Measuring and Modeling Organochlorine Pesticide Response to Activated Carbon Amendment in Tidal Sediment Mesocosms.

Activated carbon (AC) sediment amendment for hydrophobic organic contaminants (HOCs) is attracting increasing regulatory and industrial interest. However, mechanistic and well-vetted models are needed. Here, we conduct an 18 month field mesocosm trial at a site containing dichlorodiphenyltrichloroethane (DDT) and chlordane. Different AC applications were applied and, for the first time, a recently published mass transfer model was field tested under varying experimental conditions. AC treatment was effective in reducing DDT and chlordane concentration in polyethylene (PE) samplers, and contaminant extractability by Arenicola brasiliensis digestive fluids. A substantial AC particle size effect was observed. For example, chlordane concentration in PE was reduced by 93% 6 months post-treatment in the powdered AC (PAC) mesocosm, compared with 71% in the granular AC (GAC) mesocosm. Extractability of sediment-associated DDT and chlordane by A. brasiliensis digestive fluids was reduced by at least a factor of 10 in all AC treatments. The model reproduced the relative effects of varying experimental conditions (particle size, dose, mixing time) on concentrations in polyethylene passive samplers well, in most cases within 25% of experimental observations. Although uncertainties such as the effect of long-term AC fouling by organic matter remain, the study findings support the use of the model to assess long-term implications of AC amendment.

Secondary environmental impacts of remedial alternatives for sediment contaminated with hydrophobic organic contaminants.

This study evaluates secondary environmental impacts of various remedial alternatives for sediment contaminated with hydrophobic organic contaminants using life cycle assessment (LCA). Three alternatives including two conventional methods, dredge-and-fill and capping, and an innovative sediment treatment technique, in-situ activated carbon (AC) amendment, are compared for secondary environmental impacts by a case study for a site at Hunters Point Shipyard, San Francisco, CA. The LCA results show that capping generates substantially smaller impacts than dredge-and-fill and in-situ amendment using coal-based virgin AC. The secondary impacts from in-situ AC amendment can be reduced effectively by using recycled or wood-based virgin AC as production of these materials causes much smaller impacts than coal-based virgin AC. The secondary environmental impacts are highly sensitive to the dredged amount and the distance to a disposal site for dredging, the capping thickness and the distance to the cap materials for capping, and the AC dose for in-situ AC amendment. Based on the analysis, this study identifies strategies to minimize secondary impacts caused by different remediation activities: optimize the dredged amount, the capping thickness, or the AC dose by extensive site assessments, obtain source materials from local sites, and use recycled or bio-based AC.

Modeling uptake of hydrophobic organic contaminants into polyethylene passive samplers.

Single-phase passive samplers are gaining acceptance as a method to measure hydrophobic organic contaminant (HOC) concentration in water. Although the relationship between the HOC concentration in water and passive sampler is linear at equilibrium, mass transfer models are needed for nonequilibrium conditions. We report measurements of organochlorine pesticide diffusion and partition coefficients with respect to polyethylene (PE), and present a Fickian approach to modeling HOC uptake by PE in aqueous systems. The model is an analytic solution to Fick's second law applied through an aqueous diffusive boundary layer and a polyethylene layer. Comparisons of the model with existing methods indicate agreement at appropriate boundary conditions. Laboratory release experiments on the organochlorine pesticides DDT, DDE, DDD, and chlordane in well-mixed slurries support the model's applicability to aqueous systems. In general, the advantage of the model is its application in the cases of well-agitated systems, low values of polyethylene-water partioning coefficients, thick polyethylene relative to the boundary layer thickness, and/or short exposure times. Another significant advantage is the ability to estimate, or at least bound, the needed exposure time to reach a desired CPE without empirical model inputs. A further finding of this work is that polyethylene diffusivity does not vary by transport direction through the sampler thickness.

The effects of salinity and temperature on phase transformation of copper-laden sludge.

