Short-Term Effects of Arsenate-Induced Toxicity on Growth, Chlorophyll and Carotenoid Contents, and Total Content of Phenolic Compounds of Azolla filiculoides

This study evaluated the toxic effects of arsenic (As) on the growth, total antioxidant activity, total content of phenolic compounds, and content of photosynthetic pigments of Azolla filiculoides. The aquatic fern was propagated and exposed to Yoshida nutrient solution contaminated with sodium arsenate (Na₂HAsO₄??7H₂O) at six concentrations (5, 10, 20, 30, 60, and 120???g?As?mL^?1), including the control without As contamination. Azolla cultures were kept under environmental chamber conditions?26??C, 12?h photoperiod and 80% HR for 96?h. Increased As concentrations (>30???g?mL^?1) significantly diminished growth of A. filiculoides and the total content of chlorophyll and total phenolic compounds, but significantly enhanced of total carotenoid?+?xanthophylls content. The concentrations of 5 and 10???g?As?mL^?1 significantly stimulated the growth of A. filiculoides. This aquatic fern tolerates As concentrations lower than 30???g?mL^?1, and its maximum As accumulation (28???g?g^?1 dry weight) was achieved when exposed to 60???g As mL^?1, but showing clear symptoms of As toxicity.     

Effects of a Simulated Agricultural Runoff Event on Sediment Toxicity in a Managed Backwater Wetland

We examined the effects of an amended mixture of three pesticides, atrazine (72.7?g), S-metolachlor (54.5?g), and permethrin (both cis and trans isomers; 11.4?g), on 10-day sediment toxicity to Hyalella azteca in a managed natural backwater wetland after a simulated agricultural runoff event. Sediment samples were collected at 10, 40, 100, 300, and 500?m from inflow 13?days prior to amendment and 1, 5, 12, 22, and 36?days post-amendment. Background pesticide concentrations ranged from <1 to 977, <1 to 119, and <1 to 2???g?kg^?1, for atrazine, S-metolachlor, and permethrin, respectively. Average post-amendment atrazine and S-metolachlor were 2,915?C3,927 and 3?C20???g?kg^?1, respectively at 10?C40?m and 538?C872 and <1???g?kg^?1, respectively at 300?C500?m. Average post-amendment permethrin was 65?C200???g?kg^?1 at 10?C40?m and 1?C10???g?kg^?1 at 300?C500?m. H. azteca 10-day survival varied spatially and temporally up to 100?m from inflow. Animal growth, independent of survival, was reduced 40 and 100?m from inflow on day?36, showing continued sediment toxicity of up to 100?m from inflow more than 1?month after amendment. Animal survival and growth were unaffected at 300 and 500?m from inflow throughout the study period. Correlations of pesticide concentrations and H. azteca responses indicated that observed sediment toxicity was primarily from permethrin with potential additional synergistic toxicity from atrazine and methyl parathion. Study results indicate that natural backwater wetlands can be managed to ameliorate pesticide mixture 10-day sediment toxicity to H. azteca within 300?m of inflow and smaller wetlands (??100?m) may require several months of effluent retention to mitigate effects.     

Aerobic Biological Treatment of Chestnut Processing Wastewater

Chestnut agro-industrial companies consume a high volume of water for washing and processing fruit, generating a large volume of wastewater. This work studied the biodegradation of chestnut processing wastewater through aerobic assays, varying substrate, and biomass concentrations. In general, this wastewater presents a good biodegradability, especially in experiments with relatively low chemical oxygen demand (COD) (0.4 and 0.6?g O₂ L^?1) allowing a COD removal of 85?C90?%. The best results were obtained in the reactor initially loaded with 2?g?L^?1 of biomass and 0.4 or 0.6?g O₂ L^?1 of COD. These experiments also showed high COD removal rates: 4.25 and 3.88?g COD g^?1 volatile suspended solids (VSS) h^?1, respectively. The sedimentation rate, evaluated for different initial values of biomass (1, 2, and 3?g?L^?1), always presented higher values in the experiments with 2 and 3?g?L^?1 of biomass, regardless of the initial COD value used. After comparing different kinetic models (Monod, Contois, and Haldane), it was observed that the Haldane inhibition model satisfactorily describes the COD biodegradation. AQUASIM software allowed calculating the kinetic constant ranges: K _s, 1.59?C6.99?g COD L^?1; ?? _max, 25?C40?g COD g^?1 VSS day^?1; and K _i values, 0.07?C0.11. These kinetic constants corresponds to maximum rates (??*) between 1.48 and 4.25?g COD g^?1 VSS day^?1 for substrate concentrations (S*) from 0.38 to 0.88?g COD L^?1.     

