Abstract: This review presents the status of phytoremediation technologies with particular emphasis on phytoextraction of soil heavy metal contamination. Unlike organic compounds, metals cannot be degraded, and cleanup usually requires their removal. Most of the conventional remedial technologies are expensive and inhibit the soil fertility; this subsequently causes negative impacts on the ecosystem. Phytoremediation is a cost effective, environmental friendly, aesthetically pleasing approach most suitable for developing countries. Despite this potential, phytoremediation is yet to become a commercially available technology in India. This paper reports about the mobility, bioavaliability and plant response to presence of soil heavy metals. It classifies the plants according to phytoextraction mechanism and discusses the pathway of metal in plants. Various techniques to enhance phytoextraction and utilization of by-products have been elaborated. Since lot of biomass is produced during this process, it needs proper disposal and management. It also gives an insight into the work done by authors, which focuses on high biomass extractor plants. High biomas weeds were selected to restrict the passage of contaminants into the food chain by selecting non-edible, disease resistant and tolerant plants, which can provide renewable energy. Thus making phytoextraction more viable for present utilization.
Keywords: heavy metals, phytoextraction, hyperaccumulator, indicator, excluder species
Abstract: To overcome the problems associated with high concentrations of nutrient and test chemicals in laboratory Lemna gibba bioassays, a semi-continuous culture system was adopted, and specific equipment was designed and constructed to simulate steady-state conditions of the most natural aquatic systems. The equipment for Lemna semicontinuous culture consists of a growth chamber and a circulation control unit. Lemna gibba is kept in the growth chamber in a growth pot (with 1 mm diameter perforation at about 10 cm above the bottom), which retains the plant but allows an efficient exchange of the growth medium. Flow rate and composition of the medium is therefore varied independently of the L. gibba population density. The media are kept in circulation, and recharges or discharge of the media are controlled. The system took into consideration chemical processes such as O2 and CO2 exchange and maintained a degree of turbulence through continuous shaking of the growth chambers. It is also possible to investigate growth under different supply of O2 and CO2, and pH control with dissolved CO2 or reducing conditions with N2 gases. Theoretical analysis of growth in the steady state shows that integrated activation time of the dilution pump is proportional to the growth rate of L. gibba. Theoretical analysis was also used to determine the minimum flow-rate and nutrient concentration of the medium to cover the requirements of L. gibba. Experiments were carried out that demonstrated that the steady state growth could be attained and be controlled by the nutrient concentration, flow rate, and recharge intervals. The cultures could be kept at steady state over 21 days of the Lemna test period.
Keywords: Lemna gibba, steady state, semicontinuous culture, batch culture, nutrient media
Abstract: The pH and chemical composition of 126 precipitation samples, which were collected from April 1998 to November 1999 in Jinyun Mountain, Chongqing, China, were analyzed. The results showed: the average pH was 5.23 and the average electrical conductivity was 33.90 μs/cm, which showed that the pollution situation in Jinyun Mountain was more favourable than that in the other acid rain regions of southern China and Chongqing urban areas. The concentration of SO4 2- accounted for 84.61% of total anions, and the concentration of NH4 + and Ca2+ accounted for 77.36% of total cations of rainfall in Jinyun Mountain. The high concentration of NH4 + and Ca2+ neutralized greatly the acidity of acid ions, which resulted in relatively high pH and lower frequency of acid rain, but the acidifying rain may exert potential injury to forest ecosystem. The seasonal variations in the rainfall pH and chemical composition were evident, which may be related to the seasonal variations in precipitation amount in Jinyun Mountain. The effects of acid rain on forest ecosystem have time lag, so it is necessary to study the dynamic characteristics of acid deposition more carefully and comprehensively.
Keywords: pH , major ions, air pollution, acidifying rain
Abstract: Seed germination and reproductive strategies of Tithonia diversifolia and Tithonia rotundifolia, two invasive species introduced into Africa from North and Central America, were studied. The aim was to determine the characteristics that make them invasive species in the continent. Tithonia diversifolia is a perennial and polycarpic plant reproducing both sexually and asexually while Tithonia rotundifolia is an annual monocarpic plant reproducing only sexually. The seeds of these species exhibit a period of dormancy before germinating. Tithonia diversifolia produces small sized light and numerous seeds while Tithonia rotundifolia produces larger sized, heavier and fewer seeds. Tithornia rotundifolia allocates a high proportion of of dry matter (41.6 %) and Tithonia diversifolia low proportion (10.5 %) to reproduction. It is concluded that small sized light and numerous seeds produced by Tithonia diversifolia accounts for its wide dispersal and rapid spread in colonized areas. Also its perennial habit and ability to reproduce sexually and vegetatively accounts for the species colonizing and stabilizing fast in new habitats. While the larger heavier seeds and high reproductive effort of Tithonia rotundifolia ensures its early vigorous start in seedling growth, quick establishment, survival for longer and to grow to more aggressive size in an environment that is starved of resources. Seed dormancy exhibited by the two species ensures they survive adverse conditions in their environment as seeds and germinate only when the environmental conditions favour the survival of their seedlings.
Keywords: Tithonia species, reproductive strategies, seed dormancy
Abstract: The impacts of crude oil pollution on a sandy loam soil and the influence of incorporation of poultry manure alone and in combination with alternate carbon substrates (glucose or starch) and surfactants (Goldcrew or Corexit) were investigated. Oil pollution increased soil organic carbon and reduced soil nitrates and phosphorus, thus imposing a condition that impaired oil degradation in the soil. Treatment of the soil with poultry manure alone, enhanced oil degradation but the extent of this was influenced by the incorporation of alternate carbon substrates or surfactants. Addition of glucose or Corexit encouraged crude oil degradation, while addition of starch or Goldcrew reduced the extent of degradation obtained. The soil amendments interacted in affecting crude oil degradation. This was optimal with a combination of poultry manure (2.0%w/w) + glucose (2.0%w/w) which yielded a crude oil degradation of 7.42±1.02% after sixteen weeks incubation.
