Growth and nutrition of Quercus rubra L. seedlings and mature trees after three seasons of ozone exposure

Seedling growth and nutritional status have been shown to be sensitive to ozone, but the influence of multi-season ozone exposure on mature tree growth and nutrition has not been examined. To determine if seedlings and mature trees were similarly affected by ozone exposure, growth and nutrient concentrations in northern red oak (Quercus rubra L.) 4-year-old seedlings and 32-year-old mature trees were examined after treatment with subambient, ambient and twice ambient concentrations of ozone for three growing seasons. SUM00 values summed over the three growing seasons were 147, 255 and 507 ppm-h, respectively, for the subambient, ambient and twice ambient exposures. For mature trees, no influence of ozone treatment on lower stem diameter growth, stem growth within the mid-canopy and foliar biomass was observed. Seedling height was increased by ozone, but biomass and diameter were unaffected. A reduction in the specific leaf weight of leaves in response to ozone coincident with the loss of recurrent flushing was observed in seedlings. Ozone exposure reduced foliar nitrogen concentrations and increased woody tissue nutrient concentrations in seedlings and mature trees at the end of the third growing season. These results suggest an influence of ozone on retranslocation processes in seedlings and mature trees.     

Biomonitoring of air pollutants from traffic and industries employing Ramalina ecklonii (Spreng.) Mey. and Flot. in Córdoba, Argentina

The lichen Ramalina ecklonii (Spreng.) Mey. and Flot. was transplanted to 29 biomonitoring sites in the southeastern area of Córdoba, Argentina and tested for chlorophyll a, phaeophytin a, conjugated dienes concentration, malondialdehyde, soluble protein content and sulfur accumulation. The biomonitoring sites were determined according to (i) vehicular traffic levels, and (ii) industrial density, i.e. number and type of industries (small and medium) close to each of the sites. Each of the two groups were then broken down into three categories which provided a basis for performance analysis and quantification of the chemical parameters in the biomonitor. A pollution index (P.I.) was calculated based on the ratio of phaeophytin a to chlorophyll a and ratio of sulfur, malonaldehyde and conjugated dienes in transplanted specimens to sulfur, malonaldehyde and conjugated dienes in the freshly picked specimens. Significant differences were observed in sulfur content and P.I. in lichen samples that had been transplanted to sites with different vehicular traffic levels. At the same time, significant differences in the phaeophytin a concentration, phaeophytin a/chlorophyll a ratio and P.I. were observed at sites characterized by different levels of industrial density (all with low-to-medium traffic).     

The impact of SO2 and SO2 + ascorbic acid treatments on growth and partitioning of dry matter in Trigonella foenum-graecum L

To study the impact of SO(2) and SO(2) + ascorbic acid on growth and partitioning of dry matter in Trigonella foenum-graecum L., two-week-old plants were exposed to SO(2) for 2 h daily over a 42 day period. One of the exposed sets was treated with ascorbic acid. Plants were grown in a wire house and unexposed plants were used as controls for comparison. The parameters measured, such as dry weights of leaf, stem and root per plant, were found to be lower in the exposed sets than in the controls. The reductions were greater in dry weights of stem and root as compared with weights of leaves, indicating that the partitioning of the dry matter was altered. Greater amounts of soluble sugars and starch in the leaves of exposed plants, compared with the stem, also revealed that translocation was hampered. Reductions were greater in fruiting than in flowering, suggesting that fruit abortion was high. Although ascorbic acid treatment could mitigate the effect of SO(2), the differences were not found to be statistically significant. Significant changes were seen in fruit yield, suggesting that the effect of ascorbic acid is cumulative. The impact of SO(2) and SO(2) + ascorbic acid on partitioning of dry matter to different 'sinks' is discussed.     

Organic carbon concentration profiles in recent cave sediments: records of agricultural pollution or diagenesis?

Recent (<7 years old) cave sediments in Speedwell Cavern, Derbyshire, show an approximately exponential decay of organic carbon with depth. This phenomenon was thought to be due to one of two causes: (i) changing agricultural practice within the catchment feeding the cave, especially the increased use of sewage sludge and animal slurry as fertilizer; (ii) a relatively constant organic carbon concentration over time in the input sediment, with subsequent carbon mineralization during diagenesis. Carbon isotope composition of the organic material and the evolution of H/C ratio with depth indicate that the latter hypothesis is correct and that the profiles result from microbial diagenesis, not increased organic carbon inputs. By comparison with sediment of known (7 years) age, temporal decay constants for organic matter can be derived; these lie between rates previously determined for organic matter decomposition in marine sediments and soils. The H/C ratio of organic matter can be modelled as a function of time and proceeds in a similar fashion to soil organic material.     

