Relating algal-derived extracellular and intracellular dissolved organic nitrogen with nitrogenous disinfection by-product formation.

The dissolved organic nitrogen (DON) pool from algal-derived extracellular and intracellular organic matter (EOM and IOM) comprises proteins, peptides, free amino acids and carbohydrates, of which, proteins can contribute up to 100% of the DON. Previous reports of algal-derived DON character have focused on bulk properties including concentration, molecular weight and hydrophobicity. However, these can be similar between algal species and between the EOM and IOM even when the inherent molecular structures vary. A focus on bulk character presents challenges to the research on algal-derived nitrogenous-disinfection by-product (N-DBP) formation as N-DBP formation is sensitive to the changes in molecular structure. Hence, the main aim of this study was to characterize algal EOM and IOM-derived DON, specifically proteinaceous-DON, using a combination of bulk and molecular characterization techniques to enable a more detailed exploration of the relationship between the character of algal-derived proteins and the N-DBP formation potential. DON from the EOM and IOM of four commonly found algae and cyanobacteria in natural waters were evaluated, namely Chlorella vulgaris, Microcystis aeruginosa, Dolichospermum circinale, and Cylindrospermopsis raciborskii. It was observed that 77-96% of total DON in all EOM and IOM samples was of proteinaceous origin. In the proteins, DON concentrations were highest in the high molecular weight fraction of IOM-derived bulk proteins (0.13-0.75 mg N L-1) and low to medium molecular weight fraction of EOM-derived bulk proteins (0.15-0.63 mg N L-1) in all species. Similar observations were also made via sodium dodecyl sulphate polyacrylamide gel electrophoresis and liquid chromatography-high resolution mass spectrometry. Solid-state 15N nuclear magnetic resonance (NMR) spectroscopy of the EOM and IOM revealed the existence of common aliphatic and heterocyclic N-groups in all samples, including a dominant 2° amide peak. Species dependent variability was also observed in the spectra, particularly in the EOM; e.g. nitro signals were found only in the Cylindrospermopsis raciborskii EOM. Dichloroacetonitrile (DCAN) and N-nitrosamine concentrations from the EOM of the species evaluated in this study were lower than the guideline limits set by regulatory agencies. It is proposed that the dominant 2° amide in all samples decreased N-DBP formation upon chlorination. For chloramination, the presence of nitro groups and aliphatic and heterocyclic N-DBP precursors could cause variable N-nitrosamine formation. Compared to non-algal impacted waters, algae-laden waters are characterised by low organic carbon: organic nitrogen ratios of ∼7-14 and elevated DON and protein concentrations. Hence, relying only on bulk characterization increases the perceived risk of N-DBP formation from algae-laden waters.

Formation of algal-derived nitrogenous disinfection by-products during chlorination and chloramination.

Algal cells and algal organic matter (AOM) are a source of high dissolved organic carbon (DOC) and nitrogen (DON) concentrations. This poses a possible health risk due to their potential to form disinfection by-products (DBPs), some of which may be of health concern, after disinfection. While several studies have focussed on the formation of carbonaceous DBPs from AOM, only a few studies have focussed on the formation of nitrogen containing N-DBPs from AOM. Hence, the main aim of this study was to thoroughly investigate the N-DBP formation potential of the AOM from a species of cyanobacteria commonly found in natural waters, Microcystis aeruginosa. Three haloacetonitriles, two halonitromethanes, two haloacetamides, and eight N-nitrosamines were analysed by gas chromatography-mass spectrometry after chlorination and chloramination of the extracted AOM. To provide further insight into the influence of changing DON character on N-DBP formation potential, the AOM from three other species, Chlorella vulgaris, Dolichospermum circinale and Cylindrospermopsis raciborskii, were also tested. Dichloroacetonitrile (DCAN) was the DBP formed in the highest concentrations for both chlorination and chloramination of bulk AOM from all the species. Furthermore, during chlorination and chloramination, the high molecular weight fraction (>1 kDa) of AOM from M. aeruginosa had a greater DCAN formation potential (normalised to DOC or DON) than the AOM in the low molecular weight fraction (<1 kDa) of M. aeruginosa, regardless of growth stage. N-Nitrosamine formation from the bulk AOM of all species occurred only after chloramination. The molar concentration of N-nitrosodimethylamine (NDMA) was lower than the other N-nitrosamines detected. However, NDMA formation increased with culture age for all four species, in contrast to most other N-nitrosamines whose formation remained consistent or decreased with culture age. Overall, algal growth could result in elevated concentrations of N-DBPs due to the increasing concentrations of high molecular weight algal DON in the AOM. It is suggested that the AOM comprises precursors containing long C-chain amine (R1-NH-R2) or cyclic N-containing amine structures. Comparisons to previously measured N-DBP concentrations in drinking water suggest that the AOM from the algae and cyanobacteria examined in this study are not likely to be a major source of precursors for either DCAN or NDMA in real waters. However, AOM may present a major precursor source for other N-nitrosamines.

