Assessment of PAHs in water and fish tissues from Great Bitter and El Temsah lakes,Suez Canal,as chemical markers of pollution sources

Sea water and fish tissue samples were collected from nine sampling stations from the Great Bitter and El Temsah lakes in the Suez Canal and analysed for polycyclic aromatic hydrocarbon (PAH). The compositions of PAH determined in the dissolved fraction of sea water were measured in order to use them as chemical markers for identifying different sources of PAH pollution in this region. PAHs determined in fish tissues were measured for comparison with human health standards as consumption. The total mean PAHs concentrations in the sea water samples ranged from 0.28 to 39.57 μg l^?1 with an overall mean of 10.78 and 12.38 μg l^?1 for El Temsah and Bitter Lakes water, respectively. Total PAHs fractions recorded in muscle tissues of all different Osteicthyes fishes collected from Great Bitter lakes ranged from 5.8 to 218.5 μg g^?1 with an overall mean of 57.98 μg g^?1 during all seasons. However, they ranged from 68 to 623 μg g^?1 with an overall mean of 87.69 μg g^?1 recorded in El Temsah lake during four seasons (2003–2004). Benzo(a)pyrene was the most dominant PAHs found in the sea water samples from both lakes with an average concentration of 3.8 μ g l^?1. Dibenzo(a,h)anthracene (DBA) was the most dominant PAHs recorded in fish samples. A maximum of 533 μg g^?1 of DBA was recorded in Dahbana sp. collected from Bitter lakes during January 2004. However, a maximum of 68.7 μ g g^?1 was recorded in Liza carinata species collected from El Temsah lake during July, 2004. The simultaneous occurrence of isomer ratios PHE/ANT<10 for all stations indicated that the major PAH input to water was from combustion of fossil fuel (pyrolytic source). The average ratios were 1.21 and 12.9 during winter (January 2004) and 4.3 and 8.63 during spring (April 2004) for all water samples of Great Bitter lakes and El Temsah lake, respectively. In addition, the present data demonstrate that PAHs from fossil fuel sources (MW<178) were the least significant source of PAHs in this region.     

Spatial distribution of copper in relation to recreational boating in a California shallow-water basin

The overall effect of the number of boats on the copper (Cu) levels in the water column and sediment, along with their spatial variability within Shelter Island Yacht Basin (SIYB), San Diego Bay, California was examined. We identified a horizontal gradient of increasing dissolved Cu and Cu in sediment from outside to the head of SIYB which was coincident with the increasing number of boats. Spatial models of Cu distribution in water and sediment indicated the presence of ‘hotspots’ of Cu concentration. From outside to the head of SIYB, dissolved Cu ranged from 1.3 μ g L^?1 to 14.6 μ g L^?1 in surface water, and 2.0 μ g L^?1 to 10.2 μ g L^?1 in bottom water. Cu in sediment exceeded the Effect Range Low of 34 mg kg^?1 (i.e. where adverse effects to fauna may occur), with a peak concentration of 442 mg kg^?1 at the head of the basin. Free Cu⁺⁺ in surface water was several orders of magnitude higher than in sediment porewater. High-resolution data of Cu species together with probability maps presented in this paper will allow managers to easily visualise and localise areas of impaired quality and to prioritise which areas should be targeted to improve Cu-related conditions.     

The removal of arsenic from water with natural and modified clinoptilolite

The presence of increased arsenic concentrations in Eastern Croatia is a consequence of the geological composition of the soil. Because of its known harmful effects, arsenic removal is of high importance and adsorption represents an attractive and economically efficient approach to arsenic removal. The use of zeolites obtained from the Donje Jesenje deposit, Croatia (CZ) and the Zlatokop deposit in Vranjska Banja, Serbia (SZ) in Na- and Fe–Na-modified forms was investigated in order to effectively remove arsenate and arsenite from aqueous solutions. The adsorption kinetics of arsenic was studied as a function of the initial arsenate and arsenite concentrations (30–300 μg · L^?1), equilibration time (3–48 h), pH (5–10) and in the presence of sulfate and phosphate at initial concentrations of 0.2–0.5 mg · L^?1. In order to estimate sorption constants designating the sorption capacity and affinity of the zeolites samples, the experimental results were fitted to the Langmuir and Freundlich sorption isotherms. Desorption tests conducted with 1–3 mol · L^?1 HCl indicated that arsenate sorption was irreversible. The results obtained indicated that use of the Serbian zeolite in the Fe–Na-modified form (Fe–Na-SZ) was favourable for arsenate removal from water containing up to 30 μg As · L^?1.     

