bluuebunny/crossref_metadata_2025 huggingface dataset:
Toxicity and fate of two munitions constituents in spiked sediment exposures with the marine amphipod Eohaustorius estuarius
Authors: Rosen Gunther , Lotufo Guilherme R.
Published: October 2005

The lethal toxicity of the explosive compounds 14C-labeled 2,4,6-trinitrotoluene (TNT) and nonradiolabeled hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) to the estuarine amphipod Eohaustorius estuarius was investigated in 10-d spiked sediment exposures. The 10-d median lethal concentration (LC50) was determined using the sum molar initial concentration of TNT, ami-nodinitrotoluenes (ADNTs), and diaminonitrotoluenes (DANTs), as determined by high-performance liquid chromatography (HPLC), and collectively referred to as HPLC-TNT*. Despite expectations of higher toxicity in sandy sediment (Yaquina Bay [YB], OR, USA) compared to relatively fine-grained sediment (San Diego Bay [SDB], CA, USA), LC50 values were similar: 159 and 125 μmol/kg, for YB and SDB sediments, respectively. When expressed as the sum of TNT and all its degradation products (14C-TNT*), LC50s were approximately two times the corresponding LC50s determined by HPLC. The HPLC-TNT* fraction likely corresponds to the most bioavailable and toxic transformation products. The concentrations of 14C-TNT* in tissues were substantially higher than those for HPLC-TNT*, suggesting that compounds other than TNT and its major aminated transformation products were prevalent. Critical body residues were similar for exposures to SDB (11.7 μmol/kg) and YB sediments (39.4 μmol/kg), despite marked differences in the nature of compounds available for uptake in the exposure media. The critical body residues for E. estuarius are lower than those reported for other aquatic invertebrates (83–172 μmol/kg). Unlike observations for TNT, RDX was only loosely associated with SDB sediment, with near complete recovery of the parent compound by chemical analysis. Exposure to RDX did not result in significant mortality even at the highest measured sediment concentration of 10,800 μmol/kg dry weight, nor tissue concentrations as high as 96 μmol/kg wet weight. The lack of RDX lethal effects in this study is consistent with results reported for other invertebrate species.
Integrating chemical and biological criteria
Authors: Pacheco Manoel Augusto Whitaker , McIntyre Dennis Owen , Linton Tyler Keith
Published: October 2005

We present a system to derive benchmarks for protection of aquatic organisms that, as chemical criteria, promotes regulation of contaminants and, as biological criteria, focuses on an endpoint that adequately represents species abundance. The proposed method utilizes quantile regression to quantify the decline in maximum number of organisms with increasing contaminant concentrations. This limiting function then is applied to project the contaminant concentration associated with a threshold number of organisms. The threshold value is defined according to the study's objective and level of desired protection. Here, we defined it as 0.8 × 90th quantile of the number of organisms in samples from reference sites. We use the proposed system to derive taxonspecific, field-based effect concentrations (FECs) for copper and zinc in Ohio, USA, rivers and streams. Comparisons of results with respective chronic values suggest that only the draft criteria for copper are adequately protective. Projected zinc FECs were far lower than respective estimates of chronic values. The FECs likely are less sensitive to impacts of confounding factors because high numbers of organism in samples are observed when negative effects of other stressors are absent or minimal. We discuss other advantages, limitations, and potential applications of the proposed system.
Biodegradation of simple chemical mixtures in soil
Authors: Donnelly Kirby C. , Huebner Henry J. , Claxton Larry D. , Calvin James A. , Vos Gordon A. , Cizmas Leslie , He Ling-yu
Published: October 2005

Exogenous microorganisms often are used to enhance bioremediation. This study compared the capabilities of two exogenous microbial cultures and an indigenous population to detoxify a Weswood silt loam soil amended with a simple chemical mixture. The first three treatments were unamended soils inoculated with either indigenous microorganisms, Pseudomonas aeruginosa, or Phanerochaete sordida. Three additional treatments consisted of soil amended with benzo[a]pyrene, pentachlorophenol, and 2,4,6-trinitrotoluene, which were inoculated with either indigenous microorganisms, P. aeruginosa, or P. sordida. Samples were collected from the soils at several time points from 0 through 540 or 720 d, sequentially extracted with methylene chloride and methanol, and analyzed for genotoxicity (using the Salmonella/microsome assay) and chemical degradation. Although the indigenous microorganisms were effective for removal of benzo[a]pyrene, the Pseudomonas bacteria exhibited slightly greater removal rates for 2,4,6,-trinitrotoluene. The fungal cultures were significantly more effective at degrading pentachlorophenol. The day 540 extracts from all model chemical-amended treatments were genotoxic. In most cases, the day 540 extracts were more genotoxic than the day 0 extracts. The results suggest that, under appropriate conditions, enriched cultures of microorganisms may have an increased capacity to degrade individual chemicals. However, the products of degradation in some cases might be more genotoxic than the parent compounds.
Bacterial cell association and antimicrobial activity of a C60 water suspension
Authors: Lyon Delina Y. , Fortner John D. , Sayes Christie M. , Colvin Vicki L. , Hughes Joseph B.
Published: October 2005

