Effects of Acid Rain on Competitive Releases of Cd, Cu, and Zn from Two Natural Soils and Two Contaminated Soils in Hunan, China

Leaching experiments of rebuilt soil columns with two simulated acid rain solutions (pH 4.6–3.8) were conducted for two natural soils and two artificial contaminated soils from Hunan, south-central China, to study effects of acid rain on competitive releases of soil Cd, Cu, and Zn. Distilled water was used in comparison. The results showed that the total releases were Zn>Cu>Cd for the natural soils and Cd>Zn≫Cu for the contaminated soils, which reflected sensitivity of these metals to acid rain. Leached with different acid rain, about 26–76% of external Cd and 11–68% external Zn were released, but more than 99% of external Cu was adsorbed by the soils, and therefore Cu had a different sorption and desorption pattern from Cd and Zn. Metal releases were obviously correlated with releases of TOC in the leachates, which could be described as an exponential equation. Compared with the natural soils, acid rain not only led to changes in total metal contents, but also in metal fraction distributions in the contaminated soils. More acidified soils had a lower sorption capacity to metals, mostly related to soil properties such as pH, organic matter, soil particles, adsorbed SO₄ ²⁻, exchangeable Al³⁺ and H⁺, and contents of Fe₂O₃ and Al₂O₃.     

PM<Subscript>10</Subscript> and Ultrafine Particles Counts In-Vehicle and On-Road in the Athens Area

This work presents the first results of a study concerning on-road and in-vehicle exposure to particulate matter in the area of Athens. PM₁₀ concentration measurements were conducted by TSI DustTrak, while driving along routes with different characteristics of traffic density, during September 2003–March 2004. Concurrent measurements of the ultrafine particles (UFPs) number concentration were also conducted, by condensation particle counter during part of the days. Pedestrian exposure to PM₁₀ and UFPs was also studied through stationary measurements on the kerbside of selected roads on November 2003 and February 2004. A major avenue, a heavy-trafficked road across a children hospital and two central roads, one in a residential and one in a commercial area were selected for measurement. The results indicate that every day commuters are exposed to significant concentration levels. Higher exposures were observed in heavy-trafficked areas and during rush hours. Mean PM₁₀ in-vehicle and on-road concentrations ranged from 30–320 μg/m³ and 70–285 μg/m³, respectively. The ultrafine particles number concentrations were in the range of 5.0 × 10⁴–17.3 × 10⁴ particles/cm³ in-vehicle and 3.1 × 10⁴–7.3 × 10⁴ particles/cm³ on the kerbside of a central residential road. Both PM₁₀ and UFPs concentrations presented repeated short-term peak exposures. The results clearly point out the importance of the road microenvironment (in-vehicle and on kerbside) for population exposure in urban areas.     

Enzyme-Assisted Extraction and Pb<Superscript>2+</Superscript> Biosorption of Polysaccharide from <Emphasis Type="Italic">Cordyceps militaris</Emphasis>

The enzyme assisted extraction conditions of polysaccharide from Cordyceps militaris mycelia were firstly investigated by kinetics analysis and the optimal operating was found to be: extraction temperature 40 °C; solid-solvent ratio 1:20; extraction pH 4.0; cellulase concentration 2.0%. The polysaccharide extraction yield was 5.99% under these optimized conditions. Furthermore, a fundamental investigation of the biosorption of Pb²⁺ from aqueous solution by the C. militaris polysaccharide was performed under batch conditions. The suitable pH (5.0), polysaccharide concentration (0.20 g L^?1), initial Pb²⁺ concentration (300 mg L^?1) and contact time (40 min) were outlined to enhance Pb²⁺ biosorption from aqueous medium. The Langmuir isotherm model and pseudo first order kinetic model fitted well to the data of Pb²⁺ biosorption, suggesting the biosorption of Pb²⁺ onto C. militaris polysaccharide was monolayer biosorption and physical adsorption might be the rate-limiting step that controlled the adsorption process. FTIR analysis showed that the main functional groups of C. militaris polysaccharide involved in adsorption process were carbonyl, carboxyl, and hydroxyl groups.     

