Sediment quality of North Carolina estuaries: an integrative assessment of sediment contamination, toxicity, and condition of benthic fauna

Sediment quality of North Carolina estuaries was evaluated using synoptic data on sediment chemistry, toxicity, and macroinfaunal community structure from 175 subtidal stations sampled during the summers of 1994–1997. The study area included Currituck, Albemarle, and Pamlico Sounds; estuarine portions of major rivers (e.g., Chowan, Roanoke, Tar-Pamlico, Neuse, New, Cape Fear); and numerous smaller tributaries and coastal embayments between the Virginia and South Carolina borders. A probabilistic sampling design permitted statistical estimation of the spatial extent of degraded versus non-degraded condition across these estuaries. Over half (54 ± 7%) of the surveyed area had high sediment quality characterized by healthy benthic assemblages and low levels of sediment contamination and toxicity. The remaining 46% showed evidence of significant stress in one or more of the above sediment-quality-triad components. While this is a sizable area, portions of it (27 ± 6%) were represented by sites with no connection between presence of stressors and adverse biological responses. Only 19% of the total area showed evidence of an impaired benthos coupled to significant pollution exposure (high sediment contamination, toxicity, or both). Impaired benthic condition was more closely linked to sediment contamination than to low dissolved oxygen (based on instantaneous oxygen measurements). The most pervasive contaminants were the metals arsenic, mercury, chromium, and nickel; the pesticides lindane, dieldrin, DDT, and DDT derivatives; and total PCBs. Degraded condition in all three components of the sediment quality triad co-occurred in <10% of the study area, suggesting that strong contaminant-induced effects on the benthos are limited to a small (yet ecologically significant) percentage of total estuarine area. The spatial extent of sediment contamination and toxicity was much less in these estuaries in comparison to other U.S. coastal regions where similar studies have been performed.     

Ecotoxicological assessment of water and sediment of the Corumbataí River, SP, Brazil.

The Corumbataí River drains an economically important area which is mainly represented by the municipalities of Piracicaba and Rio Claro. In view of the impacts caused by the discharge of industrial waste and domestic sewage into the Piracicaba River, the Corumbataí has become increasingly significant as a source of water for the municipality of Piracicaba. However, chemical, physical, and microbiological analyses carried out prior to the present study had already indicated a decline in the quality of the Corumbataí waters. This study aimed to assess, through water and sediment samples, both acute and chronic toxicity to Daphnia magna and Daphnia similis, and to analyze acid-volatile sulfide (AVS) and simultaneously extracted metal (SEM) in the sediment. Resulting data were intended to be a contribution to future projects for the management and recuperation of this system. To that aim, water and sediment were collected at seven Corumbataí sampling stations in November 2003 and March 2004. Acute toxicity to D. similis was detected in water and sediment samples from the Piracicaba station, located at the mouth of the Corumbataí River. Chronic toxicity was identified in the water or sediment samples of all stations, with the exception of Analandia Montante (upstream), at the head of the river. This was found to affect survival, growth, and fecundity of the test-organisms. The AVS and SEM analyses showed the bioavailability of the metals, thus explaining toxicity found in bioassaying samples of water and sediment. The use of two test-organism species made it possible to obtain a better assessment of the condition of both water and sediment samples of the Corumbataí River.     

Long term diurnal variations in contaminant removal in high rate ponds treating urban wastewater

In this investigation, diurnal variations in contaminant removal in high rate ponds (HRP) treating urban wastewater were evaluated. Two experimental HRPs (surface area 1.54 m2 and depth 0.3 m), each with a clarifier in series (surface area 0.025 m2), were operated in parallel with different hydraulic retention times (3-10 days) but with the same environmental conditions over a period of one year. The operating strategies adopted only yielded a significant overall difference in removal between the two HRPs for nutrients. Effluent total suspended solids and chemical oxygen demand were slightly higher at midday than at dawn, while for total nitrogen and total phosphorous the concentrations were slightly higher at dawn. All these differences were related to the diurnal changes of DO and pH. The main conclusion of this work is that the diurnal variations of the contaminant concentrations in HRPs do not seriously affect their reliability in treating wastewater.     

