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1.
Microplastics (MPs) are frequently regarded as environmental and biota contaminants. Yet, research on the accumulation of MPs in living entities, particularly aquatic insects that serve as food resources in the aquatic food chain, is limited. This study to investigate the accumulation of MPs in aquatic insects from water and sediment in an Egyptian wastewater basin. Four typical freshwater insect groups were used. The highest MP load per gram wet weight was reported by collector-gatherers (Chironomus sp. and Hydrophilus sp.), followed by collector-filterers (Culex sp.) with the second highest MP load. However, Predators (Aeshna sp.) had the lowest values. Also, the present results showed a reduction in the number of MPs in all insect taxa tested after a 24 h depuration time, with differences in the observed egestion ability. The mean number of MPs per individual significantly reduced after 24 h in both Chironomus sp. and Culex sp. larvae, where 53% and 40% of MPs particles were ejected from them, respectively. However, the ability of MP egestion decreases in Aeshna sp. nymph (25%), and the lowest proportion of ejection was observed in Hydrophilus sp. adults (9%). Polyethylene terephthalate fibers were the most abundant type of MP in both sediment and water, followed by fragments (polyethylene and polypropylene). Yet, only polyester fibers were detected in the various insect species. The average length of fibers in the various insects was somewhat shorter than in the surrounding environment. The current study reveals that MP ingestion by aquatic insects is not always related to levels of pollution in the environment, since other factors such as feeding strategies may play a role in MP ingestion. Based on these observations, further studies should be carried out on studies on toxicological impacts of MPs on freshwater/aquatic biota.  相似文献   

2.
Adsorption of arsenic and chromium by mixed magnetite and maghemite nanoparticles from aqueous solution is a promising technology. In the present batch experimental study, a commercially grade nano-size ‘magnetite’, later identified in laboratory characterization to be mixed magnetite–maghemite nanoparticles, was used in the uptake of arsenic and chromium from different water samples. The intent was to identify or develop a practical method for future groundwater remediation. The results of the study showed 96–99% arsenic and chromium uptake under controlled pH conditions. The maximum arsenic adsorption occurred at pH 2 with values of 3.69 mg/g for arsenic(III) and 3.71 mg/g for arsenic(V) when the initial concentration was kept at 1.5 mg/L for both arsenic species, while chromium(VI) concentration was 2.4 mg/g at pH 2 with an initial chromium(VI) concentration of 1 mg/L. Thus magnetite–maghemite nanoparticles can readily adsorb arsenic and chromium in an acidic pH range. Redox potential and pH data helped to infer possible dominating species and oxidation states of arsenic and chromium in solution. The results also showed the limitation of arsenic and chromium uptake by the nano-size magnetite–maghemite mixture in the presence of a competing anion such as phosphate. At a fixed adsorbent concentration of 0.4 g/L, arsenic and chromium uptake decreased with increasing phosphate concentration. Nano-size magnetite–maghemite mixed particles adsorbed less than 50% arsenic from synthetic water containing more than 3 mg/L phosphate and 1.2 mg/L of initial arsenic concentration, and less than 50% chromium from synthetic water containing more than 5 mg/L phosphate and 1.0 mg/L of chromium(VI). In natural groundwater containing more than 5 mg/L phosphate and 1.13 mg/L of arsenic, less than 60% arsenic uptake was achieved. In this case, it is anticipated that an optimum design with magnetite–maghemite nanoparticles may achieve high arsenic uptake in field applications.  相似文献   

3.
A hyperspectral imaging system was used to monitor vegetation during a subsurface controlled release of carbon dioxide (CO2). From August 3 to 10, 2007, 0.3 tons CO2/day were released through a 70 m horizontal pipe located at a nominal depth of 1.8 m below the surface. Hyperspectral images of alfalfa plants were collected during the controlled release and used along with classification tree analysis to study changes in the reflectance spectra as a function of perpendicular distance from the horizontal pipe. Changes in the reflectance spectra near the red edge (650–750 nm) were observed over the course of the controlled release experiment for plants within a perpendicular distance of 1 m of the release pipe. These results indicate monitoring vegetation over a carbon sequestration site has the potential to allow monitoring of the integrity of the CO2 storage.  相似文献   

