Iron in boreal river catchments: Biogeochemical, ecological and management implications.

Iron (Fe) is an important element in aquatic ecosystems worldwide because it is intimately tied with multiple abiotic and biotic phenomena. Here, we give a survey of manifold influences of Fe, and the key factors affecting it in the boreal catchments and their waters. It includes the perspectives of biogeochemistry, hydrology, ecology, and river basin management. We emphasize views on the dynamics and impacts of different forms of Fe in riverine environments, including organic colloids and particles, as well as inorganic fractions. We also provide perspectives for land use management in boreal catchments and suggest guidelines for decision making and water management. Based on our survey, the main emphases of water protection and management programs should be (i) prevention of Fe mobilization from soil layers by avoiding unnecessary land-use activities and minimizing soil disturbance in high-risk areas; (ii) disconnecting Fe-rich ground water discharge from directly reaching watercourses; and (iii) decreasing transport of Fe to watercourses by applying efficient water pollution control approaches. These approaches may require specific methods that should be given attention depending on catchment conditions in different areas. Finally, we highlight issues requiring additional research on boreal catchments. A key issue is to increase our understanding of the role of Fe in the utilization of DOM in riverine food webs, which are typically highly heterotrophic. More knowledge is needed on the metabolic and behavioral resistance mechanisms that aquatic organisms, such as algae, invertebrates, and fish, have developed to counter the harmful impacts of Fe in rivers with naturally high Fe and DOM concentrations. It is also emphasized that to fulfil the needs presented above, as well as to develop effective methods for decreasing the harmful impacts of Fe in water management, the biogeochemical processes contributing to Fe transport from catchments via rivers to estuaries should be better understood.

Charge density of total organic carbon in Finnish lakes.

Ion balance calculations were used to estimate the charge density of total organic carbon (TOC) and for calibrating the model of Oliver et al. (1983) for Finnish lakes. The database consisted of samples collected in the autumn of 1987 from 955 randomly selected lakes covering the whole country. Organic anion concentrations were estimated as the difference between Sigma cations and Sigma inorganic anions. The charge density of TOC was estimated by dividing the organic anion concentration by TOC. The median charge density was 7.5 microeq (mg TOC)(-1). In lakes with pH values lower than 4.5 the average charge density was 5.2 microeq (mg TOC)(-1) and it increased to 10.3 microeq (mg TOC)(-1) in lakes with pH higher than or equal to 7.0. The calibrated model explained 79% of the observed variability in organic anion concentration. The value for the total amount of acidic functional groups per mol organic carbon in the model of Oliver et al. (1983) was slightly higher compared to the Finnish calibration. At pH values higher than 4.4 the Finnish calibration gives lower organic anion concentrations compared to the model of Oliver et al. (1983).

Arthrodesis of the knee with intramedullary nail fixation.

Thirty-three patients had an arthrodesis of the knee by means of an intramedullary nail introduced through the greater trochanter. Fifteen of the procedures were done for a failed knee arthroplasty; eight had failed because of infection and seven, because of aseptic loosening. Twenty-nine of the thirty-three knees united three to four months after the first attempt at arthrodesis and three united after technical errors were corrected. One knee had a broken nail and a non-union; this was still untreated at the time of writing. Four nails broke: three in the line of fusion and one in the line of an infected supracondylar pseudarthrosis of the femur. No new infections developed after the arthrodesis. Three patients had had an infection and a chronic fistula before the arthrodesis, and the fistulae healed six, fourteen, and eighteen months postoperatively. In another patient, who had had infection and necrosis of the skin preoperatively, the wound healed in six months. All of these knees healed without an additional major operation. The functional result was satisfactory in all patients. After the arthrodesis, seventeen of the thirty-three patients needed less aid when walking, and no patient needed more aid. Fusion of the knee with a long intramedullary nail can be safe and effective, even in the presence of infection, if the revision is performed properly and certain technical principles are followed. It is especially important to establish good contact between the resected bones.

Late urodynamic findings after surgery for cauda equina syndrome caused by a prolapsed lumbar intervertebral disk.

Bladder function was evaluated urodynamically in 17 patients operated on 2 to 3 years previously for the cauda equina syndrome caused by a prolapsed lumbar intervertebral disk. Of the patients 10 (59 per cent) reported the bladder function to be normal, while the other 7 had symptoms of obstruction or incontinence. Urodynamic findings were normal in 4 patients (24 per cent). In 3 patients (18 per cent) no detrusor contraction could be demonstrated in the pressure-flow electromyography study. Two patients (12 per cent) used the detrusor and straining during voiding. Cystometry showed an unstable detrusor in 3 patients (18 per cent). The remaining 5 patients (29 per cent) had either an increased bladder capacity or a decreased maximum flow rate. Neurological findings were normal in 2 patients (12 per cent). All of the patients with a decentralized detrusor had defective perianal sensation but detrusor contraction could be demonstrated in 3 who also had sensory impairment in the perianal region. Bladder function can be disturbed seriously in cauda equina patients without symptoms and, thus, all patients with the cauda equina syndrome should be tested urodynamically. An emergency operation seems to be capable of reducing late disturbances in bladder function. Regeneration of the autonomous nerves supplying the bladder and genitals may require an interval of several months to years.

Symptoms and signs of sciatica and their relation to the localization of the lumbar disc herniation.

Neurologic symptoms and signs in patients with sciatica were prospectively studied and compared with myelographic and operative findings in 403 cases with lumbar disc herniation as the cause of sciatica with special reference to accuracy of the clinical level diagnosis. Fifty-six percent of the herniations at L4-5. However, pain projection into the first sacral distribution was most common. Neurologic symptoms and signs of involvement of a single root were present in 239 cases and of two roots in 154 cases in L4-5 and L5S1 herniations. Pain projection into the fifth lumbar distribution was a very important symptom for identification of clinical findings of the fifth lumbar root involvement gave a level diagnostic accuracy comparable with myelography, while pain projection into the first sacral distribution was less reliable especially in cases with signs of two roots. The neurologic picture of high herniations was completely unreliable. Lumbar myelography or computer tomography is recommended as a routine preoperative study.