Thawing Yedoma permafrost is a neglected nitrous oxide source.

In contrast to the well-recognized permafrost carbon (C) feedback to climate change, the fate of permafrost nitrogen (N) after thaw is poorly understood. According to mounting evidence, part of the N liberated from permafrost may be released to the atmosphere as the strong greenhouse gas (GHG) nitrous oxide (N2O). Here, we report post-thaw N2O release from late Pleistocene permafrost deposits called Yedoma, which store a substantial part of permafrost C and N and are highly vulnerable to thaw. While freshly thawed, unvegetated Yedoma in disturbed areas emit little N2O, emissions increase within few years after stabilization, drying and revegetation with grasses to high rates (548 (133-6286) µg N m-2 day-1; median with (range)), exceeding by 1-2 orders of magnitude the typical rates from permafrost-affected soils. Using targeted metagenomics of key N cycling genes, we link the increase in in situ N2O emissions with structural changes of the microbial community responsible for N cycling. Our results highlight the importance of extra N availability from thawing Yedoma permafrost, causing a positive climate feedback from the Arctic in the form of N2O emissions.

Fluxes of nitrous oxide and methane on an abandoned peat extraction site: effect of reed canary grass cultivation.

Drained organic soils are among the most risky soil types as far as their greenhouse gas emissions are considered. Reed canary grass (RCG) is a potential bioenergy crop in the boreal region, but the atmospheric impact of its cultivation is unknown. The fluxes of N(2)O and CH(4) were measured from an abandoned peat extraction site (an organic soil) cultivated with RCG using static chamber and snow gradient techniques. The fluxes were measured also at an adjacent site which is under active peat extraction and it is devoid of any vegetation (BP site). The 4-year average annual N(2)O emissions were low being 0.1 and 0.01 g N(2)O m(-2)a(-1) at the RCG and BP sites, respectively. The corresponding mean annual CH(4) emissions from the RCG and BP sites were also low (0.4 g and 0.9 g CH(4) m(-2)a(-1)). These results highlight for the first time that there are organic soils where cultivation of perennial bioenergy crops is possible with low N(2)O and CH(4) emissions.

Microbial community structure in biofilms and water of a drinking water distribution system determined by lipid biomarkers.

The development of microbial communities in biofilms of a drinking water distribution system was monitored, and compared to the microbial communities in water. The microbial communities were studied by phospholipid fatty acid (PLFA) profiles. In drinking water samples the most common PLFAs, with the proportion of 60.9%, were monoenoic fatty acids, such as 16:1omega7c and 18:1omega7c, indicating high abundance of gram-negative bacteria. Instead, in biofilm samples saturated fatty acids, such as 16:0 and 18:0, indicating general biomass, accounted for 54.9-78.4% of the total PLFAs. The proportions of monoenoic fatty acids in biofilm increased from 11.5% to 31.2% with water aging from 22 h to 62 h in the distribution system. In conclusion, water aging affected the structure of microbial communities in biofilms, and the microbes in water differed from those in biofilms. These differences might also reflect the differences in the physiological state of the microbes, which is influenced by water chemistry and by the growth environment, i.e. water or biofilm.

Gas chromatographic-mass spectrometric detection of 2- and 3-hydroxy fatty acids as methyl esters from soil, sediment and biofilm.

Hydroxy fatty acids (OH-FAs) can be used in the characterization of microbial communities, especially Gram-negative bacteria. We prepared methyl esters of 2- and 3-OH-FAs from the lipid extraction residue of soil, sediment, and biofilm samples without further purification or derivatization of hydroxyl groups. OH-FA methyl esters were analyzed using a gas chromatograph equipped with a mass selective detector (GC-MS). The ions followed in MS were m/z 103 for 3-OH-FAs and m/z 90 and M-59 for 2-OH-FAs. The rapid determination of 3- and 2-OH-FAs concomitantly with phospholipid fatty acids provided more detailed information on the microbial communities present in soil, sediment, and drinking water biofilm.

