 3 explaining the variation of Mn concentration. Further studies on riverbed sediment metals and their effect on metal concentrations in surface water can help understand the metal sources and their potential effects on coastal aquatic ecosystems.

Distribution and Abundance of the Alligator Snapping Turtle (Macrochelys temminckii) in Southwestern Louisiana

High harvest rates during the 1900s led to declines of Macrochelys temminckii (Alligator Snapping Turtle) throughout much of its range. Recent research to determine the status of Alligator Snapping Turtles has been completed in some regions of Louisiana, but information is lacking for the southwestern region of the state. To determine the distribution and abundance of Alligator Snapping Turtles in southwestern Louisiana, we conducted trapping efforts in the lower Calcasieu, Mermentau, and lower Sabine river systems from March 2012 through October 2013 using baited hoop nets. In 731 trap nights, we captured 14 individuals (2 M, 4 F, 8 Juv) in the Mermentau and Calcasieu river systems. Our trapping efforts did not detect Alligator Snapping Turtles at Sabine River sites, although one individual was found dead on a fishing hook of a hanging limb line. Our catch per unit effort (CPUE) was 0.021 across the 3 river drainages. Population levels appear to be smaller than observed elsewhere in Louisiana and in neighboring southern states. We recommend that future surveys be conducted to determine population trajectories and that a system be implemented for monitoring commercial fishing bycatch and recreational harvest.

A Comprehensive Hydrodynamics-Salinity-pH Model for Analyzing the Effects of Freshwater Withdrawals in Calcasieu Lake and Surrounding Water Systems

The study is a continuation of the authors' previous works on hydrodynamics and sediment transport modeling for Calcasieu Lake area (located in southwest Louisiana) (Zhang, N., Zheng, Z. C., and Yadagiri, S., 2011, “A Hydrodynamic Simulation for the Circulation and Transport in Coastal Watersheds,” Comput. Fluids, 47(1), pp. 178–88; Zhang, N., Kee, D., and Li, P., 2013, “Investigation of the Impacts of Gulf Sediments on Calcasieu Ship Channel and Surrounding Water Systems,” Comput. Fluids, 77, pp. 125–133; Yadav, P. K., Thapa, S., Han, X., Richmond, C., and Zhang, N., 2015, “Investigation of the Effects of Wetland Vegetation on Coastal Flood Reduction Using Hydrodynamic Simulation,” ASME Paper No. AJKFluids2015-3044). The major purposes of the study are: (1) to demonstrate the new model features and validate the model results, (2) to disclose the effects of Gulf Intracoastal Waterway (GIWW) and determine the boundary conditions for GIWW in the model, and (3) to use the model to analyze the effects of excessive freshwater withdrawals on the changes of hydrodynamics and salinity in the Calcasieu Lake system. Several new model features were added to the existing model framework, including the extension of modeling domain, vegetation model, salinity transport model, and pH calculation. Measurement data from NOAA and USGS are used as boundary conditions for the model. Simulation results were compared with measurement data from NOAA, USGS and other sources for validation. Due to lack of measured data for GIWW in the target area, the effect of GIWW flow conditions on the modeling results was investigated and appropriate GIWW boundary condition was determined based on numerical tests. Numerous petrochemical plants in the area use tremendous amount of fresh surface water. Recent industry expansions may further increase the demands of freshwater withdrawals. One of the purposes of the study is to use developed model to test and analyze the effects of increased freshwater withdrawal from Calcasieu River at the north boundary of the study area on the hydrodynamics and salinity in the downstream Calcasieu Lake system.

Assessing dissolved carbon transport and transformation along an estuarine river with stable isotope analyses