Keywords: alternate carbon substrates, crude oil degradation, poultry manure, surfactants
Abstract: Phosphatase activity of Rivularia strains II and I isolated from a deepwater rice field was studied. When grown under conditions of P-limitation the strains did not form hair and showed great variations in induction time and pattern of enzyme activity in relation to growth. Phosphomonoesterase activity (PMEase) was induced earlier in the Rivularia strain I which was maintained in high phosphate concentration in the medium before the study. Rivularia strain II on the other hand showed induction of PMEase activity after 3-4 days and this strain was maintained in low phosphorus concentrations in the medium before the study. The comparison of Km and Vmax values early in the growth phase showed that affinity of both PMEase (phosphomonester) and PDEase (phosphodiester) for the substrate was higher in early growth phase rather than in later stages suggesting that there is presence of more than one phosphatase enzymes in these organisms. The observations from the above study have important implications in rice fields where constant fluctuations in nutrients can be observed – especially by phosphorus in its most available form phosphate. Equal enzyme activity in both light and dark for the two strains (non hair-forming) implies that phosphatase activity may not be affected by changes in light regimes in rice fields which do occur due to the plant growth. This can in turn contribute significantly to maintain the growth of cyanobacteria for prolonged periods even under unfavorable conditions of phosphorus depletions. These strains of Rivularia can therefore biotechnologically exploited as biofertilizers (phosphatic fertilizer) when there is phosphorus deficiency. During the unfavorable conditions of phosphorus deficiency, phosphatase activity may play a significant role in providing phosphate for its own growth and for the rice plants.
Keywords: PMEase, PDEase, Km, Vmax.
Abstract: The physicochemical qualities of a refinery effluent and water and sediment of an effluent receiving water body were investigated. The treated refinery effluent contained very high concentrations of phenol (11.06 mg/l), oil and grease (7.52 mg/l), ammonia (8.52 mg/l), COD (91.76 mg/l), TDS (390.6 mg/l) and phosphate (6.2 mg/l), but low in sulphide, nickel, lead, copper and chromium, which were undetectable. High concentrations of phenol (5.13–16.38 mg/l), oil and grease (10.56–15.23 mg/l), and ammonia (4.31–13.17 mg/l) were observed in water and sediment samples respectively, at the point of effluent impact. A high concentration of sulphide (3.74 mg/l) was accumulated in the sediment at the point of impact of the refinery effluent, though it was undetectable in the effluent itself or water sample. The concentrations of these parameters as well as of phosphate, nitrate, zinc and COD declined progressively with distance from the point of impact but were still significantly higher than in control water and sediment in samples 1.5 km downstream from the point of impact. Higher concentrations of the pollutants were recorded in the dry season than rainy season except for phosphate and nitrate, which showed the reverse trend. Nickel, lead, copper, chromium and cyanide were neither detected in the effluent nor impacted water body.
Keywords: contaminant concentrations, sediment accumulation, seasonal changes
Abstract: Study of fish captures could bring out valuable information on tendencies in stocks dynamics as well as on the level of “fishing pressure” on natural fish population. Decreasing amount of annual captures of marine migratory sturgeons that migrate in Danube River for spawning indicates a decline of natural stocks of these species. Present paper tries to show the main aspects of sturgeons fished in Romanian sector of Danube River, to discuss some relevant aspects that could help people to understand the real issues on this topic better and eventually find the best way to stop the decreasing tendency of wild population of three very interesting species of sturgeons: beluga (Huso huso Linnaeus, 1758), Russian sturgeon (Acipenser gueldenstaedti Brand, 1833) and stellate sturgeon (Acipenser stellatus, Brandt, 1833).
Keywords: marine sturgeons, migration, capture dynamics, stocks, protection
Abstract: Our aim was to approach an important and well-investigable phenomenon – connected to a relatively simple but real field situation – in such a way, that the results of field observations could be directly comparable with the predictions of a simulation model-system which uses a simple mathematical apparatus and to simultaneously gain such a hypothesis-system, which creates the theoretical opportunity for a later experimental series of studies. As a phenomenon of the study, we chose the seasonal coenological changes of aquatic and semiaquatic Heteroptera community. Based on the observed data, we developed such an ecological model-system, which is suitable for generating realistic patterns highly resembling to the observed temporal patterns, and by the help of which predictions can be given to alternative situations of climatic circumstances not experienced before (e.g. climate changes), and furthermore; which can simulate experimental circumstances. The stable coenological state-plane, which was constructed based on the principle of indirect ordination is suitable for unified handling of data series of monitoring and simulation, and also fits for their comparison. On the state-plane, such deviations of empirical and model-generated data can be observed and analysed, which could otherwise remain hidden.
Keywords: state-planes, NMDS, ordination, seasonality, Heteroptera, similarity patterns
Abstract: The coastal aquifers of Kerala, India experience severe degradation of water quality due to various anthropogenic activities. An attempt is made here to study the groundwater chemistry of aquifers, which lie along the coastal zone of central Kerala. Results in general indicated that the groundwaters in the shallow aquifers were found to be deteriorated. Based on Hill-Piper trilinear diagram it is confirmed that some of the dug wells were characterised by high amount of sodium and chloride (>200 mg/l) indicating the influence of saline water incursion. The presence of E. coli in all dug wells indicated potentially dangerous fecal contaminations, which require immediate attention. The study further raises points for the need of action for a sustainable utilization of precious resources.
Keywords: coastal aquifer, groundwater, trilinear diagram, saline water incursion