R. Delaune

... Table 8.1 provides a listing of some of the common chemical forms of metals, ranging from most available to least available (Gambrell and Patrick, 1991; Shannon and White, 1991):(1) readily available: dissolved and exchangeable forms;(2) potentially available: metal ...

Abstract Sedimentation processes in marshes and bays under the influence of the emerging Atchafalaya delta are described. The Atchafalaya delta is a major geological event in the Holocene history of the Mississippi River delta system because it represents the initial ...

ABSTRACT We monitored wetland biomass, decomposition, hydrology, and soil porewater chemistry at the Breton Sound estuary, which receives Mississippi River water from the Caernarvon river diversion structure. The estuary was in the direct path of hurricane Katrina in 2005, which caused a dramatic loss of wetlands in the upper basin. From March 2006 to October 2007, we made duplicate measurements at three distance classes from the diversion structure along the estuarine gradient as well as at a reference area, designated Near (N1&2), Mid (M1&2), Far (F1&2), and Ref (R1&2). Above- and belowground live biomass, porewater nutrients (NOx, NH4, and PO4), salinity, sulfide, and soil Eh were measured every 2 months. Water level was monitored with gauges. Above- and belowground decomposition was measured using the litterbag (both) and cotton strip (belowground only) methods. Analysis of porewater parameters showed that stress factors affecting biomass production (porewater salinity, sulfide, flooding, and redox potential) were generally low to moderate, while measurable porewater nutrient concentrations occurred at all sites. Aboveground end of season live (EOSL) standing crop in October ranged from 423 g/m2 at site M2 to 1,515 at site F1, and was significantly greater at site N1 than at sites N2, M1, or M2. Aboveground EOSL biomass during this study was significantly lower than previously measured in 1999, 2000, and 2001. Peak belowground biomass ranged from 8,315 g/m2 at site R2 to 17,890 g/m2 at site N1, which is among the highest reported in the literature, and there were significant increases throughout the study, suggesting recovery from hurricane Katrina. The decomposition bag data did not indicate any significant differences; however, the cotton strip decomposition rate was significantly lower at the lowest depth. Wetland surface vertical accretion ranged from 0.49 cm/year at N2 to 1.24 cm/year at N1, with site N1 significantly greater than N2, M1, F2, and R1, and site N2 significantly less than all other sites except site R1. These findings show that marsh productivity and stability is related to a number of factors and no one factor can explain the impacts of the hurricanes.

Capacity of a wetland to remove nitrate through denitrification is controlled by its physico-chemical and biological characteristics. Understanding these characteristics will help better to guide beneficial use of wetlands in processing nitrate. This study was conducted to determine the relationship between soil organic carbon (SOC) quality and denitrification rate in Louisiana coastal wetlands. Composite soil samples of different depths were collected from three different wetlands along a salinity gradient, namely, bottomland forest swamp (FS), freshwater marsh (FM), and saline marsh (SM) located in the Barataria Basin estuary. Potential denitrification rate (PDR) was measured by acetylene inhibition method and distribution of carbon (C) moieties in organic C was determined by 13C solid-state NMR. Of the three wetlands, the FM soil profile exhibited the highest PDR on both unit weight and unit volume basis as compared to FS and SM. The FM also tended to yield higher amount of N2O as compared to the FS and SM especially at earlier stages of denitrification, suggesting incomplete reduction of NO3(-) at FM and potential for emission of N2O. Saline marsh soil profile had the lowest PDR on the unit volume basis. Increasing incubation concentration from 2 to 10 mg NO3(-)-N L(-1) increased PDR by 2 to 6 fold with the highest increase in the top horizons of FS and SM soils. Regression analysis showed that across these three wetland systems, organic C has significant effect in regulating PDR. Of the compositional C moieties, polysaccharides positively influenced denitrification rate whereas phenolics (likely phenolic adehydes and ketonics) negatively affected denitrification rate in these wetland soils. These results could have significant implication in integrated assessment and management of wetlands for treating nutrient-rich biosolids and wastewaters, non-point source agricultural runoff, and nitrate found in the diverted Mississippi River water used for coastal restoration.

... 3.5 cm into the marsh surface allowing the sides of the pans to extend 3 cm above the surface. ... The collected sediment was first passed through a 35 mesh sieve to remove any macro organic material, then dried and analyzed for total plant nutrients and heavy metals. ...

