bluuebunny/crossref_metadata_2025 huggingface dataset:
Presence of nonylphenol ethoxylate surfactants in a watershed in central Mexico and removal from domestic sewage in a treatment wetland
Authors: Belmont Marco A. , Ikonomou Michael , Metcalfe Chris D.
Published: January 2006

The Texcoco River in central Mexico is polluted with domestic wastewater as a result of discharges of untreated or inadequately treated sewage. Since nonylphenol ethoxylate (NPEO) surfactants and their intermediate degradation products such as nonylphenol (NP) and NP mono- and diethoxylate (NP1EO, NP2EO) have been found in domestic wastewater and in surface waters near wastewater discharges in industrialized countries, the Texcoco River was sampled to determine whether these compounds were present. The results indicated that NPEOs were present at very high concentrations (>100 μg/L) in the lower reaches of the Texcoco River, but unlike rivers in industrialized countries, relatively low concentrations of intermediate degradation products, including NP1EO, NP2EO, and NP, were present. The presence and fate of NPEOs compounds in wastewater treatment plants have been studied only in conventional treatment systems in industrialized countries. In this study, the fate of these compounds was studied in a pilot-scale treatment wetland constructed in the small community of Santa Maria Nativitas in the Texcoco River watershed. The treatment wetland removed >75% of NPEOs from the domestic wastewater, but the greatest proportion of removal occurred in parts of the treatment wetland where sedimentation existed. This is the first report of NPEO compounds in the water resources of a developing country. These data indicate that construction of low-cost and technologically simple treatment wetlands may be one solution to reducing the impacts of contaminants from domestic sewage in developing countries, such as Mexico.
Chronic toxicity of lead to three freshwater invertebrates—Brachionus calyciflorus, Chironomus tentans, andLymnaea stagnalis
Authors: Grosell Martin , Gerdes Robert M. , Brix Kevin V.
Published: January 2006

Chronic lead (Pb) toxicity tests with Brachionus calyciflorus, Chironomus tentans, and Lymnaea stagnalis were performed in artificial freshwaters. The no-observable-effect concentration (NOEC), lowest-observable-effect concentration (LOEC), and calculated 20% effect concentration (EC20) for the rotifer B. calyciflorus were 194, 284, and 125 μg dissolved Pb/L, respectively. The midge C. tentans was less sensitive, with NOEC and LOEC of 109 and 497 μg dissolved Pb/L, respectively, and the snail L. stagnalis exhibited extreme sensitivity, evident by NOEC, LOEC, and EC20 of 12, 16, and <4 μg dissolved Pb/L, respectively. Our findings are presented in the context of other reports on chronic Pb toxicity in freshwater organisms. The L. stagnalis results are in agreement with a previous report on pulmonate snails and should be viewed in the context of current U.S. Environmental Protection Agency (U.S. EPA) hardness adjusted water quality criteria of 8 μg Pb/L. The present findings and earlier reports indicate that freshwater pulmonate snails may not be protected by current regulatory standards. Measurements of whole-snail Na+ and Ca2+ concentrations following chronic Pb exposure revealed that Na+ homeostasis is disturbed by Pb exposure in juvenile snails in a complicated pattern, suggesting two physiological modes of action depending on the Pb exposure concentration. Substantially reduced growth in the snails that exhibit very high Ca2+ requirements may be related to reduced Ca2+ uptake and thereby reduced shell formation.
Dissipation kinetics and mobility of chlortetracycline, tylosin, and monensin in an agricultural soil in Northumberland County, Ontario, Canada
Authors: Carlson Jules C. , Mabury Scott A.
Published: January 2006

A robust high-throughput method was refined to extract three growth-promoting antibiotics, tylosin (TYL), chlortetracycline (CTC), and monensin (MON), from soil. Analysis was performed by electrospray liquid chromatography tandem mass spectrometry. Soil dissipation rate studies were performed in a farm field soil for antibiotics applied with and without manure. Tylosin, CTC, and MON followed first-order dissipation kinetics with half-lives of 4.5, 24, and 3.3 d, respectively, with the addition of manure and 6.1, 21, and 3.8 d, respectively, without manure. Manure application significantly increased TYL dissipation rate, perhaps because of the introduced microbial flora, but had no significant effect on CTC or MON. Monensin dissipation half-life was found to be much shorter in the field study than in a controlled laboratory study, perhaps because of differences in microbial communities. The antimicrobials were not highly mobile. Chlortetracycline was the only antibiotic detected at 25 to 35 cm depth and only up to 2% of the initial concentration in a sandy loam soil. These antibiotics are therefore expected to degrade primarily in agricultural soils before moving to greater depths or to groundwater in significant concentrations in most agricultural systems.
Influence of developmental stage on sensitivity to ammonium nitrate of aquatic stages of amphibians
Authors: Ortiz-Santaliestra Manuel E. , Marco Adolfo , Fernández María José , Lizana Miguel
Published: January 2006