Estuaries play an important role in the dynamics of dissolved carbon from rivers to coastal oceans. However, our knowledge of dissolved carbon transport and transformation in mixing zones of the world's coastal rivers is still limited. This study aims to determine how dissolved inorganic carbon (DIC) and dissolved organic carbon (DOC) concentrations and stable isotopes (δ13CDIC and δ13CDOC) change along an 88-km long estuarine river, the Calcasieu River in Louisiana, southern USA, with salinity ranging from 0.02 to 21.92. The study is expected to elucidate which processes most likely control carbon dynamics in a freshwater-saltwater mixing system, and to evaluate the net metabolism of this estuary. Between May 2015 and February 2016, water samples were collected and in-situ measurements on ambient water conditions were performed during five field trips at six sites from upstream to downstream of the Calcasieu River, which enters the Northern Gulf of Mexico (NGOM). The DIC concentration and δ13CDIC increased rapidly with increasing salinity in the mixing zone. The average DIC concentration and δ13CDIC at the site closest to the NGOM (site 6) were 1.31 mM and −6.34‰, respectively, much higher than those at the site furthest upstream (site 1, 0.42 mM and −20.83‰). The DIC concentrations appeared to be largely influenced by conservative mixing, while high water temperature may have played a role in deviating DIC concentration from the conservative line due likely to increased respiration and decomposition. The δ13CDIC values were close to those suggested by the conservative mixing model for May, June and November, but lower than those for July and February, suggesting that an estuarine river can fluctuate from a balanced to a heterotrophic system (i.e., production/respiration (P/R) < 1) seasonally. Unlike the DIC longitudinal trend, the DOC concentrations in the river estuary decreased from upstream to downstream, but to a much smaller degree. The DOC concentrations consistently showed a deviation from those suggested by the conservative mixing model, which may have been a consequence of in-stream photosynthesis. This river estuary consistently showed depleted δ13CDOC values (i.e., from −30.56‰ to −25.92‰), suggesting that the DOC source in the mixing zone was highly terrestrially derived. However, in this relatively small isotopic range, δ13CDOC alone has limitations in differentiating carbon produced by aquatic photosynthesis from carbon produced by terrestrial photosynthesis in a river-ocean continuum.

Estuarine Plume: A Case Study by Satellite SAR Observations and &lt;italic&gt;In Situ&lt;/italic&gt; Measurements

Estuary plumes on the western Louisiana continental shelf in the Gulf of Mexico, outside of constricted channels of the Sabine and Calcasieu Lakes were observed on two RADARSAT-1 synthetic aperture radar (SAR) images. The in situ data showed a change in salinity of ~2–3 PSUs across the front on the northwest edge of the plume, corresponding to locations of vertical salinity variation of 5.5–7.5 PSU. Velocity magnitude outside of the inlet reached more than 2.3 ms $^{{\mathrm {-1}}}$ seaward and a brackish lens in the upper 4.5 m of the water column, the spread of which contributed to the development of a plume. The volume of brackish water within the plume was estimated an order of magnitude larger than the volume output from the Calcasieu River within an entire ebb tidal period. This implies that the plume was formed during multiple tidal cycles and it sustained during the flood tides because only weak diurnal tides exist. Both satellite and in situ observations showed an interesting western intensification of the plume. An analysis to the momentum/vorticity equations suggests that the western intensification is due to the asymmetry of the vorticity-divergence relationship under the Coriolis force. This can also be enhanced by an ambient coastal current that strengthens the convergence at the front. Estuary plumes are shown as bright and dark features in two SAR images. Results from a radar model simulation and in situ water temperature data showed that the SAR observed plume features were dominated by the water temperature differences.

Spatiotemporal Distributions of Sr and Ba along an Estuarine River with a Large Salinity Gradient to the Gulf of Mexico

Strontium and barium to calcium ratios are often used as proxies for tracking animal movement across salinity gradients. Many estuarine rivers face saltwater intrusion due to sea level rise, potentially causing changes in mobility and distribution of these metals upstream. From May 2013 to August 2015, monthly water samples were collected and in-situ measurements were performed at six sites along an estuary strongly affected by saltwater intrusion, the Calcasieu River, with salinity ranging from 0.02 to 29.50 Parts Per Thousand (ppt). Results showed that the total Sr concentration and the Sr/Ca ratio both increased significantly with increasing salinity. The average Sr concentration at the site closest to the Gulf of Mexico (Site 6) was 46.21 µmol/L, about 130 times higher than that of the site furthest upstream (Site 1, 0.35). The average Sr/Ca ratio at Site 6 (8.41 mmol/mol) was about three times the average Sr/Ca ratio at Site 1 (2.89). However, the spatial variation in total Ba concentration was marginal, varying from 0.36 to 0.47 µmol/L. The average Ba/Ca ratio at Site 1 (4.82 mmol/mol) was about 54 times the ratio at Site 6 (0.09), showing a negative relation between the Ba/Ca ratio and salinity. All elemental concentrations and ratios had considerable seasonal variations, with significant differences among sampling months for the Sr and Ba concentrations and the Ba/Ca ratio (p &lt; 0.01). The results suggest that for low-gradient estuarine rivers such as the Calcasieu River, water chemistry upstream would experience substantial Sr and Ca enrichment, potentially affecting aquatic environments and biological communities.