In vivo uptake of iodine from a <Emphasis Type="Italic">Fucus serratus</Emphasis> Linnaeus seaweed bath: does volatile iodine contribute?

Seaweed baths containing Fucus serratus Linnaeus are a rich source of iodine which has the potential to increase the urinary iodide concentration (UIC) of the bather. In this study, the range of total iodine concentration in seawater (22–105 µg L^?1) and seaweed baths (808–13,734 µg L^?1) was measured over 1 year. The seasonal trend shows minimum levels in summer (May–July) and maximum in winter (November–January). The bathwater pH was found to be acidic, average pH 5.9 ± 0.3. An in vivo study with 30 volunteers was undertaken to measure the UIC of 15 bathers immersed in the bath and 15 non-bathers sitting adjacent to the bath. Their UIC was analysed pre- and post-seaweed bath and corrected for creatinine concentration. The corrected UIC of the population shows an increase following the seaweed bath from a pre-treatment median of 76 µg L^?1 to a post-treatment median of 95 µg L^?1. The pre-treatment UIC for both groups did not indicate significant difference (p = 0.479); however, the post-treatment UIC for both did (p = 0.015) where the median bather test UIC was 86 µg L^?1 and the non-bather UIC test was 105 µg L^?1. Results indicate the bath has the potential to increase the UIC by a significant amount and that inhalation of volatile iodine is a more significant contributor to UIC than previously documented.     

Ultrastructural responses and oxidative stress induced by cypermethrin in the liver of Labeo rohita

The present study was conducted to establish the relationship between selected oxidative stress parameters and ultrastructural responses in liver tissue of Labeo rohita fingerlings exposed to cypermethrin. Fish were exposed to lethal (4.0 μg L^?1) and sublethal (0.4 μg L^?1) concentrations of cypermethrin for a period of 24, 48, 72 and 96 h for acute studies and 1, 5, 10 and 15 days for subacute studies, respectively. Results showed increased catalase (CAT) and protease activity, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), protein carbonyls and free amino acid (FAA) levels at both concentrations. This suggests participation of free-radical-induced oxidative cell injury in mediating the hepatotoxicity of cypermethrin. In corroboration of this, ultrastructural lesions witnessed a reduction in the number of cell organelles, swollen, vacuolated and condensed mitochondria, dilated rough endoplasmic reticulum, and reduced numbers of smooth enodplasmic reticulum, peroxisomes and lysosomes at the lethal (4.0 μg L^?1) concentration. At the sublethal (0.4 μg L^?1) concentration, cytoplasmic vacuolation, condensed, vacuolated and swollen mitochondria, dilated rough endoplasmic reticulum and an absence of hepatocyte microvilli were prominent. Ultrastructural changes were exhibited as subcellular responses due to the imbalance in cellular oxidative status by means of oxidative damage.     

High soil and groundwater arsenic levels induce high body arsenic loads,health risk and potential anemia for inhabitants of northeastern Iran