Natural attenuation of a low mobility chlorinated insecticide in low-level and high-level contaminated soil: A feasibility study

Endosulfan is an economically important insecticide and widespread environmental pollutant, originating from a wide range of agricultural activities. The major implication from the feasibility study described was that endosulfan I can be remediated by natural attenuation processes in cotton-farming soil, in which concentrations were relatively low, as well as heavily contaminated soil, from an agricultural chemical waste (evaporation) pit. Endosulfan I, the major isomer of endosulfan, was present in agricultural soils with low (2.2 mg/kg) and high (417 mg/kg) concentrations of technical-grade endosulfan. The half-lives of the major isomer of endosulfan were 94 and greater than 350 days in the low-level (cotton farming soil) and high-level (contaminated soil), respectively. Even under conditions of minimal intervention, as in the current study, endosulfan concentrations in contaminated soils can be substantially reduced. The nonbiological process of soil binding was predominantly responsible for the natural attenuation of endosulfan I in both soils. Low levels of mineralization of the chlorinated ring ¹⁴C-labelled carbons were also reported, but mineralization did not play an important role in natural attenuation of endosulfan I in either soil studied.     

Life Cycle Assessment on a Bus Body Component Based on Hemp Fiber and PTP<Superscript>®</Superscript>

The application of renewable raw materials in the automotive sector became more and more interesting in the last years. For the first time, a material system based on natural fibers and PTP^®, a vegetable based thermoset resin, was produced and manufactured into a bus body component by Sheet-Moulding-Compound-technology. The Life Cycle Assessment on this component based on renewable raw materials shows advantages especially in the categories fossil resources and global warming. It can be expected that further concepts of development and optimization lead to a more efficient use of materials and so to an additional reduction of environmental impacts.     

Whole-year-round Observation of N<Subscript>2</Subscript>O Profiles in Soil: A Lysimeter Study

Despite many studies of the N₂O emission, there is a lack of knowledge on the role of subsoil for N₂O emission, particularly in sandy soils. To obtain insight into the entrapment, diffusion, convection and ebullition of N₂O in the soil, the N₂O concentration in the soil atmosphere was measured over a period of 1 year in 4 lysimeters (agricultural soil monoliths of 1 m2 × 2 m) at 30, 50, 80, 155, and 190 cm depth with altogether 86 gas probes. Additionally the N₂O emission into the atmosphere was measured in 20 closed chambers at the soil surface. Concurrently the soil temperature and soil water content were recorded in order to quantify their effects on the fate of N₂O in the soil. Results of the continuous measurements between January and December 2006 were: N₂O concentrations were highest in the deeper soil; maximum concentration was found at a depth of 80 cm, where the water content was high and the gas transport reduced. The highest N₂O concentration was recorded after ‘special events’ like snowmelt, heavy rain, fertilization, and grubbing. The combination of fertilization and heavy rain led to an increase of up to 2,700 ppb in the subsoil.     

Fabrication of Biodegradable Superabsorbent Using RSM Design for Controlled Release of KNO<Subscript>3</Subscript>

Present study envisaged the sequential experimental design approach for the development of biodegradable Gelatin-Tapoica/polyacrylamide superabsorbent. Percentage water uptake efficacy of candidate sample was optimized using Response Surface Methodology (RSM) design under microwave irradiation. Different process variables such as potassium persulphate and ammonium persulphate (KPS:APS) ratio, pH, reaction time concentration of acrylamide and N,N-methylene-bis-acrylamide (MBA) were investigated as a function of percentage swelling using sequential experimental design. Maximum liquid efficacy of 1550% was obtained at KPS:APS?=?1.0:0.5; acrylamide?=?7.67?×?10^?1 mol L^?1; MBA?=?1.76?×?10^?2 mol L^?1; pH 10 and time?=?110 s. The 3D crosslinked network formed was characterized using Fourier Transformation Infrared spectroscopy (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopic (SEM) techniques and thermal stability was ensured by Thermal gravimetric Analysis/Differential Thermal Analysis/Differential Thermal Gravimetric (TGA/DTA/DTG) studies. Superabsorbent synthesized could increase the moisture content in different type of soils and was found to enhance the water-holding capability of the soil upto 60 days in clayey, 40 days in sandy and 51 days in mixture of two soils under controlled conditions. Further, candidate polymer was investigated for the in-vitro controlled release of the KNO₃ with diffusion exponent ‘n’ was found to be 0.4326 indicating Fickian type diffusion. Also, initial diffusion coefficient (D_I?=?3.49?×?10^?5 m² h^?1) was found to be greater than the lateral diffusion coefficient (D_L?=?3.76?×?10^?6 m² h^?1) indicated rapid release of KNO₃ during initial hours with slow release afterwards. The ecofriendly nature of the synthesized polymer was also tested by conducting biodegradation studies and it was found to degrade upto 94% and 88.1% within 70 days with degradation rate of 1.34 and 1.26% per day using composting method and vermicomposting method respectively. So, the synthesized candidate polymer was found to be boon for agriculture-horticulture sector with wide applicability.     