In static renewal experiments, we studied how developmental stage influences the effect of ammonium nitrate on embryonic and larval stages of anuran amphibians. The observed lethal effects caused by ammonium nitrate increased with both concentration and duration of exposure. Significant differences were observed in sensitivity to ammonium nitrate as a function of developmental stage in Discoglossus galganoi, Pelobates cultripes, and Bufo calamita. In D. galganoi and P. cultripes, younger individuals displayed greater acute effects from the chemical fertilizer compared with older individuals. For example, 100% of P. cultripes hatchlings died after 4 d of exposure to a nominal concentration of 225.8 mg N-NO3NH4/L, whereas less than 40% of individuals from older larval stages died when exposed to this concentration. A delay of 4 d in the beginning of the exposure to the chemical was enough to cause significant differences in sensitivity. Bufo calamita showed a higher sensitivity in later larval stages after 12 d of exposure. Hyla meridionalis and B. calamita were less sensitive than the other two species. Peak ammonium nitrate concentrations usually occur when amphibians are breeding and, thus, when the most sensitive aquatic stage is in the water. The developmental stage of the test animals should be considered when evaluating the risk of ammonium nitrate to amphibians.
Effects of microcystins on fish
Authors: Malbrouck Christelle , Kestemont Patrick
Published: January 2006

Microcystins (MCs) are hepatotoxic heptapeptides released into water during or on senescence of cyanobacterial blooms. This review details the different effects of the MCs on fish and discusses their potential consequences in aquatic food webs. In early life stages, exposure to MCs causes, in a dose-dependent manner, perturbations to embryonic hatching, decrease in survival and growth rate, as well as histopathological effects (enlarged and opaque yolk sac, small head, curved body and tail, hepatobiliary abnormalities, ultrastructural alterations in hepatocytes, heart rate perturbations). In adults and juveniles, field and experimental studies demonstrated that after ingestion MCs accumulate mainly in liver but can also be found in muscle and viscera. Microcystin exposure has been shown to affect growth rate and osmoregulation, increase liver enzyme activities in the serum and heart rate, modify behavior, and exert histopathological effects in the liver, intestine, kidneys, heart, spleen, or gills, but the degree to which these effects were seen depends on the exposure route. The detoxication pathway of MCs in fish begins with a conjugation reaction to glutathione catalyzed by glutathione S-transferases, and this is comparable to the reaction demonstrated in other organisms, from plants to mammals. It appears that MC concentrations found in nature can potently affect several trophic levels in the aquatic ecosystems, in particular by inducing failure of sensitive stages (e.g., fish fry) to develop and accumulating in the food chains. The need of further quantitative studies on the sublethal effects, accumulation, and fate of MCs in aquatic food chains still remains.
Effects of atrazine on sexual maturation in female Japanese quail induced by photostimulation or exogenous gonadotropin
Authors: Wilhelms Kelly W. , Cutler Sara A. , Proudman John A. , Anderson Lloyd L. , Scanes Colin G.
Published: January 2006

The herbicide atrazine has gained recent attention for its reported effects on reproduction in amphibians. The present study examined the putative effects of atrazine during sexual maturation in the photostimulated female Japanese quail. Furthermore, the effects of atrazine on birds administered exogenous gonadotropin (pregnant mare serum gonadotropin [PMSG]) were investigated. Atrazine was administered up to 1,000 ppm in the diet to female quail undergoing photoperiodically induced sexual maturation. At high dietary concentrations, atrazine exhibits signs of overt toxicity with reductions in growth, feed intake, and liver weights, but these effects were dependent on the timing of treatment administration. Atrazine did not influence the weights of reproductive tissues (ovary and oviduct) or circulating concentrations of luteinizing hormone (LH). However, high concentrations of atrazine depressed circulating concentrations of estradiol. Treatment with atrazine for four weeks during sexual maturation inhibited growth but did not affect any other parameter assessed (feed intake, liver, ovary, or oviduct weights or the circulating concentrations of LH and estradiol). In birds receiving daily injections of PMSG, atrazine reduced growth, feed intake, and liver weights. However, PMSG-induced gonadal and oviduct growth was not affected by atrazine. The present results suggest that dietary atrazine exhibits limited reproductive toxicity in female quail during sexual maturation and only at concentrations above ecological relevance.
A method of assessing ecological risk to night heron,Nycticorax nycticorax, population persistence from dichlorodiphenyltrichloroethane exposure
Authors: An Wei , Hu Jian-ying , Yao Fang
Published: January 2006

This paper first introduces a probabilistic method for quantitatively evaluating the effects of chemical pollutants in the environment on a wildlife population, which was applied to assess the ecological risk to night heron (Nycticorax nycticorax) population persistence from dichlorodiphenyltrichloroethane (DDE) exposure in Tai Lake, China. Intrinsic rate of population increase (r) calculated with a population age-structured matrix model was used to measure the adverse effect on population. To perform a probabilistic analysis of risk, lost intrinsic rate of population increase (ΔZ) because of DDE exposure was applied to express the exact extent of risk. The result showed that the risk (i.e., the expectancy of ΔZ of the night heron population exposed to DDE in Tai Lake) was 0.0259, indicating a decrease in gross population size of 2.56% every year compared with that of the previous year without DDE exposure.
Biochemical and spectroscopic studies of the response of Convolvulus arvensis L. to chromium(III) and chromium(VI) stress
Authors: Montes-Holguin Milka O. , Peralta-Videa Jose R. , Meitzner George , Martinez-Martinez Alejandro , de la Rosa Guadalupe , Castillo-Michel Hiram A. , Gardea-Torresdey Jorge L.
Published: January 2006