Accumulation of organochlorines and mercury in flounder — an approach to pollution assessments

Levels of PCBs, HCB and Hg were determined in the muscle tissue of flounder (Platichthys flesus L.), sampled at two sites of the highly industrialized Elbe estuary which is characterized by a decreasing gradient of contaminant levels in water and sediments towards the mouth of the river. The contaminant levels were compared to those found in muscle tissue of flounders caught in an unpolluted reference area, the Eider estuary. Juvenile flounders (1–2 cm total length) caught during their migration from the southern North Sea coast into the Elbe estuary in early summer showed a significantly higher level of contamination at both Elbe stations than those from the reference area. In the following spring, the flounders, having grown to a length of 12–14 cm, reflected the gradient of contaminants measured in water and sediment. However, during summer and late autumn a drastic increase in average contaminant concentration was observed in the muscle tissue of flounders taken from the less polluted estuarine site. It became evident that severe oxygen depletion in the heavily polluted area near Hamburg had provoked the migration of highly contaminated fish downstream to the less polluted sampling area; thus intermingling with the less contaminated flounder population of this region had occurred. The results obtained indicate that careful analysis of environmentally controlled behavioural patterns in the species used for monitoring purposes as well as an appropriate statistical treatment of the data gained from chemical analysis are essential for assessing the contaminant concentrations in organisms in relation to the pollution load of their habitats.     

Signals from the benthos: Development and evaluation of a benthic index for the nearshore Gulf of Maine

We developed a benthic index for the nearshore Gulf of Maine to provide researchers and environmental managers a way to make spatial and year-to-year comparisons of benthic condition. The data set used included 248 stations sampled for physical, chemical, and biological variables by the National Coastal Assessment in 2000–2003. We used logistic regression with 49 candidate measures of benthic species diversity, pollution sensitivity-tolerance, and community composition to discriminate sites with high and low benthic environmental quality (BEQ). BEQ was based on the concentrations of metal and organic contaminants in the sediments, total organic carbon, sediment toxicity, and dissolved oxygen level of the bottom water. An analysis of similarity test showed that the community composition of low BEQ stations was significantly different (p < 0.001) from high BEQ stations. Ten of the 49 benthic metrics showed a strong ability to discriminate stations. We developed several candidate benthic indices and tested them with independent data from Massachusetts Bay and Casco Bay to help select and validate the best index. A model using the Shannon-Wiener diversity measure, Rosenberg's species pollution tolerance measure, and the percent capitellid polychaetes (or percent Capitella spp.) strongly discriminated stations, with an area under the receiver operating characteristic (ROC) curve of 0.82 and a classification accuracy of 80%. Signal detection theory (ROC curves and positive–negative predictive value curves) was used to evaluate the index and to predict how well an index developed for one geographic area might work in another area with a different prevalence of the degraded condition. We show how these techniques can also guide decisions by environmental managers about choosing thresholds and weighing costs and benefits of particular actions.     

Distribution of Nitrogen-Fixing Microorganisms along the Neuse River Estuary,North Carolina

Nitrogen fixation genes (nifH) were amplified and sequenced from DNA extracted from surface water samples collected from six stations along the length of the Neuse River Estuary, North Carolina, in order to determine the distribution of nitrogen-fixing organisms in the transition from fresh-to saltwater. Nitrogenase genes were detected in all samples by a nested polymerase chain reaction method, and the amplification products from the upriver, midriver, and downriver stations were cloned, sequenced, and used for phylogenetic analysis. The composition of nifH clone libraries from upriver, midriver, and downriver stations (each composed of 14 randomly selected clones) were very diverse (samples from upriver and midriver stations were composed of 14 unique sequences, downriver station composed of 7 unique sequences) and differed among the stations. Some phylotypes were found at more than one station, but were usually found in the upriver and midriver stations or in the midriver and downriver stations, indicating that the phylotypes were probably transported along the river. Cyanobacterial nifH were not found at the most upriver site, but were a large fraction of sequences (50%) recovered from the downriver station, where nitrate concentration was an order of magnitude lower and salinity was higher. In contrast, γ proteobacteria nifH sequences were much more common at the midriver and upriver sites (58% and 64%, respectively), compared to the downriver site (14%). Results indicate that substantially different nitrogen-fixing assemblages are present along the river, reflecting differential watershed hydrological inputs, sedimentation, and environmental selection pressures, along the salinity gradient.     