Changes in Extractability of Cr and Pb in a Polycontaminated Soil After Bioaugmentation With Microbial Producers of Biosurfactants, Organic Acids and Siderophores

Partly because of the low bioavailability of metals, the soil cleaning-up using phytoremediation is usually time-consuming. In order to enhance the amount of metals at the plant's disposal, the soil bioaugmentation coupled together with phytoextraction is an emerging technology. In this preliminary work, two agricultural soils which mainly differed in their Cr, Hg and Pb contents (LC, low-contaminated soil; HC, high-contaminated soil) were bioaugmented in laboratory conditions by either bacterial (Bacillus subtilis, Pseudomonas aeruginosa, Pseudomonas fluorescens or Ralstonia metallidurans) or fungal inocula (Aspergillus niger or Penicillium simplicissimum) and incubated during three weeks. The LC soil pots bioaugmented with A. niger and P. aeruginosa contained higher concentrations of Cr (0.08 and 0.25 mg.kg⁻¹ dw soil) and Pb (0.25 and 0.3 mg.kg⁻¹ dw soil) in the exchangeable fraction F1 (extraction with MgCl₂) by comparison with the non-bioaugmented soil where neither Cr nor Pb was detected. Conversely, immobilization of Cr and Pb in the soil were observed with the other microorganisms. The soil bioaugmentation not only modified the metal speciation for the most easily extractable fractions but also modified the distribution of metals in the other fractions, to a lesser extent nevertheless. The difference in microbial concentrations between the bioaugmented or not HC soils reached up to 1.8 log units. Thus the microorganisms that we chose for the soil bioaugmentation were competitive towards the indigenous microflora. The PCA analysis showed close positive relationships between the microorganisms which potentially produced siderophores in the soil and the amount of Cr and Pb in the fraction F1.     

Simulation of Exterior Conditions in Permanently Closed Soil Chambers by Controlling Air Flow,Soil Water Content,and Temperature

Volatile substances and gases resulting e.g. from degradation processes of chemicals in soils emit into the atmosphere and no chemical mass balance is complete without considering this path. Closed soil chambers allow the evaluation of this transfer to the atmosphere. This study deals with the influence of soil chambers with a glass plate cover on physical soil conditions in the chambers and the possibility to simulate the exterior conditions within the chambers. The water content immediately at the soil surface is an important factor for the microbial activity and the transfer of gaseous compounds to the atmosphere as well. It is monitored by specially designed water content sensors in 1 cm depth in the chamber and as control outside. Funnels with a cross section equal to the soil surface area of the chamber collect the rain water and channel it into the soil chamber. This results in soil water content in the chambers very similar to that outside. For the purpose of analysing ¹⁴CO₂ and volatile ¹⁴C-compounds, air is permanently pumped through the chamber. In order to simulate natural conditions, the wind speed is measured 1 cm above the soil surface outside the chambers. A control circuit adjusts the air flow through the chamber to a value corresponding to the wind speed outside. Temperature measurements in 1 cm depth verify that there is no significant difference between the soil chamber and the control outside.     

