Demonstration of combined zero-valent iron and electrical resistance heating for in situ trichloroethene remediation.

The effectiveness of in situ treatment using zero-valent iron (ZVI) for nonaqueous phase or significant sediment-associated contaminant mass can be limited by relatively low rates of mass transfer to bring contaminants in contact with the reactive media. For a field test in a trichloroethene (TCE) source area, combining moderate-temperature subsurface electrical resistance heating with in situ ZVI treatment was shown to accelerate TCE treatment by a factor of about 4 based on organic daughter products and a factor about 8 based on chloride concentrations. A mass-discharge-based analysis was used to evaluate reaction, dissolution, and volatilization processes at ambient groundwater temperature (~10 °C) and as temperature was increased up to about 50 °C. Increased reaction and contaminant dissolution were observed with increased temperature, but vapor- or aqueous-phase migration of TCE out of the treatment zone was minimal during the test because reactions maintained low aqueous-phase TCE concentrations.

An experimental investigation of nitrogen gas produced during denitrification.

In situ denitrification relies on indigenous microorganisms to reduce nitrate to N(2) gas. However, when initial nitrate concentrations are large, produced gas volumes also can be very large, potentially resulting in reduced water saturation and hydraulic conductivity in the treatment zone. In this study, we investigated the fate of N(2) and other gases produced during denitrification in a laboratory flow cell containing packed sediment. Denitrifying activity was stimulated by additions of nitrate and ethanol. Microbial activity was monitored by measuring nitrate, nitrite, and ethanol concentrations; gas saturations were measured during the experiment using a gamma imaging system. Biomass was measured using phospholipid fatty acid analysis of sediment samples. Bioenergetic calculations calibrated to measured nitrate consumed and biomass produced predicted that 1.2 L N(2) gas/L water should have been produced following the addition of 100 mM nitrate. However, the maximum measured gas saturation was only 23%, indicating substantial gas loss from the sediment pack. Temporal gamma images and visual observations confirm that small gas bubbles formed in the sediment pack coalesced into larger bubbles and migrated upward through gas-filled channels to the sediment pack surface. Although gas saturations increased, there was no significant change in sediment pack hydraulic conductivity. These results suggest that in permeable reactive barriers used for in situ denitrification, gas production will not necessarily lead to unlimited gas accumulation in the pore space and that the effects of gas production on water saturation and hydraulic conductivity may be relatively minor.

In-situ oxidation of trichloroethene by permanganate: effects on porous medium hydraulic properties.

In-situ oxidation of dense nonaqueous-phase liquids (DNAPLs) by strong oxidants such as potassium permanganate (KMnO4) has been proposed as a possible DNAPL remediation strategy. In this study, we investigated the effects of in-situ trichloroethene (TCE) oxidation by KMnO4 on porous medium hydraulic properties. In particular, we wanted to determine the overall effects of concurrent solid phase (MnO2) precipitation, gas (CO2) evolution and TCE dissolution resulting from the oxidation reaction on the porous medium's aqueous-phase relative permeability, krw. Three TCE removal experiments were conducted in a 95-cm long, 5.1-cm i.d. glass column, which was homogeneously packed with well-characterized 30/40-mesh silica sand. TCE was emplaced in the sand-pack in residual, entrapped form through a sequence of water/TCE imbibition and drainage steps. The column was then flushed under constant aqueous flux conditions for up to 104 h with either deionized water (reference experiment), deionized water containing 5 mM KMnO4 or deionized water containing 5 mM KMnO4 and 300 mM Na2HPO4. Aqueous-phase relative permeabilities were computed from measured flow rates and measurements of aqueous-phase pressure head, h obtained using pressure transducers connected to tensiometers distributed along the column length. A dual-energy gamma radiation system was used to monitor changes in fluid saturation that occurred during each experiment. In addition, column effluent samples were collected for chemical analyses. Dissolution of TCE during deionized water flushing led to an increase in krw by approximately 22% and a local reduction in h. On the other hand, vigorous CO2 gas production and precipitation of MnO2 was visually observed during flushing with deionized water that contained 5 mM KMnO4. As a consequence, krw declined by approximately 96% and h increased locally by more than 1000 cm H2O during the first 24 h of the experiment, causing sand-pack ruptures and pump failure. Conversely, less CO2 gas production and MnO2 precipitation was visually observed during flushing with deionized water that contained 5 mM KMnO4 and 300 mM Na2HPO4. Consequently, only small increases in h (< 15 cm H2O) were observed in this experiment due to a reduction in krw of approximately 53%. While we must attribute changes in h due to variations in krw to our specific experimental design (constant aqueous flux, one-dimensional flow experiments), these experiments nevertheless confirm that successful application of in situ chemical oxidation of TCE requires consideration of detrimental processes such as MnO2 precipitation and CO2 gas formation. In addition, our results indicate that utilization of a buffered oxidant solution may improve the effectiveness of in-situ oxidation of TCE by KMnO4 in otherwise weakly buffered porous media.