An Inverse Analysis Approach to the Characterization of Chemical Transport in Paints

The ability to directly characterize chemical transport and interactions that occur within a material (i.e., subsurface dynamics) is a vital component in understanding contaminant mass transport and the ability to decontaminate materials. If a material is contaminated, over time, the transport of highly toxic chemicals (such as chemical warfare agent species) out of the material can result in vapor exposure or transfer to the skin, which can result in percutaneous exposure to personnel who interact with the material. Due to the high toxicity of chemical warfare agents, the release of trace chemical quantities is of significant concern. Mapping subsurface concentration distribution and transport characteristics of absorbed agents enables exposure hazards to be assessed in untested conditions. Furthermore, these tools can be used to characterize subsurface reaction dynamics to ultimately design improved decontaminants or decontamination procedures. To achieve this goal, an inverse analysis mass transport modeling approach was developed that utilizes time-resolved mass spectroscopy measurements of vapor emission from contaminated paint coatings as the input parameter for calculation of subsurface concentration profiles. Details are provided on sample preparation, including contaminant and material handling, the application of mass spectrometry for the measurement of emitted contaminant vapor, and the implementation of inverse analysis using a physics-based diffusion model to determine transport properties of live chemical warfare agents including distilled mustard (HD) and the nerve agent VX.     

Assessing water quality suitability for shortnose sturgeon in the Roanoke River,North Carolina,USA with an in situ bioassay approach

The aim of this study was to determine the suitability of water quality in the Roanoke River of North Carolina for supporting shortnose sturgeon Acipenser brevirostrum, an endangered species in the United States. Fathead minnows Pimephales promelas were also evaluated alongside the sturgeon as a comparative species to measure potential differences in fish survival, growth, contaminant accumulation, and histopathology in a 28‐day in situ toxicity test. Captively propagated juvenile shortnose sturgeon (total length 49 ± 8 mm, mean ± SD) and fathead minnows (total length 39 ± 3 mm, mean ± SD) were used in the test and their outcomes were compared to simultaneous measurements of water quality (temperature, dissolved oxygen, pH, conductivity, total ammonia nitrogen, hardness, alkalinity, turbidity) and contaminant chemistry (metals, polycyclic aromatic hydrocarbons, organochlorine pesticides, current use pesticides, polychlorinated biphenyls) in river water and sediment. In the in situ test, there were three non‐riverine control sites and eight riverine test sites with three replicate cages (25 × 15‐cm (OD) clear plexiglass with 200‐μm tear‐resistant Nitex^® screen over each end) of 20 shortnose sturgeon per cage at each site. There was a single cage of fathead minnows also deployed at each site alongside the sturgeon cages. Survival of caged shortnose sturgeon among the riverine sites averaged 9% (range 1.7–25%) on day 22 of the 28‐day study, whereas sturgeon survival at the non‐riverine control sites averaged 64% (range 33–98%). In contrast to sturgeon, only one riverine deployed fathead minnow died (average 99.4% survival) over the 28‐day test period and none of the control fathead minnows died. Although chemical analyses revealed the presence of retene (7‐isopropyl‐1‐methylphenanthrene), a pulp and paper mill derived compound with known dioxin‐like toxicity to early life stages of fish, in significant quantities in the water (251–603 ng L^?1) and sediment (up to 5000 ng g^?1 dry weight) at several river sites, no correlation was detected of adverse water quality conditions or measured contaminant concentrations to the poor survival of sturgeon among riverine test sites. Histopathology analysis determined that the mortality of the river deployed shortnose sturgeon was likely due to liver and kidney lesions from an unknown agent(s). Given the poor survival of shortnose sturgeon (9%) and high survival of fathead minnows (99.4%) at the riverine test sites, our study indicates that conditions in the Roanoke River are incongruous with the needs of juvenile shortnose sturgeon and that fathead minnows, commonly used standard toxicity test organisms, do not adequately predict the sensitivity of shortnose sturgeon. Therefore, additional research is needed to help identify specific limiting factors and management actions for the enhancement and recovery of this imperiled fish species.     