ABSTRACT Excess nitrate in Mississippi River water entering offshore areas is reported to contribute to low oxygen (hypoxia) conditions in the Gulf of Mexico. Excessive algal growth driven by the excess nitrogen results in a decrease in dissolved oxygen in bottom water. Reintroduction of Mississippi River waters into a Louisiana coastal wetland has the potential to reduce the amount of nitrate reaching offshore waters. In this study, reduction in the concentration of added NO3 was determined in sediment–water-columns collected from a wetland site in Breton Sound estuary receiving nutrient inputs from the Mississippi River. The capacity of a wetland to process nitrate in floodwater was determined in the laboratory. The rates of NO3 removal (determined from change in nitrate concentration in the floodwater) averaged 97 mg N m d over 16 d for a 1750-mg NO3-N m addition, and 170 mg N m d over 16 d for a 3500-mg NO3-N m addition. The total N2O-N emissions from the 1750- and 3500-mg NO3-N m additions were 19 and 54 mg N m accounting for 1.1% and 1.5% of the applied NO3-N, respectively. Using the acetylene-inhibition technique, the average denitrification rate was determined to be 57 and 87 mg N m d (21 and 32 g N m yr) during the most active denitrification period of 5 d after incubation for 1750 and 3500 mg NO3 -N m of added nitrate in floodwater, respectively. The total N evolved over 11 d as N2O + N2 was equivalent to 436 and 921 mg N m (24.9% and 26.3%, respectively, of added N). Increasing the amount of NO3 applied to the overlying water increased the rate of NO3 loss and N2O emission significantly. The thickness of the oxidized surface sediment layer was also influenced by the NO3 application to the floodwater with a significant linear correlation between nitrate addition and thickness of the oxidized layer (r = 0.9998, p = 0.01). This study indicates that wetlands receiving diverted Mississippi River water have the potential to process and remove NO3 in the river water, reducing the amount of NO3 reaching to offshore areas.

Louisiana is one of the world's largest producer of crayfish. Arsenic (As) and other metals (Cd, Cu, Pb and Zn) concentrations were determined in crayfish tissues, plant and soil samples collected from Louisiana paddy rice fields, where crayfish/rice rotation farming is a common practice. The samples were collected from November 2013 to April 2014 from three different crayfish farming systems. Concentration of As in rice grain, rice straw, and native vegetation ranged between 0.33 and 0.41, 3.14-4.93, and 3.26-5.89mgkg(-1), respectively. The highest As levels in the crayfish external and internal body parts were found in gill (4.04±1.70mgkg(-1)), followed by hepatopancreas (3.42±1.57mgkg(-1)), exoskeleton (1.52±0.85mgkg(-1)), and muscle (1.50±0.69mgkg(-1)). Positive correlations between As levels in the crayfish muscle and the plant tissue on which they feed were found in all farming systems (r=0.405-0.438). The biomagnification factor (BMF) of As in different tissues varied between 0.29 and 1.08, having gill and hepatopancreas were the highest As accumulation while the lowest biomagnification was observed in crayfish muscle tissues which is a food source for human. The As levels along with other metals in crayfish muscle tissue were in acceptable levels for human consumption under all crayfish/rice rotation practices. Further studies are needed in determining the percentage of organic and inorganic arsenic in crayfish tissue.

Mercury adsorption characteristics of Mississippi River deltaic plain (MRDP) freshwater marsh soil in the Louisiana Gulf coast were evaluated under various conditions. Mercury adsorption was well described by pseudo-second order and Langmuir isotherm models with maximum adsorption capacity of 39.8 mg g. Additional fitting of intraparticle model showed that mercury in the MRDP freshwater marsh soil was controlled by both external surface adsorption and intraparticle diffusion. The partition of adsorbed mercury (mg g) revealed that mercury was primarily adsorbed into organic-bond fraction (12.09) and soluble/exchangeable fraction (10.85), which accounted for 63.5% of the total adsorption, followed by manganese oxide-bound (7.50), easily mobilizable carbonate-bound (4.53), amorphous iron oxide-bound (0.55), crystalline Fe oxide-bound (0.41), and residual fraction (0.16). Mercury adsorption capacity was generally elevated along with increasing solution pH even though dominant species of...

Recycling food waste for beneficial use is becoming increasingly important in resource-limited economy. In this study, waste chicken bones of different parts from restaurant industry were pyrolyzed at 600 °C and evaluated for char physicochemical properties and Pb sorption characteristics. Lead adsorption isotherms by different chicken bone chars were carried out with initial Pb concentration range of 1-1000 mg L at pH 5. The Pb adsorption data were better described by the Langmuir model (R = 0.9289-0.9937; ARE = 22.7-29.3%) than the Freundlich model (R = 0.8684-0.9544; ARE = 35.4-72.0%). Among the chars derived from different chicken bone parts, the tibia bone char exhibited the highest maximum Pb adsorption capacity of 263 mg g followed by the pelvis (222 mg g), ribs (208 mg g), clavicle (179 mg g), vertebrae (159 mg g), and humerus (135 mg g). The Pb adsorption capacities were significantly and positively correlated with the surface area, phosphate release amount, and total phosp...