Prior to the implementation of any new technology, possible environmental and health repercussions first must be researched. Fullerenes are to be produced soon on an industrial scale, with applications quickly following. To investigate the possible environmental impact of fullerenes, a C60-water suspension (nano-C60) was synthesized and then evaluated for cell-association and toxicity, using the bacteria Escherichia coli and Bacillus subtilis as indicator species. In a defined low-salts medium, nano-C60 associated with both the Gram-negative E. coli and the Gram-positive B. subtilis, albeit more strongly with the former. Nano-C60 also displayed antimicrobial properties against both E. coli and B. subtilis, with minimal inhibitory concentrations of 0.5 to 1 mg/L and 1.5 to 3.0 mg/L, respectively. Media with higher salt contents result in the nano-C60 particles aggregating and falling out of suspension; thus, higher salt solutions reduced or eliminated the antimicrobial properties of nano-C60.
Reductive transformation of hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, and methylenedinitramine with elemental iron
Authors: Oh Seok-Young , Cha Daniel K. , Kim Byung J. , Chiu Pei C.
Published: October 2005

Reductive (pre)treatment with elemental iron is a potentiallyuseful method for degrading nitramine explosives in water and soil. In the present study, we examined the kinetics, products, and mechanisms of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) degradation with elemental iron. Both RDX and HMX were transformed with iron to formaldehyde, NH +4, N2O, and soluble products. The yields of formaldehyde were relatively constant (71% ± 5%), whereas the yields of NH +4 and N2O varied, depending on the nitramine and the mechanism. The reactions most likely were controlled by a surface process rather than by external mass transfer. Methylenedinitramine (MDNA) was an intermediate of both RDX and HMX and was transformed quantitatively to formaldehyde with iron. However, product distributions and kinetic modeling results suggest that MDNA represented a minor reaction path and accounted for only 30% of the RDX reacted and 14% of the formaldehyde produced. Additional experiments showed that RDX reduction with elemental iron could be mediated by graphite and Fe2+ sorbed to magnetite, as demonstrated previously for nitroaromatics and nitrate esters. Methylenedinitramine was degraded primarily through reduction in the presence of elemental iron, because its hydrolysis was slow compared to its reactions with elemental iron and surface-bound Fe2+. Our results show that in a cast iron-water system, RDX may be transformed via multiple mechanisms involving different reaction paths and reaction sites.
Behavior of lead in a model microbial predator-prey system
Authors: Patton Leslie E. , Shuler Michael L. , Lion Leonard W.
Published: October 2005

Predation at the microbial level can affect the fate of toxic trace metals. Metals associated with bacterial prey can be released into the dissolved phase following digestion by a predator, and/or metals can remain in the predator and be transferred potentially to the next level of the food chain. Toxic metal ions in the aqueous phase also are expected to modify the growth and predation rate of a microbial predator. A model predator-prey system was developed to test the effects of Pb on cells and to help elucidate the fate of Pb in this type of interaction. Established methods that have been shown to be suitable for distinguishing dissolved, prey-bound, predator-bound, and ingested Pb were used to establish the pathway of Pb over time. Growth parameters were measured using batch reactors for the protozoan predator Tetrahymena thermophila and the bacterial prey Pseudomonas putida without Pb and at several concentrations of Pb. The effect of prey density on predation and Pb phase distribution also was investigated. Results demonstrate that some kinetic parameters related to prey consumption and growth of T. thermophila are altered by Pb. Upon addition of predator to prey cells in equilibrium with dissolved Pb, dissolved and prey-bound Pb become associated with the predator through ingestion and adsorption. Ingested Pb is excreted later as a bound metal associated with T. thermophila waste matter. A preliminary mathematical model was developed to describe predator-prey dynamics and their influence on the behavior and fate of Pb. Growth data were used to obtain model parameters, and model simulations for Pb fractionation are compared to experimental observations.
Exposure-related effects on Cd bioaccumulation explain toxicity of Cd-phenanthrene mixtures in Hyalella azteca
Authors: Gust Kurt A. , Fleeger John W.
Published: October 2005

Little is known regarding mixture effects of metals and polynuclear aromatic hydrocarbon (PAHs) under environmentally relevant exposure regimes. Standard U.S. Environmental Protection Agency (U.S. EPA) procedures were applied and extended to test effects of phenanthrene (Phen) on sediment-Cd uptake, aqueous-Cd uptake, and Cd-elimination kinetics in the amphipod Hyalella azteca. In sediment exposures, Phen increased the projected equilibrium-tissue concentration of Cd from 47.2 (36.2–58.3) to 221.1 μg/g ([117.8–324.3], 95% confidence intervals [CI] in parentheses). Although Cd bioaccumulation increased markedly in sediment exposures, dissolved Cd concentrations and physical-chemical parameters indicative of Cd bioavailability were unaffected by Phen. Further, in water-only exposures, Phen had no effect on Cd bioaccumulation or Cd-elimination kinetics. These results indicate that increased Cd bioaccumulation in Cd-Phen mixtures occurred via a sediment-mediated process and was likely a function of increased uptake associated with feeding (i.e., Pheninduced alterations in ingestion and/or digestive processes). Observed increases in H. azteca lethality when exposed to Cd-Phen mixtures in sediment, but not in water-only exposures, likely resulted from increased Cd bioaccumulation rate rather than a true toxicological synergism. Thus, apparent synergisms and antagonisms may result from exposure-mediated effects in sediment that are unrelated to toxicological interactions. Implications of these findings regarding sediment-quality assessment and suggestions for future studies are discussed.
Calcium/cadmium interactions at uptake surfaces in rainbow trout: Waterborne versus dietary routes of exposure
Authors: Franklin Natasha M. , Glover Chris N. , Nicol James A. , Wood Chris M.
Published: October 2005