Habitat-Related Variation in Body Size and Reproductive Output and an Examination of Reproductive Allometry in the Sabine Map Turtle (Graptemys sabinensis) across Three River Drainages

The Sabine Map Turtle (Graptemys sabinensis) inhabits the Sabine-Neches, Calcasieu, and Mermentau river drainages of southwestern Louisiana and east Texas. Sparse data in the literature mark it as having among the smallest body sizes and smallest clutch sizes among the 14 species of the genus Graptemys. All available data on life history originate from the upper Sabine and upper Calcasieu drainages, which are relatively high-gradient rivers with fast currents and numerous sandbars. Downstream segments of these drainages and the entire Mermentau drainage have almost no gradient, with little perceptible current and no sandbars. We sampled G. sabinensis from the Mermentau River and upper and lower portions of both the Sabine and Calcasieu drainages. We collected data on body size and radiographed gravid females in the lower Calcasieu and Mermentau drainages to examine clutch size and egg width and compared our data to literature records and measurements of museum specimens. Both males (to 104 mm in midline p...

Three Decadal Inputs of Nitrogen and Phosphorus from Four Major Coastal Rivers to the Summer Hypoxic Zone of the Northern Gulf of Mexico

Nutrient enrichment is considered one of the most important causes for summer hypoxic conditions in the northern Gulf of Mexico (NGOM) off the Louisiana coast. While many studies on nutrient inputs from the large Mississippi-Atchafalaya River System have been conducted, little is known about nutrient inputs from other coastal rivers in Louisiana. In this study, we utilized long-term (1980–2009) records on river discharge and nutrient concentrations of four major Louisiana coastal rivers—the Sabine, Calcasieu, Mermentau, and Vermilion—to estimate daily, monthly, and annual inflows of nitrate and nitrite nitrogen (NO3 + NO2), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) into the NGOM. The three-decade-long nutrient inflows from these rivers were analyzed for their seasonal fluctuations, interannual variabilities, and decadal trends. Fluxes of NO3 + NO2, TKN, and TP for these river basins were estimated to assess land use effects on riverine nutrients. Our study found that the four coastal rivers discharged each year a considerably large amount of NO3 + NO2 (total of 1755 t), TKN (12,208 t), and TP (1833 t) into the NGOM, with a peak input of nitrogen during the spring. The Mermentau and Vermilion Rivers, which drain intensive agriculture areas, had significantly higher NO3 + NO2, TKN, and TP concentrations when compared with the Sabine and Calcasieu Rivers, which drain forest-pasture-dominated lands. The fluxes of NO3 + NO2, TKN, and TP from the Mermentau River Basin (156 kg km−2 year−1 NO3 + NO2, 942 kg km−2 year−1 TKN, and 206 kg km−2 year−1 TP) and the Vermilion River Basin (374, 1078, and 360) were much higher than those combined from the Sabine and Calcasieu River Basins (66, 710, and 62). These findings fill a major knowledge gap concerning the quantity and characteristics of nitrogen and phosphorus transport from coastal watersheds to North America’s largest hypoxic zone.

Investigation of the impacts of Gulf sediments on Calcasieu Ship Channel and surrounding water systems

Calcasieu Ship Channel is located in southwest Louisiana, connecting the port of Lake Charles to the Gulf of Mexico. The 40ft deep ship channel is surrounded by water systems including Calcasieu Lake, Gulf Intracoastal Water Way (GIWW), and several wetlands. Excessive sediment depositions were found on the bottom of the ship channel in many locations, which requires expensive dredging process to remove those unwanted sediments. There are several suspected sediment sources, such as the Gulf of Mexico, upstream Calcasieu River and GIWW, bank erosions, and discharge from surrounding wetlands. However, how significant of each source to the total sedimentation in the ship channel is unknown, which hinders the design of sediment prevention mechanism. In this study, numerical and experimental investigations were conducted to study the sediment transport and deposition in this target area. Sediment transport from one of the major sediment sources, the Gulf of Mexico, was studied to see the effects of this source on the total sedimentation in the ship channel. The effects of storm-surge flood on the sediment transport and deposition were also studied. The 2-d depth-averaged shallow water flow equation set was solved for water phase, along with a scalar transport equation for the sediment phase. Both sediment deposition and re-suspension effects are included in the model. The accumulated depositions on the seabed and wetland surface were calculated. The deposition results were compared to the sampling data in the area and yielded good agreement which verify the accuracy of the numerical model.