Arsenic bioavailability in rock, soil and water resources is notoriously hazardous. Geogenic arsenic enters the body and adversely affects many biochemical processes in animals and humans, posing risk to public health. Chelpu is located in NE Iran, where realgar, orpiment and pyrite mineralization is the source of arsenic in the macroenvironment. Using cluster random sampling strategy eight rocks, 23 soils, 12 drinking water resources, 36 human urine and hair samples and 15 adult sheep urine and wool samples in several large-scale herds in the area were randomly taken for quantification of arsenic in rock/soil/water, wool/hair/urine. Arsenic levels in rock/soil/water and wool/hair/urine were measured using inductively coupled plasma spectroscopy and atomic absorption spectrophotometry, respectively. While arsenic levels in rocks, soils and water resources hazardously ranged 9.40–25,873.3 mg kg^?1, 7.10–1448.80 mg kg^?1 and 12–606 μg L^?1, respectively, arsenic concentrations in humans’ hair and urine and sheep’s wool and urine varied from 0.37–1.37 μg g^?1 and 9–271.4 μg L^?1 and 0.3–3.11 μg g^?1 and 29.1–1015 μg L^?1, respectively. Local sheep and human were widely sick and slightly anemic. Hematological examination of the inhabitants revealed that geogenic arsenic could harm blood cells, potentially resulting in many other hematoimmunological disorders including cancer. The findings warn widespread exposure of animals and human in this agroecologically and geopolitically important region (i.e., its proximity with Afghanistan, Pakistan and Turkmenistan) and give a clue on how arsenic could induce infectious and non-infectious diseases in highly exposed human/animals.     

A novel ligand for cloud point extraction to determine gold content in ore samples

Gold is a valuable metal occurring usually at very low concentrations in complex natural samples. Gold analysis thus needs preconcentration methods. Classical liquid–liquid extraction involves hazardous organic solvents. Alternatively, cloud point extraction involves non-toxic and nonvolatile surfactants. Here, we analyzed ore samples. The complex of Au(III) with sulphapyridylazo resorcin was extracted by the cloud point method. Concentrations were measured by flame atomic absorption spectrometry. We tested the effects of pH, reagent concentration, Triton X-100 surfactant concentration, equilibration temperature and time. Results show that the best detection limit of the method was 0.48 µg L^?1 for Au with a preconcentration factor of 31 times. Calibration is linear in range of 6.4–2,000 µg L^?1, and relative standard deviations are lower than 5 %. Quantum chemical computations reveal the plausible structure of the gold–ligand complex. This report represents the first determination of gold using sulphapyridylazo resorcin as a ligand.     

Lipid and fatty acids in naturally occurring particulate matter during spring and summer in a high arctic fjord (Kongsfjorden, Svalbard)

The total lipids and fatty acid composition of natural particulate matter and nutritional quality for zooplankton grazers was studied on a seasonal basis in the Arctic fjord Kongsfjorden (Svalbard) during the spring, summer of 2007 and during the early summer of 2006. Both years were abnormally warm, and the study attempted to evaluate the potential impact of the intrusion of North Atlantic waters. Samples were collected in surface layers and at deep chlorophyll maximum (DCM when present). Both years, chlorophyll concentrations were low (<2 μg L^?1) even during bloom periods. Species determination indicated Phaeocystis spp. as main constituent of the May bloom while ciliates and flagellates dominated the rest of the survey period. Total lipids showed similar changes at both depths with maximum values in mid-summer of 2007, while it showed reverse patterns between surface and DCM in 2006. Total fatty acid composition was dominated by saturates and monoenoic acids at both depths with significant percentages of pentaenoic acids and 22:6n-3 (DHA) recorded at all times. The 2007 fatty acid dynamics identified four main successions in term of particulate assemblage related mainly to the succession of living cells versus detrital material and to a lesser extent to phytoplankton community changes (diatoms versus non-diatoms). Redundancy analysis confirmed that live phytoplankton is one of the main drivers in the fatty acid changes. Temperature and density of the surface water are also influential in relation to water mass dynamics. Concentrations of fatty acids available to consumers showed n-3 PUFA ranging from 2 to 15 μg L^?1 and n-6 PUFA ranging from 0.3 to 2 μg L^?1. Concentration of EPA (20:5) and DHA are potentially limiting, suggesting a negative impact of Phaeocystis pouchetti-type phytoplankton linked to advection of Atlantic waters in relation to global warming of Arctic waters.     

