Regrowth Potential Research Articles

Soil phosphorus and water effects on growth, nutrient and carbohydrate concentrations, δ13C, and nodulation of mimosa (Albizia julibrissin Durz.) on a highly weathered soil

Growth and physiological performance of multipurpose tree species can be severely constrained by low phosphorus (P) availability in highly weathered soils. Limitations to plant growth are accentuated by seasonal dry periods. The overall objective of this study was to examine P fertilization and irrigation effects on survival, growth, biomass partitioning, foliar nutrients, intrinsic water-use efficiency (WUE) indexed by δ13C, Rhizobium nodulation, and carbohydrate content as an indicator of resprouting potential, of mimosa (Albizia julibrissin Durz.), a N2-fixing tree species being tested for browse in agroforestry practices in south-central USA. In a field experiment carried out during two growing seasons near Booneville, Arkansas, USA, mimosa had a strong growth response to irrigation. The trial was arranged in a split plot design with three replications with irrigation as main plot treatment and P as sub-plot treatment. Mean total plant aboveground biomass at the end of the second growing season was 9.8 and 44.1 g plant−1 for the rainfed treatment without and with 300 mm of irrigation water, respectively. Placed P fertilization increased mean total aboveground biomass from 19 g plant−1 for the 0-P treatment to 69 g plant−1 for the treatment with 90 kg P ha−1 year−1. Similarly, irrigation consistently increased stem basal diameter, total height, survival, root, stem, foliar and total aboveground biomass, and number of nodules per plant. Phosphorus fertilization increased basal diameter, and root and stem biomass in both irrigation treatments, survival and nodulation in the rainfed treatment, and foliar and total aboveground biomass in the rainfed +300 mm irrigation treatment. There was a decrease of foliar δ13C suggesting that WUE decreased with P fertilization. In a pot experiment, seedlings were subjected to a factorial combination of two irrigation treatments and six P levels in a randomized complete block design. Irrigation increased basal diameter, root, stem, foliar and total biomass, leaf area and nodulation, whereas P fertilization (i.e., levels from 0 to 3.68 g P kg−1 soil) had similar effect in all the above variables except foliar biomass. Foliar P concentration to obtain 90% of the maximum total plant biomass (critical level) was estimated at 0.157%. Total nonstructural and water soluble carbohydrate, and starch concentrations increased non-linearly with irrigation and P addition suggesting impaired re-growth potential after defoliation of seedlings with reduced water supply and at low soil P availability. Results of this study indicated strong limitations for growth and regrowth potential of mimosa on a highly weathered soil with very low P availability and seasonal water content shortages. Placed (i.e., near the plant base) application of P appeared to be a good strategy to fertilize perennial woody plants.

Application of vitrification-derived cryotechniques for long-term storage of poplar and aspen (Populus spp.) germplasm

The application of three different vitrification-based freezing strategies for the cryostorage of white poplar (Populus alba L.) and hybrid aspen (P. tremula L. × P. tremuloides Michx.) have been assessed. The PVS2 vitrification protocol was successfully applied to two white poplar in vitro clones stored for more than 6 months in slow-growth conditions (4 °C, in darkness) and showing clear signs of explant etiolation and decay. After 60 min of PVS2 treatment, P. alba L. (cv. Villafranca) explants isolated from axillary buds demonstrated significantly better potential for post-freeze regrowth (64%) compared to those obtained from apical buds (17%). Similarly, a high level of survival (78%) of the frozen hybrid aspen shoot tips was recorded following the application of the same technique. Using the ‘encapsulation-vitrification’ procedure, no toxic effects of the PVS2 treatment were noticed after 120 min exposure, however none of the cryopreserved (poplar and aspen) explants survived after 3 weeks. In contrast, the ‘droplet-vitrification’ technique appeared to be very efficient in the cryopreservation of white poplar shoot tips, which increases the opportunities for wider application of this method in other woody species.;