Molecular size fractions of treated aquatic humus.

The effects of ozone, chlorine, hydrogen peroxide, and permanganate on the aquatic humic matter with different molecular size fractions and the organic acid formation in drinking water treatment were studied. Aquatic humus in lake water (LW), artificially recharged groundwater (AW), and purified artificially recharged groundwater (PW) were fractionated by high-pressure size-exclusion chromatography (HP-SEC) with UV-254nm detection before and after oxidation, a technique which resulted generally in seven peaks. The sum of the molecular size fractions (SMSF) of the LW was reduced by 47% during the bank filtration process, and the SMSF of the AW was reduced by 55% during the process in the water treatment plant. The oxidation of the AW resulted in reductions in the range of 18-35% of the SMSF; the respective range of the PW was 15-69%. However, the content of the total organic carbon (TOC) reduced only slightly, and a high correlation between the TOC and the SMSF (0.911) was observed in the whole material. The greatest decreases appeared in the highest-molecular-weight fractions while the low-molecular-weight fractions remained nearly unchanged. The total content of the six organic small-molecular-weight acids (sum of the organic acids, SOA) (formate, acetate, propionate, pyruvate, oxalate, and citrate) varied between 0.1-5.1% and 0.1-9.7% of the reduced TOC in the AW and the PW, respectively. The formation of the SOA, especially of oxalate, was the greatest after hydrogen peroxide combined with ozonation (as much as 1,100 microg/L), while chlorination resulted in the SOA of < 50 microg/L.

Disinfection by-products in Finnish drinking waters.

Disinfection by-products (DBPs) were measured in plant effluents of 35 Finnish waterworks, which utilized different treatment processes and raw water sources. DBPs were measured also from the distribution systems of three waterworks. Di- and trichloroacetic acids, and chloroform were the major DBPs found in treated water samples. The concentration of six haloacetic acids (HAA6) exceeded the concentrations of trihalomethanes (THMs). Chlorinated drinking waters (DWs) originating from surface waters contained the highest concentration of HAA6 and THMs: 108 and 26 microg/l, respectively. The lowest concentrations of DBPs were measured from ozonated and/or activated carbon filtrated and chloraminated DWs. Higher concentrations of HAA6, THMs, and adsorbable organic halogens were measured in summer compared to winter. The levels of chlorinated acetic acids, chloroform, and bromodichloromethane correlated positively with mutagenicity. Past mutagenicity levels of DWs were examined. A major reduction in the use of prechlorination, increased use of chloramine disinfection, and better removal of organic carbon were the most important reasons for the 69% decrease in mutagenicity from 1985 to 1994.

Molecular size distribution of natural organic matter in raw and drinking waters.

The purpose of this study was to compare the molecular size distribution (MSD) of natural organic matter (NOM) in raw waters (RW) and drinking waters (DW), and to find out the differences between MSD after different water treatment processes. The MSD of NOM of 34 RW and DW of Finnish waterworks were determined with high-performance size-exclusion chromatography (HPSEC). Six distinct fractions were generally separated from water samples with the TSK G3000SW column, using sodium acetate at pH 7 as an eluent. Large and intermediate humic fractions were the most dominant fractions in surface waters (lakes and rivers), while in artificially recharged groundwaters and natural groundwaters intermediate and small fractions predominated. Water treatment processes removed the two largest fractions almost completely shifting the MSD towards smaller molecular size in DW. Granular activated carbon (GAC) filtration, ozonation, and their combination reduced all humic fractions compared to the conventional treatment. Humic fractions correlated with total organic carbon (TOC) content and chemical oxygen demand, this being especially true in RW. The results demonstrate that the HPSEC method can be applied for a qualitative and also for rough estimate quantitative analyzes of NOM directly from RW and DW samples without sample pretreatment.

Microbially available organic carbon, phosphorus, and microbial growth in ozonated drinking water.