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to control, 3 μg/L waterborne Cd, or 500 mg/kg dietary Cd in combination with either a control (20 mg/g Ca2+ as CaCO3) or elevated (60 mg/g Ca2+) Ca2+ diet for 28 d. No mortality or growth effects were observed in response to either route of Cd exposure, although fish fed Ca2+-supplemented diets exhibited minor reductions in growth within the first few days of feeding. Waterborne and dietary Cd resulted in significant Cd accumulation in most tissues, with dietary uptake being far in excess of waterborne under the exposure conditions used. The order of Cd accumulation strongly reflected the exposure pathway, being gill and kidney > liver > gut > carcass (waterborne Cd); gut > kidney > liver > gill > carcass > bone (dietary Cd). On a whole-body basis, the net retention of Cd from the diet was <1%, indicating that the gut wall forms an important protective barrier reducing Cd accumulation into internal tissues. Dietary Ca2+ supplementation reduced short-term whole-body uptake rates of waterborne Ca2+ and Cd by >50% and resulted in much lower chronic accumulation of Cd (via the water and diet) in target tissues. Results suggest that Ca2+ and Cd share common pathway(s)/transport mechanism(s) in the gill and gut and that increased gastrointestinal Ca2+ uptake likely caused downregulation of branchial and gastrointestinal Ca2+ and therefore Cd uptake pathways. Because nutrient metals other than Ca2+ may also influence Cd (and other metal) uptake, new regulatory approaches to metal toxicity (e.g., biotic ligand model) require understanding of the influence of dietary status on metal accumulation.
Co-amendment with halogenated compounds enhances anaerobic microbial dechlorination of 1,2,3,4-tetrachlorodibenzo-p-dioxin and 1,2,3,4-tetrachlorodibenzofuran in estuarine sediments
Authors: Ahn Young-Beom , Häggblom Max M. , Fennell Donna E.
Published: October 2005

Halogenated coamendments enhanced dechlorination of 31 μM of spiked 1,2,3,4-tetrachlorodibenzo-p-dioxin (TeCDD) and 49 μM of spiked 1,2,3,4-tetrachlorodibenzofuran (TeCDF) in sediments from San Diego Bay (CA, USA) and Tuckerton (NJ, USA). Dechlorination of 1,2,3,4-TeCDD occurred to a greater extent under methanogenic than under sulfate-reducing conditions. The most effective stimulation of 1,2,3,4-TeCDD dechlorination occurred with coamendment of 25 μM of 1,2,3,4-tetrachlorobenzene (TeCB), 2,3,4,5-tetrachloroanisole (TeCA), 2,3,4,5-tetrachlorophenol, or 2′,3′,4′-trichloroacetophenone plus 500 μM lactate and 500 μM propionate as electron donors. The 1,2,3,4-TeCDD dechlorination was evident after three months and sequentially produced mainly 1,2,4-trichlorodibenzo-p-dioxin, 1,3-dichlorodibenzo-p-dioxin, and 2-monochlorodibenzo-p-dioxin (MCDD). Monobromo-phenols (2-bromo-, 3-bromo-, and 4-bromophenol), monochlorophenols (2-chloro-, 3-chloro-, and 4-chlorophenol), 2,3,5,6-tetra-chlorobenzoate, or electron donors alone stimulated less 1,2,3,4-TeCDD dechlorination, with activity apparent only after six months. The 1,2,3,4-TeCDD dechlorination produced 50 mol % 2-MCDD after six months in sediments from the more contaminated Graving Dock and Paleta Creek sites in San Diego Bay. The 1,2,3,4-TeCDD dechlorination by sediments from the less contaminated Shelter Island site in San Diego Bay and in pristine Tuckerton sediments did not produce 2-MCDD. Dechlorination of 1,2,3,4-TeCDF to tri- and dichlorinated daughter products was significantly enhanced by TeCB and TeCA. These results suggest that halogenated aromatic compounds with structural similarity to 1,2,3,4-TeCDD/F stimulate bacteria with the ability to dechlorinate chlorinated dibenzo-p-dioxin and furans.
Toxic effect of biosurfactant addition on the biodegradation of phenanthrene
Authors: Shin Kyung-Hee , Ahn Yeonghee , Kim Kyoung-Woong
Published: October 2005

The effect of the biosurfactant rhamnolipid on phenanthrene biodegradation and cell growth of phenanthrene degraders was investigated. To compare the effect of rhamnolipid addition, two bacterial strains, 3Y and 4–3, which were isolated from a diesel-contaminated site in Korea, were selected. Without the biosurfactant, large amounts of phenanthrene were degraded with both strains at neutral pH, with higher rates of phenanthrene degradation when the cell growth was higher. Upon the addition of 240 mg/L rhamnolipid, the phenanthrene degradation and optical density were reduced, with this inhibitory effect similar for both 3Y and 4–3. To explain this inhibition, the cell growths of both strains were monitored with various concentrations of rhamnolipid, which showed significant toxic effects toward strain 3Y, but was nontoxic toward 4–3. Combining the inhibitory and toxicity results with regard to the biodegradation, different mechanisms can be suggested for each strain. In the biodegradation experiments, the toxicity of rhamnolipid itself mainly was responsible for the inhibitory effect in the case of 3Y, whereas the toxicity of solubilized phenanthrene or the increased toxicity of rhamnolipid in the presence of solubilized phenanthrene could have resulted in the inhibitory effect in the case of 4–3. This study demonstrated that the effectiveness of biosurfactant-enhanced biodegradation can be significantly different depending on the strain, and the toxicity of the biosurfactant should be considered as an important factor.
Multigenerational acclimation of Daphnia magna to mercury: Relationships between biokinetics and toxicity
Authors: Tsui Martin T. K. , Wang Wen-Xiong
Published: October 2005