Revitalization of a northcentral Texas river,as indicated by benthic macroinvertebrate communities

Macrobenthic communities were surveyed in 1987–88 as part of acomprehensive study of fish kills and water quality in the upper TrinityRiver. The purpose was to characterize macrobenthic integrity in relation toambient and storm-associated water quality and other environmental factors.No physical habitat features were found to be substantially limiting toaquatic life. Water and sediment quality generally were good, andmacrobenthic communities typically were healthy. Ecological conditions werevastly improved compared to the recent past, attributable mainly todecreased contaminant loading from wastewater treatment plants and reducedincidence of raw sewage bypassing. Nonetheless, some impact was evident incertain reaches. Deleterious effects at Beach St. evidently resulted frompesticides derived from urban runoff. Slight impacts by dissolved metalswere suggested for Grand Prairie and Continental Ave.; possible sourcesincluded urban runoff and wastewater treatment plant effluents. Moderateimpacts at S. Loop 12 were attributed to low-flow toxicity induced by awastewater treatment plant discharge; ammonia and chlorine were consideredprimarily responsible, with metals and pesticides possibly involved.Macrobenthic communities were somewhat degraded from Trinidad to US 79, dueto storm-related stresses by DO depression, pesticides, and metallic oxides.Overall impacts were relatively slight on a long-term basis, however, and ahigh aquatic life use was attained at most sites. The degree of macrobenthicintegrity was considered remarkable for an effluent-dominated system withsuch extensive urbanization in the watershed.     

表面活性剂、酸雨和Cd^2＋复合污染对蚕豆胚根细胞核的毒性

用蚕豆根尖微核技术研究了Cd^2+单因子以及与表面活性剂、模拟酸雨复合污染时对植物细胞的毒性作用。结果表明,Cd^2+浓度在0～10．0mg·L^-1范围内,对蚕豆胚根细胞微核的形成有强烈的诱导作用,Cd^2+浓度6．0mg·L^-1时的细胞微核率为13．85‰,对照组的微核率为4．53‰,此时污染影响指数(PI)为3．06;当环境中存在表面活性剂LAS1．0mg·L^-1或pH值降到4．5和3．5时,同-Cd^2+浓度下,蚕豆根尖细胞微核率、PI降低,同时伴有核变形,细胞中颗粒物增多,胚根组织不容易分散等症状,根的生长受到抑制,说明表面活性剂、酸雨对Cd^2+的毒性有协同作用。pH3．5的酸雨环境中Cd^2+对蚕豆细胞的损伤程度比pH4．5酸雨环境高,在检测高浓度、强毒性污染物的致突变效应时,应作至少3个稀释倍数,找出蚕豆根尖细胞最高微核率及PI。     

Bioremediation of soils contaminated with the herbicide 2-sec-butyl-4,6-dinitrophenol (dinoseb).

A novel soil treatment method for achieving the removal of dinoseb (2-sec-butyl-4,6-dinitrophenol) from contaminated soils was investigated. One soil contained dinoseb as the major contaminant, although several other hazardous compounds were also present. A second soil was highly contaminated with dinoseb. Dinoseb was not degraded in these soils under the aerobic conditions at each site. Pretreatment of the soils by the addition of a starchy potato-processing by-product and flooding with phosphate buffer stimulated the consumption of oxygen and nitrate from the soils, thereby lowering the redox potential and creating anaerobic conditions. Anaerobiosis (Eh less than -200 mV) promoted the establishment of an anaerobic microbial consortium that degraded dinoseb completely, without the formation of the polymerization products seen under aerobic or microaerophilic conditions. When dinoseb was present at low concentrations in a chronically contaminated soil, the natural microflora was capable of establishing anaerobic conditions and degrading dinoseb as a result of starch degradation. Inoculation of this soil with an aerobic starch-degrading microorganism and then an acclimated, anaerobic, dinoseb-degrading consortium did not improve dinoseb degradation. In a second acutely contaminated soil, these inoculations improved dinoseb degradation rates over those of uninoculated controls.     