Polybrominated Diphenyl Ether Dynamics in Ambient Air and Atmospheric Bulk/Wet Deposition in Downtown Paris (France)

This study reports on the polybrominated diphenyl ether (PBDE) atmospheric dynamics in the dense urban environment of downtown Paris (France). Eight PBDE congeners (BDE-28, BDE-47, BDE-100, BDE-99, BDE-154, BDE-153, BDE-183 and BDE-209) were simultaneously analysed in bulk and wet atmospheric deposition, as well as in ambient air (gaseous/particulate phases), twice a month over a 12-month period (May 2008–May 2009). The total air concentration of Σ 8PBDEs ranged between 12 and 185 pg m⁻³, and the seasonal variations of PBDE levels were controlled by air temperature (except for BDE-209). Regarding bulk deposition, Σ 8PBDE flux was in the range 5–94 ng m⁻² day⁻¹, and it was positively correlated with atmospheric particulate phase PBDE concentrations. Meanwhile, the measured wet deposition flux of Σ 8PBDE ranged between 2 and 24 ng m⁻² day⁻¹, and its median contribution to bulk deposition was 39% only, which highlights the importance of dry deposition.     

Characterization of AMD Pollution in the River Tinto (SW Spain). Geochemical Comparison Between Generating Source and Receiving Environment

With the aim of obtaining precise knowledge of the spatial?Ctemporal behavior of the chemistry of the river Tinto, both in the area of the headwaters, close to the point at which the acid mine drainage (AMD) pollution is carried into this river, and in the area before tidal influence, daily sampling was carried out from the end of October 2007 to the beginning of June 2008. In addition to pH, conductivity, and redox potential, sulfates, As, Cd, Fe, Cu, Zn, and Mn were determined for each sample. By studying the results obtained from the statistical processing applied, it can be deduced, first and foremost, that the river Tinto is a watercourse which is highly polluted by acid mine drainage throughout its length. It can also be determined that the order of abundance of the polluting elements, in terms of the concentration of the various parameters in milligrams per liter, follows the pattern, both in the generating source and the receiving environment: SO₄ > Fe > Cu > Zn > Mn > Cd > As. The concentration values for As carried into the river in the generating source, with average values of 640???g?l^?1 and with a maximum of 1,540???g?l^?1 (ten times greater than the maximum found in the receiving environment), far exceed 10???g?l^?1, the value established by the EU as the maximum permissible concentration in drinking water, as a consequence of the high eco-toxicity of this element. Specifically, in the correlation matrix, no correlation was found between the variables for both points. It can only be made out in the cross-correlation function graphs through low correlation, prior to time t?=?0, that pollution in the generating source leads to pollution in the receiving environment.     

Influence of a Marine Diatom on the Embryonic Toxicity of 17α-Ethynylestradiol to the Abalone Haliotis diversicolor supertexta

The embryos of a marine abalone, Haliotis diversicolor supertexta, were exposed to a typical environmental estrogen, 17??-ethynylestradiol (EE2), for 96?h, to examine the acute toxicity of EE2 to the embryogenesis of the abalone. A marine diatom, Navicula incerta, was used in the test media as settlement substrate and food for the abalone larvae. During the embryo culture, more than 30?% of EE2 could be removed from the test media by the diatom, mainly via biodegradation, leading to a decrease of water-borne exposure dose. Further, the exposure concentrations of EE2 around the living microenvironment of the abalone larvae could be magnified 350?C468 times after the larvae settled on the diatom, as indicated by the bioconcentration factors of EE2 in the diatom. Increased bioaccumulation of EE2 in the diatom caused greater inhibition on the metamorphosis of the abalone larvae by enhancing the uptake of EE2 in the larvae via dietary exposure, while declined water-borne exposure dose did not affect the embryonic toxicity of EE2 and its uptake in the abalone larvae. The 96-h median effective concentration of EE2 to the metamorphosis of the abalone larvae was 10.01???g?L^?1, when the exposure doses in both the test media and the diatom were controlled stable. The 96-h hazard concentration for 5?% of the species was 1.20???g?L^?1, which was still higher than but close to the reported upper contamination level of EE2 and could be employed as the safety threshold for the metamorphosis of the abalone embryos.     

