The use of the cotton-strip assay to assess cellulose decomposition in heavy metal-contaminated sewage sludge-amended soils

Cellulose decomposition in soils amended over twenty year ago with heavy metal-contaminated sewage sludges was assessed by using the cotton-strip assay. The soils of the Luddington Experiment now contain concentrations of Cu, Ni and Zn in selected plots that approximate to or exceed the statutory limits for these elements in sewage sludge-amended soils. The rates of cellulose decomposition were generally lower in the plots with elevated metal concentrations, relative to uncontaminated sludge-amended and unsludged controls. Generally, the metal-rich plots showed reductions in the time taken to reach 50% cotton-tensile-strength loss (CTSL). However, the reductions could not be consistently related to any one metal. The difference in decomposition rates between treatments was systematically reduced over the duration of a time-course experiment. A lower initial population of the appropriate decomposer community of micro-organisms may account for the observed short-term lag in decomposition rates.     

A teratological assessment of four trihalomethanes in the rat

Four trihalomethanes were administered by gavage to Sprague-Dawley rats from day 6 to day 15 of gestation. Chloroform (Ch) was administered at levels of 100, 200 and 400 mg/kg and bromoform (Br), bromodichloromethane (BDCM) and chlorodibromomethane (CDBM) were administered at levels of 50, 100 or 200 mg/kg/day. A separate control was used for each compound. Maternal weight gain was depressed in all groups receiving Ch and at the highest dose levels of BDCM and CDBM. Ch administration caused decreased maternal hemoglobin and hematocrit values at all dose levels and also produced increased serum inorganic phosphorus and cholesterol at the highest dose. Liver enlargement was observed at all dose levels of Ch but in no other treatment groups. Evidence of a fetotoxic response was observed with Ch, CDBM and Br but not BDCM. No dose-related histopathological changes were observed in either mothers or fetuses as a result of treatment. None of the chemicals tested produced any teratogenic effects.     

Assessment of hazards associated with pesticide container disposal and of rinsing procedures as a means of enabling disposal of pesticide containers in sanitary landfills

To study problems associated with pesticide container disposal, a small vegetable production area in southwestern Ontario, the Thedford Marsh, was selected as the site for a model study. A container collection system was organized during the 1981 growing season, with collections being made from the ca. 50 growers on the marsh twice each month. In addition to the regular collection program a cleanup service for empty pesticide containers stored on farms or discarded on public lands also was initiated. More than 3600 containers were collected and disposed of at an authorized landfill site. Ca. 2/3 were herbicide containers, ca. 1/4 were insecticide containers, and 3% were fungicide containers. Unrinsed containers contained as much as 5 1/2% of the original contents with an average of 1%. Containers rinsed by the triple rinse method or using rinsing devices (E-Z Rinse, JET Rinse) generally contained less than 0.1% of the original content. Some formulations presented rinsing problems due to settling and caking. The results indicated that, while unacceptable quantities of pesticide residues remain in unrinsed containers, most rinsed pesticide containers will be acceptable for disposal at municipal sanitary landfill sites.     

Aerobic ethanol production by leaves: Evidence for air pollution stress in trees of the Ohio River Valley, USA

We measured the frequency with which leaves of trees in the Ohio River Valley produced ethanol aerobically, to determine if aerobic ethanol production might provide a viable field assay for air pollution stress. Leaves were collected from trees during the summers of 1985 and 1986 and ethanol production was determined using headspace GC. Frequency of ethanol production was compared with environmental factors, including air pollution concentrations. We found frequent foliar ethanol production and elevated alcohol dehydrogenase activity in the leaves of several species of trees in the Ohio River Valley, USA. The ethanol concentrations measured were often equivalent to those produced by anaerobic leaves. Ethanol production was associated with hot, hazy weather and elevated NO(2) concentrations. Ethanol production was more frequent in urban and industrialized areas. Ethanol production was not associated with natural stresses such as flooding and herbivory. We propose that aerobic ethanol production is the result of cell acidification due to the accumulation of acidic gases in the cytoplasm. The use of ethanol production as a diagnostic tool for detecting stress imposed by acidic gases is discussed.     

Loss of HCH from surface soil layers under subtropical conditions

The loss of HCH (hexachlorocyclohexane) at an application rate of 25 kg ha(-1) was studied under field conditions from two surface soil layers, each of 7.5 cm, at two sites in Delhi. The soil at both sites was sandy loam type, with a pH of 8.2, and 0.8 to 1.0% organic matter content. At site 1, which was kept fallow and not watered, the upper 7.5-cm layer of soil initially lost HCH more rapidly than the lower layer. The half-life of the HCH in the upper and lower 7.5-cm layers was 21 and 41 days, respectively, and it was 26 days for the total HCH in the combined 15-cm soil layer. At site 2, which contained ornamental plants and was watered regularly, there was not much difference in the loss of HCH between the upper and lower layers. The half-life of HCH was 17 and 25 days for the upper and lower 7.5-cm layers, respectively, and it was 20 days for the total 15-cm soil layer, at this site. The loss was greatest initially at the sites, and was faster in wet soil than in dry soil.     

Temporal and spatial variation of RNA content in nymphs of the mayfly, Stenonema femoratum (Say)

Temporal variation of RNA: weight, RNA: protein, RNA: DNA, and protein: DNA ratios in Stenonema femoratum (Say) was assessed by monitoring at the same site in a small midwestern stream over a two-year period. Variation components were estimated using a two-way mixed model analysis of variance with weight class and collection date as main effects. About 30% of the variation in RNA concentration was within-cell variation associated with differences among individuals and analytical error. Temporal variation accounted for about 50% of the total variability in RNA concentration data. RNA: weight had 11% and RNA: protein had 17% variation attributed to weight class effects indicating that these ratios were dependent on the size of the mayfly. RNA: DNA ratios were not influenced by mayfly weight, suggesting that this ratio would be the most appropriate for comparing populations based on means of mixed individual sizes. Comparison of mean RNA: DNA ratios among collection dates yielded significant increases in the ratio during late fall in two consecutive years. Spatial variations in RNA: DNA ratios of S. femoratum collected from sites of similar habitats were not significantly different. These data encourage the future development of RNA concentration as an in situ biochemical indicator of growth rate and possibly of stress related effects on growth rate.