In vitro toxicity and interactions of environmental contaminants (Arochlor 1254 and mercury) and immunomodulatory agents (lipopolysaccharide and cortisol) on thymocytes from lake trout (Salvelinus namaycush)

The immunotoxicity of chemical combinations commonly encountered by the lake trout (Salvelinus namaycush) immune system was the focus of this study. It was hypothesised that combinations of an environmental contaminant (mercuric chloride or Aroclor 1254) and an immunomodulatory agent (bacterial endotoxin or cortisol) might interact to produce a greater toxicity than that of the environmental contaminant alone at concentrations typically encountered in piscine blood and other tissues. Thus lake trout thymocytes were isolated and treated with mercuric chloride or Aroclor 1254 in the presence and absence of cortisol or lipopolysaccharide. Incubations were performed for 6 or 20 h at 4 degrees C or 10 degrees C. Lipopolysaccharide did not affect the toxicity of either contaminant. In contrast, cortisol enhanced the toxicity of both environmental contaminants. Hence, stressors that lead to increased cortisol production, but not lipopolysaccharide directly, may increase the toxicity of mercury and Aroclor 1254 to lake trout thymocytes.     

Bioremediation of soils contaminated with the herbicide 2-sec-butyl-4,6-dinitrophenol (dinoseb).

A novel soil treatment method for achieving the removal of dinoseb (2-sec-butyl-4,6-dinitrophenol) from contaminated soils was investigated. One soil contained dinoseb as the major contaminant, although several other hazardous compounds were also present. A second soil was highly contaminated with dinoseb. Dinoseb was not degraded in these soils under the aerobic conditions at each site. Pretreatment of the soils by the addition of a starchy potato-processing by-product and flooding with phosphate buffer stimulated the consumption of oxygen and nitrate from the soils, thereby lowering the redox potential and creating anaerobic conditions. Anaerobiosis (Eh less than -200 mV) promoted the establishment of an anaerobic microbial consortium that degraded dinoseb completely, without the formation of the polymerization products seen under aerobic or microaerophilic conditions. When dinoseb was present at low concentrations in a chronically contaminated soil, the natural microflora was capable of establishing anaerobic conditions and degrading dinoseb as a result of starch degradation. Inoculation of this soil with an aerobic starch-degrading microorganism and then an acclimated, anaerobic, dinoseb-degrading consortium did not improve dinoseb degradation. In a second acutely contaminated soil, these inoculations improved dinoseb degradation rates over those of uninoculated controls.     

Characterization of microbial isolates from an estuarine ecosystem: relationship of hydrocarbon utilization to ambient hydrocarbon concentrations.

Water collected at 12 sites in the Neuse River estuary of North Carolina was analyzed for total viable counts on three isolation media (Trypticase soy agar [TSA], marine agar 2216, Sabouraud agar) and total hydrocarbons by fluorescence spectroscopy. Counts of 3.9 X 10(1) to 3.8 X 10(3) cells/ml were found for total heterotrophs, well within the range commonly reported for marine and estuarine waters. Generally, marine agar 2216 gave higher counts than TSA at stations with salinities greater than 6.0 mg/ml; TSA gave higher counts than marine agar 2216 at sites with salinities less than 4.0 mg/ml. The microbial species isolated on the three media agree well with those previously reported for estuarine microbial communities. Water analyses, using XAD-2 resin and fluorescence spectroscopy, revealed petroleum hydrocarbon concentrations in the range of 5 to 79 ng/ml. Representatives of the microbial species isolated from these communities were tested individually for their ability to grow using kerosene as a sole source of carbon and energy. At all but two stations, the majority of the species isolated were able to grow on hydrocarbons, indicating that this ability is widespread even in environments not subjected to high levels of hydrocarbon pollution.     