An evaluation of measurement techniques for algal-derived organic nitrogen.

Algal-derived organic matter (AOM) from algal blooms in water supply systems contains dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) among other constituents. The DON and DOC are disinfection by-product (DBP) precursor compounds, and must be well characterised to facilitate effective removal, thus minimising DBP formation during disinfection. While DOC character has been studied extensively, DON analysis suffers from inaccuracies due to sample pre-treatment and instrument sensitivities. A liquid chromatography method that combines size exclusion chromatography with highly sensitive organic carbon and nitrogen detectors (LC-OCND) has been widely adopted for DOC analysis; however, its potential for application for DON charactersation has been suggested as a viable alternative to existing DON characterisation techniquesnot been assessed despite its potential. Hence, the aim was to compare the effectiveness of conventional total dissolved N-dissolved inorganic N (TN-DIN), and LC-OCND methods for analysing DON in AOM. A suite of N-containing model compounds representative of DON and AOM extracted from Chlorella vulgaris CS-42/7 and Microcystis aeruginosa CS-555/1 were used to evaluate the techniques. The DON of both model compounds and AOM was first analysed using the conventional method and, then, via LC-OCND. It was observed that LC-OCND had a better precision for DON when TN contained more DIN. LC-OCND provided direct quantitative measurements for bulk and fractionated DON and DIN, with little interference caused by DIN. Additionally, LC-OCND provided information on MW distribution and protein content of the AOM. For example, LC-OCND results showed that M. aeruginosa AOM contained more HMW material than C. vulgaris AOM. However, as LC-OCND uses UV oxidation, it could not completely oxidise complex aromatic structures, and thus had a lower recovery for HMW model compounds and algal DON in comparison to the conventional method that used high temperature catalytic oxidation. Overall, it is advised that a combination of LC-OCND and TN analysis be used to provide a more detailed characterisation of N-containing AOM and other similar HMW aquatic NOM samples.

Behaviour and fate of nine recycled water trace organics during managed aquifer recharge in an aerobic aquifer.

The fate of nine trace organic compounds was evaluated during a 12month large-scale laboratory column experiment. The columns were packed with aquifer sediment and evaluated under natural aerobic and artificial anaerobic geochemical conditions, to assess the potential for natural attenuation of these compounds during aquifer passage associated with managed aquifer recharge (MAR). The nine trace organic compounds were bisphenol A (BPA), 17ß-estradiol (E2), 17α-ethynylestradiol (EE2), N-nitrosodimethylamine (NDMA), N-nitrosomorpholine (NMOR), carbamazepine, oxazepam, iohexol and iodipamide. In the low organic carbon content Spearwood sediment, all trace organics were non-retarded with retardation coefficients between 1.0 and 1.2, indicating that these compounds would travel at near groundwater velocities within the aquifer. The natural aerobic geochemical conditions provided a suitable environment for the rapid degradation for BPA, E2, iohexol (half life <1day). Lag-times for the start of degradation of these compounds ranged from <15 to 30days. While iodipamide was persistent under aerobic conditions, artificial reductive geochemical conditions promoted via the addition of ethanol, resulted in rapid degradation (half life <1days). Pharmaceuticals (carbamazepine and oxazepam) and disinfection by-products (NDMA and NMOR) did not degrade under either aerobic or anaerobic aquifer geochemical conditions (half life >50days). Field-based validation experiments with carbamazepine and oxazepam also showed no degradation. If persistent trace organics are present in recycled waters at concentrations in excess of their intended use, natural attenuation during aquifer passage alone may not result in extracted water meeting regulatory requirements. Additional pre treatment of the recycled water would therefore be required.