Seasonal variations in physicochemical characteristics and cyanobacterial diversity of a lake in Northern India

Physicochemical analyses and cyanobacterial diversity of Ramgarh Lake water were performed at five sampling sites during winter, summer, and monsoon seasons. Higher load of solids, carbon, and nutrients were persistent throughout the analysis that indicates the conversion of lake from oligotrophic to eutrophic nature. High nutrients load enhanced cyanobacterial biomass, while low nutrients load produced relatively less biomass. The physicochemical parameters of water samples revealed minimum 2.9 mg L^?1 dissolved oxygen (DO) at site-1 during summer, while maximum (5.6 mg L^?1) at site-4 in monsoon season. Maximum biochemical oxygen demand (BOD) (40 mg L^?1) and chemical oxygen demand (COD) (126 mg L^?1) were recorded at site-1 during summer, whereas minimum BOD (18 mg L^?1) and COD (52 mg L^?1) were evident at site-3 in monsoon season. Minimum concentration of nitrate (0.72 mg L^?1) was recorded at site-3 in summer, whereas maximum 2.7 mg L^?1 was present at site-5 in winter season. The phosphate concentration was maximum (0.52 mg L^?1) at site-5 in summer, and minimum (0.18 mg L^?1) was observed at site-4 in monsoon season. Cyanobacterial diversity was higher during all the seasons, and dominated by the species of Microcystis at all the five sampling sites.     

Thermal treatment of plasma-synthesized goethite improves Fenton-like degradation of orange II dye

Various iron oxides are used for Fenton reactions to degrade organic pollutants. The degradation efficiency may be improved by transforming an iron oxide phase to another. Here, we report on the transformation of goethite into hematite by thermal treatment at 400 °C. The products were analyzed by X-ray diffractometry, Raman spectroscopy, scanning electron microscopy and N₂-physisorption. The catalytic activities were measured for orange II bleaching at initial concentration of 25 mg L^?1, pH 3, catalyst concentration of 0.2 g L^?1; 5 mM H₂O₂, 30 °C. Results show that the synthesized goethite was successfully transformed into hematite, and the specific surface area of the material increased from 134 to 163 m² g^?1. The bleaching efficiency of the orange II dye reached 100 % for the hematite product, versus 78 % for goethite. Therefore, a moderate thermal treatment of a plasma-synthesized goethite improves the catalytic oxidation of organic pollutants.     

New estimates of microalgae production based upon nitrate reductions under sea ice in Canadian shelf seas and the Canada Basin of the Arctic Ocean

New estimates of production of sub-ice and ice microalgae in the shelf seas of the Canadian Arctic and in the Canada Basin of the Arctic Ocean derived from reduction of nitrates in the water column, as recorded in time series available in publicly held data bases, suggest that it is of greater magnitude (up to 30 g C m^?2 year^?1) and represent a higher proportion (up to 50 % on the shelf and 90 % in the Canada Basin) of net community production than previously estimated for both areas.     

Effect of increasing salinity on the acute toxicity of a commercial endosulfan formulation to the bdelloid rotifer Philodina acuticornis odiosa

Pesticides, such as endosulfan, can enter surface waters such as lakes and rivers, potentially posing an ecological risk. Rotifers are a dominant zooplankton species in many inland freshwater lakes in Australia; such lakes can also experience increased salinities. Acute toxicity tests (24?h) were conducted to determine the toxicity of a commercial formaulation of endosulfan to the freshwater rotifer Philodina sp. and to investigate the influence of increasing salinity on endosulfan toxicity. Rotifers were found to be relatively tolerant to endosulfan with an EC50 of 1.75?mg?L^?1 (a.i.), with results also suggesting that there are no interactive effects of salinity on endosulfan toxicity.     

Heavy metals in the polychaete Glycera longipinnis from the southwest of India

Metal concentrations in sediment and in whole tissue of the benthic polychaete Glycera longipinnis collected along the southwest coast of India were analysed. Relative seasonal accumulation of metals (Cu, Pb, Cr, Ni, Zn, Cd, Hg) was studied by categorising the habitat as less polluted or highly polluted based on metal contamination routed through industrial and urban sources. The metal content in tissues varied seasonally in the ranges, Cu: 2.21–27.08 μg·g^?1, Pb: 0.06–4.92 μg·g^?1, Cr: 1.73–29.20 μg·g^?1, Ni: 1.60–4.61 μg·g^?1, Zn: 14.72–82.30 μg·g^?1, Cd: 0.04–1.38 μg·g^?1and Hg: below decetable limits to 0.86 μg·g^?1. Concentration of heavy metals was found to be high in the whole body of G. longipinnis pooled from the polluted transects. The results of this study suggest that G. longipinnis may act as a useful biological indicator for heavy metal pollution along the southwest coast of India.     