The objective of the present study was to determine the oxidative stress caused by hexavalent chromium (Cr[VI]), the chromium (Cr) uptake, and the Cr speciation in Convolvulus arvensis L. plants grown in hydroponics media containing either Cr(VI) or Cr(III). The results demonstrated that C. arvensis plants exposed to Cr(VI) concentrations ranging from 0 to 40 mg/L expressed higher ascorbate peroxidase specific activity in roots than in shoots. On the other hand, catalase activity monitored in plants exposed to 2 mg/L of Cr(VI) for 24 h increased in roots after a few hours of exposure. However, catalase activity in shoots revealed a decrement almost immediately after treatment was initiated. The results from x-ray absorption spectroscopic studies indicated that the oxidation state of the supplied Cr(III) remained the same in plant tissues. The supplied Cr(VI), however, was reduced to the trivalent form in plant tissues. The results of inductively coupled plasma/optical emission spectroscopy demonstrated that after 5 d, the roots of plants exposed to 40 mg/L of Cr(III) or Cr(VI) accumulated approximately 25,000 and 3,500 mg/kg dry weight of Cr, respectively. Nevertheless, shoots concentrated 1,500 and 2,000 mg/kg dry weight of Cr from Cr(III) and Cr(VI), respectively, which indicated that Cr moved faster into C. arvensis plants when supplied as Cr(VI).
Measurement of total polycyclic aromatic hydrocarbon concentrations in sediments and toxic units used for estimating risk to benthic invertebrates at manufactured gas plant sites
Authors: Hawthorne Steven B. , Miller David J. , Kreitinger Joseph P.
Published: January 2006

The U.S. Environmental Protection Agency's (U.S. EPA) narcosis model requires the measurement of 18 parent and 16 groups of alkyl polycyclic aromatic hydrocarbons (PAHs) (so-called 34 PAHs) in sediments to calculate the number of PAH toxic units (TU) available to benthic organisms. If data for the 34 PAHs are not available, the U.S. EPA proposes estimating the risk by multiplying the TU for 13 parent PAHs by 11.5 (95% confidence interval) based on data from 488 sediments. This estimate is overly conservative for PAHs from pyrogenic manufactured gas plant (MGP) processes based on the analysis of 45 sediments from six sites. Parent PAHs contributed approximately 40% of the total concentrations and TU for MGP sediments. In contrast, parent PAHs from diesel fuel and petroleum crude oil contributed only 2 and 1%, respectively, of the PAH concentrations and TU, compared to approximately 98 to 99% contributed by the alkyl PAHs. Statistical comparison of the TU based on the measured 34 alkyl and parent PAHs and those based on only 13 parent PAHs demonstrated that a factor of 4.2 (rather than 11.5) is sufficient to estimate total TU within a 95% confidence level for MGP sites. Similarly, measurement of parent PAHs is sufficient to accurately estimate the total 34 alkyl and parent PAH concentrations for MGP-impacted sediments.
Sorption of humic acids and α-endosulfan by clay minerals
Authors: Hengpraprom Sarunya , Lee Cindy M. , Coates John T.
Published: January 2006

Sorption of α-endosulfan by kaolinite and montmorillonite alone and in the presence of sorbed and dissolved humic acid (HA) was investigated (pH 8 and 25°C). Three types of HA, Elliot soil HA (EHA), Peat HA (PHA), and Summit Hill HA (SHHA), were used to represent typical humic substances found in soils. For sorption of HA by either mineral, Freundlich sorption coefficient (Kf) values appeared to decrease in the order of EHA > PHA > SHHA, which followed increasing polarity (expressed as the O/C atomic ratio) and decreasing percent-carbon content. For both clays, sorption of α-endosulfan by the HA mineral complex was greater than for sorption by the clay alone. Sorption of α-endosulfan by the HA mineral complexes followed the same order as the Kf of the HAs (EHA > PHA > SHHA). Based on the amount of HA adsorbed by each mineral, organic carbon partition coefficients (KOC) were determined for sorption of α-endosulfan by two of the HA mineral complexes. The value of KOC for α-endosulfan sorption was greater for kaolinite EHA than kaolinite SHHA. However, the opposite trend was found with the montmorillonite HA complexes. Montmorillonite appeared to sorb α-endosulfan and/or HA with higher affinity than kaolinite, which likely is due to its 2:1 layer structure and higher surface area. Sorption of endosulfan diol, a hydrolysis product, by the minerals was much less than the parent pesticide.
Effects of nitrate and atrazine on larval development and sexual differentiation in the northern leopard frog Rana pipiens
Authors: Orton Frances , Carr James A. , Handy Richard D.
Published: January 2006

Pollution from agrochemicals may be contributing to the global decline in amphibian populations. Environmentally relevant concentrations of nitrate and/or atrazine on anuran development and gonadal differentiation were tested. Four replicates of 20 tadpoles per tank (80/treatment) were exposed from Taylor–Kollros stage 2 to 3 to stage 23 to 34 to either 10 mg/L nitrate, 10 μg/L atrazine, a combined exposure of 10 mg/L nitrate plus 10 μg/L atrazine, or untreated controls. No treatment-dependent effects on weight, snout-vent or hind limb length, or time to forelimb emergence were observed. The proportions of females increased in all treatments compared to the controls, especially in the combined treatment (X2 = 17.90, df = 6, p = 0.0065, combined = 66.4% female, control = 41% female). The frequency of intersex was low in all treatments. No treatment-related effects on the total number of spermatogenic cells were observed, but the ratio of cell types differed in that testes from animals in the treated groups exhibited more spermatogonia, fewer spermatocytes, and more spermatids than the control (significantly different, Kruskal–Wallis, p < 0.05). Ovaries from animals treated with nitrate or atrazine exhibited larger immature (previtellogenic) and mature (vitellogenic) follicles, but ovaries from the combined treatment had larger immature follicles only. Testicular oocytes were observed in the nitrate-only and atrazine-only treatments, and the control treatment, but not the combined treatment. Overall, this study has demonstrated changes in sex ratios that are more marked in response to combined nitrate/atrazine exposure than with these chemicals alone. Histological evidence suggests that premature maturation of gonad may occur as a result of nitrate and/or atrazine exposure during larval development.
Identification of mobile aliphatic sorptive domains in soil humin by solid-state 13C nuclear magnetic resonance
Authors: Simpson Myrna J. , Johnson Philippe C. E.
Published: January 2006