Assessing the Relative Contribution of Wastewater Treatment Plants to Levels of Metals in Receiving Waters for Catchment Management

The selection of control measures for reducing metal contamination in rivers has targeted point sources such as wastewater treatment plants (WWTPs) and industrial discharges without a proper evaluation of their relative contribution to metal loads at the catchment level. The necessity of controlling pollutant inputs in a sound and cost-effective way to prevent the deterioration of chemical and ecological quality of receiving waters has highlighted the need for appropriate source assessment. As metals in rivers emanate from a wide range of sources, it is necessary to understand their relative contribution in order to reduce effectively the concentrations in receiving waters. This study presents a simple method for calculating the relative contribution of WWTPs to levels of metals in receiving waters as applied to the Aire?CCalder catchment in the UK. In this catchment, the apportionments to WWTP effluents of metal levels in rivers were 37, 31, 36 and 60?% of total cadmium (Cd), lead (Pb), mercury (Hg) and nickel (Ni), respectively. Spatial metal distribution in rivers with maximum concentrations of 0.47???g?L^?1 for Cd, 8.54???g?L^?1 for Pb, 0.05???g?L^?1 for Hg and 10.17???g?L^?1 for Ni caused by the discharge of WWTP effluents was estimated. The findings demonstrate that the proposed approach using quantification of metal loads and estimation of concentrations in receiving waters could adequately calculate the relative contribution of WWTP effluents to metal levels in receiving waters. Applications to various river catchments using site-specific data would further validate the effectiveness of the approach proposed.     

Can Phosphate Help Acidified Lakes to Recover?

Experimental addition of phosphate to enclosures in an acidified lake in Southern Norway was performed to study the effect on nitrate, pH and labile aluminium along a gradient of phosphate from 4–19 µg P L^?1. Nitrate decreased from 180 µg L^?1 to below detection limit after three weeks at P-concentrations > 17 µg L^?1, due to phytoplankton uptake. pH increased from 4.9 to 5.2, corresponding to a 50% decrease of H⁺-equivalents from 12 to 6 µg P L^?1 due to algal uptake of H⁺-ions when assimilating NO₃ ^?-ions. Due to the increased pH and probably also precipitation with phosphate, concentrations of labile aluminium decreased from 150 to 100 µg L^?1 within the P-interval 4–19 µg L^?1. Algal biomass increased from 0.5 to 6 µg chlorophyll a L^?1 along the same P-gradient. The results suggest that moderate P-addition (< 15 µg P L^?1 to avoid eutrophication problems) can improve water quality in moderately acidified lakes, and also increase nitrate retention in strongly acidified lakes. In humic lakes, the treatment will be less efficient due to light limitation of primary production and the presence of organic acids.     

The Determination of Ozone in Ambient Air with Free Hanging Filters as Passive Samplers

This paper describes the use of dry free hanging filters, as passive samplers to determine ozone in the ambient air. The filters, with a diameter of 25?mm, were impregnated with 5,5??-disodium indigo disulphonate (IDS), a reagent for ozone. From the amount of reacted indigo compound, found on the filter, and the ozone concentration in the ambient air, a pseudo rate constant k ₁, of the reaction between ozone (O₃) and IDS on the filter, is calculated. The range of measurement is between 9 and 205???g/m³ ambient ozone. The dry filter method is specific for ozone, while the Dutch standard method NEN2789, based on an aqueous solution of IDS, has to be corrected for the presence of NO _x . From wind tunnel and field experiments, k ₁ proved to vary between 0.7 and 1.5?×?10^?6?m³?s^?1 (??g O₃)^?1 at wind velocities between 1 and 3?m/s and at an exposure time of 60?min. Within these conditions, ozone concentrations have been determined with free hanging filters in four busy streets in Yogyakarta, Indonesia and at two background sites using an average value of k ₁ of 1.2?×?10^?6. Subsequently, the traffic NO emission was estimated from the difference of the O₃ concentrations at both sides of a road. For an arbitrary situation, an NO emission of 255???g/s per metre road length was calculated. The filter method is inexpensive and practical, needs no electricity, is easily assembled and can be used to perform measurements in remote areas. It is shown here that this simple measurement technique may support air quality studies, e.g., in developing countries.     