Riverine sediment inflow to Louisiana Chenier Plain in the Northern Gulf of Mexico

The Louisiana Chenier Plain is a geomorphologic extension of the Mississippi Deltaic Plain, highly influenced by sediments originating from the Mississippi River. With the Mississippi River unable to avulse closer to the Plain local riverine sediment resources are integral to maintaining the physical and ecological integrity of the estuaries and marshlands. To gain insight into the sediment resources, this study assessed two decades (1990–2009) of discharge and total suspended solids (TSS) of four rivers, Sabine River, Calcasieu River, Mermentau River, and Vermilion River that flow into the Chenier Plain. The study quantified long-term sediment delivery, analyzed seasonal and inter-annual trends of sediment transport, and investigated the effect of hydrometeorological conditions on sediment yields. Total sediment delivery from the rivers over the 20-year period was 6.86 × 10 6 tonnes, with the Sabine River contributing 62% of the sediment load. The Sabine River also showed a significant decreasing trend ( p = 0.03) in annual sediment yield. Long-term trends of sediment loads in all the rivers were influenced by their discharge, not their TSS concentrations. Annual mean sediment load was 342,950 tonnes with higher sediment loading during the winter and spring months and lower during the summer and fall months. Annual sediment inflow has the capacity to create 2.3 × 10 7 m 2 of land to the depth of 1 cm, but most of this sediment is unable to reach the coastline. The greatest asset that these rivers provide for the Chenier Plain is sediment and freshwater for restoration of marsh lost to salinization or inundation.

Sources and Delivery of Nutrients to the Northwestern Gulf of Mexico from Streams in the South-Central United States1

SPAtially Referenced Regressions On Watershed attributes (SPARROW) models were developed to estimate nutrient inputs [total nitrogen (TN) and total phosphorus (TP)] to the northwestern part of the Gulf of Mexico from streams in the South-Central United States (U.S.). This area included drainages of the Lower Mississippi, Arkansas-White-Red, and Texas-Gulf hydrologic regions. The models were standardized to reflect nutrient sources and stream conditions during 2002. Model predictions of nutrient loads (mass per time) and yields (mass per area per time) generally were greatest in streams in the eastern part of the region and along reaches near the Texas and Louisiana shoreline. The Mississippi River and Atchafalaya River watersheds, which drain nearly two-thirds of the conterminous U.S., delivered the largest nutrient loads to the Gulf of Mexico, as expected. However, the three largest delivered TN yields were from the Trinity River/Galveston Bay, Calcasieu River, and Aransas River watersheds, while the three largest delivered TP yields were from the Calcasieu River, Mermentau River, and Trinity River/Galveston Bay watersheds. Model output indicated that the three largest sources of nitrogen from the region were atmospheric deposition (42%), commercial fertilizer (20%), and livestock manure (unconfined, 17%). The three largest sources of phosphorus were commercial fertilizer (28%), urban runoff (23%), and livestock manure (confined and unconfined, 23%).

Baseline Ecological Risk Assessment of the Calcasieu Estuary, Louisiana: Part 1. Overview and Problem Formulation

A remedial investigation/feasibility study (RI/FS) of the Calcasieu Estuary cooperative site was initiated in 1998. This site, which is located in the southwestern portion of Louisiana in the vicinity of Lake Charles, includes the portion of the estuary from the saltwater barrier on the Calcasieu River to Moss Lake. As part of the RI/FS, a baseline ecological risk assessment (BERA) was conducted to assess the risks to aquatic organisms and aquatic-dependent wildlife exposed to environmental contaminants. The purpose of the BERA was to determine if adverse effects on ecological receptors are occurring in the estuary; to evaluate the nature, severity, and areal extent of any such effects; and to identify the substances that are causing or substantially contributing to effects on ecological receptors. This article describes the environmental setting and site history, identifies the chemicals of potential concern, presents the exposure scenarios and conceptual model for the site, and summarizes the assessment and measurement endpoints that were used in the investigation. Two additional articles in this series describe the results of an evaluation of effects-based sediment-quality guidelines as well as an assessment of risks to benthic invertebrates associated with exposure to contaminated sediment.