Ozonation is a disinfection technique commonly used in the treatment of drinking water. It destroys harmful microbes, but it also degrades organic matter in water, increasing the bioavailability of organic matter. Recently, it was found that not only organic carbon but also phosphorus can limit the microbial growth in drinking water, which contains high amount of organic matter. We used a bioassay to analyze whether ozone could also increase the microbially available phosphorus (MAP) in drinking water, and whether MAP in ozone-treated water was associated with the growth of heterotrophic microbes. We found that both assimilable organic carbon and MAP concentrations were increased by ozone treatment. In ozonated water, microbial growth was mainly limited by phosphorus, and even minor changes in MAP concentration dramatically increased the growth potential of heterotrophic microbes. In this study, ozonation increased the MAP by 0.08-0.73 microgram P/l, resulting in an increase of 80,000-730,000 CFU/ml in water samples. In contrast to MAP, the content of assimilable organic carbon (AOCpotential) did not correlate with microbial growth. The results show that in water treatment not only AOCpotential but also MAP should be considered as an important factor that can limit microbial growth in drinking water.

Soft deposits, the key site for microbial growth in drinking water distribution networks.

In this project we studied the microbiological quality of soft pipeline deposits removed from drinking water distribution networks during mechanical cleaning. Drinking water and deposit samples were collected from 16 drinking water distribution networks located at eight towns in different parts of Finland. Soft pipeline deposits were found to be the key site for microbial growth in the distribution networks. The microbial numbers in the soft deposits were significantly higher than numbers in running water. The highest microbial numbers were detected in the main deposit pushed ahead by the first swab. The deposits contained high numbers of heterotrophic bacteria, actinomycetes and fungi. Also coliform bacteria were often isolated from deposit samples. Manganese and copper in the deposits correlated negatively with the numbers of heterotrophic bacteria. After a year, the viable microbial numbers in the new deposits were almost as high as in the old deposits before the first mechanical cleaning. The bacterial biomass production was higher in the new than in the old deposits.

Greenhouse gases in non-oxygenated and artificially oxygenated eutrophied lakes during winter stratification.

Concentrations of dissolved methane (CH4), carbon dioxide (CO2), and nitrous oxide (N2O) were measured in the water columns of non-oxygenated and artificially oxygenated, ice-covered eutrophied lakes in the mid-boreal zone in Finland during late winter 1997 and 1999. Sampling was conducted during winter stratification, the critical period for oxygen (O2) deficiency in seasonally ice-covered, thermally stratified lakes. Oxygen concentrations were maintained at least at a moderate level throughout the oxygenated water columns, whereas the non-oxygenated columns suffered anoxic hypolimnia. The mean concentrations of dissolved CH4 exceeding the atmospheric equilibrium were greater in the non-oxygenated water columns (20.6-154 microM) than in the oxygenated ones (0.01-1.41 microM). In contrast, the mean excess CO2 concentrations varied less between the non-oxygenated and oxygenated sites (0.28-0.47 and 0.25-0.31 mM, respectively). Oxygenated water columns had greater mean excess concentrations of N2O (0.018-0.032 microM) than the non-oxygenated ones (0.005-0.024 microM). If the accumulated greenhouse gas stores in the water columns during winter are assumed to be released to the atmosphere during the spring overturn, the global warming potentials (GWP, time horizon 100 yr) of these potential emissions at the non-oxygenated, eutrophic study sites ranged from 177 to 654 g CO2 equivalent (CO2-e) m-2 compared with 144 to 173 g CO2-e m-2 at the oxygenated sites. The increase in the accumulation of CH4 was the main reason for the higher GWP of the non-oxygenated sites. Anthropogenic eutrophication of lake ecosystems can generate increased CH4 emissions due to associated O2 depletion of their sediment and water column.

A novel sediment gas sampler and a subsurface gas collector used for measurement of the ebullition of methane and carbon dioxide from a eutrophied lake.