Fate of nine recycled water trace organic contaminants and metal(loid)s during managed aquifer recharge into a anaerobic aquifer: Column studies.

Water quality changes associated with the passage of aerobic reverse osmosis (RO) treated recycled water through a deep anaerobic pyritic aquifer system was evaluated in sediment-filled laboratory columns as part of a managed aquifer recharge (MAR) strategy. The fate of nine recycled water trace organic compounds along with potential negative water quality changes such as the release of metal(loid)s were investigated in large-scale columns over a period of 12 months. The anaerobic geochemical conditions provided a suitable environment for denitrification, and rapid (half-life <1-25 days) degradation of the endocrine disrupting compounds (bisphenol A, 17beta-estradiol, 17alpha-ethynylestradiol), and iodipamide. However, pharmaceuticals (carbamazepine and oxazepam), disinfection by-products (N-nitrosodimethylamine, N-nitrosomorpholine) and iohexol did not degrade rapidly (half-life > 100 days). High retardation coefficients (R) determined for many of the trace organics (R 13 to 67) would increase aquifer residence time and be beneficial for many of the slow degrading compounds. However, for the trace organics with low R values (1.1-2.6) and slow degradation rates (half-life > 100 days), such as N-nitrosodimethylamine, N-nitrosomorpholine and iohexol, substantial biodegradation during aquifer passage may not occur and additional investigations are required. Only minor transient increases in some metal(loid) concentrations were observed, as a result of either pyrite oxidation, mineral dissolution or pH induced metal desorption, followed by metal re-sorption downgradient in the oxygen depleted zone.

The adaptation of the foot to heavy loads: plantar foot pressures study.

INTRODUCTION:: The foot serves as the main shock absorber during various activities as walking running and jumping. There are static and dynamic mechanisms which play a role in the adaptation of the foot to weight bearing walking with weights. The function of the foot while weight bearing was studied mainly under static conditions. We designed an experiment to explore dynamically the adaptation of the foot to weight bearing walking with weights. METHODS:: Ten healthy subjects participated the study. They walked barefoot over an EMED force plate which based on multiple pressure capacitance sensors. Each subject walked three times. The first walk was without any weight, the second walk with weight of 20 kg in backpack and the third walk with weight of 40 kg. Contact area, peak pressures, peak forces and duration of contact time were measured in seven areas of interest of the foot-heel, midfoot, lateral, central and medial forefoot, lateral toes and hallux. RESULTS:: The pressure time integral and force time integral increased in most areas of the foot except for the midfoot in the 20 kg walk. The largest increase was at the central and medial forefoot. Adding additional 20 kg to the load did not increased the loads on the midfoot but increased further the loads mainly at the central and medial forefoot. CONCLUSIONS:: The human foot adapts itself under loading condition by maintaining the medial longitudinal arch. Increasing the loading further activates compensatory mechanisms which maintain the longitudinal arch and shifts the the loads to the central and medial forefoot.

Plantar foot pressures during treadmill walking with high-heel and low-heel shoes.

