In Situ emulsification and mobilization of gasoline range hydrocarbons using surfactants

In this article the conditions that govern surfactant‐enhanced emulsification and mobilization of petroleum hydrocarbons in soil are reviewed. The effect of soil properties, groundwater constituents, and differing surfactant solutions on the emulsification process is discussed. A constant head soil flushing apparatus used to characterize surfactant‐enhanced mobilization of m‐xylene is described. Data showing the effect of surfactant‐enhanced mobilization on m‐xylene removal efficiency in washed sand is presented. Flushing solutions were used at concentrations from below to well above the critical micelle concentration (CMC) of the surfactants used. Removal efficiencies are shown to vary with surfactant concentration and with surfactant type. Flushing solutions of anionic, nonionic, and anionic/nonionic surfactant mixtures were evaluated.     

Evaluation of the water quality of future tributaries to the planned Dobczyce reservoir (Poland) using macroinvertebrates

The bottom fauna of 5 tributaries of the planned Dobczyce reservoir and the River Raba below the dam was investigated in the preimpoundment period (1983–84). The abundance of macrofauna varied between 46 taxa (Wolnica stream) and 66 taxa (Brzezówka stream). Each station showed individual taxa composition except for the RABA-u and RABA-d (84% similarity). On the basis of 7 different biological indices the stations were divided into 3 categories: unpolluted (Brzezówka), slightly polluted (Bulinka, Trzemésnia and both Raba stations), and moderately polluted (Wolnica). Most sensitive to chemical pollution was the BIOTIC-index. The combination of environmental variables was used to predict biological indices. The most significant relationship (P < 0.01, R ² = 0.71) was found between the BIOTIC-index and physico-chemical factors. Some problems in the application of indices (sampling, indicator organisms and interpretation of the results) are discussed and local adaptations of methods used are recommended.     

Relationship between growth irradiance and the xanthophyll cycle pool in the diatom Nitzschia palea

The size and de-epoxidation state of the xanthophyll cycle pool was measured in cultures of Nitzschia palea grown at six fluence rates in continuous light or with a 12 h photoperiod. In both series the size of the pool increased with increasing irradiance. The de-epoxidized form, diatoxanthin, was only present at fluence rates saturating for growth. The portion of diadinoxanthin, which was not readily de-epoxidized in saturating light, was constant and not related to the size of the pool. In the culture grown in a light-dark cycle at 300 μmol photons m^-2 s^-1 (PAR) increasing de-epoxidation took place in the latter half of the photoperiod, when the rate of photosynthesis was decreasing. A rapid, spectrophotometric method for measuring the extent of de-epoxidation of the xanthophyll cycle pool in a culture of diatoms is described. Upon addition of a small volume of hydrochloric acid to an extract of pigments in 90% acetone, the absorbance at 480 nm is reduced. The size of the reduction is a measure of the state of the xanthophyll cycle pool, since the absorbance of diatoxanthin is reduced by 5%, but the absorbance of diadinoxanthin by 87% due to an epoxide-furanoid rearrangement, which causes the absorption spectrum to be shifted by ca 20 nm towards shorter wavelengths.     

The rate of development of water deficits affects Saxifraga cernua leaf respiration

We allowed plant water deficits to develop at two different rates following the cessation of watering in order to investigate the effects of water stress on cytochrome pathway and alternative pathway respiration in the leaves of the arctic herb Saxifraga cernua. Plants were pretreated by growth in either a commercial organic (CO) mixture or a vermiculite-perlite (VP) mixture, which allowed the complete development of water deficits in 19 and 8 days, respectively. The rate of water potential reduction was approximately 0.11 MPa day⁻¹ in the leaves of CO plants, compared to a reduction of 0.21 MPa day⁻¹ in leaves of VP plants. Osmotic adjustment occurred to a greater extent in leaves of CO plants and corresponded with an increase in ethanol-soluble sugars. In leaves of CO plants, cytochrome pathway activity gradually declined from that of control rates until day 11, and then declined more rapidly. In contrast, cytochrome pathway activity significantly increased in response to water deficits in leaves of VP plants. In leaves of both CO and VP plants, alternative pathway activity declined as water stress progressed. Relatively severe water deficits reduced alternative pathway capacity in leaves of both CO and VP plants. We also investigated the effect of previous exposure to water deficits on leaf respiration. In plants that had previously experienced three cycles of water stress, the increase in cytochrome pathway activity during the fourth water stress cycle was small compared to the increase observed in leaves of plants experiencing water stress for the first time. These results suggest that cytochrome pathway activity is differentially sensitive to the rate of development of plant water deficits and that respiratory responses to acute water stress are not necessarily similar to the responses to chronic water stress.     