Bioassay responses to sediment elutriates and multivariate data analysis for hazard assessment of sediment-bound chemicals

A sediment study, involving both chemical and biological analyses, was carried out in the Hamburg harbour area. A total of 71 stations were sampled during 1988 and the sediments extracted using a 1:4 sediment:water ratio either with or without an addition of a water-soluble detergent to solubilize organic compounds. The resulting extracts were applied in algal and bacterial assays to measure toxicity. A principal components analysis showed that no single bioassay explained all the variation in toxicity among the locations studied. Hierarchical cluster analysis was used to rank sediments into four groups based on their toxicity. The relationship of toxic responses to the chemistry of the sediments was determined using varimax factor analysis. One factor was loaded with algal responses and mercury contents of sediments, another with bacterial responses and Lindane contents of sediments.     

GROWTH, PRIMARY PRODUCTIVITY, AND NITROGEN FIXATION POTENTIAL OF NODULARIA SPP. (CYANOPHYCEAE) IN WATER FROM A SUBTROPICAL ESTUARY IN THE UNITED STATES

Nodularia is a halotolerant, filamentous, dinitrogen-fixing cyanobacterium that forms massive blooms in some coastal oceans, estuaries, and saline lakes worldwide. Although the genus is globally distributed, its blooms are sporadic and appear to be confined to certain water bodies. Blooms are frequently associated with phosphorus enrichment; therefore Nodularia may benefit from increased anthropogenic nutrient loading to coastal waters. We studied the potential for Nodularia to grow in the nitrogen-limited Neuse River Estuary (North Carolina, U.S.A.) with laboratory growth experiments in Neuse River Estuary water and by examining physico-chemical data from the estuary. Analysis of nutrients (nitrogen and phosphorus), salinity, and temperature data from the Neuse River Estuary between 1994 and 1998 revealed that suitable conditions for Nodularia prevailed during the summer of each of these years for time spans ranging from 1.5 to 5 months. Growth of two laboratory strains in Neuse River Estuary water was as fast or slightly slower than in artificial growth medium, as long as the culture inoculum had phosphorus reserves. Phosphorus addition did not stimulate growth of already phosphorus-sufficient inocula. Phosphorus starvation of the inoculum before the experiment decreased growth rates in the estuarine water unless additional phosphorus was supplied. Although phosphorus addition had a stimulatory effect on dinitrogen fixation and productivity, the effect differed for the two Nodularia strains. Results suggest that growth of Nodularia in North Carolinian estuaries is possible, and that such growth would be phosphorus-limited at times. Phosphorus availability may determine the times and locations for potential establishment of Nodularia in this and similar estuarine ecosystems.     

Effects of a sewage treatment plant outlet pipe extension on the distribution of contaminants in the sediments of the Bay of Vidy, Lake Geneva, Switzerland

In 2001, the municipality of Lausanne extended the outlet pipe of the sewage treatment plant into the Bay of Vidy (Lake Geneva, Switzerland) as a measure to reduce bacterial water pollution and sediment contamination close to the lake beaches. The aim of the present study was to assess the impact of this measure. Lake bottom sediments were collected and analyzed for grain size, organic matter, organic carbon, nitrogen, phosphorus, heavy metals and hydrophobic organic compounds to evaluate their concentration and spatial distribution. Our results demonstrate that, compared to results obtained before the outlet pipe prolongation, the surface area of highly contaminated sediments was reduced by one third after the pipe extension. However, contaminant concentrations are still high and the accumulation of pollutants may represent a significant source of toxicity for benthic organisms. One concludes that contaminant reduction at the source will be necessary for a further improvement.     