To stabilize the copper and aluminum ions in simulated sludge, a series of sintering processes were conducted to transform Cu/Al precipitation into spinel structure, CuAl(2)O(4). The results indicated that the large amount of salt content in the simulated sludge would hinder the formation of crystalline CuAl(2)O(4) generated from the incorporation of CuO and Al(2)O(3), even after the sintering process at 1200 °C. Opposite to the amorphous CuAl(2)O(4), the crystalline CuAl(2)O(4) can be formed in the sintering process at 700-1100 °C for 3 h with the desalinating procedure. According to the theory of free energy, the experimental data and references, the best formation temperature of CuAl(2)O(4) was determined at 900-1000 °C. As the temperature rose to 1200 °C, CuAlO(2) was formed with the dissociation of CuAl(2)O(4). The XPS analysis also showed that the binding energy of copper species in the simulated sludge was switched from 933.8 eV for Cu(II) to 932.8 eV for Cu(I) with the variation of temperature. In this system, the leaching concentration of copper and aluminum ions from sintered simulated sludge was decreased with ascending temperature and reached the lowest level at 1000 °C. Furthermore, the descending tendency coincided with the formation tendency of spinel structure and the diminishing of copper oxide.

Stabilization of nickel-laden sludge by a high-temperature NiCr2O4 synthesis process.

The feasibility of stabilizing nickel-laden sludge by a high-temperature NiCr(2)O(4) synthesis process was investigated with different sintering temperatures, salt contents, molar ratios, and reaction atmospheres. The crystalline phases of species were investigated by using an X-ray diffraction, and the surface characteristics of particles were observed by scanning electron microscopy. The leaching behavior of the stabilized sludge was evaluated by Toxicity Characteristic Leaching Procedure (TCLP) test. The results indicated that NiCr(2)O(4) was formed at around 800°C by transforming NiO and Cr(2)O(3) into a spinel structure. Leaching concentrations of both nickel and chromium decreased with an increase in the sintering temperature. The existence of salt in the sludge disturbed the formation of spinel, but a moderate salt content contributed to stabilization efficiency. A Cr/Ni molar ratio >2 also contributed to the stabilization efficiency of heavy metals after the thermal process. NiCr(2)O(4) was transformed from simulated sludge under both an N(2) and air atmosphere. The sintering strategy designed for nickel-laden sludge was proven to be beneficial in stabilizing nickel and chromium.

Stabilization and phase transformation of CuFe2O4 sintered from simulated copper-laden sludge.

The feasibility of stabilizing copper-laden sludge by high-temperature CuFe(2)O(4) ferritization process is investigated with different sintering temperature, and the prolonged leaching test. The thermal behavior, structural morphology, phase composition, and phase transformation of the stabilized sludge were investigated by using thermal gravimetry-differential scanning calorimetry, scanning electron microscopy and X-ray diffraction. The leaching behavior of the stabilized sludge under acidic environment was evaluated by modified Toxicity Characteristic Leaching Procedure (TCLP). The results indicated that CuFe(2)O(4) could be effectively formed at around 800°C by the iron oxide precursor with a 3h of short sintering. The transformation was discovered on crystallographic spinel structures: the low-temperature (800-900°C) tetragonal phase (t-CuFe(2)O(4)) and the high-temperature (∼ 1000°C) cubic phase (c-CuFe(2)O(4)). At higher temperatures (∼ 1100°C), the formation of cuprous ferrite delafossite phase (CuFeO(2)) from the dissociation of CuFe(2)O(4) was also noticed. Both CuFe(2)O(4) spinel and CuFeO(2) delafossite phase have a better intrinsic resistance to acidic environment when compared to that of CuO phase by the modified TCLP test. The sintering strategy designed for copper-laden sludge is proven to be beneficial in stabilizing copper.

Stabilization of copper-contaminated sludge using the microwave sintering.

A sintering with a microwave process was considered to stabilize copper-contaminated sludge and transform it into a sinter because microwave can provide uniform and quick heating. The parameters of addition of iron powder and ferric oxide, crucible modification, and air-forced leading were used in the microwave sintering. The results showed that reduced copper was present and some holes, caused by the high copper-contaminated synthetic sludge passing through the microwave sintering, were distributed throughout the sinters. However, when microwave sintering with the modification of parameters (improved microwave sintering) was used, the phenomena of copper reduction and hole formation were dispelled. Moreover, the improved microwave sintering of synthetic sludge with iron powder at 800W at 30 min formed cuprospinel with peaks of 2theta degrees of 18.508 and 57.05 shifting to 18.9 and 56.55 and the leaching concentration from this sinter passed the limit of toxicity characteristic leaching procedure (TCLP) for copper.

Sintering of MSWI fly ash by microwave energy.