Microbial communities play vital roles in the biogeochemistry of nutrients in coastal saltmarshes, ultimately controlling water quality, nutrient cycling, and detoxification. We determined the structure of microbial populations inhabiting coastal saltmarsh sediments from northern Barataria Bay, Louisiana, USA to gain insight into impacts on the biogeochemical cycles affected by Macondo oil from the 2010 Deepwater Horizon well blowout two years after the accident. Quantitative PCR directed toward specific functional genes revealed that oiled marshes were greatly diminished in the population sizes of diazotrophs, denitrifiers, nitrate-reducers to ammonia, methanogens, sulfate-reducers and anaerobic aromatic degraders, and harbored elevated numbers of alkane-degraders. Illumina 16S rRNA gene sequencing indicated that oiling greatly changed the structure of the microbial communities, including significant decreases in diversity. Oil-driven changes were also demonstrated in the structure...

This study was conducted to evaluate the catalytic activity of Fe-impregnated sugarcane biochar (FSB) for removing azo dye Orange G (OG) from solution under various Fenton-like oxidation conditions. The optimum molar Fe concentration for impregnation to achieve maximum catalytic activity of FSB in Fenton-like reaction with acceptable effluent Fe release was 0.25 M (163.4 Fe mg/g in FSB). High removal efficiency of 99.7% was achieved within 2 h of reaction at optimum conditions of 0.075 g/L H2O2, 0.5 g/L FSB for 0.1 g/L OG at initial pH 5.5 under 25 °C. For every 10 °C increase, the time for maximum OG degradation efficiency decreased by 0.5 h. The OG removal by FSB exhibited a slow induction reaction followed by fast OG decomposition. FSB can be used successively for at least 4 runs with >89.3% OG removal. The FSB was more economical, efficient, and recyclable than other conventional Fenton oxidation catalysts.

... and gJ LAW 2 Laboratory for Wetland Soils and Sediments and Nuclear Science Center ... of the growing season significant treat-ment differences varied and the 300kg urea-N treatment ... They also showed that the main CH 4 transport mechanism to the atmosphere was through ...

Pesticides may enter water bodies in areas with a high proportion of agricultural land use through surface runoff, groundwater discharge, and erosion and thus negatively impact nontarget aquatic organisms. The herbicide atrazine is used extensively throughout the Midwest and enters the Mississippi River through surface runoff and groundwater discharge. The purpose of this study was to determine the extent of atrazine contamination in Louisiana's estuaries from Mississippi River water under different flow and nutrient regimes (spring and summer) and its effect on the biomass and oxygen production of the local phytoplankton community. The results showed that atrazine was consistently present in these systems at low levels. Microcosm experiments exposed to an atrazine-dilution series under low and high nutrient conditions to determine the phytoplankton stress response showed that high atrazine levels greatly decreased phytoplankton biomass and oxygen production. Phytoplankton expos...

The seasonal variation in physico-chemical properties, anions, and the heavy metal (Cd, Co, Cr, Cu, Mn, Ni, Pb, and Zn) concentration was evaluated in water from nine different rivers in Lake Pontchartrain Basin, Louisiana, USA. The water quality parameters were compared with toxicity reference values (TRV), US Environmental Protection Agency (USEPA) drinking/aquatic life protection, and WHO standards. Among physico-chemical properties, pH, DO, and turbidity were high during spring, while, EC, temperature, and DOC were high during summer and vice versa. The anion study revealed that the concentrations of F(-), Cl(-), and NO3(-) were higher during summer and Br(-) and SO4(-) were higher during spring. Our research findings showed anion concentration decreased in the order of Cl(-) > SO4(-) > NO3(-) > Br(-) > F(-), in accordance with the global mean anion concentration. The dissolved heavy metals (Cd, Co, Cr, Cu, Mn, Ni, Pb) except Zn were higher during spring than summer. None of the rivers showed any Cd pollution for both seasons. Co showed higher concentrations in Amite River, Mississippi River, Industrial Canal, and Lacombe Bayou during summer. The Cr concentration was higher than WHO drinking water standards, implicating water unsuitability for drinking purposes in all the rivers associated with the Lake Pontchartrain Basin. Cu showed no pollution risk for the study area. Mn and Co were similar to concentration in Lacombe Bayou, Liberty Bayou, Blind River, and Industrial Canal. Mn levels were greater than WHO standards for the Tickfaw River, Tangipahoa River, and Blind River in both seasons. Blind River, Tangipahoa River, Tickfaw River, and Amite River will require more monitoring for determining possible Mn pollution. Ni content in river water during both seasons showed low pollution risk. Liberty Bayou and Industrial Canal concentrations were closer to the WHO regulatory standards, indicating possible risk of Pb pollution in these water bodies. The Zn content was near the USEPA aquatic life standards in summer for all water bodies. None of the rivers showed any risk associated with Cd, Co, Cu, and Ni levels but medium to higher risk to aquatic life from Cr and Zn for both seasons for most of the rivers. Metal fractionation revealed the decreasing order of inert > labile > organic. The high inert fraction in the rivers under study reflects the major contribution of natural sources in Lake Pontchartrain Basin. The labile and organic forms of Cd, Cu, Ni, and Zn pose potential higher risk to the aquatic life in the Lake Pontchartrain Basin.