Adsorption Kinetics of 2,2′,4,4′-Tetrabromodiphenyl Ether(BDE-47) on Maize Straw-Derived Biochars

The chars in the natural environment can affect the migration of polybrominated diphenyl ethers(PBDEs). However, there is insufficient research relating to the adsorption behavior and mechanisms of PBDEs on biochars. This study examined the adsorption kinetics of 2,2′,4,4′-tetrabromodiphenyl ether(BDE-47) on maize straw-derived biochars(MSBCs) pyrolyzed at four different temperatures via batch experiments. The biochar samples were characterized using Fourier transform infrared(FTIR) spectroscopy,Raman spectra, and elemental analysis. A two-compartment first-order model and pseudo-second-order model exhibited a better fit compared to a pseudo-first-order model in describing the BDE-47 adsorption on biochars, which was dominated by a slow adsorption compartment and chemisorption. The MSBC pyrolyzed at 600 °C had the highest BDE-47 adsorption capacity owing to its relatively large specific surface area and relatively high aromaticity compared with the other three MSBCs pyrolyzed at 300, 400, and 500 ℃.However, there was no significant difference in adsorption capacity among the other three biochars. The organic functional groups coupled with the graphene structures of biochars and the hydrophobic effect of the functional groups promoted the adsorption of BDE-47. Pore diffusion was not the sole rate-limiting step; film diffusion was also involved in the adsorption process of BDE-47 on biochars. The overall results demonstrate the transport and potential treatment of PBDEs using biochars.     

Polybrominated Diphenyl Ethers Mobility in Biosolids-Amended Soils Using Leaching Column Tests

Leaching column tests were conducted to determine the mobility of polybrominated diphenyl ethers (PBDEs) in biosolids-amended soils. Deionized water was introduced from the bottom of a glass leaching column containing a 14-mm layer of biosolids-amended soils (210 g) under 42 mm of agricultural soil (600 g). After 4 weeks of leaching, 3.75 L of deionized water had passed through the 210-g biosolids?Csoil layer and 600 g soil, corresponding to 34 volumes of the leachate per volume of solid. The agricultural soil was divided into three 14-mm layers to determine the PBDE distribution along the flow path of the infiltrating water. PBDEs were found to leach from the biosolids-amended soils layer and migrate through the soil. The predominant congeners BDE47, 85, 99, 100, 153, 154, 183, and 209 decreased to 3?C98% of their initial concentrations in the biosolids-amended soil, whereas the total concentration of these eight congeners decreased by 38%. PBDE concentrations in the first 14-mm soil layer increased from not detected (nd) to up to 234?×?10³ pg/g dry weight basis (dw). Concentrations in the second and third soil layers increased from nd to 20 and 25 pg/g dw. PBDE in the leachate increased from nd to 310?×?10³ pg/L. Mobilization of PBDEs is likely associated with dissolved organic matter and colloids in the infiltrating water.     

Variation of Antioxidant Activity in Dreissena polymorpha Specimens Exposed to 2,2′,4,4′,5,6′-Hexa BDE (BDE-154)

We evaluated the imbalance of the oxidative status in zebra mussel (Dreissena polymorpha) specimens exposed for 96?h to environmentally relevant concentrations (0.1, 0.5, and 1???g/L) of the 2,2??,4,4??,5,6??-hexa BDE (BDE-154). The activities of three antioxidant enzymes, catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), and the phase II detoxifying enzyme glutathione S-transferase (GST), were measured in the cytosolic fraction from a pool of zebra mussels. Significant variations in the activity of each single enzyme were noticed at each treatment, indicating that exposure to BDE-154 was able to impair the oxidative status of treated bivalves through the increase of reactive oxygen species. In detail, SOD and GPx were significantly induced, while CAT and GST were depressed with respect to the baseline levels. These data have confirmed that the raise of oxidative stress is the main cause of the BDE-154-induced genetic damage observed in a previous study on the zebra mussel.     