Many sorption studies aim to elucidate organic matter structure and contaminant sorption relationships. Through this pursuit, a great deal of insight has been gained about contaminant interactions with humic fractions, namely the fulvic and humic acid isolates. Comparatively, less is known about the structure and environmental reactivity of the humin fraction; however, researchers have reported that the humin fraction consistently produces higher sorption coefficients than the corresponding source material and other humic fractions. In this paper, we report on a study that uses solid-state 13C nuclear magnetic resonance (NMR) to characterize six humin samples extracted from soil. In addition, 1-naphthol sorption was measured for each whole-soil and humin sample. With the exception of the peat sample, the humin samples yielded significantly higher organic carbon–normalized sorption coefficients (Koc) compared with the whole-soil samples. The solid-state 13C NMR analysis reveals the presence of amorphous, polymethylene-rich domains in all of the humin samples. Other researchers have indicated that these domains exhibit a high affinity for hydrophobic organic contaminants. Consequently, we hypothesize that the concentration of amorphous, polymethylene-rich domains in soil humin is responsible for the high sorption coefficients reported here and by other researchers.
Interspecific relationships among soil invertebrates influence pollutant effects of phenanthrene
Authors: Cortet Jérôme , Joffre Richard , Elmholt Susanne , Coeurdassier Michael , Scheifler Renaud , Krogh Paul Henning
Published: January 2006

Five mesofauna communities varying in both structure and composition were exposed to phenanthrene in mesocosms for up to four months. Effects of phenanthrene were assessed on mesofauna population dynamics, fungal biomass (ergosterol concentrations), and litter decomposition (litter mass loss, nitrogen concentration). The effects of each community on the fate of phenanthrene were also assessed. We hypothesize that phenanthrene affects the population dynamics of mesofauna and soil biological functioning depending on exposure duration, type of community, or both. Results show that phenanthrene exerted an effect on mesofauna and that the effects on some species, like Folsomia fimetaria, were influenced by the species composition in the mesocosms, the soil layer, and the sampling date. However, the effects of phenanthrene on ergosterol content and organic matter decomposition were not significantly influenced by community composition. These results demonstrate that interspecific relationships are needed to assess the toxicity of pollutants and should be taken into account in ecotoxicological risk assessment. Furthermore, this work does not support the hypothesis of a direct link between toxic effects of organic pollutants on mesofauna species and soil biological functioning.
Ecotoxicological risk of pharmaceuticals from wastewater treatment plants in Korea: Occurrence and toxicity to Daphnia magna
Authors: Han Guk H. , Hur Hor G. , Kim Sang D.
Published: January 2006

The overall ecotoxicological effect of pharmaceutically active compounds (PhACs) detected in the effluents of Korean wastewater treatment plants (WWTPs) to Daphnia magna was investigated using biological and chemical analyses. The bioassay results showed median lethal concentrations and no-observed-effect concentrations ranging from a few to tens of ppm levels for nine PhACs in 48-h acute and 21-d chronic tests. The mixture effects of pharmaceuticals also were examined by other acute and chronic tests, which showed no significant toxicity despite a slightly increased combined effect of approximately twofold. The residual concentrations of nine PhACs were analyzed at concentrations ranging from 10 ng/L to 89 μg/L in the influents and from 10 ng/L to 11 μg/L in the effluents from four metropolitan cities in South Korea between January and November of 2004. Through repeated investigations of the influents and the effluents from different WWTPs, relatively higher removal efficiencies (23.9–91.3%) compared with those of previous surveys performed in other countries were observed for most pharmaceuticals, with the exception of acetaminophen (8.7%). The present study showed no significant risk effects of the effluents from WWTPs containing pharmaceuticals (i.e., hazard quotient < 1), even at the 95th percentile contamination range, although a risk assessment factor of 1,000 was applied. Therefore, it can be concluded that the potential risk of pharmaceuticals should be monitored carefully with more bioassay data, because many uncertainties still exist in the determination and toxicity of metabolites in water environments. No significant risk was observed, however, from the selected PhACs in the effluents from WWTPs discharged into surface waters.
Deriving effects onChironomuspopulation carrying capacity from standard toxicity tests
Authors: Péry Alexandre R. R. , Babut Marc P. , Mons Raphaël , Garric Jeanne
Published: January 2006