This study presents the sintering of municipal solid waste incineration (MSWI) fly ash assisted by microwave energy. The composition of fly ash was investigated by chemical sequential extraction and modified microwave digestion method. Effects of process time, container materials, aging time and salt contents were also discussed. The major elements of fly ash are Ca, Cl, Na, Si, K, Al, Mg, and Zn, and the metal species, Zn, Cr, Pb, Ca, and Cu, are mainly in the oxide phase. Under microwave processing, the fly ash was sintered into a glass-ceramics and the leaching concentrations of heavy metals were restrained. The stabilization efficiency increased with an increase in processing time in most of the cases. Better stabilization efficiency of fly ash was discovered by using the SiO(2) or Al(2)O(3) container than by using the graphite plate/SiC plate. The presence of salt in the fly ash could enhance the sintering and stabilization of fly ash. During the aging time of 0-30 days, negligible Pb in the sintered fly ash was leached out, and the leaching concentration was lower than the criterion.

Thermal detoxification of hazardous metal sludge by applied electromagnetic energy.

Industrial wastewater sludge was treated by microwave processes to enhance the stabilization of laden copper. The effects of additives, processing time, microwave adsorbents, moisture content, reaction atmosphere, and cooling gas were investigated. The stabilization results were significantly enhanced by metal powder additives, prolonged microwave processing time, proper moisture content, the addition of carbonaceous materials, and a reaction environment with inert gas. It was also found that the moisture content would increase the homogeneity of applied microwave energy, and thus achieve a better overall efficiency between stabilizing agents and copper. The added metal powders may reduce Cu(II) to Cu(0) in the sludge or TCLP. The resulting thermal energy of microwave radiation, and microarcing process and the oxidation heat of Al powder may also assist the transformation of Cu(II) into CuO and CuAl2O4 phases. Part of the sludge was vitrified within inert gas environment when the processing time was longer than 18 min and active carbon dosage was more than 3g. Reduction reactions also occurred in the hybrid microwave processes, leading to the reduction of sulfates and metal ions, and the formation of Cu2S and FeS. Moreover, the microwave radiation can also enhance the feasibility of co-treating of inorganic and organic solid waste.

The assistance of microwave process in sludge stabilization with sodium sulfide and sodium phosphate.

After industrial wastewater sludge passed through an acid-extraction process to reclaim most of the copper ions in it, the residue may still need to be treated by stabilization technologies. The common method for the stabilization of hazardous waste in Taiwan is by cement solidification. However, this method has the disadvantage of an increase in waste volume. In this study, it was tried to combine the advantages of sulfur anions and phosphate anions with the characteristics of microwave energy to offer a new method which can avoid the disadvantage of cement solidification. From the results, it was found that the assistance of heating in sludge stabilization with additives was effective. Huge amounts of additives were saved. Compared with the assistance of the traditional electrical-heating in sludge stabilization with additives, that of the microwave process saved much time and was more powerful. However, when the reaction time was longer, a re-leaching situation would occur. The hybrid microwave process, a procedure of leading an inert gas into the microwave process, could overcome the disadvantage of the microwave process with regard to the long reaction time. Finally, a modified hybrid microwave process which reduced the use of gas was performed and recommended.

Microwave enhanced stabilization of heavy metal sludge.

A microwave process can be utilized to stabilize the copper ions in heavy metal sludge. The effects of microwave processing on stabilization of heavy metal sludge were studied as a function of additive, power, process time, reaction atmosphere, cooling gas, organic substance, and temperature. Copper leach resistance increased with addition of aluminum metal powder, with increased microwave power, increased processing time, and using a gaseous environment of nitrogen for processing and air for cooling [N2/air]. The organic in the sludge affected stabilization, whether or not the organic smoldered. During heating in conventional ovens, exothermic oxidation of the organic resulted in sludge temperatures of about 500 degrees C for oven control temperatures of 200-500 degrees C. After microwave heating dried the sludge, the sludge temperature rose to 500 degrees C. The reaction between copper ions and metal aluminum in the dried sludge should be regarded as a solid phase reaction. Adding aluminum metal powder and reaction temperature were the key parameters in stabilizing copper in the heavy metal sludge, whether heated by microwave radiation or conventional oven. The mass balance indicates insignificant volatization of the copper during heating.

Adsorption of copper ions onto microwave stabilized heavy metal sludge.