Preparation,Characterization, and Rapid Adsorption of Hg<Superscript>2+</Superscript> on Nanoscale Aramid-based Adsorbent

A series of nanaoscale aramid-based adsorbents were prepared by the functionalization of poly (p-phenylene terephthalamide) (PPTA) with different content of ethylenediamine (EDA). Their structures were characterized by field emission scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, and elemental analysis. Metal ions, including Hg²⁺, Pb²⁺, Ag⁺, Cu²⁺, Cd²⁺, and Ni²⁺ were chosen as the models to explore the binding behaviors of PPTA–ECH–EDA in aqueous medium. Results showed that PPTA–ECH–EDA exhibited higher adsorption capacity for Hg²⁺ due to their nanoscale structures. In particular, the adsorption rate was so high that equilibrium was achieved within 15 min for Hg²⁺. The adsorption of Hg²⁺ on PPTA–ECH–EDA followed the pseudo second-order model well. Langmuir and Freundlich models were employed to fit the isothermal adsorption, and the results revealed that Freundlich isotherm was a better model to predict the experimental data. The adsorption mechanism was revealed by X-ray photoelectron spectroscopy. It is preconceived that PPTA–ECH–EDA could be used as an effective adsorbent for fast removal of heavy ions from wastewater.     

Effect of the water–oil ratio on brine/surfactant/alcohol/oil systems optimized for soil remediation

The optimum middle-phase microemulsion used for remediation of oily contaminated soils is often obtained by mixing a certain amount of a surfactant/alcohol mixture with oil and adjusting the salinity concentrations at a constant water–oil ratio. Upon introduction to the subsurface, however, the system may not be in the optimum state throughout the remediation process owing to the change in the water–oil ratio. This research has attempted to investigate the effect of the water–oil ratio on the phase behavior of systems containing brine, anionic surfactant, alcohols, and different oils. By systematically changing the water–oil ratio, while keeping the others variables constant, the systems exhibited different phase behavior. The results revealed that the effect of the water–oil ratio on system behavior was significant, and analogous to that of salinity. Increasing the water–oil ratio led the system change from winsor I → winsor III → winsor II. The greater the water–oil ratio the lower the salinity required to produce the middle-phase microemulsion, but the narrower the salinity range of the three-phase region. An empirical correlation has been developed in order to predict the changes in phase behavior with the changes in water–oil ratio. This provides a useful tool for designing optimum formulations suitable for soil remediation. Received: October 5, 1999 / Accepted: March 27, 2000     

Fate and behavior of metal(loid) contaminants in an organic matter-rich shooting range soil: Implications for remediation

This study investigates the fate and behavior of lead (Pb), copper (Cu), antimony (Sb), and arsenic (As) in a shooting range soil. The soil samples were collected from the surface (0–15 cm) and the subsurface (15–40 cm and 40–55 cm) of a grassy and wood chip covered impact area behind a firing position. Optical microscopy images indicate significant amounts of corroded bullet fragments and organic wood chips in the surface soil. Analysis by X-ray powder diffraction (XRPD) and scanning electron microscopy electron dispersive X-ray spectroscopy (SEM-EDS) showed that metallic Pb was transformed into lead oxides (litharge PbO and massicot PbO) and lead carbonates (hydrocerussite Pb₃(CO₃)₂(OH)₂, cerussite PbCO₃, and plumbonacrite Pb₅(CO₃)₃O(OH)₂). Rietveld quantification indicated the surface soil contained 14.1% metallic Pb, 17.9% hydrocerussite, 5.2% plumbonacrite, 5.9% litharge, and 3.9% massicot on a dry weight basis, or a total of 39.7% Pb, far in excess of lead concentrations typically found in US shooting range soils. Metallic Cu (bullet jacket material) appeared stable as no secondary minerals were detected in the surface soil. As and Sb concentrations were on the order of 1,057 mg/kg and 845 mg/kg respectively. The elevated soil pH coupled with high organic carbon content is thought to have caused downward migration of metals, especially for Pb, since 4,153 mg Pb/kg was observed at a depth of 55 cm. More than 60% of Pb was concentrated in the coarse soil (> 0.425 mm) fraction, suggesting soil clean-up possible by physical soil washing may be viable. The concentrations of Pb, As, and Sb in the toxicity characteristic leaching procedure (TCLP) extracts were 8,869 mg/L, 6.72 mg/L, and 6.42 mg/L respectively, were above the USEPA non-hazardous regulatory limit (As and Pb) of 5 mg/L. The elevated Sb and As concentrations draw concern because there is historically limited information concerning these metals at firing ranges and several values exceeded local soil cleanup criteria. As the high Pb concentrations appeared to be linked to the presence of organic-rich berm cover materials, the use of wood chips as berm cover to prevent soil erosion requires reconsideration as a shooting range management practice.     