Ecotoxicological risks of the abandoned F–Ba–Pb–Zn mining area of Osor (Spain)

Due to its potential toxic properties, metal mobilization is of major concern in areas surrounding Pb–Zn mines. In the present study, metal contents and toxicity of soils, aqueous extracts from soils and mine drainage waters from an abandoned F–Ba–Pb–Zn mining area in Osor (Girona, NE Spain) were evaluated through chemical extractions and ecotoxicity bioassays. Toxicity assessment in the terrestrial compartment included lethal and sublethal endpoints on earthworms Eisenia fetida, arthropods Folsomia candida and several plant species, whereas aquatic tests involved bacteria Vibrio fischeri, microalgae Raphidocelis subcapitata and crustaceans Daphnia magna. Total concentrations of Ba (250–5110 mg kg^?1), Pb (940 to >5000 mg kg^?1) and Zn (2370–11,300 mg kg^?1) in soils exceeded intervention values to protect human health. Risks for the aquatic compartment were identified in the release of drainage waters and in the potential leaching and runoff of metals from contaminated soils, with Cd (1.98–9.15 µg L^?1), Pb (2.11–326 µg L^?1) and Zn (280–2900 µg L^?1) concentrations in filtered water samples surpassing US EPA Water Quality Criteria (2016a, b). Terrestrial ecotoxicity tests were in accordance with metal quantifications and identified the most polluted soil as the most toxic. Avoidance and reproduction tests with earthworms showed the highest sensitivity to metal contamination. Aquatic bioassays performed in aqueous extracts from soils confirmed the results from terrestrial tests and also detected toxic effects caused by the mine drainage waters. Algal growth inhibition was the most sensitive aquatic endpoint. In view of the results, the application of a containment or remediative procedure in the area is encouraged.     

Evaluation of kinetics and energy consumption of the electrochemical oxidation of Acid Red 73 in aqueous media

A laboratory scale, undivided electrolysis cell with platinum anode and cathode was used for electrochemical oxidation of the azo dye Acid Red 73 in simulated wastewater. The influence of the supporting electrolyte, applied voltage, pH, initial dye concentration and temperature was studied, and decolorization was monitored by UV/Vis spectroscopy. Energy consumption, current efficiency and the electric energy per order have been also determined. With NaCl (1.5 g L^?1) as supporting electrolyte, at a voltage of 6 V, at neutral pH (6.9) and at 25 °C, the solution of the dye (50 mg L^?1) was completely decolorized within 15 min. The apparent activation energy for electrochemical decolorization was determined as ?1.9 kJ mol^?1.     

Rapid liquid–liquid extraction for the reliable GC/MS analysis of volatile priority pollutants

Mass spectrometry is a powerful tool for the analysis of organic pollutants in the environment. Nevertheless, sample preparation for GC/MS analysis is often criticized for being too laborious and requiring expensive equipment. Thus, purge-and-trap or headspace devices are the most popular nowadays to investigate volatile organic pollutants. At the same time, modern commercial high-resolution mass spectrometers allow for the significant simplification of the sample preparation procedures due to better acquisition rate, accurate mass measurements, and improved sensitivity. Here, we used a time-of-flight high-resolution mass spectrometer Pegasus GC-HRT (LECO, USA) to identify and quantify 47 volatile priority organic pollutants in water. The developed accelerated water sample preparation approach requires just 1 mL of water and 1 mL of dichloromethane. The detection limits of the analytes are about 1 μg L^?1, while the quantification limits are approximately 5 μg L^?1. These limits correspond to those required by Method 8260C of the United States Environmental Protection Agency. Here, we demonstrate that sample preparation for the reliable and sensitive GC/MS analysis of volatile organic priority pollutants may be achieved in 5 min in 5-mL vials in the field or just prior to GC/MS analysis in the laboratory without the use of any expensive equipment.     

Bioaccumulation and toxic effects of copper in common onion Allium cepa L.