Microwave stabilized heavy metal sludge was used as an adsorbent to remove the copper ions from aqueous solution. The adsorption characteristics of copper on the stabilized-sludge were studied by various models, such as Freundlich and Langmuir isotherm equation. Results show that the pH(zpc) of stabilized-sludge was at 9.2-9.5. Moreover, the adsorption of copper ions onto the stabilized-sludge surface was mainly on account of the heterogeneous surface of the stabilized-sludge. In the dynamic study, the experimental data was fitted to the intraparticle diffusion model, pseudo-first order model and pseudo-second order model. However, the experimental data was only well correlated with pseudo-second order model with the correlation coefficient>0.995. Furthermore, both Freundlich and Langmuir isotherm equations were found to represent the measured adsorption data well. From the Langmuir equation, the adsorption capacity increased from 18 to 28 mg/g as the temperature rose from 15 to 55 degrees C, since this adsorption process was an endothermic reaction. After this adsorption process, copper ions can be concentrated on and in a small bead and recovery efficiently.

NPC-14686 (Fmoc-l-homophenylalanine)-induced CaCa2+ increases and death in human prostate cancer cells.

The effect of NPC-14686, a potential anti-inflammatory drug, on cytosolic free Ca2+ levels ([Ca2+]i) and growth in PC3 human prostate cancer cells was examined by using fura-2 as a fluorescent Ca2+ indicator and WST-1 as a fluorescent growth dye. NPC-14686 at concentrations above 10 microM increased [Ca2+]i in a concentration-dependent manner with an EC50 value of 100 microM. NPC-14686-induced Ca2+ influx was confirmed by Mn2+ quench of fura-2 fluorescence. The Ca2+ signal was also reduced by removing extracellular Ca2+. Pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) to deplete the endoplasmic reticulum Ca2+ nearly abolished 200 microM NPC-14686-induced Ca2+ release; and conversely pretreatment with NPC-14686 completely inhibited thapsigargin-induced Ca2+ release. The Ca2+ release induced by 200 microM NPC-14686 was not affected by inhibiting phospholipase C with 2 microM U73122. Overnight treatment with 1-500 microM NPC-14686 decreased cell viability in a concentration-dependent manner. These findings suggest that in human PC3 prostate cancer cells, NPC-14686 increases [Ca2+]i by evoking extracellular Ca2+ influx and releasing intracellular Ca2+ from the endoplasmic reticulum via a phospholiase C-independent manner. NPC-14686 may be cytotoxic to prostate cancer cells.

Effects of econazole on Ca2+ levels in and the growth of human prostate cancer PC3 cells.

1. Econazole is used clinically as an antifungal drug with many different in vitro effects. However, the effects of econazole on prostate cancer cells are unknown. The effects of econazole on intracellular Ca2+ concentrations ([Ca2+]i) in and the proliferation of human PC3 prostate cancer cells was explored in the present study using fura-2 and tetrazolium as fluorescent dyes. 2. At a concentration of 0.1 micromol/L, econazole started to increase [Ca2+]i in a concentration-dependent manner. The econazole-induced increase in [Ca2+]i was reduced by 48% by removal of extracellular Ca2+, suggesting that the econazole-induced increase in [Ca2+]i was composed of extracellular Ca2+ influx and intracellular Ca2+. 3. This econazole-induced Ca2+ influx was via an L-type Ca2+ channel-like pathway. In Ca2+-free medium, 1 micromol/L thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a monophasic increase in [Ca2+]i, after which the effect of econazole to increase [Ca2+]i was substantially inhibited. Conversely, pretreatment with 5 micromol/L econazole to deplete intracellular Ca2+ stores totally prevented thapsigargin from releasing more Ca2+. 4. The phospholipase C (PLC) inhibitor U73122 (2 micromol/L) abolished the increase in [Ca2+]i induced by 10 micromol/L ATP (a Ca2+ mobilizer that needs inositol 1,4,5-trisphosphate). 5. Overnight incubation with 1-30 micromol/L econazole inhibited proliferation of PC3 cells in a concentration-dependent manner. 6. These findings suggest that, in PC3 cells, econazole increases [Ca2+]i by stimulating Ca2+ influx into cells and Ca2+ release from the endoplasmic reticulum via a PLC-independent mechanism. Econazole is cytotoxic at submicromolar concentrations.

Nonylphenol-induced Ca2+ elevation and Ca2+-independent cell death in human osteosarcoma cells.