Desiccation of contaminant barrier materials amended with aqueous carboxymethyl cellulose solution

The stabilization potential of negatively charged sodium carboxymethyl cellulose (CMC) solution was assessed through investigation of its retention on clays under environmental conditions that promote soil desiccation. Sodium montmorillonite and kaolinite, commonly used in clayey soils, were mixed with aqueous CMC solutions in concentrations ranging from 0 to 10 g/L. These samples were dried in a specially-designed desiccation chamber which was operated at a temperature of 25°C and relative humidity of 30%. The results show an inverse proportionality between liquid loss and CMC concentration. Liquid loss from clayey soil follows the first-order reaction with a rate constant in the range of 4.6–6.7 mg/h. CMC half-lives on sodium montmorillonite during desiccation ranged from 103 to 181 h for an aqueous concentration range of 0.5–10 g/L compared to 108 h for distilled water. For kaolinite, more liquid was retained at 10 g/L CMC concentration than at other concentrations, but liquid retention was generally insignificant. These conclusions are valid for a desiccation duration of 890 h, a time that is reasonably simulative of the duration of exposures of bare ground surfaces to weather elements. The experimental results are explained in terms of the role of CMC molecular interactions with clay minerals in controlling fluid flow to desiccating clay surfaces.     

Sustainability of Current Agricultural Practices in The Cameron Highlands, Malaysia

Cameron Highlands is a mountainous region with steep slopes. Gradients exceeding 20^∘ are common. The climate is favourable to the cultivation of tea, sub-tropical vegetables and flowers (under rain-shelter). Crop production is sustained by high fertiliser and manure applications. However, agriculture in this environment is characterised by high levels of soil erosion and environmental pollution. A study on the sustainability of these agro-ecosystems was conducted. Results indicated that soil loss was in the range of 24–42 ton/ha/yr under vegetables and 1.3 ton under rain-shelter. Sediment load in the vegetable sub-catchment reached 3.5 g/L, 50 times higher than that associated with flowers under rain-shelter and tea. The sediments contained high nutrient loads of up to 470 kg N/ha/yr. The N, P and K lost in runoff from cabbage farms was 154 kg/season/ha, whereas in chrysanthemum farms it was 5 kg. In cabbage farms, the N, P, and K lost through leaching was 193 kg/season/ha. The NO₃–N concentration in the runoff from the cabbage farms reached 25 ppm but less than 10 ppm in runoff from rain-shelters. Inorganic pollution in the rivers was within the acceptable limit of 10 ppm. The sustainability of the agro-ecosystems is in the order of tea { > } rain–shelter ≫ vegetables.     

Biodegradation of Epoxy and MF Modified Polyurethane Films Derived from a Sustainable Resource

Mesua ferrea L. seed oil (MFLSO) modified polyurethanes blends with epoxy and melamine formaldehyde (MF) resins have been studied for biodegradation with two techniques, namely microbial degradation (broth culture technique) and natural soil burial degradation. In the former technique, rate of increase in bacterial growth in polymer matrix was monitored for 12 days via a visible spectrophotometer at the wavelength of 600 nm using McFarland turbidity as the standard. The soil burial method was performed using three different soils under ambient conditions over a period of 6 months to correlate with natural degradation. Microorganism attack after the soil burial biodegradation of 180 days was realized by the measurement of loss of weight and mechanical properties. Biodegradation of the films was also evidenced by SEM, TGA and FTIR spectroscopic studies. The loss in intensity of the bands at ca. 1735 cm⁻¹ and ca. 1050 cm⁻¹ for ester linkages indicates biodegradation of the blends through degradation of ester group. Both microbial and soil burial studies showed polyurethane/epoxy blends to be more biodegradable than polyurethane/MF blends. Further almost one step degradation in TG analysis suggests degradation for both the blends to occur by breakage of ester links. The biodegradation of the blends were further confirmed by SEM analyses. The study reveals that the modified MFLSO based polyurethane blends deserve the potential to be applicable as “green binders” for polymer composite and surface coating applications.     