Toxicity of Benzalkonium Chloride on Monoalgal Cultures and Natural Assemblages of Marine Phytoplankton

The current widespread use of benzalkonium chloride (BAC) in different cleaning and disinfecting products led us to investigate its potential toxic effect on phytoplankton. To this aim, different physiological variables were monitored to detect toxicity of four ecologically relevant concentrations of BAC (15–200 μg l^?1) on batch cultures of the microalgae Isochrysis galbana and Chaetoceros gracilis, and on a coastal phytoplankton assemblage. Fluorescence variables measured by fast repetition rate fluorometry, specifically variable fluorescence (F _v), were the most suitable to be used as endpoint among all the variables recorded (biomass, growth rate, size structure, and species composition). Calculated effective concentrations from F _v data provided evidences of higher sensitivity in the natural assemblage at short exposure times (natural assemblage—EC₅₀ [24 h]?=?36.4 μg l^?1 vs. monoalgae—EC₅₀ [24 h]?>?120 μg l^?1). Despite these differences, standard monoalgal laboratory toxicity tests provided comparable estimates of safe concentrations for microalgae in the environment. Assessed EC₁₀ fall within the range of BAC concentrations reported in the literature for different effluents.

     

Insecticide (Carbaryl, 1-napthyl-N-methylcarbamate) effects on a freshwater plankton community: Zooplankton size,biomass, and algal abundance

Natural plankton communities were enclosed in mesocosms and exposed to nine dose levels (0 to 100 μg L^?1) of the insecticide Carbaryl. Plankton responses were determined after 4 day in situ incubations. Total Zooplankton biomass and mean individual biomass declined significantly across the range of treatments. Daphnia were not found at concentrations above 20 μg L^?1 and all cladocerans were absent at > 50 μg L^?1 Carbaryl. In the higher dose treatment, copepods (Skistodiaptomus and Mesocyclops) became extreme dominants. The decline in Zooplankton biomass, and the selective elimination of Daphnia led to increases in algal biomass, especially among small flagellates which are unavailable to the raptorial copepods. Across the range of insecticide dose levels, there was a repartitioning of biomass from Zooplankton to phytoplankton, while total plankton biomass was unchanged.     

Long-Term Annual and Seasonal Patterns of Acidic Deposition and Stream Water Quality in a Great Smoky Mountains High-Elevation Watershed

The recovery potential of stream acidification from years of acidic deposition is dependent on biogeochemical processes and varies among different acid-sensitive regions. Studies that investigate long-term trends and seasonal variability of stream chemistry in the context of atmospheric deposition and watershed setting provide crucial assessments on governing biogeochemical processes. In this study, water chemistries were investigated in Noland Divide watershed (NDW), a high-elevation watershed in the Great Smoky Mountains National Park (GRSM) of the southern Appalachian region. Monitoring data from 1991 to 2007 for deposition and stream water chemistries were statistically analyzed for long-term trends and seasonal patterns by using Seasonal Kendall Tau tests. Precipitation declined over this study period, where throughfall (TF) declined significantly by 5.76?cm?year^?1. Precipitation patterns play a key role in the fate and transport of acid pollutants. On a monthly volume-weighted basis, pH of TF and wet deposition, and stream water did not significantly change over time remaining around 4.3, 4.7, and 5.8, respectively. Per NDW area, TF SO₄ ^2- flux declined 356.16?eq?year^?1 and SO₄ ^2- concentrations did not change significantly over time. Stream SO₄ ^2- remained about 30???eq L^?1 exhibiting no long-term trends or seasonal patterns. SO₄ ^2- retention was generally greater during drier months. TF monthly volume-weighted NH₄ ⁺ and NO₃ ^- concentrations significantly increased by 0.80???eq L^?1?year^?1 and 1.24???eq L^?1?year^?1, respectively. TF NH₄ ⁺ fluxes increased by 95.76?eq?year^?1. Most of NH₄ ⁺ was retained in the watershed, and NO₃ ^- retention was much lower than NH₄ ⁺. Stream monthly volume-weighted NO₃ ^- concentrations and fluxes significantly declined by 0.56???eq L^?1?year^?1 and 139.56?eq?year^?1, respectively. Overall, in NDW, inorganic nitrogen was exported before 1999 and retained since then, presumably from forest regrowth after Frazer fir die-off in the 1970s from balsam wooly adelgid infestation. Stream export of NO₃ ^- was greater during winter than summer months. During the period from 1999 to 2007, stream base cations did not exhibit significant changes, apparently regulated by soil supply. Statistical models predicting stream pH, ANC, SO₄ ^2-, and NO₃ ^- concentrations were largely correlated with stream discharge and number of dry days between precipitation events and SO₄ ^2- deposition. Dependent on precipitation, governing biogeochemical processes in NDW appear to be SO₄ ^2- adsorption, nitrification, and NO₃ ^- forest uptake. This study provided essential information to aid the GRSM management for developing predictive models of the future water quality and potential impacts from climate change.     