Translating effects from individual to population level is a crucial issue in ecological risk assessment of bed sediments. We first propose a modeling package to tackle this question for the species Chironomus riparius with biology- and ecology-based models to deduce effects on chironomid production per generation or per year. However, this approach requires the performance of many toxicity tests. Currently, the information available to perform this scaling is limited to a few data from standardized tests, mainly growth and survival after a certain period of time and sometimes emergence after 28 d. We propose here to simplify our model to make it able to deal with only data from standardized tests. The daily death rate is assumed to be constant throughout each instar, the effects on growth to be independent of time, and the effects on reproduction to be negligible. The reliability of this approach is first tested by comparing the population effects on organisms exposed to copper-spiked sediments calculated with the simple model and the more exhaustive one from which it was derived. The simple model just slightly underestimated the effects at the population level. Second, data from tests performed either with unpolluted sediment or with field sediment with different degrees of contamination are used to propose an effect threshold for populations. It appears that control sediments lead to less than 20% effects at population level, which may help define a natural variability range. For polluted sediments, we could find effects up to 42%. Implications of these findings are discussed in a sediment risk assessment perspective.
Estrogenic endpoints in fish early life-stage tests: Luciferase and vitellogenin induction in estrogen-responsive transgenic zebrafish
Authors: Bogers Rinus , Mutsaerds Esther , Druke Jeanette , De Roode Daphne F. , Murk Albertinka J. , Van Der Burg Bart , Legler Juliette
Published: January 2006

This study incorporated specific endpoints for estrogenic activity in the early life-stage (ELS) test, as described in Guideline 210 of the Organization for Economic Cooperation and Development and traditionally used for toxicity screening of chemicals. A transgenic zebrafish model expressing an estrogen receptor–mediated luciferase reporter gene was exposed to ethi-nylestradiol (EE2), and luciferase activity as well as vitellogenin (VTG) was measured. Concentrations of EE2 were tested at 1, 3, or 10 ng/L for 30 d from fertilization or during only the last 4 d with dimethylsulfoxide (DMSO) as presolvent (0.01%). Exposure to EE2 induced no toxic effects. Mean body weights were significantly higher in groups exposed for 30 d in the presence of DMSO, but condition factors were not affected. Significant luciferase and VTG induction occurred following 30-d exposure (3 and 10 ng EE2/L), while only VTG levels were affected in the 4-d exposure (10 ng EE2/L). This study demonstrated the usefulness of incorporating estrogenic endpoints in the OECD ELS test, fitting the requirements for screening estrogenic activity of chemicals. Quantitative measurement of both VTG and luciferase activity proved to be rapid and sensitive. Additional value of using transgenic zebrafish lies in combining VTG measurement with the more mechanistic approach of luciferase induction in one experiment.
A simulation study comparing different experimental designs for estimating uptake and elimination rates
Authors: Bell Bryan R. , Bailer A. John , Wright Stephen E.
Published: January 2006

The design of ecotoxicological studies requires decisions about the number and spacing of exposure groups tested, the number of replications, the spacing of sampling times, the duration of the study, and other considerations. For example, geometric spacing of sampling times or toxicant concentrations is often used as a default design. Optimal design methods in statistics can suggest alternative spacing of sampling times that yield more precise estimates of regression coefficients. In this study, we use a computer simulation to explore the impact of the spacing of sampling times and other factors on the estimation of uptake and elimination rate constants in an experiment addressing the bioaccumulation of a contaminant. Careful selection of sampling times can result in smaller standard errors for the parameter estimates, thereby allowing the construction of smaller, more precise confidence intervals. Thus, the effort invested in constructing an optimal experimental design may result in more precise inference or in a reduction of replications in an experimental design.
Anodic stripping voltammetry measures copper bioavailability for sea urchin larvae in the presence of fulvic acids
Authors: Lorenzo J. Ignacio , Nieto Oscar , Beiras Ricardo
Published: January 2006

Copper speciation in the presence of fulvic acids (FAs) was studied in chemically defined seawater by square wave anodic stripping voltammetry (SQWASV). A simple complexation model assuming a single type of ligand and a 1:1 reaction stoichiometry successfully explained the measured data. A conditional stability constant of 5.80 ± 0.07 and a complexing capacity of 610 ± 80 μmol Cu/g FAs were obtained. This conditional stability constant would correspond to 7.23 on a free copper ion basis. The complexation kinetics was easily followed by anodic stripping voltammetry (ASV) measurements, and complexation equilibria were not reached until approximately 12 h. Coupled to speciation studies, the toxicity of copper in the presence of FAs was studied with the sea urchin Paracentrotus lividus embryogenesis bioassay. A clear protective effect of FAs was observed on Cu toxicity, and this effect could be accurately explained by SQWASV Cu speciation measurements. Additional experiments in the presence of high Cu and FA concentrations were performed, and no extra toxicity of Cu–FA complexes was observed. These results are in agreement with metal bioavailability models and also underline the usefulness of ASV for determining copper bioavailability in the presence of natural organic matter.
Comparative toxicity of cadmium, zinc, and mixtures of cadmium and zinc to daphnids
Authors: Shaw Joseph R. , Dempsey Thomas D. , Chen Celia Y. , Hamilton Joshua W. , Folt Carol L.
Published: January 2006