表面活性剂、酸雨和Cd2+复合污染对蚕豆胚根细胞核的毒性

用蚕豆根尖微核技术研究了Cd²⁺单因子以及与表面活性剂、模拟酸雨复合污染时对植物细胞的毒性作用.结果表明,Cd²⁺浓度在0～10.0mg·L^-1范围内,对蚕豆胚根细胞微核的形成有强烈的诱导作用,Cd²⁺浓度6.0mg·L^-1时的细胞微核率为13.85‰,对照组的微核率为4.53‰,此时污染影响指数(PI)为3.06;当环境中存在表面活性剂LAS1.0mg·L^-1或pH值降到4.5和3.5时,同一Cd²⁺浓度下,蚕豆根尖细胞微核率、PI降低,同时伴有核变形,细胞中颗粒物增多,胚根组织不容易分散等症状,根的生长受到抑制,说明表面活性剂、酸雨对Cd²⁺的毒性有协同作用.pH3.5的酸雨环境中Cd²⁺对蚕豆细胞的损伤程度比pH4.5酸雨环境高.在检测高浓度、强毒性污染物的致突变效应时,应作至少3个稀释倍数,找出蚕豆根尖细胞最高微核率及PI.     

Synergy of light and nutrients on the photosynthetic efficiency of phytoplankton populations from the Neuse River Estuary, North Carolina

A series of mesocosm studies were conducted using natural phytoplanktoncommunities isolated from the Neuse River Estuary in the springof 1998 and 1999 to assess the interactions between nutrientlimitation and ultraviolet (UV) radiation on photosyntheticparameters. Treatments consisted of the addition of differentforms of nutrients typically found in estuarine environmentsand the exclusion of ambient UV radiation (wavelengths <400 nm). The quantum yield of photochemistry (F_v/F_m), speciescomposition, and photosynthesis irradiance parameters were measuredrepeatedly over the course of 4 days. In spring 1998, duringa period of stratification and low run-off, nutrient limitationwas observed in the Neuse River. The F_v/F_m parameters in allthe mesocosm treatments responded to the addition of nitrogen.The form of the nitrogen addition (nitrate, ammonium, or urea)was insignificant and the addition of phosphorus had no observableeffect. Conversely, during a period of high mixing in spring1999, there was no nutrient addition effect on F_v/F_m. Duringboth experiments F_v/F_m exhibited midday light-driven depressionsin response to high irradiances, with complete recovery at night.UV radiation accounted for a significant fraction of the middaydepression seen in F_v/F_m. Samples treated with the D1 proteinsynthesis inhibitor lincomycin showed that the midday decreasein photochemical efficiency was mostly due to photoinduced damageto the D1 protein. As an upper limit estimate, 80% of the decreasein F_v/F_m centered around local noon appears to be related tothis damage. The decrease in photochemical efficiency seen athigh light levels in both UV-exposed and UV-excluded treatmentswas not correlated with a decrease in carbon fixation parameters.     

Experimental Evaluation of Catalyzed Hydrogen Peroxide and Sodium Persulfate for Destruction of BTEX Contaminants

Due to the toxicity and prevalence of BTEX contaminants (benzene, toluene, ethylbenzene, and xylenes) at hazardous waste sites, approaches for their remediation are of interest, especially those that particularly address benzene, which is often the limiting factor for achieving regulatory cleanup at these contaminated sites. In situ chemical oxidation (ISCO) is a viable technology for BTEX destruction, and hydrogen peroxide and sodium persulfate are two oxidants of interest for BTEX treatment.

Laboratory studies were conducted to compare BTEX contaminant destruction and oxidant persistence for these two oxidants and for varied methods of oxidant activation/propagation. Additionally, studies were performed to compare contaminant destruction and oxidant persistence in laboratory contaminant spike systems vs. field site contaminant systems. Finally, contaminant destruction and oxidant persistence in field porous media with varied characteristics were evaluated. Contaminant and oxidant concentrations were measured at multiple time points over a three-week reaction period in each oxidant and oxidant activation/propagation system.

Under the comparable conditions evaluated here, sodium persulfate systems demonstrated greater BTEX contaminant destruction and greater oxidant persistence than hydrogen peroxide systems. FeSO₄ and citric acid activation of sodium persulfate resulted in greater BTEX destruction and greater oxidant persistence than pH adjustment or hydrogen peroxide activation in both laboratory contaminant spike systems and field gas condensate systems. Additionally, results indicate that the response of the contaminant(s) and oxidant (extent and rate of depletion) are both contaminant-and porous media type-dependent.