4.
The objectives of this study were to (1) evaluate the performance of the Multi‐Radar Multi‐Sensor (MRMS) system in capturing precipitation compared to gauge data, and (2) assess the effects of spatial (1–50 km) and temporal (15–120 min) data aggregation scales on the performance of the MRMS system. Point‐to‐grid comparisons were conducted between 215 rain gauges and the MRMS system. The MRMS system at 1 km spatial and 15 min temporal resolutions captured precipitation reasonably well with average R2, root mean square error (RMSE), and percent bias (PBIAS) values of 0.65, 0.5 mm, and 11.9 mm; whereas Threat Score, probability of detection, and false alarm ratio were 0.57, 0.92, and 0.40, respectively. Decreasing temporal resolution from 15 min to two hours resulted in an increase in R2 and a decrease in RMSE, whereas PBIAS was not affected. Reducing spatial resolution from 1 to 50 km resulted in increases in R2 and PBIAS, whereas RMSE was decreased. Increasing spatial aggregation scale from 1 to 50 km resulted in an R2 increase of only 0.08. Similarly, improvement in R2 was only modest (0.17) compared to an eightfold reduction in temporal resolution (from 15 min to two hours). While aggregating data at coarser temporal resolutions resolved some of the under/overestimation issues of the MRMS system, it was apparent even at coarser spatial and temporal resolutions the MRMS system inherently overestimated smaller precipitation events while underestimated bigger events.  相似文献   

5.
Speciation of some heavy metals in River Nile sediments,Cairo, Egypt   总被引:1,自引:0,他引:1  
River sediments are basic components of our environment. It also constitutes a major source of persistent bioaccumulative toxic chemicals which may pose threats to ecological and human health even after contaminants are no longer released from point and non-point sources. Therefore, the aim of this study was to investigate the mobility and the availability of metals in sediments from different sites along the Nile River in Cairo district using sequential chemical extraction technique. The speciation data showed that most metals were associated with organic/sulfide and residual fractions. The order of total metal concentrations in sediment samples was found to be Fe > Mn > Zn > Ni > Cu ≥ Cr > Pb > Cd.  相似文献   

6.
Activated carbon was prepared from coconut shell, an agricultural waste, for the removal of phosphorus from synthetic phosphorus‐containing wastewater. The activated carbon obtained from the coconut shell was characterized using Fourier‐transform infrared (FTIR) spectroscopy. Batch mode experiments were conducted to study the effects of pH, particle size, adsorbent dosage, and sorption time on the adsorptive potential of the prepared activated carbon. Response surface methodology was employed to study the interactions among the variables and to optimize the process conditions for the maximum removal of phosphorus using the coconut shell–based activated carbon (CNS). The characterization results from the FTIR showed the presence of variety of functional groups, such as ?OH, ?NH, C=O, C?H, C?N, CH3, and CH2, which explains the CNS's improved adsorption behavior on the colloidal particles. A maximum performance of 95.22% was obtained for CNS at the optimum conditions of adsorbent dosage = 1,000 milligrams (local variable), pH 2 (local variable), particle size = 0.2 millimeters (local variable), and sorption time = 4.2 hours (global variable).  相似文献   

7.
A laboratory study was conducted to investigate the efficiency of hydroxyapatite (HAP) towards removal of nitrate from synthetic nitrate solution. In the present research HAP synthesized from egg-shell was characterized using SEM, XRD, FTIR and TGA–DSC. The removal of nitrate was 96% under neutral conditions, using 0.3 g of adsorbent in 100 mL of nitrate solution having an initial concentration of 100 mg/L. An adsorption kinetic study revealed that the adsorption process followed first order kinetics. Adsorption data were fitted to a linearly transformed Langmuir isotherm with correlation coefficient (R2) > 0.98. Thermodynamic parameters were also calculated to study the effect of temperature on the removal process. In order to understand the adsorption type, equilibrium data were tested with the Dubinin–Radushkevich isotherm. The process was rapid and equilibrium was established within the first 40 min.  相似文献   