We examined the effects of multigenerational exposure of mercury (Hg) on Hg toxicity and biokinetics in a population of Daphnia magna. After chronic Hg exposure at 3.8 μg Hg/L, the first generation (F0) adults had an elevated 24-h median lethal concentration (LC50) of Hg (76 μg/L) when compared to the control adults (56 μg/L). The dissolved influx rate of Hg was depressed significantly in the Hg-treated adults, which was accompanied by a reduced ingestion rate and enhanced induction of metallothionein-like proteins (MTLP). The second-generation (F1) juveniles originating from the control and exposed lines had no major differences in these parameters (except the dietary assimilation efficiency). Recovery from Hg stress enhanced the vulnerability of F1 adults to Hg toxicity, with a reduced 48-h LC50 (44 μg/L) and a decreased concentration of MTLP (80% of control). Nevertheless, Hgtreated F1 adults had similar tolerance (in terms of LC50s) as the control line, indicating that D. magna acclimated to Hg stress after the first generation of exposure. No major difference occurred in the Hg biokinetics and toxicity among different groups of F2 daphnids. However, the F2 neonates produced by the Hg-treated F1 adults had much higher 48-h LC50 (149 μg/L) and MTLP concentration (148% of control) when there was continuous Hg exposure after birth. We concluded that acclimation to Hg stress occurred quickly in D. magna, though animals recovering from Hg stress were more vulnerable to Hg toxicity. Both ingestion rate and MTLP may not be good biomarkers of Hg stress in the field, because acclimation can be achieved through multigenerational exposure to elevated Hg concentrations.
In vivo bioassay-guided fractionation of marine sediment extracts from the Southern California Bight, USA, for estrogenic activity
Authors: Schlenk Daniel , Sapozhnikova Yelena , Irwin Mary Ann , Xie Lingtian , Hwang Wendy , Reddy Sharanya , Brownawell Bruce J. , Armstrong Jeff , Kelly Mike , Montagne David E. , Kolodziej Edward P. , Sedlak David , Snyder Shane
Published: October 2005

The exposure and uptake of environmental estrogenic compounds have been reported in previouss studies of demersal flatfish species in the central Southern California Bight (SCB), USA. The objective of this study was to evaluate the estrogenic or feminizing activity of marine sediments from the SCB by using in vivo vitellogenin (VTG) assays in male or juvenile fish. In 2003, sediments were collected near wastewater outfalls serving the counties of Los Angeles (LACSD) and Orange (OCSD), and the city of San Diego (SD), California, USA. Cultured male California halibut (CH; Paralichthys californicus) were either directly exposed to sediments for 7 d or treated with two intraperitoneal injections of sediment extract over 7 d. The 17β-estradiol (E2) equivalent values ranged from 1 to 90 μg/kg with LACSD > SD > OCSD. Measurable concentrations of E2 were observed in all sediment extracts and ranged from 0.16 to 0.45 ng/g. Estrone (E1) was only observed in sediments near the LACSD outfall (0.6 ng/g). Alkylphenols and alkylphenol ethoxylates were observed in all sediment samples, but were highest near the OCSD outfall, where concentrations of nonylphenol were 3,200 ng/g. Fractionation studies of the LACSD sediment extract collected in 2004 failed to demonstrate relationships between VTG expression and 62 analytes, including E2, which was observed in the whole extract (2.9 ng/g). Oxybenzone (1.6 ng/g) was identified in bioactive fractions as well as unknown compounds of relatively high polarity. These results indicate that estrogen receptor-based assays may underestimate environmental estrogenic activity and estrogenic compounds other than classic natural and xenoestrogens may contribute to estrogenic activity of sediments from the SCB.
Biodegradation during contaminant transport in porous media: 7. Impact of multiple-degrader community dynamics
Authors: Wang Jiann-Ming , Patterson Brandolyn , Bodour Adria , Maier Raina M. , Brusseau Mark L.
Published: October 2005

The biodegradation and transport of phenanthrene in porous media containing multiple populations of phenanthrene degraders is examined with a series of miscible-displacement experiments. A long-term experiment was conducted with a soil containing an indigenous microbial community comprised of 25 identified phenanthrene-degrading isolates. The rate and magnitude of phenanthrene biodegradation oscillated throughout the six-month experiment. This behavior, at least in part, is attributed to multiple-population dynamics associated with the indigenous community of phenanthrene degraders, the composition of which changed during the experiment. This hypothesis is supported by the results of experiments conducted using sterilized porous media that were inoculated with selected isolates obtained from the indigenous soil community. The results of experiments conducted with sterilized soil inoculated with isolate A exhibited an initial extended period of steady phenanthrene effluent concentrations, followed by a uniform decline. The results of experiments conducted using sterilized sand for single-isolate systems with one of three selected isolates and for systems of two-isolate combinations, indicate the existence of apparent synergistic and antagonistic interactions among the isolates. For example, phenanthrene biodegradation was relatively extensive and occurred without a lag phase for isolate A alone. However, biodegradation was constrained when isolate A and B were combined, indicating an antagonistic interaction. Conversely, whereas extensive lag phases were exhibited by both isolates B and C for the single-isolate experiments, there was minimal lag when isolates B and C were combined, indicating a synergistic interaction.
Uptake of nonylphenol and nonylphenol ethoxylates by crested wheatgrass
Authors: Doucette William J. , Wheeler Bryan R. , Chard Julie K. , Bugbee Bruce , Naylor Carter G. , Carbone John P. , Sims Ronald C.
Published: October 2005