The effect of walking with high-heel shoes on plantar foot pressure distribution was investigated. Ten normal women walking in shoes with low heels were compared to women walking in high-heel shoes. It was shown that high-heel shoes increased the load on the forefoot and relieved it on the hindfoot. The load passed toward the medial forefoot and the hallux. The lateral side of the forefoot showed a decrease in contact area, reduced forces, and peak pressures. The medial side of the forefoot had a higher force-time and pressure-time integral. It is suggested that these higher loads on the medial forefoot may aggravate symptoms in patients with hallux valgus deformity.

A preliminary objective evaluation of leprosy footwear using in-shoe pressure measurement.

The primary function of leprosy shoes, insoles and podiatric orthoses is to provide an underfoot environment capable of distributing the inevitable vertical forces, so reducing areas of peak pressure and ideally the period through which they are applied. Many patients with Hansen's disease have both skeletal deformity and anesthetised feet and the presence of high plantar pressures is the key reason for foot ulceration. This objective investigation using in-shoe dynamic pressure measurements showed that the addition of a shank to control insole rigidity reduced the overall peak pressures under the foot. When a deep canvas shoe was used to test single- and double-thickness insoles of two different types of material it was found in each case that the double-thickness mode was advantageous overall. Microcellular rubber insoles in two types of leprosy shoe were replaced by the polymer Poron. The Poron proved to be superior to both microcellular rubbers. The peak pressure and pressure-time integral should be considered as complimentary variables when determining the efficacy of footwear.

Effect of the shoe on plantar foot pressures.

The bare foot plantar pressures were compared to in-shoe pressure measurements in 11 normal male volunteers using the EMED system. Shoes diminished pressures and forces in most areas under the foot except the medial forefoot. The hallux showed less force, a smaller contact area and a reduced contact time. Therefore a shoe can interfere with the toe-off mechanism. There was no difference between various types of shoes with rubber and leather soles. Heavier subjects tended to put less weight on the medial forefoot.

Forefoot arthroplasty and changes in plantar foot pressures.

The aim of this study was to determine how effective forefoot arthroplasty is at reducing the pressures under the forefoot. The EMED F pressure measuring system was used. Fifteen patients (23 feet) were included in the study. All patients had foot pressure studies performed before and after surgery. Our results show a significant increase in total pressure and pressure-time integral under the foot after surgery. This increase was most marked under the first metatarsal head region (P < .005). However, the midmetatarsal region showed a slight decrease in pressure, but this was not significant. Symptomatically, 13 patients felt improved by the operation. The results suggest that the procedure is successful because it transfers the pressure to areas better able to tolerate it, rather than reduces the total pressure.

A comparison of two studies of the pressure distribution under the feet of normal subjects using different equipment.

There is growing interest in the use of foot pressure measurement both clinically and in the study of normal subjects. A number of systems are now commercially available, but comparison of the results is complicated by the different techniques employed. This paper compares the results of two studies. The first examined a large group of normal subjects using the dynamic pedobarograph. The second was identical to the first except that the EMED F system was used. The second study was carried out in order to verify existing results and to assess the clinical significance of the expected differences. Comparison of the results from the two studies showed that the median peak pressures demonstrated similar patterns with the highest pressure in the forefoot under the second/third metatarsal heads and the toes taking gradually reduced pressure from the first to the fifth toe. The EMED F showed higher peak pressures than the dynamic pedobarograph under the heel, the medial four metatarsal heads, and the great toe and showed lower peak pressures and shorter contact times under the lateral four toes. The pattern of loading across the metatarsal heads was further analyzed using an objective method of splitting the subjects into groups. Four groups were isolated from both sets of results, and this has confirmed that only a proportion of normal subjects demonstrate highest loading under the first metatarsal head whereas the remainder show highest loading centrally within the forefoot.

Double-blind comparison of captopril with nifedipine in hypertension complicated by intermittent claudication.

In a double-blind, crossover trial 12 patients with hypertension and peripheral arterial disease were randomized to three months' treatment with captopril 25-50 mg twice daily or nifedipine SR 20-40 mg twice daily. While both treatments were equally effective at lowering blood pressure, postexercise calf blood flow availability was greater during treatment with captopril (P less than 0.04). This was not reflected in walking capacity assessed by treadmill exercise. The results suggest that both captopril and nifedipine are appropriate antihypertensive agents in patients with peripheral arterial disease.