A measurement of social support in epidemiological research: the social experiences checklist tested in a general population in The Netherlands.

STUDY OBJECTIVE: This study aimed to examine in a general population the psychometric qualities of an instrument designed to measure positive and negative social experiences that had been developed in a clinical setting. DESIGN: The Netherlands monitoring project on cardiovascular disease risk factors, a large scale population based study (comprising 36,588 men and women aged 20 to 59 years) carried out in three Dutch towns (Amsterdam, Doetinchem, and Maastricht) offered the possibility of testing the strength of this instrument cross sectionally. MEASUREMENTS AND MAIN RESULTS: The social experiences checklist (SEC) which resulted from a research project on the quality of life of cancer patients was used. The independence of positive and negative experiences was confirmed. The reliability of both the positive and negative experiences dimension was good (Cronbach's alpha = 0.82 and 0.72 respectively). In accordance with the results of a study on cancer patients, the theoretically derived four dimensions in the experience of social support did not seem to be independent. The validity of the SEC was confirmed by Pearson correlations with neuroticism and coping styles. Neuroticism seemed to be negatively correlated with positive social experiences and was positively correlated with negative social experiences. The coping style of seeking information and direct action was positively correlated with positive social experiences. Coping by withdrawal was negatively correlated with negative social experiences. Women and highly educated people seemed to have more positive and fewer negative social experiences than men and people with less education. Younger people had more positive social experiences than older people. The oldest group in the study, those aged 50 to 59, reported fewer negative social experiences than any other age group. CONCLUSIONS: Similar results were found in a study of cancer patients. This underlines the usefulness of the instrument not only for cancer patients but also in survey research in a general population.

Changes in major risk factors for cardiovascular diseases over 25 years in the Serbian cohorts of the Seven Countries Study.

The Serbian cohorts of the Seven Countries Study were examined four times during a 25-year period. Large changes were observed in average serum cholesterol, blood pressure and the prevalence of smoking in these ageing cohorts. Comparison of men of the same age strata e.g. men aged 50-59 examined at baseline and after 10 years of follow-up and of men aged 65-69 examined after 10 and 25 years of follow-up showed that serum cholesterol increased by about 45% in Zrenjanin, 35% in Velika Krsna and 15% in Belgrade over the last 25 years. Systolic blood pressure increased by 9% in Zrenjanin and 7% in Velika Krsna. No significant increase in systolic blood pressure was observed in Belgrade. There was no major secular trend in smoking and the changes observed during 25 years were mainly due to ageing. No major change was observed in body mass index. The increases in serum cholesterol and blood pressure observed in the Serbian cohorts during the last 25 years are compatible with the increase in cardiovascular disease mortality observed in Yugoslavian men aged 30-69 during the period 1970-1984.

The effect of radical and conserving surgery on the quality of life of early breast cancer patients.

In a randomized trial at the Leiden University Hospital, comparing (modified) radical mastectomy with tumorectomy followed by radiotherapy, all patients have been studied with respect to the quality of their lives 11 months and 18 months after surgery. The body image of women was more severely impaired after mastectomy than it was after breast conserving treatment (P less than 0.01). This was true for both younger and older women. Fear of recurrence of cancer was not related to the type of treatment. Thus, from a psychological point of view, breast conserving treatment is to be preferred in women of all ages. The overall quality of life improved and the suffering from psychological and physical complaints decreased with time in both groups of patients. This change may, therefore, have to be attributed to getting over the experience of having had cancer, and not to the treatment schedule.