8.
The 2010 dam breach and consequent anomalous flood event on the Cedar River in Nebraska, USA provided an opportunity to study the following objectives: (1) evaluate the impact of an extreme flood event on streambank retreat along a 45 km stretch relative to the average annual retreat; (2) quantify the changes in streambank retreat for each km segment downstream of the breach; and (3) examine the influence of riparian vegetation and radius of curvature on meander bank erosion rate. During the hydrologic event, discharge peaked at nearly three times greater than the next highest recorded rate and equated to a return period of 2,000 years. Aerial images and ArcGIS were utilized to calculate the average annual streambank retreat for each year during the preflood (2006–2010), flood (2010), and postflood (2010–2016) periods. The 2010 flood period had a significantly higher average annual streambank retreat of 2,820 m2/km/yr than the preflood and postflood periods, which, respectively, measured 576 and 384 m2/km/yr. From 2006 to 2016, 29% of all streambank erosion was from this one extreme flood event, thus demonstrating the impact that one extreme flood event can have on streambank retreat and the geomorphology of a stream system.  相似文献   

9.
A geomechanical assessment of the Naylor Field, Otway Basin, Australia has been undertaken to investigate the possible geomechanical effects of CO2 injection and storage. The study aims to evaluate the geomechanical behaviour of the caprock/reservoir system and to estimate the risk of fault reactivation. The stress regime in the onshore Victorian Otway Basin is inferred to be strike–slip if the maximum horizontal stress is calculated using frictional limits and DITF (drilling induced tensile fracture) occurrence, or normal if maximum horizontal stress is based on analysis of dipole sonic log data. The NW–SE maximum horizontal stress orientation (142°N) determined from a resistivity image log is broadly consistent with previous estimates and confirms a NW–SE maximum horizontal stress orientation for the Otway Basin.An analytical geomechanical solution is used to describe stress changes in the subsurface of the Naylor Field. The computed reservoir stress path for the Naylor Field is then incorporated into fault reactivation analysis to estimate the minimum pore pressure increase required to cause fault reactivation (ΔPp).The highest reactivation propensity (for critically-oriented faults) ranges from an estimated pore pressure increase (ΔPp) of 1 MPa to 15.7 MPa (estimated pore pressure of 18.5–33.2 MPa) depending on assumptions made about maximum horizontal stress magnitude, fault strength, reservoir stress path and Biot's coefficient. The critical pore pressure changes for known faults at Naylor Field range from an estimated pore pressure increase (ΔPp) of 2 MPa to 17 MPa (estimated pore pressure of 19.5–34.5 MPa).  相似文献   

10.
Idealized, basin-scale sharp-interface models of CO2 injection were constructed for the Illinois basin. Porosity and permeability were decreased with depth within the Mount Simon Formation. Eau Claire confining unit porosity and permeability were kept fixed. We used 726 injection wells located near 42 power plants to deliver 80 million metric tons of CO2/year. After 100 years of continuous injection, deviatoric fluid pressures varied between 5.6 and 18 MPa across central and southern part of the Illinois basin. Maximum deviatoric pressure reached about 50% of lithostatic levels to the south. The pressure disturbance (>0.03 MPa) propagated 10–25 km away from the injection wells resulting in significant well–well pressure interference. These findings are consistent with single-phase analytical solutions of injection. The radial footprint of the CO2 plume at each well was only 0.5–2 km after 100 years of injection. Net lateral brine displacement was insignificant due to increasing radial distance from injection well and leakage across the Eau Claire confining unit. On geologic time scales CO2 would migrate northward at a rate of about 6 m/1000 years. Because of paleo-seismic events in this region (M5.5–M7.5), care should be taken to avoid high pore pressures in the southern Illinois basin.  相似文献   