Radium-226 in cattails, Typha latifolia, and bone of muskrat, Ondatra zibethica (L.), from a watershed with uranium tailings near the city of Elliot Lake, Canada

Radium-226 concentrations were measured in the main food plants (cattails, Typha latifolia) and bone of adult muskrats (Ondatra zibethica (L.)), taken from a study area near Quirke Lake in the Serpent River drainage basin. This watershed receives drainage containing radionuclides from the U tailings near the City of Elliot Lake, Ontario, Canada. Two control sites (one local, one 130 km distant) were also sampled. Radium-226 levels in cattails varied by plant part and place of collection. Roots sampled in the study area had the highest mean (226)Ra level (1135.0 mBq g(-1)), stems and leaves had 284.2 and 275.9 mBq g(-1), respectively (dry-weight basis, n = 6 in all cases). Local and distant control cattails carried much lower (226)Ra levels (20.2 and 15.2 mBq g(-1) dry weight, respectively, using pooled equal portions of all plant parts, n = 3 in both cases). Muskrats from waters with mean total (226)Ra levels in the period, 1984-1987 greater than 75.0 mBq litre(-1) ('study-high' sites), near U tailings within 10 km of Quirke Lake, had a mean (geometric) bone level of (226)Ra of 344.9 mBq g(-1) (dry-weight basis, n = 36); those from nearby waters, containing < 75.0 mBq litre(-1) of (226)Ra ('study-low' sites), had a mean bone level (80.3 mBq g(-1), n = 9) similar to animals taken in unaffected local control areas 20 km from the tailings (79.1 mBq g(-1), n = 12); animals from the distant control area, near Sudbury, Ontario, had the lowest mean burden (11.5 mBq g(-1), n = 24). Levels were unrelated to age or sex of the animals. Dry-weight based (226)Ra concentration ratios (bone concentration/plant tissue concentration) were calculated to range from 0.3-1.4 in the study-high area to 2.4-6.3 in the local control area. Wet-weight based concentration ratios were about 4.3 times higher. Concentration ratios were similar to values calculated for other species and in general agreement with values calculated for humans. The muskrat is judged to be a useful indicator (biomonitor) of environmental (226)Ra levels as there is a highly significant positive correlation coefficient (r = 0.74) between bone and ambient (water) concentrations of the radionuclide (F79 = 95.04, P < 0.0001) Estimated yearly (226)Ra intake by people eating muskrats was calculated to be below the current allowable level set by Canadian regulatory authorities.     

U- and Th-series radionuclides in snowshoe hare (Lepus americanus) taken near U mill tailings close to Elliot Lake, Ontario, Canada

Snowshoe hare (Lepus americanus) trapped near U tailings had higher concentrations of (226)Ra in their bones (250 +/- 94 mBq g(-1) dry wt) than those from local control sites 3-15 km from the tailings (20-30 mBq g(-1) dry wt) and those from a distant control site 880 km away from the U mining area, which were below the detection limit (DL) (3.7 mBq g(-1) dry wt). Most chyme (stomach content) samples contained 226Ra below DL. Concentration ratios of 226Ra from tissues of local plants, considered important in the hare's diet, to bone ranged from 0.22 to 8.60. Concentrations of 210Pb and 210Po (95-245 mBq g(-1) dry wt) were not significantly different among tailings and control site populations. Disequilibrium between these isotopes and their precursors was noted. No significant accumulation of U and Th was noted at any site. Higher concentrations of 228Th compared to 232Th are attributed to accumulation of 228Ra in a manner similar to that of 226Ra. Based on bone 226Ra and 210Po contents, the maximum internal dose rates to the skeleton and the maximum life-time dose of hare living near tailings were 3.9 x 10(-5) Gy d(-1) and 4.2 x 10(-2) Gy, respectively. These rates were below the threshold required to produce osteosarcoma in other mammals and were considered unlikely to adversely affect hare during their lifetime. Radionuclide uptake by the animals was concluded to have no environmental significance in the transport of radionuclides from tailings to other locations.     

Effect of ozone on net photosynthesis in oat (Avena sativa) and duckweed (Lemna gibba)

Short exposure to ozone depressed photosynthesis in both oat and duckweed at concentrations above 140 microg m(-3) and 300 microg m(-3), respectively. The effect on exposed oat flag leaves was age-dependent, with maximum susceptibility to ozone 10-20 days after emergence of the panicle. In duckweed, photosynthesis was more sensitive to differences in ozone concentration than to differences in duration of exposure.     

Studies on water hyacinth as a biological filtre for treating contaminants from agricultural wastes and industrial effluents

The aquatic weed--water hyacinth [Eichhornia crassipes (Mart) Solms] showed a remarkable capacity to withstand the effects of pH changes ranging from 5 to 8 in the aquatic environment. Growth continued to be normal except when placed for longer periods in medium containing iron ions at pH 3.3. The ability of this plant to neutralize some very acid solutions of heavy metals such as salts of copper, cadmium and zinc individually and in combinations, is being reported. Plants placed in pure acid and alkali solutions were also able to neutralize the medium. Calcium appears to play an important role in the mechanism involved in the adaptability of these plants to such environments.