Nonylphenol (NP) and other hydrophobic biodegradation intermediates of nonylphenol ethoxylate (NPE) surfactants have been identified in wastewater treatment biosolids. These biosolids often are land applied, but little is known regarding the potential uptake of biosolid-derived contaminants by plants. Hydroponic experiments, 11 to 14 weeks in duration, were conducted to examine the uptake and translocation of 14C and unlabeled NP, nonylphenol tetraethoxylate (NPE4), and nonylphenol nonylethoxylate (NPE9) by crested wheatgrass (Agropyron cristatum). Phenol also was evaluated for comparison. Plant tissue was analyzed for 14C and for the parent compounds. Volatilization from the hydroponic system and rhizosphere mineralization also were quantified. At the conclusion of the study, most of the plant-associated 14C was found in the roots (NP = 98%, NPE4 = 92%, and NPE9 = 81%). Concentrations of 14C in the foliar tissue ranged from 0.002 to 0.045 mg—equivalent per kg (dry wt), but no parent compounds were detected, implying that the 14C was unextractable or in the form of metabolites. Transpiration stream concentration factors for NP, NPE4, and NPE9, calculated assuming the 14C was parent compound, were 0.012, 0.032, and 0.066, respectively. Little mineralization was observed for NP, NPE4, and NPE9 in the hydroponic system; however, for phenol, 16 to 30% of the added 14C was mineralized.
Distinctive sorption mechanisms of soil organic matter and mineral components as elucidated by organic vapor uptake kinetics
Authors: Shih Yang-Hsin , Wu Shian-Chee
Published: October 2005

Sorption kinetics and capacities of volatile organic compounds (VOCs) affect the remediation and fate of these pollutants in soils. The soil organic-mineral compositional heterogeneity complicates the transport and fate of VOCs in soils. The sorption kinetics of toluene vapor with two common soil components, kaolinite and humic acid, shows two distinct sorption patterns. Results with kaolinite are characteristic of surface adsorption, whereas results with humic acid are characteristic of solvation and partition effects. On soils, the kinetics of toluene vapor sorption show a two-stage sorption phenomenon. The first stage is reflective of surface adsorption (1–4 h to completion) and the second stage of much slower partitioning into soil organic matter, which was preceded by a lag phase (∼4 h) and took as long as 15 h for completion. The relative contributions of these two stages to soil uptake are quantifiable by two independent parameters, the soil organic fraction and the surface area. A better understanding of the effect of soil compositional heterogeneity on sorption kinetics and capacities facilitates our understanding of the prediction for the fate of organic contaminants in the environment.
Predicting single and mixture toxicity of petrogenic polycyclic aromatic hydrocarbons to the copepod Oithona davisae
Authors: Barata Carlos , Calbet Albert , Saiz Enric , Ortiz Laura , Bayona Josep Maria
Published: October 2005

In the present study, the acute toxicity of 10 polycyclic aromatic hydrocarbons (PAH) associated with the Prestige fuel oil spill (Spain, 2002) were evaluated, either as single substances or in mixtures, in adults of the copepod Oithona davisae. All but dimethylphenanthrene had negative effects on O. davisae survival at concentrations below their water solubility, with 48-h median lethal concentrations for naphthalene and pyrene of 56.1 and 0.8 μmol/L, respectively, making these the least and most toxic compounds. Polycyclic aromatic hydrocarbons had narcotic effects on copepods, as evidenced by the lack of motility at lower concentrations than those causing death. Naphthalene showed the greatest narcotic effects, and phenanthrene showed minor effects. Acute toxicity of the tested PAHs was inversely related (r2 = 0.9) with their octanol—water partition coefficient, thereby confirming the validity of the baseline quantitative structure—activity regression models for predicting the toxicity of PAH compounds in copepod species. When supplied in mixtures, the toxic effect of PAHs was additive. These results indicate that the many PAHs in an oil spill can be considered unambiguous baseline toxicants (class 1) acting additively as nonpolar narcotics in copepods; hence, their individual and combined toxicity can be predicted using their octanol—water partition coefficient.
Movement of Diuron and Hexazinone in Clay Soil and Infiltrated Pond Water
Authors: Prichard Terry , Troiano John , Marade Joe , Guo Fengmao , Canevari Mick
Published: October 2005

Pre‐emergence herbicide residues were detected in domestic wells sampled near Tracy, CA. This study sought to determine the source of contamination by comparing soil distribution of diuron [N′‐(3,4‐dichlorophenyl)‐N,N‐dimethylurea] and hexazinone [3‐cyclohexyl‐6‐(dimethylamino)‐1‐methyl‐1,3,5‐triazine‐2,4(1H,3H)‐dione] in an agricultural field where the soil was a cracking clay to infiltration of residues in water captured by an adjacent holding pond. Diuron and hexazinone were applied in December to a 3‐yr‐old alfalfa (Medicago sativa L.) crop. Water content of soil taken after major rainfall but before irrigation at 106 d after application was elevated at the lowest depth sampled centered at 953 mm, indicating water was available for percolation. Herbicide residues (reporting limit 8 μg kg−1) were confined above the 152 mm soil depth, even after subsequent application of two border‐check surface irrigations. The pattern of distribution and concentration of residues in the soil were similar to results obtained from the LEACHM model, suggesting that macropore flow was limited to a shallow depth of soil. Herbicide residues were measured in runoff water at the first irrigation at 20 μg L−1 for diuron and 1 μg L−1 for hexazinone. Runoff water captured in the pond rapidly infiltrated into the subsurface soil, causing a concomitant rise in ground water elevation near the pond. Herbicide residues were also detected in the sampled ground water. We concluded that the pond was the predominant source for movement to ground water. Since addition of a surfactant to the spray mixture did not reduce concentrations in runoff water, mitigation methods will focus on minimizing infiltration of water from the pond.
Multivariate Statistical Characterization of Water Quality in Lake Lanier, Georgia, USA
Authors: Zeng Xiaoqing , Rasmussen Todd C.
Published: October 2005