Tapani red clover

Tapani is a 21-clone diploid synthetic cultivar of red clover (Trifolium pratense L.). It was developed by phenotypic selection at Agriculture and Agri-Food Canada, Crops and Livestock Research Centre, in Charlottetown, Prince Edward Island, and at the Soils and Crops Research and Development Centre in Quebec City, Quebec. The original material for this strain was selected from collections made in old stands of red clover in three Atlantic Provinces of Canada. Tapani is early flowering and winterhardy. In Atlantic Canada, Tapani yielded an average of 109% of the check cultivar Marino over three production years. This cultivar has superior re-growth potential with high second-cut herbage yield. Key words: Red clover, Trifolium pratense L., cultivar description

A carbon flow-based modelling approach to ecophysiological processes and biomass dynamics of Vallisneria americana, with applications to temperate and tropical water bodies

A dynamic simulation modelling approach to submersed plant biomass formation has been developed to provide a tool for water resource managers to evaluate key environmental conditions in which submersed aquatic vegetation (SAV) would persist or produce excessive biomass with ensuing consequences for the systems in which they grow, either or not affected by management measures. The model species is Vallisneria americana (American wildcelery) and the model name is VALLA. The model describes major, carbon flow-based ecophysiological processes and biomass dynamics of a common plant species. The model contains unique descriptions of: (1) species-characteristic vertical distribution of shoot biomass in the water column, that enables the calculation of the fraction of irradiance actually available for absorption by the SAV; (2) recalculation procedures of this vertical distribution with daily changes in water level and/or shoot mass removal at various levels within the water column, that enables the evaluation of regrowth potential; (3) species-characteristic effects of current velocity on photosynthesis, that enables the evaluation of the effects of hydraulic water body alterations; and (4) relationships of plant process parameters with site-specific climate, that enables the evaluation of effects of different climates. Generally, a good fit was found between simulated and measured biomass in the field. Sensitivity analysis showed that the model is very sensitive to changes in process parameters influencing carbon flow.

Community scale non-potable reuse in London using an MBR

Due to increasing pressure on water resources in southeast England, Thames Water are currently installing the first membrane bioreactor (MBR) plant for reuse (toilet flushing and irrigation) in the UK, at Beddington Zero Energy Development (BedZED), a prestigious sustainable development in south London. Thames Water will operate and evaluate the system via an in depth research programme for a 3 year period. A case study, the Solaire in New York (US), informed the BedZED Wastewater Reclamation Plant (BWRP) design and is presented. The BWRP process stream comprises 3mm screens, MBR, granular activated carbon and chlorination. Research will include process optimisation, water quality and water saving studies, post treatment efficiency and effectiveness, energy usage, studies of biofilm regrowth potential and householder perception studies. A comprehensive metering system consisting of hardwired pulse, electromagnetic and radio meters will monitor reclaimed and potable water throughout the site. The metering data will be used to calculate water balances and water savings at various scales. Research using the radio meters (AMR) will cover areas such as customer side leakage and usage patterns. This research will allow a holistic and complete understanding of water use and recycling in a sustainable community.

Effect of the foliar application of diquat herbicide on selected natural area and field crop species

Field experiments were conducted to determine the non‐target impact of foliar‐applied diquat on selected plant species. Diquat was applied to emerged bracken fern, chain fern, slash pine, soybean, sunflower, cotton, corn, and onion at rates varying from 0.02–4.5 kg ai ha−1 of diquat cation, which allowed for the determination of the no‐effect rate and the rate that caused 25, 50, and 100% injury, as measured by visual injury ratings, plant heights, and dry weights. Bracken fern, chain fern, and slash pine were more tolerant to diquat and exhibited regrowth potential at the higher rates. The other six species were not only more susceptible to diquat, but they did not exhibit regrowth potential at high rates. However, these species were able to recover from slight injury caused by the lower rates of diquat.