The aim of this study was to investigate the potential utility of Allium cepa L. as a bioindicator organism for measuring copper bioaccumulation and toxicity in laboratory conditions. Onions were exposed to increasing concentrations of the metal (0, 0.1, 0.5, 1, 5 and 10 μg mL^?1) for 7 days. Root and leaf development were chosen as biological endpoints, while bioaccumulation was evaluated in roots, bulbs and leaves. Copper caused inhibition of root elongation with increasing effects at the higher doses, growth being reduced by almost 60% at 0.1 μg mL^?1 and up to 95% at 10 μg mL^?1. The elongation of leaves was significantly lower only in specimens exposed at 0.5 μg mL^?1, but a total absence of newly formed tissues was observed at 10 μg mL^?1. A marked bioaccumulation of copper was measured in roots, with values increasing up to almost four orders of magnitude compared to controls; only slight or even no significant differences were observed for copper levels in leaves and bulbs of treated A. cepa. Multiple linear correlations revealed a significant inverse relationship between copper concentrations and tissue length in both the roots and leaves, evidencing a sensitive responsiveness of this biological model. The overall results suggest the suitability of A. cepa as a robust species for easy and simple ecotoxicological bioassays to test the toxic effects and bioavailability of environmental pollutants, especially trace metals.     

Arsenic contamination of natural waters in San Juan and La Pampa, Argentina

Arsenic (As) speciation in surface and groundwater from two provinces in Argentina (San Juan and La Pampa) was investigated using solid phase extraction (SPE) cartridge methodology with comparison to total arsenic concentrations. A third province, Río Negro, was used as a control to the study. Strong cation exchange (SCX) and strong anion exchange (SAX) cartridges were utilised in series for the separation and preservation of arsenite (As^III), arsenate (As^V), monomethylarsonic acid (MA^V) and dimethylarsinic acid (DMA^V). Samples were collected from a range of water outlets (rivers/streams, wells, untreated domestic taps, well water treatment works) to assess the relationship between total arsenic and arsenic species, water type and water parameters (pH, conductivity and total dissolved solids, TDS). Analysis of the waters for arsenic (total and species) was performed by inductively coupled plasma mass spectrometry (ICP-MS) in collision cell mode. Total arsenic concentrations in the surface and groundwater from Encon and the San José de Jáchal region of San Juan (north-west Argentina within the Cuyo region) ranged from 9 to 357 μg l^?1 As. Groundwater from Eduardo Castex (EC) and Ingeniero Luiggi (LU) in La Pampa (central Argentina within the Chaco-Pampean Plain) ranged from 3 to 1326 μg l^?1 As. The pH range for the provinces of San Juan (7.2–9.7) and La Pampa (7.0–9.9) are in agreement with other published literature. The highest total arsenic concentrations were found in La Pampa well waters (both rural farms and pre-treated urban sources), particularly where there was high pH (typically > 8.2), conductivity (>2,600 μS cm^?1) and TDS (>1,400 mg l^?1). Reverse osmosis (RO) treatment of well waters in La Pampa for domestic drinking water in EC and LU significantly reduced total arsenic concentrations from a range of 216–224 μg l^?1 As to 0.3–0.8 μg l^?1 As. Arsenic species for both provinces were predominantly As^III and As^V. As^III and As^V concentrations in San Juan ranged from 4–138 μg l^?1 to <0.02–22 μg l^?1 for surface waters (in the San José de Jáchal region) and 23–346 μg l^?1 and 0.04–76 μg l^?1 for groundwater, respectively. This translates to a relative As^III abundance of 69–100% of the total arsenic in surface waters and 32–100% in groundwater. This is unexpected because it is typically thought that in oxidising conditions (surface waters), the dominant arsenic species is As^V. However, data from the SPE methodology suggests that As^III is the prevalent species in San Juan, indicating a greater influence from reductive processes. La Pampa groundwater had As^III and As^V concentrations of 5–1,332 μg l^?1 and 0.09–592 μg l^?1 for EC and 32–242 μg l^?1 and 30–277 μg l^?1 As for LU, respectively. Detectable levels of MA^V were reported in both provinces up to a concentration of 79 μg l^?1 (equating to up to 33% of the total arsenic). Previously published literature has focused primarily on the inorganic arsenic species, however this study highlights the potentially significant concentrations of organoarsenicals present in natural waters. The potential for separating and preserving individual arsenic species in the field to avoid transformation during transport to the laboratory, enabling an accurate assessment of in situ arsenic speciation in water supplies is discussed.     