11.
In this work, unburnt coal (UC) in bottom ash from coal-fired power plants was soaked in KOH solution and activated for 1 h at 780 °C. The yield of activated carbons varied from 47.8 to 54.8% when the KOH/UC weight ratio changed from 2 to 4. Pore properties of these activated carbons including the BET surface area, pore volume, pore size distribution, and pore diameter were characterized based on N2 adsorption isotherms. It was shown that the isotherms for the adsorption of methylene blue, acid blue 74, and 4-chlorophenol from aqueous solutions on these activated carbons at 30 °C were well fitted by the Langmuir equation (correlation coefficient r2 > 0.9968). The adsorption capacities of methylene blue, acid blue 74, and 4-chlorophenol were obtained to be 2.40–2.88, 0.57–1.29, and 2.34–5.62 mmol/g, respectively. Moreover, the adsorption kinetics could be suitably described by the Elovich equation.  相似文献   

12.
The concern related to the drinking of reverse osmosis (RO) water containing low levels of minerals is growing day by day. This study involves the analysis of water samples from various drinking water sources in a rural site, Mirchpur village, an Indus Valley civilization site (grid location: 29° 18′ 42.3″ N, 76° 10′ 33.0″ E) of Hisar, India, along with the health survey of human subjects. The hydrochemistry of water collected from hand pumps, river canals, tube wells, submersibles, and the RO systems installed in various homes was explored for pH, EC, TH, TDS, turbidity, cations (Na+, Ca2+, Mg2+), anions (CO32−, HCO3, Cl, SO42−, NO3, F), and elements (Fe, Pb, Se) employing the ion chromatography, flame photometry, and ICP-AES techniques. Lead (Pb) and Selenium (Se) were detected in trace amounts (0.30–2.6 μg L−1; 0.10–4.1 μg L−1, respectively) in all the samples, including the samples collected from RO purifiers, but Iron (Fe) was not detected in RO samples even in trace amounts. The F-levels in hand pump water (HPW) and submersible water (SW) (1.9  and 1.7 mg L−1, respectively) and TDS levels in SW (3048 mg L−1) were found to be above WHO and BIS safe limits. TDS levels in the river canal (900 mg L−1), tube well (1104 mg L−1), hand pump (1170 mg L−1), and submersible samples (3048 mg L−1) were found significantly higher as compared to the RO personal water (ROPW; 216 mg L−1) and RO supply water (ROSW; 90 mg L−1). The collected epidemiological data reveals that 21%, 19%, 13%, and 12% of natives reported skin, kidney, hair fall, liver, and stomach issues, respectively, suspecting the crucial role of high TDS and fluoride levels in the area. This study also provides a comparison between the quality of RO and the direct supply water, along with correlation matrices for different parameters, which gives a rationale for the limitations of drinking direct supply water without any purification and RO water containing low mineral content.  相似文献   

13.
Increased water-dependent development and utilization have led to significant environmental and hydrological degradation of the Tarim River in western China and its dependent ecosystems. Between the 1950s and 1970s, 350 km of the lower reaches were drained and between 1960 and 1980 the water-table fell from between −2 and −3 m to between −8 and −10 m. Subsequently, riparian ecosystems were seriously degraded. In 2000, the Chinese government launched a program to restore the lower reaches of the river. Four environmental flows of 1034×106 m3 were released from 2000 to 2002. This paper interprets and discusses the ecological significance of changes following the releases and identifies the relationship between water-table dynamics and vegetation responses. Short-term objectives for river restoration are proposed with possible monitoring parameters suggested.  相似文献   

14.
Assessment of regional scale soil spatial variation and mapping their distribution is constrained by sparse data which are collected using field surveys that are labor intensive and cost prohibitive. We explored geostatistical (ordinary kriging-OK), regression (Regression Tree-RT), and hybrid methods (RT plus residual Sequential Gaussian Simulation-SGS) to map soil textural fractions across the Santa Fe River Watershed (3585 km2) in north-east Florida. Soil samples collected from four depths (L1: 0–30 cm, L2: 30–60 cm, L3: 60–120 cm, and L4: 120–180 cm) at 141 locations were analyzed for soil textural fractions (sand, silt and clay contents), and combined with textural data (15 profiles) assembled under the Florida Soil Characterization program. Textural fractions in L1 and L2 were autocorrelated, and spatially mapped across the watershed. OK performance was poor, which may be attributed to the sparse sampling. RT model structure varied among textural fractions, and the model explained variations ranged from 25% for L1 silt to 61% for L2 clay content. Regression residuals were simulated using SGS, and the average of simulated residuals were used to approximate regression residual distribution map, which were added to regression trend maps. Independent validation of the prediction maps showed that regression models performed slightly better than OK, and regression combined with average of simulated regression residuals improved predictions beyond the regression model. Sand content >90% in both 0–30 and 30–60 cm covered 80.6% of the watershed area.  相似文献   