Pathogen Re-Growth in UASB Effluent Disinfected By UV, O3, H2O2, and Advanced Oxidation Processes

Disinfection of anaerobically treated effluent (UASB) was carried out to eliminate the enteric pathogens by using UV irradiation, peracetic acid, H2O2, O3 and advanced oxidation processes (O3/H2O2, O3/UV and H2O2/UV). Re-growth potential of these pathogens was monitored in terms of time and temperature. Inactivation of pathogens by ozone at the rate of 300 mg/h for 20 minutes approached 99%. UV irradiation resulted in 99% pathogen removal at irradiation time of 120 seconds. A dose of 170 mg/L H2O2 eliminated more than 99% pathogens. Samples disinfected with UV, H2O2 and O3 showed gradual re-growth with an increase in time and temperature (from 20 to 35°C). However, disinfection with AOPs proved to be the most effective tool resulting in reduction of treatment time taken by individual processes, also the disinfected samples showed minimal re-growth revealing the superiority of their combined effects.

MHC I expression and synaptic plasticity in different mice strains after axotomy

The success of axonal regeneration has been attributed to a co-operation between the severed neurons and the surrounding environment, including non-neuronal cells and the extracellular matrix. Important differences regarding the regeneration potential after injury have been described among inbred mice strains. To date, there is only limited knowledge of how such variation can be linked with the genetic background. It has recently been demonstrated that MHC class I molecules have an influence on the spinal cord synaptic plasticity elicited by a peripheral lesion, and the regenerative capacity following such a lesion. Therefore, in the present work we compared the MHC I expression after axotomy in three isogenic mice strains, namely C57BL/6J, Balb/cJ, and A/J, and investigated the fine ultrastructure of the synaptic elimination process that follows such lesion. The results show that C57BL/6J mice, that have a comparatively poor regenerative potential, display a lower upregulation of MHC I in the spinal cord, coupled with a slower synaptic stripping. On the other hand, A/J mice, which have been shown to have a stronger axonal regrowth potential, showed a clear upregulation of MHC I and a sharp acute loss of afferents, at 1 week after lesion. Our results suggest that a more prominent expression of MHC I in the first week after lesion may positively influence the regenerative outcome associated with a more effective axonal regrowth.

Control of residual organic matter to reduce bacterial regrowth potential for wastewater reuse

Several problems have been reported about accumulated microorganisms in reclaimed water distribution systems. This paper presents the results of residual organic matter (OM) removal and apparent bacterial regrowth potential of treated wastewater obtained from laboratory-scale experiments using advanced biological treatments: two immobilization processes in series and a membrane bioreactor (MBR) process. Furthermore, a nanofiltration (NF) membrane process was applied to effluents of both advanced biological treatments. The immobilization process removed large molecular weight (MW) fractions >5,000 since immobilized microorganisms had sufficiently acclimated. The NF membrane was more effective in rejecting large MW fractions in the effluents of the immobilization and the MBR treatments. But it was difficult to reject small MW fractions <1,000 by NF. Neutral hydrophilic fraction of DOC was reduced by both advanced biological processes, and it can be thought that the microorganisms in the advanced processes could decompose and grow on some part of the neutral hydrophilic fraction. Quantity of attached microorganisms in the second immobilization reactor was significantly reduced compared to that in the first immobilization reactor. This suggests that apparent bacterial regrowth potential is controlled by the accumulation of effective microorganisms in the first reactor.

Tonsillar regrowth following partial tonsillectomy with radiofrequency

To assess regrowth potential of the tonsils following partial tonsillectomy performed by using radiofrequency. Follow-up results of 42 children (aged from 1 to 10 years) who consecutively had partial tonsillectomy with radiofrequency due to obstructive sleep apnea or snoring were evaluated for regrowth of the tonsils. Regrowth of the remaining tonsillar tissue was observed in 7 of 42 patients (16.6%). The upper respiratory tract obstruction symptoms recurred in 5 of these 7 patients while the remaining 2 patients were asymptomatic. The tonsils of symptomatic patients were removed completely. Partial tonsillectomy may have a significant potential for regrowth and thereby recurrence of the obstructive symptoms. Although the cause of this regrowth remains unknown, this problem should be remembered by the surgeons, and an informed consent should be obtained from the families prior to radiofrequency tonsillotomy.