Investigations were conducted to determine acute (48-h) effects of cadmium and zinc presented individually and in combination on Ceriodaphnia dubia, Daphnia magna, Daphnia ambigua, and Daphnia pulex. Toxicity tests were conducted with single metals to determine lethal effects concentrations (lethal concentrations predicted for a given percent [x] of a population, LCx value). These were used to derive metal combinations that spanned a range of effects and included mixtures of LC15, LC50, and LC85 values calculated for each metal and species. In single-metal tests, 48-h LC50 values ranged from 0.09 to 0.9 μmol/L and 4 to 12.54 μmol/L for cadmium and zinc, respectively. For each metal, D. magna was most tolerant and showed a different pattern of response from all others as determined by slope of concentration–response curves. In the combined metal treatments, all daphnids showed a similar pattern of response when LC15 concentrations were combined. This trend continued with few exceptions when LC15 concentrations of cadmium were combined with LC50 or LC85 values for zinc. However, when this treatment was reversed (LC15, zinc + LC50 or LC85, cadmium), responses of all species except D. magna indicated less-than-additive effects. For C. dubia, a near complete reduction in toxicity was observed when the LC15 for zinc was combined with LC85 for cadmium. Multimetal tests with D. magna did not differ from additive. Collectively, these studies suggest that D. magna may not be representative of other cladocerans.
Composition and production of thiol constituents induced by cadmium in the marine microalga Tetraselmis suecica
Authors: Pérez-Rama Mónica , Vaamonde Enrique Torres , Alonso Julio Abalde
Published: January 2006

Time course of intracellular levels of different thiols (phytochelatins, desglycyl-phytochelatins, glutathione, γ-glutamylcysteine [γ-Glu-Cys], and cysteine) were studied in the microalga Tetraselmis suecica exposed to different cadmium concentrations for 8 d. The cadmium concentrations assayed were 3, 7.9, 15, and 30 mg/L. Contents of thiol compounds synthesized by this microalga changed with cadmium concentration and with time of exposure. Cysteine concentrations increased significantly compared with those of γ-Glu-Cys and glutathione in cultures containing 7.9, 15, and 30 mg/L. The increase in the amount of glutathione was significant only in cells exposed to the higher cadmium concentrations (15 and 30 mg/L). Nevertheless, in all the cadmium concentrations assayed, γ-Glu-Cys levels were constant. A rapid increase in phytochelatins was observed with increased cadmium concentration during the first days of culture. The type of phytochelatins (number of subunits) also was dependent on the concentration of cadmium. The rate of (γ-Glu-Cys)3-Gly accumulation was higher than those of other types of phytochelatins throughout the culture in cells exposed to 3, 15, and 30 mg/L. However, in cultures treated with 7.9 mg/L, (γ-Glu-Cys)4-Gly increased substantially after 8 d of culture, exceeding the amount of (γ-Glu-Cys)3-Gly. Cultures exposed to the higher cadmium concentrations (15 and 30 mg/L) showed a decrease in phytochelatins after 4 and 3 d of culture, respectively, whereas an increase in cysteine and glutathione occurred at the same time. A rapid decrease in phytochelatins also was measured when cells were placed into cadmium-free medium. This decrease is consistent with a degradation of the phytochelatins.
The use and misuse of biomarkers in ecotoxicology
Authors: Forbes Valery E. , Palmqvist Annemette , Bach Lis
Published: January 2006

Substantial efforts have been devoted to developing and applying biomarkers for use in ecotoxicology. These efforts have resulted partly from a desire for early warning indicators that respond before measurable effects on individuals and populations occur and partly as an aid to identifying the causes of observed population- and community-level effects. Whereas older biomarkers focused on measures of organism physiology or biochemistry, advances in molecular biology are extending the biomarker philosophy to the level of the genes (i.e., ecotoxicogenomics). However, the extent to which biomarkers are able to provide unambiguous and ecologically relevant indicators of exposure to or effects of toxicants remains highly controversial. In the present paper, we briefly discuss the application of biomarkers in ecotoxicology and ecological risk assessment, and we provide examples of how they have been applied. We conclude that although biomarkers can be helpful for gaining insight regarding the mechanisms causing observed effects of chemicals on whole-organism performance and may, in some cases, provide useful indicators of exposure, individual biomarker responses should not be expected to provide useful predictions of relevant ecological effects—and probably not even predictions of whole-organism effects. Suites of biomarkers are only likely to provide increased predictability if they can be used in a comprehensive mechanistic model that integrates them into a measure of fitness. Until this can be achieved, biomarkers may be useful for hypothesis generation in carefully controlled experiments. However, because the aims of environmental monitoring and ecological risk assessment are to detect and/or predict adverse chemical impacts on populations, communities, and ecosystems, we should be focusing our efforts on improving methods to do this directly. This will involve developing and testing models of appropriate complexity that can describe real-world systems at multiple scales.
Effects of atrazine and iridovirus infection on survival and life-history traits of the long-toed salamander (Ambystoma macrodactylum)
Authors: Forson Diane , Storfer Andrew
Published: January 2006