15.
This study aims to prepare a low-cost, environmentally friendly, and alternative, biosorbent to remove chromium Cr (III) and lead Pb (II) from polluted water and to find out the highest removal efficiencies using 2k factorial experiments. The Cr (III) and Pb (II) tolerant fungal strain identified as Penicillium chrysogenum was isolated from ceramic industrial sludge. The impact of process variables on biosorption of Cr (III) and Pb (II) by P. chrysogenum was first evaluated with the Taguchi screening design. Factors and levels were determined to optimize Cr (III) and Pb (II) removal efficiency. According to this, five factors; initial concentration, pH, biosorbent dose, temperature, and inactivation methods were determined for both metals, each factor defined as a fixed factor with two levels. Optimization of the parameters affecting the removal process was determined by the Taguchi method and the signal-to-noise (S/N) ratios are calculated. The maximum removal efficiency (99.92%) was observed at pH 7, biosorbent 1 mg L–1, inactivation with autoclaving, and at 20°C with an initial metal concentration of 50 mg L–1 Cr (III). On the other hand, the maximum removal efficiency (98.99%) was observed at pH 4, biosorbent 5 mg L–1, inactivation with autoclaving, and at 20°C with an initial metal concentration of 50 mg L–1 Pb (II). Furthermore, metal ions removal by P. chrysogenum was also confirmed by scanning electron microscopy (SEM) combined with an energy dispersive X-ray spectrometer (EDS). The presence of functional groups on fungal cells of metal binding was investigated by Fourier transform infrared (FT-IR).  相似文献   

16.
In this study, the mechanism for the stabilization/solidification (S/S) of arsenic (As)-contaminated soils with Portland cement (PC), and cement kiln dust (CKD) using 1 N HCl extraction fluid, X-ray powder diffraction (XRPD), X-ray absorption near edge structure (XANES) and Extended X-ray absorption fine structure (EXAFS) spectroscopy was investigated. The degree of As immobilization after stabilization was assessed using a 1 N HCl extraction on the basis of the Korean Standard Test (KST). After 1 day of curing with 30 wt% PC and 7 days of curing with 50 wt% CKD, the concentration of As leached from the amended soils was less than the Korean countermeasure standard (3 mg L?1). The As concentrations in the leachate treated with PC and CKD were significantly decreased at pH > 3, indicating that pH had a prevailing influence on As mobility. XRPD results indicated that calcium arsenite (Ca–As–O) and sodium calcium arsenate hydrate (NaCaAsO4·7.5H2O) were present in the PC- and CKD-treated slurries as the key phases responsible for As(III) and As(V) immobilization, respectively. The XANES spectroscopy confirmed that the As(III) and As(V) oxidation states of the PC and CKD slurry samples were consistent with the speciated forms in the crystals identified by XRPD. EXAFS spectroscopy showed As–Ca bonding in the As(III)-PC and As(III)-CKD slurries. The main mechanism for the immobilization of As-contaminated soils with PC and CKD was strongly associated with the bonding between As(III) or As(V) and Ca.  相似文献   

17.
The Missouri Department of Natural Resources (MDNR) has closed or posted advisories at public beaches at Lake of the Ozarks State Park in Missouri because of Escherichia coli (E. coli) concentration exceedances in recent years. Spatial and temporal patterns of E. coli concentrations, microbial source tracking, novel sampling techniques, and beach‐use patterns were studied during the 2012 recreational season to identify possible sources, origins, and occurrence of E. coli contamination at Grand Glaize Beach (GGB). Results indicate an important source of E. coli contamination at GGB was E. coli released into the water column by bathers resuspending avian‐contaminated sediments, especially during high‐use days early in the recreational season. Escherichia coli concentrations in water, sediment, and resuspended sediment samples all decreased throughout the recreational season likely because of decreasing lake levels resulting in sampling locations receding away from the initial spring shoreline as well as natural decay and physical transport out of the cove. Weekly MDNR beach monitoring, based solely on E. coli concentrations, at GGB during this study inaccurately predicted E. coli exceedances, especially on weekends and holidays. Interestingly, E. coli of human origin were measured at concentrations indicative of raw sewage in runoff from an excavation of a nearby abandoned septic tank that had not been used for nearly two years.  相似文献   