Analysis of land-cover/use change dynamics in Manica Province in Mozambique in a period of transition (1990–2004)

The land-cover/use change dynamics in Manica Province in Mozambique are analysed, based upon interpretation of LANDSAT images, to assess trends and highlight management suggestions considering current policies in place that include the ownership and participation of local communities in natural resources management and the recognition of traditional ownership systems. Applying an object-oriented approach to compare the year 2004 with 1990, one observes that land-cover/use changes are not distributed evenly in the province. A substantial decrease in areas with trees belonging to the ‘ miombo ecosystem’ occurred and an increase of cultivated areas. The nature of agriculture is changing from shifting cultivation to more permanent types. These changes are found in prevalence on gentle slopes and close to the road network. The shift in equilibrium between the cultivated and (semi-) natural vegetated areas to cultivated areas may reduce the availability of forest products and reduce the free ecological services provided by trees. Prolonged cultivation in the same area represents a critical limit for destruction of rootstock and therefore miombo regrowth potential. Community-based management of the natural resources should thus be careful not to disturb the delicate balance of remaining miombo and give emphasis to the regulation of land-use activities, otherwise the negative impacts of land-cover/use change dynamics may fall disproportionately on the poorest members of society.

Restoration potential of Brigalow regrowth: Insights from a cross‐sectional study in southern Queensland

The study was undertaken at Bulli State Forest, in the eastern Darling Downs, Queensland, Australia. The State Forest includes a minor area (65 ha) of sedentary cracking clay in the western portion with limited gilgai development. This area supports remnant (undisturbed) open forest of Brigalow and Belah (Casuarina cristata Miq.) (Regional Ecosystem 11.9.5, Young et al. 1999) and adjacent regrowth Brigalow communities of two ages (39 and 27 years old). Clearing permits indicate that the 39-year old regrowth (herein referred to as ‘old regrowth’) was originally cleared by ringbarking in 1968 and has been allowed to regenerate without subsequent clearing or thinning. The 27-year-old regrowth (herein referred to as ‘young regrowth’) was first cleared in 1968 by pulling and was later re-pulled in the early 1980s. Mean annual rainfall is 578 mm, with December, the wettest month, receiving 76.5 mm on average.

Bacterial Regrowth Potential in Alkaline Sludges from Open-Sun and Covered Sludge Drying Beds

The aim of this study was to compare the regrowth potentials of wastewater sludges dried in two pilot-scale drying processes namely, Open-Sun Sludge Drying Bed (OSDB) and Covered Sludge Drying Bed (CSDB). Quicklime and/or coal fly ash were added to raw sludge samples prior to drying processes in order to enhance bacterial inactivation. Following three drying cycles (March-April, June-July and August-October), sludge samples were taken from the beds for the regrowth experiments. Addition of alkaline materials prevented the regrowth of faecal coliforms in all rewetted samples except for the samples obtained after the rainfall events in OSDB. Rewetting of these samples in the regrowth experiments increased faecal coliform numbers by 3.5-7 log units. In contradiction, the observed bacterial numbers in rewetted alkaline samples from CSDB were below the EPA Class B criterion (2 million MPN g-1 dry sludge). The combination of additional heat from solar collectors, protection from the rain and the unfavourable living conditions owing to alkaline materials appeared to inactivate bacteria more effectively in CSDB and hence eliminated regrowth potential more efficiently.

배양적 및 비배양적 방법에 의한 생물활성탄 부착세균 군집 특성

The Biological Activated Carbon (BAC) process in the water treatments represents a kind of biofiltration process which capabilities of bacteria to remove organic matters are maximized. It enables to eliminate organic matters and effectively reduce microbial regrowth potentials. As attached bacteria employ natural organic matter as a substrate, they are significantly dependent on indigenous microorganisms. In this study, characteristics of bacterial community by culturable and unculturable Methods have been conducted in a pilot plant using SAC in water treatment process at the downstream of the Nakdong River. Based on the results, HPC and bacterial- production for coal-based activated carbon material were cfu/g and , respectively, in the SAC process. The highest level of attached bacteria biomass and organic carbon removal efficiency was found in the coal-based activated carbon. The genera Pseudomonas, Flavobacterium, Alcaligenes, Acilzetobacter, and Spingomonas were identified for each activated carbon material. Pseudomonas vesicularis was the dominant species in the coconut- and coal-based materials, where as Pseudomonas cepacia was the dominant species in the wood-based material. The Scanning Electron Microscope (SEM) observation of the activated carbon surface also found the widespread distribution of rod form and coccus. The community of attached bacteria was investigated by performing Fluorescent in situ hybridization (FISH) analysis. a group was dominant in coal, wood and coccunt-based materials, group ranged from 27.0 43.0%, 7.1 22.0%, 11.3 28.6%, respectively. These results suggest that a group bacterial community appears to be regulated removal efficiency of organic material in water treatment process.