Watershed monitoring programs depend on water quality characterization data collected for many parameters, at many times and places, and with limited resources. Our objective is to present a strategy that reduces the measured parameters, locations, and frequency without compromising the quality of the monitoring program. One year of twice‐monthly (growing season) and monthly (dormant season) water quality data collected from 17 lake and 10 tributary sites are used in conjunction with multivariate statistical techniques to improve the utility of collected data by identifying key parameters and monitoring locations. Factor analysis shows that tributary water quality data consists of three components—stormwater runoff, municipal and industrial discharges, and ground water—which can be distinguished using total suspended solids, total dissolved solids, and alkalinity plus soluble reactive P, respectively. Lake water quality characterization is more ambiguous than tributary water quality characterization, but factor analysis indicates that anoxia associated with lake stratification is the largest source of lake water quality variation, followed by nutrient abundance, and finally by biomass abundance. Cluster analysis suggests that tributary and lake monitoring stations can be consolidated. Reducing the number of parameters and stations frees up resources for increased monitoring elsewhere.
Is the Transfer Factor a Relevant Tool to Assess the Soil‐to‐Plant Transfer of Radionuclides under Field Conditions?
Authors: Centofanti T. , Penfield R. , Albrecht A. , Pellerin S. , Flühler H. , Frossard E.
Published: October 2005

The radiological impact of radionuclides released to the terrestrial environment is usually predicted with mathematical models in which the transfer of radionuclides from soil to the plant is described with the transfer factor (TF). This paper questions the validity of the protocols proposed by the International Atomic Energy Agency to measure TF in the field and in greenhouses conditions. We grew maize (Zea maysL.) both in the field after a surface application of radionuclides (54Mn,57Co,65Zn, and134Cs) and in a greenhouse with the same soil that has received the same fertilization and that had been previously sieved and homogeneously labeled with the same radionuclides before being repacked in pots. The analysis of the displacement of radionuclides in the field soil profile showed a higher concentration of the surface‐applied radionuclides in the preferential flow path (PFP) in comparison to the soil matrix indicating that they infiltrated heterogeneously in the soil profile due to the structure‐induced non‐uniform water flow. A significantly higher recovery of57Co and134Cs was observed in the plants grown in the field soil, whereas no differences in the recovery of54Mn and65Zn between the two experiments were detected. These results suggest that (i) under field conditions the soil‐to‐plant transfer of radionuclides that co‐exist as stable elements present at low concentrations in the soil and in the plant is higher than that measured under greenhouse conditions and (ii) the implicit assumption made when calculating the TF (that radionuclides are homogeneously distributed in the soil profile) is not valid, thereby preventing the calculation of an average concentration to obtain the TF parameter.
Denitrification as a Nitrogen Removal Mechanism in a Vermont Peatland
Authors: Hayden Melissa J. , Ross Donald S.
Published: October 2005

Atmospheric deposition of nitrogenous compounds to ombrotrophic peatlands (i.e., those that have peat layers higher than their surroundings and receive nutrients and minerals exclusively by precipitation) has the potential to significantly alter ecosystem functioning. This study utilized the acetylene inhibition technique to estimate the relative importance of denitrification in nitrogen removal from a primarily ombrotrophic peatland, in an attempt to estimate the threat of increased nitrogen loadings to these areas. Estimates of mean rates of denitrification ranged from −2.76 to 84.0 ng N2O‐N cm−3 h−1 (equivalent to −150 to 4800 μg N2O‐N m−2 h−1) using an ex situ core technique and from −8.30 to 5.98 μg N2O‐N m−2 h−1 using an in situ chamber technique. Core rates may have been elevated over natural field levels due to effects of disturbance on substrate availability, and chamber rates may have been low due to diffusional constraints on acetylene and N2O. Net nitrification was also measured in an attempt to evaluate this process as a source of nitrate for denitrifiers. The low rates of net nitrification measured, in combination with the low rates of in situ denitrification and the very low amounts of free nitrate measured in this peatland, suggests that inorganic N turnover in this wetland is low. Results showed that nitrate was a limiting factor for denitrification in this peatland, with mean rates from nitrate‐amended cores ranging from 13.1 to 260 ng N2O‐N cm−3 h−1, and it is expected that increases in nitrogen loadings will increase denitrification rates in this ecosystem.
Evaluation of Simplifying Assumptions on Pesticide Degradation in Soil
Authors: Beulke Sabine , van Beinum Wendy , Brown Colin D. , Mitchell Matthew , Walker Allan
Published: October 2005