Production and characterization of KOH-activated carbon derived from polychlorinated biphenyl residue generated by the sodium dispersion process

Polychlorinated biphenyl (PCB) residues from the sodium dispersion (SD) process were employed as the raw materials for the production of activated carbon using KOH activation. The pore properties, such as the specific surface area and pore size distribution, were characterized using the Barrett–Joyner–Halenda method and the Horvath–Kawazoe method based on the N₂ adsorption isotherm at 77 K. The activated carbon produced showed similar adsorption capacities and specific surface areas to the commercially available product. The effects of the activation conditions on the porosity of the activated carbon produced were studied. The most significant factor affecting the specific surface proved to be the activation temperature. The activated carbon produced from PCB residues from the high-temperature (423–443 K) SD process had a binary pore size distribution well developed in the 4 nm region and in the micropore region. The pore structure of the carbon produced from PCB residues from the low-temperature (333–393 K) SD process had a wide range of micropores and mesopores.     

Fate of Chlorothalonil, Chlorpyrifos and Profenofos in a Vegetable Farm in cameron Highlands, Malaysia

The fate of chlorothalonil, chlorpyrifos and profenofos in sandy loam soil under tropical condition was studied in a vegetable plot in the Cameron Highlands, Malaysia. The plot was treated with chlorothalonil, chlorpyrifos and profenofos according to normal agricultural practices of the Cameron Highlands. Water (runoff and lysimeter), soil and bedload sediment samples were taken according to a sampling schedule. Residues in water, soil and bedload sediment samples were laboratory analysed to determine amount. Chlorothalonil residues were detected in the range of < 0.01–0.08 mg/kg in the soil, < 0.01–0.02 ng/mL in the leachate, < 0.01–0.02 ng/mL in the runoff and < 0.01–0.11mg/kg in the sediment. Field studies of chlorpyrifos showed residue levels of < 0.01–0.06 mg/kg in the soil, < 0.01–0.07 ng/mL in the leachate, < 0.01–0.08 ng/mL in the runoff and < 0.01–0.62 mg/kg in the sediment. Residue levels of profenofos were detected in the range of < 0.01–0.02 mg/kg in the soil, < 0.01–0.87 ng/mL in the leachate, < 0.01–0.08 ng/mL in the runoff and < 0.01–0.35 mg/kg in the sediment. The three pesticides dissipated rapidly, with DT50 (time for 50% loss) of less than two days. The study showed that these pesticides dissipated rapidly under the climatic conditions of the Cameron Highlands in Malaysia.     

Construction, Characterization and Biological Activity of Chiral and Thermally Stable Nanostructured Poly(Ester-Imide)s as Tyrosine-Containing Pseudo-Poly(Amino Acid)s

In this paper we studied the synthesis of biodegradable optically active poly(ester-imide)s containing different amino acid residues in the main chain. These pseudo-poly(amino acid)s were synthesized by polycondensation of N,N′-(pyromellitoyl)-bis-l-tyrosine dimethyl ester as a diphenolic monomer and two chiral trimellitic anhydride-derived diacid monomers containing s-valine and l-methionine. The direct polycondensation reaction of these diacids with aromatic diol was carried out in a system of tosyl chloride (TsCl), pyridine (Py) and N,N′-dimethylformamide (DMF) as a condensing agent. The structures and morphology of these polymers were studied by FT-IR, ¹H-NMR, powder X-ray diffraction, field emission scanning electron microscopy (FE-SEM), specific rotation, elemental and thermogravimetric analysis (TGA) techniques. TGA profiles indicate that the resulting PEIs have a good thermal stability. Morphology probes showed these polymers were noncrystalline and nanostructured polymers. The monomers and prepared polymers were buried under the soil to study the sensitivity of the monomers and the obtained polymers to microbial degradation. The high microbial population and prominent dehydrogenase activity in the soil containing polymers showed that the synthesized polymers are biologically active and microbiologically biodegradable. Wheat seedling growth in the soil buried with synthetic polymers not only confirmed non-toxicity of polymers but also showed possibility of phyto-remediation in polymer-contaminated soils.     

