Ground discarded tires remove naphthalene, toluene, and mercury from water

Ground discarded tires adsorb naphthalene, toluene, and mercury ions (Hg2+) from aqueous solutions. Their sorption properties and kinetics were determined by batch equilibration techniques at 20 degrees C. The isotherms were linear for naphthalene and toluene and their sorption coefficients were about 1340 and 255 (ml/g), respectively. Sorption of the organic compounds by the ground rubber particles was relatively fast (within 30 min). However, the mercury isotherms were non-linear, and its sorption was slow as compared to the sorption of the organics. The rubber particles had a strong affinity for Hg2+. These results show that ground discarded tires are effective in removing organic compounds and Hg2+ from wastewater and other contaminated environments. In addition it would be a useful, environmentally friendly use of discarded tires (one tire per year per capita is discarded in the United States).     

Microbial degradation of phthalic acid esters under anaerobic digestion of sludge

The microbial degradation by anaerobic sludge of three phthalates, priority pollutants, listed by both China National Environmental Monitoring Center and the U.S.EPA, namely, dimethyl (DMP), di-n-butyl (DBP) and di-n-octyl (DOP) phthalates was investigated. The experimental results indicated that the biodegradation rate and the biodegradability of three phthalates under anaerobic conditions appeared to be related to the length of the alkyl-side chains. More than 90% of DMP and DBP with the short alkyl-side chain phthalates can be degraded, whereas the DOP degradation appeared to be relatively slow under the same experimental conditions. The quantity of methane produced was measured and the results showed that both the ester groups and the phthalate ring were mineralized at a significant rate. The kinetics study demonstrated that the biodegradation of three phthalates conformed to the first-order model with respect to their concentrations.     

Application of a stochastic, Weibull probability generator for replacing missing data on ambient concentrations of gaseous pollutants

A stochastic, three-parameter, Weibull frequency distribution, probability generator was tested by using theoretical data. Subsequently, it was applied to replace missing values of hourly atmospheric concentrations of trace gases that were continuously monitored at three study sites, for 2 years. The results were highly accurate and realistic. The cumulative means and the medians calculated by the Weibull method were intermediate between corresponding values calculated by uniform substitution of missing values with 'zero' or with half of the minimum detection limit of the appropriate measurement instrument used. Furthermore, the Weibull method allowed the replacement of as many as 100 missing values on either side of a measured data sub-set, without altering the overall characteristics of the true frequency distribution of the entire data set.     

Seedling insensitivity to ozone for three conifer species native to Great Smoky Mountains National Park

Field symptoms typical of ozone injury have been observed on several conifer species in Great Smoky Mountains National Park, and tropospheric ozone levels in the Park can be high, suggesting that ozone may be causing growth impairment of these plants. The objective of this research was to test the ozone sensitivity of selected conifer species under controlled exposure conditions. Seedlings of three species of conifers, Table Mountain pine (Pinus pungens), Virginia pine (Pinus virginiana), and eastern hemlock (Tsuga canadensis), were exposed to various levels of ozone in open-top chambers for one to three seasons in Great Smoky Mountains National Park in Tennessee, USA. A combination of episodic profiles (1988) and modified ambient exposure regimes (1989-92) were used. Episodic profiles simulated an average 7-day period from a monitoring station in the Park. Treatments used in 1988 were: charcoal-filtered (CF), 1.0x ambient, 2.0x ambient, and ambient air-no chamber (AA). In 1989 a 1.5x ambient treatment was added, and in 1990, additional chambers were made available, allowing a 0.5x ambient treatment to be added. Height, diameter, and foliar injury were measured most years. Exposures were 3 years for Table Mountain pine (1988-90), 3 years for hemlock (1989-91), and 1 and 2 years for three different sets of Virginia pine (1990, 1990-91, and 1992). There were no significant (p<0.05) effects of ozone on any biomass fraction for any of the species, except for older needles in Table Mountain and Virginia pine, which decreased with ozone exposure. There were also no changes in biomass allocation patterns among species due to ozone exposure, except for Virginia pine in 1990, which showed an increase in the root:shoot ratio. There was foliar injury (chlorotic mottling) in the higher two treatments (1.0x and 2.0x for Table Mountain and 2.0x for Virginia pine), but high plant-to-plant variability obscured formal statistical significance in many cases. We conclude, at least for growth in the short-term, that seedlings of these three conifer species are insensitive to ambient and elevated levels of ozone, and that current levels of ozone in the Park are probably having minimal impacts on these particular species.     

Monitoring, modelling and environmental exposure assessment of industrial chemicals in the aquatic environment

Monitoring and laboratory data play integral roles alongside fate and exposure models in comprehensive risk assessments. The principle in the European Union Technical Guidance Documents for risk assessment is that measured data may take precedence over model results but only after they are judged to be of adequate reliability and to be representative of the particular environmental compartments to which they are applied. In practice, laboratory and field data are used to provide parameters for the models, while monitoring data are used to validate the models' predictions. Thus, comprehensive risk assessments require the integration of laboratory and monitoring data with the model predictions. However, this interplay is often overlooked. Discrepancies between the results of models and monitoring should be investigated in terms of the representativeness of both. Certainly, in the context of the EU risk assessment of existing chemicals, the specific requirements for monitoring data have not been adequately addressed. The resources required for environmental monitoring, both in terms of manpower and equipment, can be very significant. The design of monitoring programmes to optimise the use of resources and the use of models as a cost-effective alternative are increasing in importance. Generic considerations and criteria for the design of new monitoring programmes to generate representative quality data for the aquatic compartment are outlined and the criteria for the use of existing data are discussed. In particular, there is a need to improve the accessibility to data sets, to standardise the data sets, to promote communication and harmonisation of programmes and to incorporate the flexibility to change monitoring protocols to amend the chemicals under investigation in line with changing needs and priorities.     