Pomegranate husk as an adsorbent in the removal of toxic chromium from wastewater

The use of a new sorbent developed from the husk of pomegranate, a famous fruit in Egypt, for the removal of toxic chromium from aqueous solution has been investigated. The batch experiment was conducted to determine the adsorption capacity of the pomegranate husk. The effects of initial metal concentration (25 and 50 mg l^?1), pH, contact time, and sorbent concentration (2–6 g l^?1) have been studied at room temperature. A strong dependence of the adsorption capacity on pH was observed, the capacity increased as the pH decreased, and the optimum pH value was pH 1.0. Adsorption equilibrium and kinetics were studied with different sorbent and metal concentrations. The adsorption process was fast, and equilibrium was reached within 3 h. The maximum removal was 100% for 25 mg l^?1 of Cr⁶⁺ concentration on 5 g l^?1 pomegranate husk concentration, and the maximum adsorption capacity was 10.59 mg g^?1. The kinetic data were analysed using various kinetic models—pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion equations—and the equilibrium data were tested using several isotherm models, Langmuir, Freundlich, Tempkin, Dubinin–Radushkevich, and Generalized isotherm equations. The Elovich and pseudo-second-order equations provided the greatest accuracy for the kinetic data, while Langmuir and Generalized isotherm models were the closest fit for the equilibrium data. The activation energy of sorption has also been evaluated as 0.236 and 0.707 kJ mol^?1 for 25 and 50 mg l^?1 chromium concentration, respectively.     

Direct and indirect effects of pesticides on a benthic grazer during its life cycle

Background

Macroinvertebrates in aquatic ecosystems are repeatedly exposed to pesticides during their life cycle. Effects of consecutive exposure during different life stages and possible synergistic effects are not addressed in the standardized hazard assessment. The present study investigated two environmentally relevant exposure scenarios in batch (microcosm) and artificial indoor stream (mesocosm) experiments using the larvae of the mayfly Rhithrogena semicolorata (grazer) and natural aufwuchs. Grazers were analysed regarding growth, physiological condition, and drift behaviour, while the aufwuchs was analysed in terms of biomass using the particulate organic carbon as well as the chlorophyll a content. The aim was to reveal direct and indirect effects of an herbicide exposure during autumn on juvenile grazers and an insecticide exposure during spring on semi-juvenile grazers.

Results

Direct and indirect effects were found in both exposure scenarios at environmentally relevant concentrations. In the herbicide exposure scenario with terbutryn, clear direct effects on the aufwuchs community with a LOEC of 0.38 µg L^?1 were found. Effect levels of grazers due to indirect effects were equal, with the overnight drift being the most sensitive grazer endpoint. In the insecticide exposure scenario, clear lethal and sub lethal effects of lambda-cyhalothrin were evident. Derived LC₅₀ values for the artificial indoor stream and batch experiment were 2.42 µg g^?1 OC (69 days) and 1.2 µg g^?1 OC (28 days), respectively. Sub lethal effects in terms of increased drift as well-reduced growth and triglyceride levels were found at concentrations of 1.4 and 0.09 µg g^?1 OC (LOECs). These results were confirmed by the batch experiment, which revealed effect values in the similar range. Finally, a clear indirect effect of the insecticide on the aufwuchs was evident in the batch experiment with an LOEC at 0.9 µg g^?1 OC.

Conclusion

Toxicity Exposure Ratios calculated with the derived effect values indicate a risk for the investigated grazer by both pesticides. Moreover, observed indirect effects during the herbicide exposure seem to be able to affect the grazers during a second exposure with an insecticide, due to reduced physiological conditions. We suggest further research with time-shifted exposure scenarios to gain a better understanding of the complex interactions of pesticides with the life cycle and the food webs of macroinvertebrates.