18.
Adsorption is one of the most promising technologies for reducing CO2 emissions and at present several different types of sorbents are being investigated. The use of sorbents obtained from low-cost and abundant precursors (i.e. solid wastes) appears an attractive strategy to adopt because it will contribute to a reduction not only in operational costs but also in the amount of waste that is dumped and burned in landfills every year. Following on from previous studies by the authors, in this work several carbon-based adsorbents were developed from different carpet wastes (pre-consumer and post-consumer wastes) by chemical activation with KOH at various activation temperatures (600–900 °C) and KOH:char impregnation ratios (0.5:1 to 4:1). The prepared materials were characterised by chemical analysis and gas adsorption (N2, −196 °C; CO2, 0 °C), and tested for CO2 adsorption at temperatures of 25 and 100 °C. It was found that both the type of precursor and the conditions of activation (i.e. impregnation ratios, and activation temperatures), had a huge influence on the microporosity of the resultant samples and their CO2 capture capacities. The carbon-based adsorbent that presented the maximum CO2 capture capacities at 25 and 100 °C (13.8 wt.% and 3.1 wt.%, respectively), was prepared from a pre-consumer carpet waste and was activated at 700 °C using a KOH:char impregnation ratio of 1:1. This sample showed the highest narrow microporosity volume (0.47 cm3 g−1), thus confirming that only pores of less than 1 nm are effective for CO2 adsorption at atmospheric pressure.  相似文献   

19.
In our previous work, the prepared high-impact polystyrene (HIPS) membranes, synthesized using four concentrations (20, 25, 30, and 35 wt%) of waste HIPS, were proved to be promising for water purification by microfiltration process (MF). However, the fabricated membranes' mechanical properties and microfiltration process parameters were not investigated. Consequently, in this study, various parameters affecting the previously fabricated membranes' performance in the filtration process, such as membrane mechanical properties, feeding pressure, fouling behavior, and polymer concentration, were thoroughly investigated. With increasing polystyrene concentrations, the ultimate tensile strength of the fabricated membranes increased. When the concentration was increased from 20 to 25 wt percent, the elongation at break rose, but as the concentration was increased further, the membrane became brittle. Permeate flux and rejection both declined as polymer content was raised. Accordingly, the highest flux and humic acid (HA) rejection were shown by 20 wt% (14.18 L/m2h (LMH) and 98.95%, respectively). The antifouling properties declined when the polymer concentration was raised, and 20 wt% had the lowest total fouling resistance. Furthermore, the permeate flux was reduced while increasing the HA initial concentration.  相似文献   

20.
In this study the biosorption of Yellow RL, a metal-complex anionic dye, by dried Rhizopus arrhizus, a filamentous fungus, was investigated as a function of initial solution pH, initial dye concentration and initial salt (sodium chloride) concentration. The fungus exhibited the maximal dye uptake at pH 2 in the absence and in the presence of salt. Dye uptake increased with the dye concentration up to 1000 mg l?1 and diminished considerably in the presence of increasing concentrations of salt up to 50 g l?1. The fungus biosorbed 85.4 mg dye g?1of dried biomass at 100 mg l?1 initial dye concentration in the absence of salt. When 50 g l?1 salt was added to the biosorption medium, this value dropped to 60.8 mg g?1 resulting in 28.8% reduction in biosorption capacity. The Redlich–Peterson and Langmuir–Freundlich were the most suitable adsorption models for describing the biosorption equilibrium data of the dye both individually and in salt containing medium. The pseudo-second-order and saturation type kinetic models depicted the biosorption kinetics accurately for all cases studied. Equilibrium and kinetic constants varied with the level of salt were expressed as a function of salt concentration.  相似文献   

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