Changes in stature during exercise and sports training.

Shrinkage in stature is used in ergonomics and sports contexts as an index of load on the spine. Measurement is now computer-aided to facilitate data collection. Applications of the technique to sport and exercise have included evaluations of weight-training, running and jumping drills. The technique has also been employed in assessing procedures for spinal unloading such as gravity inversion. Future applications include investigations of procedures used to prevent back injury as well as studies of sports that impose high transient loads on the spine.

Reliability of pressure measurements: the EM ED F system.

The reliability of foot pressure measurement using the EMED F system has been tested by recording 25 walks with 10 volunteer subjects at three different speeds. Coefficients of reliability calculated for 1-25 walks showed that a good level of reliability was achieved using one measurement for most force/pressure variables but when the mean result of three or more walks was used reliability was excellent. Measurements related to time were more variable than the total force, the peak pressure and the area. The total force and peak pressure were also shown to increase with increasing speed but this was not true for all sites on the foot.

Changes in stature following drop jumping and post-exercise gravity inversion.

Spinal shrinkage, measured by changes in stature, is used as an index of spinal loading as alterations reflect changes in intervertebral disc height. Shrinkage induced by various physical activities may be reversed using gravity inversion. The present purpose was to examine the shrinkage induced by a drop jumping regimen and evaluate gravity inversion post-exercise. Eight males, aged 20-31, performed two separate experimental protocols, each on different dates at 1400 h. Subjects stood for 30 min before undertaking an exercise regimen, consisting of five sets of five drop jumps from a height of 1 m, rebounding over a hurdle 0.5 m high. For 20 min, directly following the exercise regimen, subjects on one occasion stood and on a second occasion undertook gravity inversion. Shrinkage was monitored for 40 min after this post-exercise treatment. The stadiometer used to measure shrinkage was accurate to 0.05 mm. The exercise regimen caused a mean shrinkage of 1.68 and 1.81 mm for the two testing sessions. Post-exercise inversion and standing for 20 min increased stature by 5.18 and 0.76 mm, respectively (P less than 0.01). The 40-min standing period following inversion caused a rapid loss in stature (4.07 mm). At 30 min into this recovery period, there was no significant difference in shrinkage for either of the regimens. Results suggest that effects of an inversion treatment are short-lasting.

The importance of heel compression in the measurement of diurnal stature variation.

Heel pad thickness was measured in 20 subjects (18 males aged 21-39 years and two females aged 21 and 25 years) using a 2 MHz ultrasound transducer linked to an Echo Scan body composition meter, Thandar SC110A oscilloscope and M150 amplifier. With the subjects standing erect and weight-bearing equally through both feet, the average time to achieve equilibrium heel compression was 81.7 s. Compression of the heel pad soft tissue averaged 4.4 mm (range 0.8-8.9 mm). Following equilibrium with one foot weight-bearing, an additional average loss of 1.6 mm of thickness (range 0-4 mm) was observed occurring after an average time period of 51 s. This study has confirmed the suspicion that heel pad shrinkage may be a confounding factor in measurements of change of stature. The results of this study have indicated that a period of 2 min is needed for the heel pad thickness to compress sufficiently before measurements are taken.

Indirect measurement of skin blood flow and transcutaneous oxygen tension in patients with peripheral vascular disease.

The transcutaneous oxygen monitor was used in the vascular laboratory to give an objective measurement of the severity of arteriosclerotic disease in patients presenting with intermittent claudication. With the electrode operating at 44 degrees C on the leg, patients and normal volunteers performed treadmill exercises. It was observed that the resulting electrode heat consumption correlated closely with the degree of exercise. Claudicants, however, showed smaller changes than the normal group, the relationship forming an index of the severity of the disease.