Environmental contaminants and emerging infectious diseases are implicated as factors contributing to global amphibian declines. However, few studies have tested the interaction of these factors. We exposed six-week-old, larval long-toed salamanders (Ambystoma macrodactylum) to Ambystoma tigrinum virus (ATV; 0 or 103.5 plaque-forming units/ml) and sublethal concentrations of atrazine (0, 1.84, 18.4, and 184 μg/L) in a 4 × 2 factorial design for 30 d. We tested the effects of atrazine and virus on mass and snout-vent length (SVL) at metamorphosis and larval period as well as on rates of mortality and viral infectivity. We confirmed ATV transmission to A. macrodactylum via polymerase chain reaction, but infection rates were lower than expected, consistent with the theory predicting lower pathogen transmission to nonnative hosts. Larvae exposed to both atrazine and ATV had lower levels of mortality and ATV infectivity compared to larvae exposed to virus alone, suggesting atrazine may compromise virus efficacy. The highest atrazine level (184 μg/L) accelerated metamorphosis and reduced mass and SVL at metamorphosis significantly relative to controls. Exposure to ATV also significantly reduced SVL at metamorphosis. The present study suggests moderate concentrations of atrazine may ameliorate effects of ATV on long-toed salamanders, whereas higher concentrations initiate metamorphosis at a smaller size, with potential negative consequences to fitness.
Subcellular cadmium distribution, accumulation, and toxicity in a predatory gastropod,Thais clavigera, fed different prey
Authors: Cheung Ma-Shan , Fok Edmond M. W. , Ng Tania Y.-T. , Yen Yu-Fong , Wang Wen-Xiong
Published: January 2006

Bioaccumulation and toxicity of Cd were investigated in a marine predatory whelk, Thais clavigera, after being fed with the rock oyster, Saccostrea cucullata, or the herbivorous snail, Monodonta labio, for up to four weeks. The oysters and snails had different subcellular Cd distributions and concentrations in their bodies given their different metal-handling strategies and were exposed to dissolved Cd for two weeks before being fed to the whelks. After four weeks of dietary exposure, the Cd body concentrations in T. clavigera increased from 3.1 μg/g to between 22.9 and 41.8 μg/g and to between 22.7 and 24.1 μg/g when they were fed with oyster and snail prey, respectively. An increasing proportion of Cd was found to be distributed in the metallothionein (MT)-like proteins and organelle fractions, whereas the relative distribution in the metal-rich granules fraction decreased when the whelks were fed Cd-exposed prey. At the highest Cd dosage, more Cd was distributed in the pool of metal-rich granules when the whelks were fed the oysters than when they were fed the snails. Among all the biomarkers measured (MT induction, condition index, lipid peroxidation, and total energy reserve including carbohydrate, lipid, and protein), only MT showed a significant difference from the control treatments, and MT was the most sensitive biomarker for dietary Cd exposure. No toxicity was found in the whelks fed different Cd-exposed prey as revealed by various biomarkers at the different biological levels. Our results imply that metal fractionation in prey can alter the subsequent subcellular metal distribution in predators and that dietary Cd toxicity to the whelks was low, even when the accumulated Cd body concentrations were high.
Population growth and development of the earthwormLumbricus rubellusin a polluted field soil: Possible consequences for the godwit (Limosa limosa)
Authors: Klok Chris , van der Hout Annemariet , Bodt Jos
Published: January 2006

Many soils are polluted with mixtures of moderate levels of contaminants. In The Netherlands 175,000 sites in rural areas are classified as highly polluted. However, it remains unclear to what extent local ecosystems are endangered. In this paper, we report on the effect of contaminants on earthworms in a meadow system. We tested a polluted and a reference field soil with similar soil characteristics and agricultural use. In the polluted soil copper, mercury, and lead were elevated by more than 200% compared with the reference soil. Bioassays on growth and reproduction in the earthworm species Lumbricus rubellus were executed in both soils, and a population model was used to assess the population-level consequences of changes in growth and reproduction. No significant effects were seen on reproduction and survival in L. rubellus, but development was retarded in the polluted soil. This resulted in a 23% lower growth rate and a change in demography toward younger individuals. Field data on population composition of earthworms were used to support the laboratory results, and the relevance of the results for the godwit (Limosa limosa), which mainly feeds on earthworms during the breeding season, is discussed.
Evaluation of a predictive model for air/surface adsorption equilibrium constants and enthalpies
Authors: Arp Hans Peter H. , Goss Kai-Uwe , Schwarzenbach René P.
Published: January 2006

A model used to predict equilibrium adsorption to surfaces using a poly-parameter linear free-energy relationship as well as an empirical model used to predict enthalpies of adsorption of volatile compounds were evaluated with new experimental data to cover semivolatile compounds and a larger variability of compound classes. Equilibrium adsorption constants on a quartz surface ranging over seven orders of magnitude were measured for 142 compounds, and enthalpies of adsorption on a quartz surface from −33.7 to −99.8 kJ/mol were measured for 76 compounds. Agreement between experimental and predicted data was within a factor of two (82.1%) or three (100.0%) for the equilibrium adsorption constants and within 20% for the enthalpy of adsorption values. Thus, the scatter in the validation data sets reported here were practically the same as that for the calibration data sets used to derive the models. The few outliers that we identified in the prediction of equilibrium adsorption constants likely are caused by either shortcomings of the reported sorbate parameters or the occurrence of chemical speciation in the water layer on the surface of the quartz.
Acid exposure is an immune disruptor in adult Rana pipiens
Authors: Vatnick Itzick , Andrews Jaime , Colombo Matthew , Madhoun Hareth , Rameswaran Muthuramanan , Brodkin Marc A.
Published: January 2006