Baseline Ecological Risk Assessment of the Calcasieu Estuary, Louisiana: Part 3. An Evaluation of the Risks to Benthic Invertebrates Associated With Exposure to Contaminated Sediments

The sediments in the Calcasieu Estuary are contaminated with a wide variety of chemicals of potential concern (COPCs), including heavy metals, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalates, chlorinated benzenes, and polychlorinated dibenzo-p-dioxins and dibenzofurans. The sources of these COPCs include both point and non-point source discharges. As part of a baseline ecological risk assessment, the risks to benthic invertebrates posed by exposure to sediment-associated COPCs were assessed using five lines of evidence, including whole-sediment chemistry, pore-water chemistry, whole-sediment toxicity, pore-water toxicity, and benthic invertebrate community structure. The results of this assessment indicated that exposure to whole sediments and/or pore water from the Calcasieu Estuary generally posed low risks to benthic invertebrate communities (i.e., risks were classified as low for 68% of the sampling locations investigated). However, incremental risks to benthic invertebrates (i.e., compared with those associated with exposure to conditions in reference areas) were indicated for 32% of the sampling locations within the estuary. Of the three areas of concern (AOCs) investigated, the risks to benthic invertebrates were highest in the Bayou d'Inde AOC; risks were generally lower in the Upper Calcasieu River AOC and Middle Calcasieu River AOC. The areas showing the highest risks to sediment-dwelling organisms were generally located in the vicinity of point source discharges of COPCs. These results provided risk managers with the information required to make decisions regarding the need for remedial actions at the site.

Mapping Hurricane Rita inland storm tide

AbstractFlood‐inundation data are most useful for decision makers when presented in the context of maps of affected communities and (or) areas. But because the data are scarce and rarely cover the full extent of the flooding, interpolation and extrapolation of the information are needed. Many geographic information systems provide various interpolation tools, but these tools often ignore the effects of the topographic and hydraulic features that influence flooding. A barrier mapping method was developed to improve maps of storm tide produced by Hurricane Rita. Maps were developed for the maximum storm tide and at 3‐h intervals from midnight (00:00 hours) through noon (12:00 hours) on 24 September 2005. The improved maps depict storm‐tide elevations and the extent of flooding. The extent of storm‐tide inundation from the improved maximum storm‐tide map was compared with the extent of flood inundation from a map prepared by the Federal Emergency Management Agency (FEMA). The boundaries from these two maps generally compared quite well especially along the Calcasieu River. Also a cross‐section profile that parallels the Louisiana coast was developed from the maximum storm‐tide map and included FEMA high‐water marks.

COAST GUARD AND INDUSTRY COOPERATION: DEVELOPMENT OF ESSENTIAL ELEMENTS OF INFORMATION

ABSTRACT In June 2006, two million gallons of oil spilled in to the Calcasieu River near Lake Charles, Louisiana. In response to the spill, the U.S. Coast Guard activated the first Marine Transportation System Recovery Unit (MTSRU) within the Incident Command System (ICS). A MTSRU tracks and reports on the status of the Marine Transportation System (MTS), identifies critical pathways for recovery, recommends courses of action, and provides MTS stakeholders with a means of input to the response organization. The MTSRU was successful in providing valuable recommendations and priorities to the Unified Command; these recommendations mitigated the impact of the spill on both the local and national economies. Due to its success at the Lake Charles event, the MTSRU is now an integral part of the Coast Guard ICS.

A new crayfish, Procambarus (Pennides) pentastylus, from southwestern Louisiana (Crustacea: Decapoda: Cambaridae), with a key to western species of the subgenus

ABSTRACT Procambarus pentastylus, a new crayfish of the subgenus Pennides, is described from the Calcasieu River drainage of southwestern Louisiana. The species formerly was confused with Procambarus dupratzi Penn, 1953 but differs in several details of the form I male pleopod, including shorter terminal elements and the presence of a large adventitious process (here termed the pentastyle) mesial to the central projection. Procambarus dupratzi as here restricted is known only from the Sabine, Neches, and Trinity River drainages in Louisiana and Texas. A key to form I males of Pennides species known from west of the Mississippi River is presented.