Effect of Solvent Composition on Porosity,Surface Morphology and Thermal Behavior of Metal Alginate Prepared from Algae (<Emphasis Type="Italic">Undaria pinnatifida</Emphasis>)

Alginates, extracted from algae are linear unbranched polymers containing β-(1→4)-linked d-mannuronic acid (M) and α-(1→4)-linked l-guluronic acid (G) residues. The conversion of alginic acid into the metal alginate is confirmed using FTIR spectroscopy. Asymmetric and symmetric stretching of free carboxyl group present in metal alginate occurs almost at the same position in various solvent compositions. Total intrusion volume of metal alginate prepared in propanol (0.0742 mL/g) is greater compared to those in ethanol (0.0648 mL/g) and methanol (0.0393 mL/g) as solvent. Surface morphology as well as porosity and pore size distribution of metal alginate are greatly influenced by solvent. It can be seen from thermal analysis results that calcium alginate prepared using different solvent compositions started decomposing at 100 °C, but rapid degradation started around 200 °C. The results showed a stepwise weight loss during thermal sweep, indicating different types of reactions during degradation. First and second step of rapid degradation was situated around 200–300 and 300–550 °C, respectively; whereas the final step is situated around 550–650 °C. The trend of degradation was similar for all the solvents, although the amount of final residue varied from one solvent to another. At the same time, lower thermal stability was also observed with higher heating rates. Additionally, a kinetic analysis was performed to fit with TGA data, where the entire degradation process has been considered as three consecutive first order reactions.     

Remediation of Soil and Ground Water Contaminated with PAH using Heat and Fe(II)-EDTA Catalyzed Persulfate Oxidation

The feasibility of degrading 16 USEPA priority polycyclic aromatic (PAH) hydrocarbons (PAHs) with heat and Fe(II)-EDTA catalyzed persulfate oxidation was investigated in the laboratory. The experiments were conducted to determine the effects of temperature (i.e. 20 ^∘C, 30 ^∘C and 40 ^∘ C) and iron-chelate levels (i.e., 250 mg/L-, 375 mg/L- and 500 mg/L-Fe(II)) on the degradation of dissolved PAHs in aqueous systems, using a series of amber glass jars as the reactors that were placed on a shaker inside an incubator for temperature control. Each experiment was run in duplicate and had two controls (i.e., no persulfate in systems). Samples were collected after a reaction period of 144 hrs and measured for PAHs, pH and sodium persulfate levels. The extent of degradation of PAHs was determined by comparing the data for samples with the controls. The experimental results showed that persulfate oxidation under each of the tested conditions effectively degraded the 16 target PAHs. All of the targeted PAHs were degraded to below the instrument detection limits (∼4 μ/L) from a range of initial concentration (i.e., 5 μ/L for benzo(a)pyrene to 57 μ/L for Phenanthrene) within 144 hrs with 5 g/L of sodium persulfate at 20 ^∘ C, 30 ^∘C and 40 ^∘C. The data indicated that the persulfate oxidation was effective in degrading the PAHs and that external heat and iron catalysts might not be needed for the degradation of PAHs. The Fe(II)-EDTA catalyzed persulfate also effectively degraded PAHs in the study. In addition, the data on the variation of persulfate concentrations during the experiments indicated that Fe(II)-EDTA accelerated the consumption of persulfate ions. The obtained degradation data cannot be used to evaluate the influence of temperature and Fe(II) levels on the PAH degradation because the PAHs under each of the tested conditions were degraded to below the instrument detection limit within the first sampling point. However, these experiments have demonstrated the feasibility of degrading PAHs in aqueous systems with persulfate oxidation. Additional tests are being conducted to evaluate the effectiveness of treating PAHs in soils and obtaining the rate of degradation of PAHs with persulfate oxidation. Two sets of laboratory experiments were conducted to evaluate the ability of sodium persulfate in oxidizing real world PAH-contaminated soils collected from a Superfund site in Connecticut. The first set of soil sample were treated only with persulfate and to the second batch, mixture of persulfate and Fe(II)-EDTA solutions were added. The results of the second test showed that within 24 hours, 75% to 100% of the initial concentrations of seven PAH compounds detected in the soil samples were degraded by sodium persulfate mixed with FE(II)-EDTA.