Three-dimensional patterns of moisture, water repellency, bromide and pH in a sandy soil

Soil water repellency might lead to preferential flow of water and solutes through the unsaturated zone of soils. To study this process in a water repellent sandy field soil, a bromide tracer had been applied on a 2.2 m long and 0.4 m wide plot. The bromide application rate was 8 g/m², and the plot was sampled using 100 cm³ steel cylinders after 52 mm of rainfall in 12 days. A total of seven layers were sampled to a depth of 74 cm. Each layer was sampled at 240 locations in a 40 by 6 grid. All samples were used for the determination of soil water content, degree of actual and potential water repellency, bromide concentration and pH. The spatial distribution of these properties was visualized three-dimensionally and compared. The degree of water repellency, bromide concentration, and pH distribution bore close resemblance to the fingered flow induced soil water content distribution. The degree of potential water repellency was relatively low in places with such fingers. Actual water repellency occurred between the fingers at the dry spots. Bromide was not found, or only in very low concentrations, in such places. Bromide depth profiles clearly indicated the occurrence of diverging flow in the wetter subsoil. Most likely, manuring activities during the last decades resulted in relatively high pH values in the topsoil, and in the subsoil along the recurring fingered flow pathways.     

Chlorohydrocarbons, PCB congeners, polychlorodioxins, furans and dibenzothiophenes in pine needles in the vicinity of a metal reclamation plant

Chlorohydrocarbons, PCB congeners, polychlorodioxins, furans and dibenzothiophenes in pine needles in the vicinity of a metal reclamation plant were analyzed by GC/ECD and GC/MS. Wax and the rest of the needles were analyzed separately. As a rule the concentrations of -HCH (0.5–13.6 ng/g), γ-HCH (0.4–7.3 ng/g), HCB (0.2–3.4 ng/g), PCB congeners (0.2–67 ng/g), PCDDs and PCDFs were higher in the older needles. The ratio of the concentration in the wax to the concentration in the rest of the needles was higher in the younger needles. The concentrations of PCB congeners, TeCDDs and TeCDFs were higher in the needles collected in the area nearest to the plant. The samples, obviously, contained tri- and tetrachlorodibenzothiophenes but these were not determined quantitatively due to interfering peaks in GC/MS.     

Natural phillipsite as a matrix for a slow-release formulation of oxamyl

The performance of phillipsite as a matrix for slow-release formulation of oxamyl [N,N-dimethyl-2-methylcarbamoyl-oxymino-2-(methylthio)acetamide] was tested. The adsorption kinetics followed a first-order law, and the adsorption isotherm fitted well in a two-surface Langmuir model, suggesting a double mechanism of interaction between oxamyl and the sorbent. The sorption mechanism, studied by FTIR, provided two fractions of oxamyl. The first one is sorbed on the mineral surface, linked by H-bonding, and the second one is constituted by a multilayer of oxamyl molecules linked by a water bridge between them. The release kinetics of oxamyl from a substratum zeolite-oxamyl also follows a first-order law, with two stages that correspond to both fractions of oxamyl previously detected.     

Pharmacokinetic model of dioxin and furan levels in adipose tissue from Sawmill work involving chlorophenate fungicides

Sawmill workers in British Columbia (B.C.), Canada, have been exposed to chlorophenate fungicides which are known to be contaminated with polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs). Due to concern about the potential of these workers to have significant body burdens of PCDD/Fs, and the absence of measurements in these worker, a single-compartment pharmacokinetic model was developed to estimate the concentration of PCDD/Fs in the fat tissue of the sawmill workers. Data from a large cohort of B.C. sawmill workers and literature-based data on chlorophenate exposures and PCDD/F concentrations in chlorophenates were used in Monte Carlo simulations to predict a PCDD/F body burden distribution. The median concentrations of HxCDF and HpCDF predicted using the model for the B.C. sawmill worker population exceeded the range measured in unexposed populations. PeCDF and OCDF concentrations exceeded the range measured in unexposed populations at the 70th percentile of the model-predicted distribution, and PeCDD at the 90th percentile. The primary limitation of the model was the scarcity of input data about actual dermal and inhalation exposures to chlorophenates.     

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.     

Cationic surfactant as a sensitizer for the spectrophotometric determination of hydrogen sulphide in air and evaluation of a new absorbing medium containing triethanolamine-zinc acetate-sodium hydroxide

An extractive spectrophotometric method for the determination of trace amounts of hydrogen sulphide after fixing the gas in triethanolamine (TEA)-zinc acetate-sodium hydroxide solution is described. The method is based on the reaction of iodate with hydrogen sulphide in the presence of acid and excess chloride ion leading to the formation of ICl2- species which is used to iodinate 2',7'-dichlorofluorescein to form 2',7'-dichloro-4',5'-diiodofluorescein. The iodinated product formed is extracted into an organic solvent and sensitized by equilibrating with a cationic surfactant, cetrimide, in the presence of acetate buffer (pH 5.9 +/- 0.1). The colour system obeys Beer's law over the range 0-1 microg of hydrogen sulphide and the relative standard deviation is 2.4% for 10 determinations at 0.75 microg of hydrogen sulphide. The effect of interfering gases on the determination is discussed. The proposed absorbing solution has been evaluated using a hydrogen sulphide permeation device. This absorbing solution has an absorption efficiency of > 93% at a flow rate of 1.5 litre min(-1) for a sampling period of 2 h. The fixed H2S is stable for 40 days. The method has been applied to determine residual H2S levels in a laboratory fume hood and in the vicinity of sewage pumping station. The method can be used to determine as little as 0.05 microg of hydrogen sulphide.     

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.     

Sequential extraction analysis of heavy metals using a chelating agent (NTA) to counteract resorption

The geochemical partitioning of Pb, Ni and Zn in contaminated quartz-rich sediment and soil samples was characterized by sequential extraction analysis in the presence and absence of nitrilotriacetic acid (NTA). With NTA, levels of metals recovered are higher in the earlier steps and lower in the later steps of the procedure. This suggests that post-extraction resorption is effectively counteracted by chelation, thereby improving the accuracy of the method. An NTA concentration of 200 mg liter(-1) appears to be sufficient for counteracting resorption without causing significant dissolution of non-targeted phases in the samples studied. However, experiments using reference materials spiked with solutions containing Pb, Ni, Cu and Zn suggest that resorption will remain a problem when large amounts of strong sorbents such as organic matter are present. The results also show that although post-extraction resorption does occur in the absence of NTA, the magnitude of resorption is small (<20 to 30% of the summed total of metal present in the sample) in quartz-rich sediments.     

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.