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.

Emission of the greenhouse gases nitrous oxide and methane from constructed wetlands in europe.

The potential atmospheric impact of constructed wetlands (CWs) should be examined as there is a worldwide increase in the development of these systems. Fluxes of N(2)O, CH(4), and CO(2) have been measured from CWs in Estonia, Finland, Norway, and Poland during winter and summer in horizontal and vertical subsurface flow (HSSF and VSSF), free surface water (FSW), and overland and groundwater flow (OGF) wetlands. The fluxes of N(2)O-N, CH(4)-C, and CO(2)-C ranged from -2.1 to 1000, -32 to 38 000, and -840 to 93 000 mg m(-2) d(-1), respectively. Emissions of N(2)O and CH(4) were significantly higher during summer than during winter. The VSSF wetlands had the highest fluxes of N(2)O during both summer and winter. Methane emissions were highest from the FSW wetlands during wintertime. In the HSSF wetlands, the emissions of N(2)O and CH(4) were in general highest in the inlet section. The vegetated ponds in the FSW wetlands released more N(2)O than the nonvegetated ponds. The global warming potential (GWP), summarizing the mean N(2)O and CH(4) emissions, ranged from 5700 to 26000 and 830 to 5100 mg CO(2) equivalents m(-2) d(-1) for the four CW types in summer and winter, respectively. The wintertime GWP was 8.5 to 89.5% of the corresponding summertime GWP, which highlights the importance of the cold season in the annual greenhouse gas release from north temperate and boreal CWs. However, due to their generally small area North European CWs were suggested to represent only a minor source for atmospheric N(2)O and CH(4).

Calcium and other salivary factors in periodontitis-affected subjects prior to treatment.

Salivary calcium was shown to be higher in treated periodontitis-affected subjects (P+) than in periodontitis-free patients (P-). Here the aim was to study whether differences in calcium or other salivary factors exist prior to treatment. The test group consisted of 20 (15 men, 5 women) periodontitis-affected subjects and the control group 15 subjects (10 men, 5 women) free from periodontitis. Paraffin-stimulated whole saliva was collected to determine the flow-rate, calcium and phosphate concentrations, pH, buffering capacity, numbers of mutans streptococci, lactobacilli and yeasts. The results showed a higher calcium concentration (p < 0.05) in the P+ group (mean: 1.68 mmol/l; SE: 0.06 in men and mean: 1.49 mmol/l; SE: 0.10 in women) than in the P-group (mean: 1.48 mmol/l; SE: 0.09 in men and mean: 1.18 mmol/l; SE: 0.10 in women). The P+ group had more intact teeth (mean +/- SE: 9.9 +/- 0.8 in men and 11.2 +/- 2.0 in women) than the P-group (mean +/- SE: 8.3 +/- 0.7 in men and 8.2 +/- 2.4 in women). The present findings may indicate that an elevated level of salivary Ca is characteristic of P+ patients both before and after periodontal treatment.

Associations between salivary calcium and oral health.

Recently, we have shown positive correlations between high salivary calcium content and periodontitis, and between high salivary calcium level and the number of intact teeth in selected groups of subjects. The aim of our present study was to determine whether these correlations could be seen in a randomized group of healthy adults. A thorough oral examination including orthopantomograms was carried out for a total of 137 healthy subjects, 63 men (35.4+/-5.6 years) and 74 women (33.2+/-4.7 years). Paraffin-stimulated saliva was collected from the subjects and salivary flow (ml/min), buffering capacity, calcium (mMol/l) and microbial variables including lactobacilli, yeasts, mutans streptococci, total streptococci, total number of aerobes, and anaerobes were determined. The calcium level of whole saliva had a median of 1.23 mMol/l. Subjects with calcium level below the median were categorized as 'low', while those with higher values formed the 'high' salivary calcium group. There were more men than women in the 'High' salivary calcium group (p=0.025). Subjects in the 'high' calcium group showed more bleeding on probing (p=0.026), had more intact teeth (p=0.045), and lower DMF-scores (p=0.025) than their counterparts. No other differences were found between the two groups. We found clear associations between the level of salivary calcium and factors reflecting gingival health on one hand, and dental health on the other in a randomly selected group of healthy subjects, and conclude that salivary calcium may be important with regard to both dental and gingival health.