Effect of nitrogen on drought strain and nutrient uptake in Norway spruce Picea abies (L.) Karst.) trees

A field lysimeter study was established with the aim of investigating the effect of nitrogen availability upon drought strain in Norway spruce trees. Forest soil (Typic Udipsamment) was filled in lysimeters 1 m in diameter and 1 m deep. Small trees of Norway spruce from five different clones were planted in the lysimeters. Roofs under the canopy of the trees ensured full control of water and nutrient input. Three levels of nitrogen were given to the trees during five years; ambient rainwater, and five and fifteen times this N concentration, respectively. Additional N was given as NH₄NO₃ in irrigation water. Mean annual N-addition during the five years corresponded to 5, 27 and 82 kg per ha and year for the three treatments, respectively. During the third and fifth growth season drought was artificially induced. In addition to a watered control, two levels of drought were applied, representing water deprivation for 2 and 3 months, respectively, in 1990 and 3 and 4 months, respectively in 1992. A higher water consumption in the nitrogen fertilized trees during the droughts resulted in a significantly lower pre-dawn shoot water potential compared to the trees receiving ambient rain N. The interaction between drought and nitrogen fertilization was clear also for photosynthesis and transpiration. A decrease in height- and diameter increment caused by drought was most pronounced in the 82 kg N ha^–1 yr^–1 treatment. A water strain integral showed a strong positive correlation to the needle biomass of the trees. Foliar concentrations of several nutrients decreased significantly with increasing drought strain in the trees. Concentration of potassium and boron were especially low and visual symptoms of deficiency occurred.     

The effect of water stress on the vacuole-extravacuole compartmentation of proline in potato cell suspension cultures

Solute compartmentation in cells is an important component of metabolic regulation. There is only little information on how stress treatment of cells effects this component. Therefore, the effect of water stress [10% (w/v) PEG 6000] on the vacuolar-extravacuolar proline compartmentation was studied in a cell suspension culture of Svlanum tuberosum L, cv, HH258, In non-stressed cells 34% of the total cellular proline was located in the vacuole. After 20 h of water stress the proline pool of the cells was increased 4-6 fold and only t6% of it was found in the vacuole. A negative correlation between the total cellular proline content and its percentage in the vacuole was observed, irrespective of the culture method (stress or non-stress culture). The stress-induced changes in proline compartmentation are discussed.     

Regional ecological risk assessment using a relative risk model: A case study of the Darwin Harbour,Darwin, Australia

There are many proposed and ongoing commercial, industrial, and residential developments within the Darwin Harbour catchment in Northern Australia, to accommodate the projected population growth over the next 20 years. Hence, it is necessary to ensure the balance between these developments and ecosystem conservation. We evaluated ecological risk for the Darwin Harbour using a relative risk model (RRM). The catchment was divided into 22 risk regions based on small catchment boundaries and their homogeneity. Through the RRM, we ranked and summed the stressors and habitats within regions. The interaction between stressors and habitats were modeled through exposure and effect filters. The ecological assessment endpoints were maintenance of the mangrove health and the maintenance of water quality. The risk regions—Myrmidon Creek, Blackmore River, Bleesers Creek, and Elizabeth River—showed the highest total relative risk for ecological assets. These risk regions had a high percentage cover of industrial, commercial, and residential areas; diffuse entry points; and climate change effects. Creek A, Sandy Creek, West Arm, and Pioneer Creek were the risk regions with lowest total relative risk scores. The RRM is a robust application that is suitable for a large geographic area where multiple stressors are of concern.     

Distribution of legionellae in a hospital water system: prevalence of immunologically and genetically related Legionella pneumophila serogroup 6 isolates

A hospital warm water system was monitored for the presence and distribution of legionellae. Subtyping of ten selected Legionella pneumophila isolates, originating from four different sites in the system by using serogroup specific antisera in an indirect immunofluorescence test, revealed that nine of the ten isolates belong to serogroup 6, while the remaining one was serogroup 10. Two monoclonal antibodies (mAbs) specific for a subgroup of serogroup 6 strains were further used for characterization. None of the strains reacted with these mAbs. Genome analysis by elaborating NotI profiles using the pulsed field gel electrophoresis (PFGE) technique revealed that nearly all serogroup 6 isolates derived from different sites, including a new building connected by a ring pipe, were identical according to restriction fragment patterns. The patterns were distinguishable from those of the two L. pneumophila serogroup 6 reference strains, and from that of the L. pneumophila serogroup 10 isolate. These data argue for a relatively homogeneous L. pneumophila serogroup 6 population in the entire water system.     

Photoinhibition of radish (Raphanus sativus L) seed germination: control of growth potential by cell-wall yielding in the embryo

The biophysical mechanism underlying photoinhibition of radish (Raphanus sativus L.) seed germination was investigated using three cultivars differing in sensitivity to continuous irradiation with far-red light (high-irradiance reaction of phytochrome). Sensitivity of germination to the inhibitory action of light was assessed by probing germination under osmotic stress (incubation in media of low water potentials adjusted with polyethylene glycol 6000) and expressed in terms of ‘germination potential’ (positive value of the water potential at which germination is inhibited by 50%). Far-red light decreases the germination potential to various degrees in the different cultivars, reflecting the light-sensitivity of germination in water. Removal of the seed coat increases the germination potential by a constant amount in darkness and light. It is concluded that germination depends on the expansive force of the embryo which can be drastically diminished by far-red light. Seed-coat constraint and expansive force of the embryo interact additively on the level of the germination potential. Photoinhibition of germination was accompanied by an inhibition of water uptake into the seed. Analysis of seed water relations showed that osmotic pressure and turgor assumed higher levels in photoinhibited seeds, compared to seeds germinating in darkness, while the water potential was close to zero under both conditions. Far-red light produced a shift (to less negative values) in the curve relating water-uptake rate to external water potential, i.e. a reduction in the driving force for water uptake. It is concluded that photoinhibition of germination results from the maintenance of a high threshold of cell-wall extensibility in the embryo.