Acidic environments are physiological stressors for amphibians. The objective of the present study was to document the effect of an acidic environment on innate immune system function under controlled experimental conditions in Rana pipiens. We developed an in vivo assay, by injecting a suspension of 1-μm fluorescent beads in fluid thioglycollate, to induce peritonitis. The number of peritoneal exudate leukocytes and their phagocytic activity did not increase with thioglycollate injection when frogs were exposed to pH 5.5 compared to when frogs were exposed to pH 7.0. An environment of pH 5.5 disrupted the inflammatory response of frogs compared to an environment of pH 7.0; at pH 5.5, more nonphagocytic leukocytes and fewer highly phagocytic leukocytes were found compared to those in frogs exposed to pH 7.0. Frogs stimulated by thioglycollate injection and exposed to pH 5.5 had a 50% increase in cells that did not exhibit phagocytosis and a 4- to 10-fold reduction in the number of highly phagocytic cells. This is evidence that acid exposure functions as an immune disruptor in adult R. pipiens under laboratory conditions.
Boron Fertilization Influences on Soybean Yield and Leaf and Seed Boron Concentrations
Authors: Ross Joni R. , Slaton Nathan A. , Brye Kristofor R. , DeLong Russell E.
Published: January 2006

Soybean [Glycine max (Merr.) L.] is considered relatively insensitive to B deficiency. However, B deficiency has recently become a common nutrient deficiency of soybean in northeast Arkansas. Field studies were conducted on four alkaline silt‐loam soils in northeast Arkansas to determine the influence of B application time and rate on soybean growth, tissue B concentration, and seed yield. Boron fertilizer was applied at 0, 0.28, 0.56, 1.12, and 2.24 kg B ha−1 near the V2 or R2 growth stages. Boron fertilization had no significant effect on soybean yield at one site but increased seed yields from 4 to 130% at three sites. At the most responsive site, B application at V2 increased yields by 13% compared with applications at R2. In contrast, at a site where leaf B concentrations were sufficient for soybean receiving no B, B applied at the R2 stage significantly increased seed yields by 5% compared with V2 B applications. Trifoliate leaf B concentrations at the R2 stage increased as B rate increased. Seed B concentrations also increased as B rate increased. Boron applied at the R2 stage resulted in equal or greater seed B concentrations than B applied at the V2 stage. Application of 0.28 to 1.12 kg B ha−1 during early vegetative or reproductive growth was sufficient to produce near maximal yields. The expected severity of B deficiency plus fertilizer and application costs associated with B fertilization should be considered when selecting the most appropriate B fertilization strategy.
Potential Interaction of Pendimethalin and Systemic Insecticides for Thrips Control in Cotton
Authors: Grey Timothy L. , Buntin G. David , Roberts Phillip M. , Bridges David C.
Published: January 2006

Pendimethalin (N‐(1‐ethylpropyl)‐3,4‐dimethyl‐2,6‐dinitrobenzenamine) can be preemergence (PRE) applied to cotton (Gossypium hirsutum L.) up to 2 d after planting (DAP). Delayed application in combination with excessive moisture (rainfall or irrigation) can result in seedling injury. The systemic insecticides aldicarb [(2‐methyl‐2‐(methylthio)propanal O‐[(methylamino)carbonyl]oxime] and imidacloprid [(EZ)‐1‐(6‐chloro‐3‐pyridylmethyl)‐N‐nitroimidazolidin‐2‐ylideneamine] are used at planting for thrips (Frankliniella fusca Hinds) control. Experiments were conducted in Georgia to determine if pendimethalin injury to cotton would reduce insecticide efficacy and thus lead to increased thrips injury and subsequent reduced cotton growth or delayed maturity. Treatments included three insecticide treatments; none, imidacloprid at 0.044 kg ha−1 a.i., and aldicarb 15G at 0.8 kg ha−1 a.i., in combination with five herbicide applications; none and pendimethalin at 1.1 and 2.2 kg ha−1 a.i. applied either PRE or 2 DAP. Variables measured included thrips infestation, stand count, leaf area, root length, stem length, dry weights, nodes above white flower, first position boll retention, and seed cotton yield. Results indicate significant differences in early season cotton growth relative to herbicidal injury and lack of insecticidal thrips control. However, there was no significant insecticide × herbicide interactions, indicating no apparent loss of insecticide efficacy after pendimethalin injury.
Micro‐Basin Tillage for Grain Sorghum Production in Semiarid Areas of Northern Ethiopia
Authors: Brhane Gebreyesus , Wortmann Charles S. , Mamo Martha , Gebrekidan Heluf , Belay Amare
Published: January 2006

The yield of grain sorghum (Sorghum bicolor L. Moench) and other crops is often constrained by soil water deficits in semiarid areas of Ethiopia. The effectiveness of micro‐basin tillage, in the form of tied‐ridging, was evaluated as a means of improving soil water availability through reduced runoff and to increase grain and stover yield. Field research was conducted on a clay soil with vertic properties (Typic Pellustert) in northern Ethiopia in 2003 and 2004. Tied‐ridging conducted before planting, at planting, and after planting was compared with planting on a flat soil surface without ridging and with a traditional ridging practice known as shilshalo Planting in‐furrow was compared with planting on‐ridge. Tied‐ridging before or at planting resulted in the best soil water status throughout the season and the best crop performance, especially when planting was in‐furrow. Mean soil water content with the most effective tied‐ridge treatment was on average 42% and 49% more than with flat tillage and planting in 2003 and 2004, respectively. Overall crop performance was generally worst for flat soil surface planting and for the shilshalo treatment, where the respective grain yield was 45% and 62% of yield with in‐furrow planting, respectively. Soil water availability in the 0‐ to 0.90‐m soil depth dropped below the permanent wilting point for all treatments before the grain was physiologically mature. Yield can be increased by tied‐ridging before or at planting. The results indicate that mean yield can be improved by planting with the onset of the rains.