There is evidence that degradation of pesticides in simple laboratory systems may differ from that in the field, but it is not clear which of the simplifications inherent in laboratory studies present serious shortcomings. Laboratory experiments evaluated several simplifying assumptions for a clay loam soil and contrasting pesticides. Degradation of cyanazine [2‐(4‐chloro‐6‐ethylamino‐1,3,5‐triazin‐2‐ylamino)‐2‐methylpropiononitrile] and bentazone [3‐isopropyl‐1H‐2,1,3‐benzothiadiazin‐4(3H)‐one 2,2‐dioxide] at fluctuating temperature and moisture was predicted reasonably well based on parameters derived from degradation under constant conditions. There was a tendency for slower degradation of cyanazine and bentazone in soil aggregates of 3 to 5 mm in diameter (DT50 at 15°C and 40% maximum water holding capacity of 25.1 and 58.2 d, where DT50 is the time for 50% decline of the initial pesticide concentration) than in soil sieved to <3 mm (DT50 of 19.1 and 37.6 d), but the differences were not significant for most datasets. Degradation of cyanazine, isoproturon [3‐(4‐isopropylphenyl)‐1,1‐dimethylurea], and chlorotoluron [3‐(3‐chloro‐p‐tolyl)‐1,1‐dimethylurea] was measured in soil amended with different amounts of lignin. The effect of lignin on degradation was small despite considerable differences in sorption. The DT50 values of cyanazine, isoproturon, and chlorotoluron were 16.2, 18.6, and 33.0 d, respectively, in soil without lignin and 19.0, 23.4, and 34.6 d, respectively, in soil amended with 2% lignin. Degradation of bentazone and cyanazine in repacked soil columns was similar under static and flow conditions with 50.1 and 47.2% of applied bentazone and 74.7 and 73.6% of applied cyanazine, respectively, degraded within 20 d of application. Thus, the assumptions underpinning laboratory to field extrapolation tested here were considered to hold for our experimental system. Additional work is required before general conclusions can be drawn.
Rapid Removal of Nitrate and Sulfate in Freshwater Wetland Sediments
Authors: Whitmire Stefanie L. , Hamilton Stephen K.
Published: October 2005

Anaerobic microbial processes play particularly important roles in the biogeochemical functions of wetlands, affecting water quality, nutrient transport, and greenhouse gas fluxes. This study simultaneously examined nitrate and sulfate removal rates in sediments of five southwestern Michigan wetlands varying in their predominant water sources from ground water to precipitation. Rates were estimated using in situ push–pull experiments, in which 500 mL of anoxic local ground water containing ambient nitrate and sulfate and amended with bromide was injected into the near‐surface sediments and subsequently withdrawn over time. All wetlands rapidly depleted nitrate added at ambient ground water concentrations within 5 to 20 h, with the rate dependent on concentration. Sulfate, which was variably present in porewaters, was also removed from injected ground water in all wetlands, but only after nitrate was depleted. The sulfate removal rate in ground water–fed wetlands was independent of concentration, in contrast to rates in precipitation‐fed wetlands. Sulfate production was observed in some sites during the period of nitrate removal, suggesting that the added nitrate either stimulated sulfur oxidation, possibly by bacteria that can utilize nitrate as an oxidant, or inhibited sulfate reduction by stimulating denitrification. All wetland sediments examined were consistently capable of removing nitrate and sulfate at concentrations found in ground water and precipitation inputs, over short time and space scales. These results demonstrate how a remarkably small area of wetland sediment can strongly influence water quality, such as in the cases of narrow riparian zones or small isolated wetlands, which may be excluded from legal protection.
Nitrogen Fertilizer Recommendations for Corn Grown on Soils Amended with Oily Food Waste
Authors: Rashid M. T. , Voroney R. P.
Published: October 2005

Soil and plant indices of soil fertility status have traditionally been developed using conventional soil and crop management practices. Data on managing N fertilizer for corn (Zea maysL.) produced on soils amended with C‐rich organic materials, such as oily food waste (OFW) is scarce. Identification of a reliable method for making N fertilizer recommendations under these conditions is imperative. The objective of this research was to evaluate soil NO3–N (0‐ to 30‐cm depth) at preplant and presidedress (PSNT) times of sampling for predicting N requirements for corn grown on fields receiving OFW. Experiments were conducted at two locations in Ontario, Canada over 3 yr (1995–1997) where OFW was applied at different rates (0, 10, and 20 Mg ha−1), times (fall and spring), and slope positions (upper, mid, and lower) within the same field. Presidedress soil NO3–N contents were higher compared with preplant time of sampling under all OFW management conditions. Corn grain yields were significantly affected by OFW management and N fertilizer application rates. Maximum economic rate of N application (MERN) varied depending on OFW management conditions. Presidedress soil NO3–N contents had a higher inverse relationship with MERN (r= −0.88) compared with soil NO3–N at preplant (r= −0.74) time of sampling. A linear regression model (Y= 180.1 − 8.22 NO3–N at PSNT) is proposed for making N fertilizer recommendations to corn grown on soils amended with OFW in this geographical region.
Autoclaving Soil Samples Affects Algal‐Available Phosphorus
Authors: Anderson Brandon H. , Magdoff Frederick R.
Published: October 2005

Unwanted microbial interference in samples used for biological assays of P availability has routinely been eliminated by autoclaving samples before inoculation with algae. Twenty‐three soils were selected to evaluate the relationship between algal growth in P‐deficient solutions containing small quantities of soil and the level of P determined by a variety of tests used to evaluate P availability in soils and sediments. Soils were either autoclaved or not before addition to flasks containing P‐starved algae in a nutrient solution without P. Compared to non‐autoclaved samples, autoclaving soil resulted in approximately 60% more available P as estimated by increased algal growth. However, algal growth in the presence of autoclaved soil was highly correlated with growth in the presence of non‐autoclaved samples. There was no consistent change in the correlations (r) between autoclaving or non‐autoclaving samples in the relationships of algal numbers with P extracted by a number of soil tests. The effect of autoclaving soil on soluble P was also evaluated for a subset of six soils. Autoclaved soils had significantly greater concentrations of soluble P than non‐autoclaved soils, with 78% more orthophosphate monoesters, 60% more orthophosphate diesters, and 54% more soluble inorganic P. Inhibition of algal growth may have occurred with two high‐Zn soils that produced relatively low numbers of algae despite being very high in estimated available P by all extraction methods. Removing those samples from the calculations dramatically improved correlations between soil P measured by various methods and algal growth. With these two soils removed from calculations, algal growth with autoclaved soil was most highly correlated with Olsen P (r= 0.95), with other correlations as follows: Fe‐oxide strip (r= 0.80), Mehlich 3 (r= 0.75,), modified Morgan (r= 0.61), and Bray–Kurtz 1 (r= 0.57).
Antibiotic Uptake by Plants from Soil Fertilized with Animal Manure
Authors: Kumar K. , Gupta S. C. , Baidoo S. K. , Chander Y. , Rosen C. J.
Published: October 2005