Interpreting the relationship between pheromone component emission from commercial lures and captures of Helicoverpa zea (Boddie) in bucket and cone traps

Male corn earworm moths, Helicoverpa zea (Boddie), were captured in conical Texas pheromone traps (cone traps) and bucket traps baited with four different commercial lures manufactured by three different manufacturers. Because significant numbers were captured in bucket traps baited with some of the lures, and none with others, the volatile emissions from all of the lures were sampled and analyzed by gas chromatographic methods. The numbers of males captured in two types of trap were compared with bait emissions in an endeavor to define a more effective lure for bucket traps. The lure from one manufacturer captured the same numbers of males in both trap types; one captured more in bucket traps than in cone traps, and another captured only a small number in bucket traps. The emission rate of all active compounds from each of the different lures was approximately linear for the duration of the assays. A gas-liquid chromatographic peak associated with a third compound, (Z)-9-tetradecenal, which reduces behavioral responses, was observed in the emissions from all lures evaluated. The effectiveness of the Hercon (Emmigsville, PA) lure in capturing males in both types of trap was associated with a lower emission of (Z)-11-hexadecenal, (Z)-9-hexadecenal and (Z)-9-tetradecenal than from the other lures.     

Lead exposure of small herbivorous vertebrates from atmospheric pollution

Concentrations of Pb in livers of willow grouse (Lagopus lagopus), black grouse (Tetrao tetrix), and hare (Lepus timidus) were determined in samples collected during the period 1990-92 from 77 locations distributed across Norway. Our objective was to elucidate the impact of long-range atmospheric transport on the Pb exposure of the animals. The moss Hylocomium splendens was measured for atmospheric Pb deposition and Pb in soil at 60-cm depth was determined to reflect the natural geochemical background at the study locations. Strong positive relationships were found between Pb in liver and atmospheric deposition of Pb for all species and age groups studied. Results indicate that long-range atmospheric transport was the main source of Pb in the animals studied. This conclusion was supported by Pb analysis of typical food plants for the animals. Correlation between Pb in liver and Pb in soil mineral matter was observed only when considering sites with very low impact of atmospheric deposition. Even though the observed liver Pb concentrations may seem low (< or =12 microg g(-1) dw) they approach levels where sub-lethal effects cannot be ignored.     

Glutamine synthetase and protease enzyme activities and growth response of ruminal bacterium Prevotella ruminicola strain B(1)4 to nitrogen source and concentration

The objective of this study was to determine the effects of varying nitrogen sources and concentrations upon glutamine synthetase and protease activities in Prevotella ruminicola strain B(1)4. Based on growth response it appears that ammonium chloride or pepticase limited P. ruminicola becomes nitrogen limited when nitrogen concentration is at 0.5 mM. However, when casein was provided as the sole source of nitrogen P. ruminicola becomes nitrogen limited at 2.5 mM. Glutamine synthetase activity was measured from mid-log phase cells grown in either nitrogen-limited or non-limited conditions. No activity was detectable in the non-limited treatments. However, in the N-limited treatments, pepticase had the highest activity (20.76 units), followed by ammonium chloride (18.72 units) and casein (14.42 units). Protease activity assays indicated that nitrogen-limited cultures had higher proteolytic activity than non-limited cultures. Moreover, these activities appeared to follow the same response pattern as the previously observed glutamine synthetase activities. The results of this study indicate that P. ruminicola strain B(1)4 protease activity may be influenced by nitrogen concentration such that activity increases when nitrogen availability decreases.     

Evaluation of ecological disturbance and intrinsic bioremediation potential of pulp mill-contaminated lake sediment using key enzymes as probes

A rapid protocol was developed to measure 10 different enzymic activities from a large number of 1-cm-sliced freshly collected lake sediments. Layers heavily polluted by organic halogens (4900 mg Cl kg(-1)) revealed severe depression of phosphatase, sulfatase, leucine-aminopeptidase, chitinase, acetate esterase and butyrate esterase activities as compared to layers above and below the most polluted zone. alpha-Glucosidase, beta-glucosidase, beta-xylosidase and palmitate esterase were less affected. Methane oxidation potential was dramatically depressed in the polluted strata whereas tetrachloromethane dehalogenating activity was observed in the polluted sediment only. The sediment layers formed after the chlorine discharges into the lake had diminished to 1/10, and showed restoration of the activities close to those observed in non-recipient sediment, in spite of the persisting presence of >1000 mg of organic chlorine (kg dry wt)(-1). We conclude that certain enzymic activities involved in breakdown or oxidation of organic matter in the sediments are useful probes for assessing the degree of ecological damage and its potential for restoration in recipient lakes of industrial discharges.     

What is the potential measurement error in occupational exposure studies?

This paper demonstrates statistical methods that estimate measurement error from available industrial hygiene data. Errors in measuring a continuous exposure variable may arise when all individuals in a work area are assigned the same exposure. An example is when the mean of exposure measurements obtained on a sample of individuals is assigned to all workers with similar jobs. This may lead to inaccurate point and interval estimates in exposure-response modeling. A method of simulating the distribution of true (i.e., unobserved) individual exposures is described in order to estimate the mean and variance of measurement error. The minimum variance unbiased estimator approximates the mean of lognormally distributed exposure measurements. The distribution of true individual exposures is approximated by the distribution of simulated estimates of mean exposure. The methodology is illustrated by exposure data from work areas manufacturing refractory ceramic fiber (RCF) and RCF products. Results show that exposure is slightly underestimated in work areas with between 25 and 113 exposure measurements; measurement error variance averages about 1.3% of the total variance.