A site-specific evaluation of mercury toxicity in sediment.

A site-specific evaluation of mercury toxicity was conducted for sediments of the Calcasieu River estuary (Louisiana, USA). Ten-day whole-sediment toxicity tests assessed survival and growth (dry weight) of the amphipods Hyalella azteca and Leptocheirus plumulosus under estuarine conditions (10 ppt salinity). A total of 32 sediment samples were tested for toxicity, including 14 undiluted site sediment samples and 6 sediment dilution series. All sediment samples were analyzed for total mercury and numerous other chemical parameters, including acid volatile sulfide (AVS) and simultaneously extracted metals (SEM). No toxicity attributable to mercury was observed, indicating that a site-specific threshold for total mercury toxicity to amphipods exceeds 4.1 mg/kg dry weight. Site-specific factors that may limit mercury bioavailability and toxicity include relatively high sulfide levels. Additionally, the chemical extractability of mercury in site sediments is low, as indicated by SEM mercury analyses for three sediment samples containing a range of total mercury concentrations.http://link. springer-ny.com/link/service/journals/00244/bibs/37n4p488.++ +html</HEA

Reliability and Reproducibility of a Sequential Extraction Procedure for Trace Metal Determination in Marsh Sediments in Southwest Louisiana

This work describes the rationale used to substantiate the reliability and reproducibility of results obtained from a sequential extraction procedure employed to determine trace metals in restored marsh sediments originating from Calcasieu River ship channel dredge spoils in southwestern Louisiana. The determination was conducted using flame and graphite furnace atomic absorption spectrometry. Metals determined were Cr, Cu, Fe, Mn, Ni, Pb, and Zn. The variations in concentrations between replicate samples and duplicate samples were not statistically significant. Concentrations of all trace metals studied were in agreement with previous studies.

Determination of Semivolatile Organic Compounds by Gas Chromatography–Mass Spectrometry in Reclaimed Marsh Sediments in Southwest Louisiana

This work describes the measurement of polyaromatic hydrocarbons (PAHs) in soil samples originating from restored marsh at Sabine National Wildlife Refuge in southwestern Louisiana. The analysis was conducted using gas chromatography–mass spectrometry (GC–MS). The sediments used to restore the marsh were taken from the Calcasieu River ship channel. Large quantities of refined and crude petroleum hydrocarbons are transported along the ship channel, which has long been suspected to be highly contaminated. No PAHs were detected in any samples above lower levels of detection. However, hexachlorobenzene and hexachlorobutadiene were detected at levels just below the practical quantitation limit. Based on these results, use of Calcasieu River Ship Channel dredge spoils to restore Sabine National Wildlife Refuge marsh sediments should not lead to ecological problems.

Sediment toxicity testing with the amphipod Ampelisca abdita in Calcasieu estuary, Louisiana

Discharges from chemical and petrochemical manufacturing facilities have contaminated portions of Louisiana's Calcasieu River estuary with a variety of organic and inorganic contaminants. As part of a special study, sediment toxicity testing was conducted to assess potential impact to the benthic community. Ten-day flow-through sediment toxicity tests with the amphipod Ampelisca abdita revealed significant toxicity at 68% (26 of 38) of the stations tested. A. abdita mortality was highest in the effluent-dominated bayous, which are tributaries to the Calcasieu River. Mortality was correlated with total heavy metal and total organic compound concentrations in the sediments. Ancillary experiments showed that sediment interstitial water salinity as low as 2.5 o/oo did not significantly affect A. abdita's response in the flow-through system; sediment storage for 7 weeks at 4°C did not significantly affect toxicity. Sediment toxicity to A. abdita was more prevalent than receiving water toxicity using three short-term chronic bioassays. Results suggest that toxicity testing using this amphipod is a valuable tool when assessing sediments containing complex contaminant mixtures and for assessing effects of pollutant loading over time. In conjunction with chemical analyses, the testing indicated that the effluent-dominated, brackish bayous (Bayou d'Inde and Bayou Verdine) were the portions of the estuary most impacted by toxicity.