Antibiotics are commonly added to animal feed as supplements to promote growth of food animals. However, absorption of antibiotics in the animal gut is not complete and as a result substantial amounts of antibiotics are excreted in urine and feces that end up in manure. Manure is used worldwide not only as a source of plant nutrients but also as a source of organic matter to improve soil quality especially in organic and sustainable agriculture. Greenhouse studies were conducted to determine whether or not plants grown in manure‐applied soil absorb antibiotics present in manure. The test crops were corn (Zea maysL.), green onion (Allium cepaL.), and cabbage (Brassica oleraceaL. Capitata group). All three crops absorbed chlortetracycline but not tylosin. The concentrations of chlortetracycline in plant tissues were small (2–17 ng g−1fresh weight), but these concentrations increased with increasing amount of antibiotics present in the manure. This study points out the potential human health risks associated with consumption of fresh vegetables grown in soil amended with antibiotic laden manures. The risks may be higher for people who are allergic to antibiotics and there is also the possibility of enhanced antimicrobial resistance as a result of human consumption of these vegetables.
Temporal and Spatial Development of Surface Soil Conditions at Two Created Riverine Marshes
Authors: Anderson Christopher J. , Mitsch William J. , Nairn Robert W.
Published: October 2005

The amount of time it takes for created wetlands to develop soils comparable to natural wetlands is relatively unknown. Surface soil changes over time were evaluated in two created wetlands (approximately 1 ha each) at the Olentangy River Wetland Research Park in Columbus, Ohio. The two wetlands were constructed in 1993 to be identical in size and geomorphology, and maintained to have the same hydrology. The only initial difference between the wetlands was that one was planted with native macrophytes while the other was not. In May 2004, soil samples were collected (10 yr and 2 mo after the wetlands were flooded) and compared to samples collected in 1993 (after the wetlands were excavated but before flooding) and 1995 (18 mo after the wetlands were flooded). In all three years, soils were split into surface (0–8 cm) and subsurface (8–16 cm) depths and analyzed for soil organic matter, total C, total P, available P, exchangeable cations, and pH. Soils in the two wetlands have changed substantially through sedimentation and organic accretion. Between 1993 and 1995, soils were most influenced by the deposition of senescent macroalgae, the mobilization of soluble nutrients, and the precipitation of CaCO3 Between 1995 and 2004, soil parameters were influenced more by the deposition of organic matter from colonized macrophyte communities. Mean percent organic matter at the surface increased from 5.3 ± 0.1% in 1993, 6.1 ± 0.2% in 1995, to 9.5 ± 0.2% in 2004. Mean total P increased from 493 ± 18 μg g−1 in 1993, 600 ± 23 μg g−1 in 1995, to 724 ± 20 μg g−1 in 2004. Spatial analyses of percent organic matter (a commonly used indicator of hydric soil condition) at both wetlands in 1993, 1995, and 2004 showed that soil conditions have become increasingly more variable. High spatial structure (autocorrelation) between data points was detected in 1993 and 2004, with data in 2004 exhibiting a much higher overall variance and narrower range of spatial structure than in 1993.
Modeling the Primary Drainage Curve of Prefractal Porous Media
Authors: Perfect E.
Published: October 2005

Fractal models for the soil water retention curve have largely ignored hysteresis. Such models generally require that all pores be connected to the atmosphere via a network of similar‐sized or larger pores. In random mass fractals and natural porous media, however, not all pores of a given size class empty during drainage due to incomplete pore connectivity and/or the presence of surrounding smaller pores. A modification of Rieu and Sposito's (1991a) prefractal water retention equation is proposed to accommodate this hysteresis during monotonic drying. The resulting expression is identical in form to the empirical Brooks and Corey (1964) model and contains three physically‐based parameters: the proportion of nondraining pores (Pd), the scale factor (b), and the apparent fractal dimension of the primary drainage curve (Dd), which is related to the underlying mass fractal dimension (D) of the porous medium by Dd = D + [log(Pd)]/[log(b)]. Model testing consisted of fitting the modified equation to previously published water retention data for 30 randomized Sierpinski carpets and seven soils. Error sums of squares ranged from 0.001 to 0.093 for the carpets, and from 0.015 to 0.047 for the soils. In contrast, the unmodified Rieu and Sposito (1991a) equation performed very poorly. Best fit estimates of Dd ranged from 0.295… to 1.640… for the two‐dimensional carpets, and from 2.467… to 2.902… for the three‐dimensional soils. Prediction of D, based on estimates of Dd derived from the primary drainage curve, will require additional research on how to obtain Pd and b. Based on the analytical approach outlined here, it should also be possible to model the primary wetting curve, thus providing a more complete fractal description of soil water hysteresis.