The effect of the environmental toxicant nonylphenol on cytosolic free Ca2+ concentration ([Ca2+]i) and proliferation has not been explored in human osteoblast-like cells. This study examined whether nonylphenol alters Ca2+ levels and causes cell death in MG63 human osteosarcoma cells. [Ca2+]i and cell death were measured using the fluorescent dyes fura-2 and WST-1 respectively. Nonylphenol at concentrations above 3 microM increased [Ca2+]i in a concentration-dependent manner. The Ca2+ signal was reduced by 90% by removing extracellular Ca2+. The nonylphenol-induced Ca2+ influx was insensitive to blockade of L-type Ca2+ channel blockers. After pretreatment with 10 microM nonylphenol, 1 microM thapsigargin (an endoplasmic reticulum Ca2+ pump inhibitor) failed to induce [Ca2+]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change nonylphenol-induced [Ca2+]i rises. The nonylphenol-induced [Ca2+]i rises were enhanced or inhibited by phorbol myristate acetate or GF 109203X, respectively. At concentrations of 10 and 20 microM nonylphenol killed 55% and 100% cells, respectively. The cytotoxic effect of 10 microM nonylphenol was unaltered by pre-chelating cytosolic Ca2+ with BAPTA. Collectively, in MG63 cells, nonylphenol induced [Ca2+]i rises by causing Ca2+ release from intracellular stores and Ca2+ influx from extracellular space. Furthermore, nonylphenol can cause Ca2+-unrelated cytotoxicity in a concentration-dependent manner.

Thimerosal-induced cytosolic Ca2+ elevation and subsequent cell death in human osteosarcoma cells.

The effect of the oxidizing agent thimerosal on cytosolic free Ca(2+) concentration ([Ca(2+)]i) and proliferation has not been explored in human osteoblast-like cells. This study examined whether thimerosal alters Ca(2+) levels and causes cell death in MG63 human osteosarcoma cells. [Ca(2+)]i and cell death were measured using the fluorescent dyes fura-2 and WST-1, respectively. Thimerosal at concentrations above 5 microM increased [Ca(2+)]i in a concentration-dependent manner. The Ca(2+) signal was reduced by 80% by removing extracellular Ca(2+). The thimerosal-induced Ca(2+) influx was sensitive to blockade of La(3+), and dithiothreitol (50 microM) but was insensitive to nickel and several L-type Ca(2+) channel blockers. After pretreatment with 1 microM thapsigargin (an endoplasmic reticulum Ca(2+) pump inhibitor), thimerosal failed to induce [Ca(2+)]i rises. Inhibition of phospholipase C with 2 microM U73122 did not change thimerosal-induced [Ca(2+)]i rises. At concentrations of 5, 10 and 20 microM thimerosal killed 33, 55 and 100% cells, respectively. The cytotoxic effect of 5 microM thimerosal was reversed by 54% by prechelating cytosolic Ca(2+) with BAPTA. Collectively, in MG63 cells, thimerosal induced a [Ca(2+)]i rise by causing Ca(2+) release from endoplasmic reticulum stores and Ca(2+) influx from extracellular space. Furthermore, thimerosal can cause Ca(2+)-related cytotoxicity in a concentration-dependent manner.

Stabilization of Cu in acid-extracted industrial sludge using a microwave process.

The leaching concentration of copper ions from the industrial sludge that has been extracted using sulfuric acid may still exceed 15 mg/L, which is the leaching standard of the toxicity characteristic leaching procedure (TCLP) for hazardous waste in Taiwan. Therefore, the acid-extracted industrial sludge is still an important source of hazardous waste. Usually, hazardous waste in Taiwan must be solidified and passed through the TCLP test before it is disposed in a landfill. The aim of this study is to develop a microwave process to stabilize copper ions in the sludge to replace the use of traditional solidification. In this study, two parameters--the reaction time of the microwave process and the additive reagents--were considered. The efficiency of stabilization of the microwave process was evaluated from the result of the TCLP test. The results showed that the stabilization efficiency of copper ions obtained using a microwave process without any added reagent depends highly on the property of the original acid-extracted sludge. Under some conditions, the leaching concentrations were much lower than those of the raw sludge. In additive reagent systems, the results showed that iron powder promoted the stabilization of copper ions more than the other additives such as sodium carbonate and sodium silicate. The leaching concentration of copper ions decreased dramatically from 179.4 to 6.5mg/L below in the iron additive system.