ABSTRACT The passage of hurricane Andrew across the Louisiana coastal zone in 1992 was used to study the effects of hurricane sedimentation on estuarine marshes. (1) The thickness and nutrient content of hurricane sediments, (2) the composition of hurricane sediments relative to pre-existing sediments, and (3) the relationship between hurricane sedimentation and small-scale heterogeneity in the emergent plant community were investigated. Vertical accretion resulting from the hurricane was 4-11 times greater than the long-term (30 year) annual rate. The hurricane sediments will be within the root zone of emergent vegetation for 35-50 years, depending on the local marsh vertical accretion rate. Element concentration, organic matter content, and texture of hurricane sediments varied over a wide area, which suggested that hurricane sediments did not originate from a common sediment pool. The concentration of most elements analysed did not differ between hurricane sediments and pre-existing sediments, which suggested that hurricane sediments originated primarily from the same local bays and lakes that provide material for other sedimentation events. Hurricane sediments were thicker in Juncus roemerianus stands than in surrounding Spartina alterniflora stands. Greater hurricane sedimentation in J. roemerianus stands was attributed to greater stem density there and may help maintain plant community heterogeneity if J. roemerianus is less flood-tolerant than S. alterniflora, as previous work suggests. Previous studies have noted the effect of environmental gradients on plant species distribution, but our data indicate that plant species can also generate different environmental conditions associated with their distribution.

... Sediment pH and redox conditions have been found to play an important role in the microbial ... Aerobic microorganisms in the oxidized sediment were more capable of de-grading hydrocarbons than anaerobic microorgan-isms in ... Hydrocarbon Fate in Coastal Environments 75 ...

One lake sediment and three soils for rice production were used to test the effectiveness of inhibiting of nitrous oxide (N2O) reduction to dinitrogen gas (N2) by acetylene (C2H2) using N tracer. Regardless of the sources of the samples, results show that in presence of C2H2, significant isotopic enrichment of N of N2 was found at end of a typical

Paraquat adsorption, degradation, and remobilization were investigated in representative tropical soils of Yom River Basin, Thailand. Adsorption of paraquat in eight soil samples using batch equilibration techniques indicated that adsorption depended on soil characteristics, including exchangeable basic cations and iron content. Multiple regression analysis indicated significant contribution of exchangeable calcium percentage (ECP), total iron content (TFe) and exchangeable sodium percentage (ESP) to paraquat sorption (Q). ESP and TFe were significant at all adsorption stages, whereas ESP was significant only at the initial stage of paraquat adsorption. Adsorption studies using two soils representing clay and sandy loam textures showed that paraquat adsorption followed the Freundlich model, exhibiting a nonlinear sorption curve. Paraquat adsorption was higher in the clay soil compared to the sandy loam soil with Kf values of 787 and 18, respectively. Desorption was low with 0.04 to 0.17% and 0.80 to 5.83% desorbed in clay and sandy loam soil, respectively, indicating some hysteresis effect. Time-dependent paraquat adsorption fitted to the Elovich kinetic model indicated that diffusion was a rate-limiting process. Paraquat mobility and degradation studies conducted using both field and laboratory soil column experiments with clay soil showed low mobility of paraquat with accumulation only in the surface 0-5 cm layer under field conditions and in the 0-1 cm layer in a laboratory soil column experiment. Degradation of paraquat in soil was faster under field conditions than at ambient laboratory conditions. The degradation rate followed a first-order kinetic model with the DT50 at 36-46 days and DT90 around 119-152 days.