Plasma B-esterase and Glutathione S-transferase Activities in the South American Reptiles Caiman latirostris (Crocodylia, Alligatoridae) and Phrynops hilarii (Testudines, Chelidae)

We determined normal plasma butyrylcholinesterase (BChE), carboxylesterase (CbE using ??-NA substrate), and glutathione S-transferase (GST) activities in Caiman latirostris and Phrynops hilarii to obtain reference values for organophosphorus (OP) pesticide monitoring. BChE and CbE sensitivity to malaoxon was also evaluated. C. latirostris (N?=?12; six males and six females) and P. hilarii (N?=?12; seven males and five females) were obtained from the programs Yacaré (Entre Ríos Province, Argentina) and Zoo of Córdoba (Córdoba Province, Argentina). Mean total (female and male) plasma BChE activity was significantly different between reptile species, ranging between 0.337?±?0.085???mol?min^?1?ml^?1 of plasma for C. latirostris and 0.251?±?0.070???mol?min^?1?ml^?1 of plasma for P. hilarii. However, plasma CbE (??-NA) and GST activities were significantly higher in P. hilarii (4.81?±?1.00 and 0.145?±?0.045???mol?min^?1?ml^?1 of plasma, respectively) than in C. latirostris (0.57?±?0.20 and 0.059?±?0.013???mol?min^?1?ml^?1 of plasma, respectively). No significant differences in B-esterase and GST activities were detected between sexes, except CbE (??-NA) for C. latirostris. IC₅₀ values for BChE and CbE (??-NA) suggested different sensitivity levels between species and between sexes. The results demonstrate that plasma esterase activity varied between species, but not between sexes (except CbE for C. latirostris). The in vitro inhibition tests indicated that CbE (??-NA) is more sensitive to inhibition than BChE. C. latirostris may be the reptile species most vulnerable to field pesticide exposure because this reptile presents the lowest CbE activity levels and its B-esterase levels seem more sensitive to OP.     

Sorption and Desorption Processes of Selenium (VI) Using Non-Living Biomasses of Aquatic Weeds in Horizontal Flow

The sorption and desorption processes of Se(VI) onto non-living Eichhornia crassipes (E. crassipes) and Lemna minor (L. minor) were evaluated. Different pH values of the initial Se solution (20???g?L^?1) were tested at static conditions. At dynamic conditions of horizontal flow, biomass-packed columns (BPC) were estimated as prepared (pH 4) and unprepared (pH 6?C7) and at different flow rates. The desorption process was tested using HCl (0.1?M) as the eluent. The maximum Se uptake took place at a pH of 4 for both biomasses. The lowest flow rate improves major Se removal due to the increase in contact time. The Se was desorbed from the biomass with elution efficiencies of 5 and 18?% for E. crassipes and L. minor, respectively. Nevertheless, more time was needed to increase these efficiencies and reach desaturation times. The breakthrough curves showed that unprepared E. crassipes and L. minor BPC at horizontal flow, with a flow rate of 6 and 4?mL?min^?1 respectively, had a biomass removal capacity of 0.135 and 0.743???g?g^?1 correspondingly. The system of E. crassipes is more efficient, suggesting an ion exchange sorption mechanism. This demonstrates that non-living E. crassipes and L. minor have the capacity to remove Se from very dilute solutions.     

Extraction and speciation analysis of roxarsone and its metabolites from soils with different physicochemical properties

Purpose

The application of roxarsone (ROX), an arsenic-containing compound, as a feed additive in the animal production industry results in elevated soil levels of ROX and its metabolites, namely, monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), arsenate (As(V)), and arsenite (As(III)). This study was conducted to study the extraction and speciation analysis of ROX-related arsenicals in soils with different physicochemical properties and the possible effects of soil properties on the extraction of ROX and its metabolites.