Membrane bioreactor process for removing biodegradable organic matter from water

This research investigated a membrane bioreactor (MBR) process for removing biodegradable organic matter (BOM) and trihalomethane (THM) precursors from pre-ozonated water. Bench-scale and mini-pilot-scale MBR experiments were conducted using powdered activated carbon (PAC) and acclimated biomass. Dissolved organic carbon (DOC) was removed through a combination of adsorption and biodegradation mechanisms, and the initial DOC removals depended on carbon dose, while steady-state removals were in the 20–60 percent range under various operating conditions. Both assimilable organic carbon (AOC) and total aldehydes were mostly removed to near detection limits and were not affected by PAC dosage. The AOC NOX removals were significantly higher than AOC P17 or total AOC removals probably because the MBR microbial consortium was closer in characteristics to Aquaspirillum NOX than to Pseudomonas fluorescens (P17). The DOC was used instead of biodegradable organic carbon (BDOC) as a parameter for evaluating disinfection byproduct formation and bacterial regrowth potentials because BDOC assays did not yield consistent and conclusive results due to analytical difficulties. The removals of THM precursors were high when PAC was added; however, steady-state removals were a function of operating conditions and PAC dosage. Addition of PAC enhanced DOC removals and membrane permeate fluxes. Furthermore, pre-ozonation reduced membrane fouling and enhanced membrane permeate flux.

Removal of Escherichia coli after Treatment Using Ozonation-Ultrafiltration with Iron Oxide-Coated Membranes

The effect of membrane filtration, ozonation, and combined ozonation-membrane filtration on the removal of Escherichia coli was studied. Commercially available ceramic membranes with a molecular weight cutoff (MWCO) of 5kDa were used as is, and also coated with iron oxide nanoparticles and sintered at 900°C. With membrane filtration and ozonation-membrane filtration using the uncoated membrane, 7 log removal of E. coli was achieved, as compared to 7.5 log removal with ozonation-membrane filtration with the coated membrane. A Live-Dead assay indicated that the mortality of E. coli in the product water was 15%, ∼50%, ∼86%, and >99% with membrane filtration, ozonation, combined ozonation-membrane filtration with the uncoated membrane and the coated membrane, respectively. With the coated membrane, the concentration of assimilated organic carbon (AOC) was reduced by up to 50% more than with the uncoated membrane filtration (with both systems operated using ozone). This indicates that there is a reduced potential for regrowth after treatment using the coated membranes and ozone. Scanning electron micrographs (SEM) of the membrane surface suggest that after filtration there is less detritus on the surface of the coated membrane than on the uncoated membrane. As a result of the inactivation of the E. coli and the lower AOC concentrations observed using combined catalytic ozonation-membrane filtration this process is likely to be very effective to both disinfect the water and control bacterial regrowth in the distribution system.

Chlorine decay in drinking-water transmission and distribution systems: Pipe service age effect

Water quality can deteriorate in the transmission and distribution system beyond the treatment plant. Minimizing the potential for biological regrowth can be attained by chlorinating the finished water. While flowing through pipes, the chlorine concentration decreases for different reasons. Reaction with the pipe material itself and the reaction with both the biofilm and tubercles formed on the pipe wall are known as pipe wall demand, which may vary with pipe parameters. The aim of this paper was to assess the impact of the service age of pipes on the effective chlorine wall decay constant. Three hundred and two pipe sections of different sizes and eight different pipe materials were collected and tested for their chlorine first-order wall decay constants. The results showed that pipe service age was an important factor that must not be ignored in some pipes such as cast iron, steel, cement-lined ductile iron (CLDI), and cement-lined cast iron (CLCI) pipes especially when the bulk decay is not significant relative to the wall decay. For the range of the 55 years of pipe service age used in this study, effective wall decay constants ranged from a decrease by −92% to an increase by +431% from the corresponding values in the recently installed pipes. The effect of service age on the effective wall decay constants was most evident in cast iron pipes, whereas steel pipes were less affected. Effective chlorine wall decay for CLCI and CLDI pipes was less affected by service age as compared to steel and cast iron pipes. Chlorine wall decay constants for PVC, uPVC, and polyethylene pipes were affected negatively by pipe service age and such effect was relatively small.