Three heptapeptide toxins, microcystin-RR, microcystin-RY and microcystin-LR, which can cause health problems in animals and humans were monitored in Bang Phra Reservoir, Thailand using reversed-phase high performance liquid chromatography. The concentrations of the three toxins in the reservoir varied greatly depending on location and time water samples were collected. Water quality parameters such as light intensity, temperature, pH, dissolved oxygen, suspended solid, chemical oxygen demand, dissolved organic carbon, total nitrogen, total phosphorus, ammonia, nitrate, phosphate, total dissolved nitrogen, total dissolved phosphorus and chlorophyll-a were also measured in parallel with microcystin determinations. Relationships among water quality parameters, toxins and chlorophyll-a were established. Toxin concentration increased in proportion to increases in total phosphorus, fraction of dissolved phosphorus, but was inversely correlated with water pH and total suspended solids. The other measured parameters in the study showed no correlations to toxin level in reservoir water. Significant correlations between chlorophyll-a and suspended solids, phosphate, nitrate and ammonia were observed suggesting that nitrogen and phosphorus are the two major nutrients governing growth of algae in the reservoir. This relationship suggests that algal production as well as toxin concentration are dependant on nutrient levels in the water body, since both measured light intensity and temperature level was favorable for algal growth. A small algal bloom observed in the rainy season of each year (lasting for only a couple of months) paralleled measured increases in toxin concentration, chlorophyll-a, TP and TN in the water column. Toxin level in the water column remain detectable for 3-4 months period following the initiation of algal bloom. Results indicate that major blooms are likely to occur following the raining season which usually occurs near the end of October when runoff would increase nutrient level entering the reservoir. This study also demonstrated that an ongoing field-monitoring program is needed in these lakes and reservoirs for predicting toxic level of microcystin production for use in risk assessment and for alerting the public to potential health hazards. Concentration of toxin in the reservoir can perhaps be controlled by reducing non point source nutrient input within the watershed.

Microbial mineralization rates of a 14C-labelled PCB mixture were determined in PCB-contaminated Capitol Lake, LA, sediment under controlled pH and redox conditions. Mineralization rates were inferred from the activity of 14CO2 evolved from the sediment suspensions. Sediment pH and redox potential significantly affected PCB mineralization. Mineralization rates were higher under moderately aerobic conditions (microaerophilic) ( + 250 mV) than under

Bald cypress (Taxodiumdistichum L.) seedlings were subjected to flooding with saline water containing 0 to 8 parts per thousand (137 mequiv. L−1 NaCl) under controlled environment conditions. Imposition of flooding and salinity stresses was designed to simulate the increase in submergence and salinity level which Louisiana's extensive cypress forests are currently experiencing as a result of rapid subsidence. The effect of flooding and salt water intrusion on subsequent stomatal behaviour and net photosynthesis for leaves developed before and after salt exposure were measured. Flooding and salinity resulted in a substantial decrease in stomatal conductance and net photosynthesis in both young and old leaves. Leaf aging did not significantly affect stomatal conductance and photosynthesis. Only plants flooded with freshwater and those flooded with low salinity concentration produced new leaves with improved stomatal conductance and net photosynthesis, which suggests some stomatal and photosynthetic acclimation to flooding and low salinity for bald cypress. Increase in salinity, however, caused more extensive impact and greater reductions of stomatal conductance and net photosynthesis in both leaf ages.

Untreated or partially treated waste water discharge from industrial and domestic sources entering the Upper Gulf of Thailand have been reported to increase cadmium concentration in bottom sediment. This study was directed at providing a better understanding of cadmium transformation in the sediment from the area. Sediment samples collected from Chao Phraya River mouth (CPY), Bang Pakong River mouth (BPK) and Klong Dan estuary (KD) located in the Upper Gulf of Thailand were analyzed for cadmium concentration in various sediment particle size fractions. Using laboratory microcosms, cadmium release from sediment as affected by salinity and sediment redox condition was studied. A higher concentration of cadmium (0.2-0.6 microg/g dry weight) was measured in finer sediment particle size fractions (<0.075 mm) as compared to courser fractions at all sampling stations. Cadmium release from the sediment to water was influenced by both salinity and redox condition. Sediment was spiked with 10 ppm cadmium which is the cadmium level in sediment adopted by the Australia and New Zealand sediment quality guidelines which can cause adverse environmental impacts. Experiments conducted showed soluble cadmium concentration at sediment oxidation reduction conditions representative of bottom sediment were at levels that can adversely impact aquatic organisms, according to the PCADMIUM water quality guideline. In Thailand, there is no sediment quality guideline. Based on these experiments, 10 ppm of cadmium in sediment was recommended as a regulatory guidelines for allowable levels of cadmium in sediment in the study area.