Materials and methods

Analytical method based on high-performance liquid chromatography (HPLC)-inductively coupled plasma–mass spectrometry (ICP-MS) was employed to determine the concentrations of As(III), DMA, MMA, As(V), and ROX extracted by different extraction solvents from different soils spiked by arsenicals. Validity of the developed method was assessed by the recovery efficiencies of arsenic species in soil-dissolved matter solutions containing 20 μg As?·?L^?1 of each arsenic species. Effects of soil properties on the extraction of ROX and its metabolites were analyzed by Pearson’s correlation.

Results and discussion

Arsenic species were separated using gradient elution of water and 20 mmol?·?L^?1 (NH₄)₂HPO₄ + 20 mmol?·?L^?1 NH₄NO₃ + 5 % methanol (v/v) within 27 min. The linear ranges of all arsenicals were 0–200 μg As?·?L^?1 with R ²?>?0.9996. The developed method provided lower limits of detection for As(III), DMA, MMA, As(V), and ROX (0.80, 0.58, 0.35, 0.24, and 1.52 μg As?·?L^?1, respectively) and excellent recoveries (92.52–102.2 %) for all five species. Arsenic speciation was not altered by 0.1 mol?·?L^?1 NaH₂PO₄ + 0.1 mol?·?L^?1 H₃PO₄ (9:1, v/v), which offered better average extraction efficiencies for As(III), As(V), DMA, MMA, and ROX (32.49, 92.50, 78.24, 77.64, and 84.54 %, respectively). Extraction performance of arsenicals was influenced by soil properties, including pH, cation exchange capacity (CEC), total Fe, and amorphous Fe.

Conclusions

ROX and its metabolites from soils could be satisfactorily separated by the developed method for the studied arsenicals. To extract arsenic species from soils, 0.1 mol?·?L^?1 NaH₂PO₄ + 0.1 mol?·?L^?1 H₃PO₄ (9:1, v/v) was recommended. Extraction efficiencies of arsenicals were influenced more by solvent composition than soil physicochemical properties. The present study provides a valuable tool and useful information for determining the concentrations of ROX and its metabolites in contaminated soils.

     

Toxicity of uranium to Daphnia magna

The toxicity of U to Daphnia magna was determined in acute and chronic tests. The 48-hr LC₅₀ of U (VI) in Columbia River water was 6 mg L^?1. Acute toxicity diminished by a factor of 7.5 as mean water hardness and alkalinity values increased from 70 mg L^?1. and 57 mg L^?1. to 195 mg L^?1. and 130 mg L^?1. respectively. This effect was most likely the result of complexation of uranyl ion with carbonate ions. D. magna reproduction was suppressed in Columbia River water at U concentrations between 0.5 and 3.5 mg L^?1. Potential hazards of U to aquatic life are discussed as they relate to mining practices.     

Salix rubens and Salix triandra Species as Phytoremediators of Soil Contaminated with Petroleum-Derived Hydrocarbons

The petroleum industry activities provide potential risks to the environment because they can contaminate ecosystems with different organic compounds in the production chain. Several accidents with transport and handling of petroleum and related products occurred in urban areas with harmful effects to the quality of life and economy. In the 1990s, bioremediation and phytoremediation technologies as economically feasible alternatives to repair the environmental damage were developed. In this study, the potential of the willows Salix rubens and Salix triandra were evaluated with regard to the phytoremediation of soils contaminated with petroleum-derived hydrocarbons (total hydrocarbons and polycyclic aromatic hydrocarbons (PAHs)). The PAHs were quantified by extraction from soils and plants using dichloromethane under ultrasonication. The HPLC analysis was performed with GC/MSD equipment. The total hydrocarbons present in uncontaminated soil were quantified by the sum of animal/vegetable oils and greases and mineral oils and greases according to Standard Methods 5520 (1997). The two willows species S. rubens and S. triandra were resistant during the project development. In the contaminated soil, in which both species were planted, the total hydrocarbons concentration was reduced near 98?%. The PAHs content was remarkably reduced as well. Pyrene showed an initial concentration of 23.06???g?kg^?1, decreasing in most cases to 0.1???g?kg^?1 or to undetectable levels. Chrysene decreased from 126.27???g?kg^?1 to undetectable levels. Benzo[k]fluoranthene and benzo[a]pyrene concentrations had also showed a decrease from 28.44 and 3.82???g?kg^?1, respectively, to undetectable levels.