Variation of dissolved organic matter and microbial regrowth potential through drinking water treatment processes

We investigated how various water treatment processes affect AOC (assimilable organic carbon) and MAP (microbially available phosphorus), which nutrient limits microbial growth between organic carbon and phosphorus, and what extent AOC is related to the MW fractions of NOM for raw waters of the Han River and process waters of two water treatment plants in Korea. In view of our results so far achieved, a significant difference was observed between MAP and MAP-P (potential MAP), while little difference was observed between AOC and AOC-P (potential AOC) for raw and pre-chlorinated waters, suggesting that organic carbon limits microbial growth instead of phosphorus. Conventional treatment processes poorly removed AOC-P (42.8%), since the AOC, which was mainly related to the small-molecular DOC, was hardly removed by conventional processes. Oxidants such as chlorine and ozone increased both of the AOC (AOC-P) and MAP (MAP-P), particularly ozone having the stronger oxidation power resulted in a larger increase. However, BAC and GAC removed AOC to less than 60 μg/L which meets the level for biological stability.

Sheep grazing vs. cutting: regeneration and soil nutrient exploitation of the grassland weed Rumex obtusifolius

Broad-leaved dock (Rumex obtusifolius L., Polygonaceae) is an agronomically important perennial weed causing decreases in pasture yields and fodder quality. Non-chemical control measures for dock are often limited to frequent pulling and cutting, additionally it is usually avoided by grazing animals. Here, the regeneration of R. obtusifolius in a Rumex-infested grassland grazed by a sheep breed that explicitly feeds on dock (Ovis aries L. cv. East Prussian Skudden) was compared to cutting. Therefore, regeneration of 90 R. obtusifolius plants of three different size classes was monitored in three plots during three grazing and cutting cycles. Plant height and number of fruit-stands of regrown R. obtusifolius was significantly lower, number of leaves significantly higher after grazing than after cutting, while plant diameter was unaffected. Initially medium and large-sized plants (>40 cm diameter) were significantly more sensitive to grazing or cutting than initially smaller sized plants. Soil nitrate and ammonium concentrations in the vicinity of R. obtusifolius correlated with some regrowth parameters but were not affected by grazing or cutting. Sheep-grazed grassland communities comprised fewer legumes (p = 0.002), more grasses (p = 0.010) and fewer sward gaps (p = 0.025) than cut grassland. At the end of the experiment, abundance of R. obtusifolius in sheep grazed plots was lower than in cut plots (p = 0.089) suggesting that regrowth potential of this weed was depleted by continuous grazing and higher sward density. In conclusion, these data suggest that sheep could be considered in grassland management schemes to both directly and indirectly control Rumex infestations.

Influence of humic substances on the ultraviolet disinfection of surface waters

AbstractThe efficiency of ultraviolet (UV) disinfection and the regrowth potential of total coliforms were investigated in humic waters. Experiments were conducted according to an experimental design in which a UV radiation dose range of 68–681 mW s/cm2 was applied to waters containing various concentrations (0–10 mg/L) of fulvic acid. Experimental results strongly suggested that the harmful effect of UV radiation on bacteria was diminished in humic waters due to absorption of UV light. Increasing concentrations of fulvic acid appeared to enhance its influence with elevated doses of UV radiation. Measured inactivation responses were on the order of 1–6 log10 units for the UV dose range used. Comparison of k (inactivation coefficient) values for nonhumic water to highly humic water indicated that k decreased proportionally as the fulvic acid concentration of water was increased. The results of dark‐incubation tests indicated significant regrowth of bacteria in fulvic acid‐containing waters.