A novel sediment bubble gas sampler and a subsurface bubble gas collector were designed to measure the ebullition of gases from profundal sediments of aquatic ecosystems. The sediment gas sampler was constructed to collect bubble gas samples directly from the uppermost sediment layers for gas composition analysis. The floating subsurface gas collector, designed to trap the bubbles released naturally from sediments, permitted the measurement of both the volume and the composition of the bubble gas. Due to its low cost, light weight and rapid sampling capability, the gas collector is ideal for studies requiring many replicate collectors. These devices were used for measurement of the ebullition of methane (CH4) and carbon dioxide (CO2) during an open water period from hypereutrophic Lake Postilampi, situated within the midboreal zone in Finland. The bubble gas obtained from the sediment with the sediment gas sampler had higher concentrations of CH4 and CO2 than the bubbles trapped in the gas collectors. This indicated that the bubble gas composition changed, either naturally during the migration of the bubbles from the sediment through the water column to the gas collectors, and/or during their storage in the collectors prior to sampling. The mean CH4 ebullition from Lake Postilampi was estimated to be in the range from 36 to 46 mg m(-2 d(-1), based on the bubble gas CH4 concentrations measured from the gas collectors and sediment, respectively. The bubbles contained only 0.02-0.57% of CO2 and thus, the ebullition had no significance in the release of CO2 from the lake.

Carbon disulfide and hydrogen sulfide removal with a peat biofilter.

Simultaneous removal of H2S and CS2 was studied with a peat biofilter inoculated with a Thiobacillus strain that oxidizes both compounds in an acidic environment. Both sulfurous gases at concentrations below 600 mg S/m3 were efficiently removed, and the removal efficiencies were similar, 99%, with an empty bed retention time (EBRT) of more than 60 sec. Concentrations greater than 1300-5000 mg S/m3 caused overloading of the filter material, resulting in high H2SO4 production, accumulation of elemental sulfur, and reduced removal efficiency. The highest sulfur removal rate achieved was 4500 g-S/day/m3 filter material. These results indicate that peat is suitable as a biofilter material for the removal of a mixture of H2S and CS2 when concentrations of gases to be purified are low (less than 600 mg/m3), but it is still odorous and toxic to the environment and humans.

Oxidation of gas mixtures containing dimethyl sulfide, hydrogen sulfide, and methanethiol using a two-stage biotrickling filter.

A biofiltration technique was developed for removing a mixture of hydrogen sulfide (H2S), methanethiol (MeSH), and dimethyl sulfide (Me2S) from waste gases. Since H2S, especially at high concentrations, disturbs the removal of Me2S, two biotrickling filters with different microbes and operating pH levels were connected in series to create a two-stage system. Different loads of these gases were studied in order to determine their impact on the removal capacity of the system. The microbial consortia for these filters were enriched from the sludge of a Finnish refinery with bubbling H2S or Me2S. Acclimation for Me2S took 2 weeks, though no acclimation time was needed for the other gases. The first filter, at a pH of 2, removed most of the H2S and some of the MeSH and Me2S. The second filter, at a pH of approximately 6.5, removed the rest of the MeSH and most of the Me2S. The total maximum loads of the whole two-stage biotrickling filter were 1150 g/m3/day for H2S-S (suffix S indicates the results are counted as sulfur amounts), 879 g/m3/day for Me2S-S, and 66 g/m3/day for MeSH-S treated in a gas mixture. The average removal efficiencies for all gases tested were 99% or higher.

Copper and silver ions more effective against legionellae than against mycobacteria in a hospital warm water system.

We studied the influence of electrolytically released copper and silver ions on the microbiological quality in a warm water system of a hospital. The concentration of nontuberculous mycobacteria was followed for three, and that of legionellae and other heterotrophic bacteria in the water for four years. The highest concentrations of copper and silver ions were 220 and 68 microg/l, respectively. Silver ion concentration of about 3 microg/l was sufficient to control the growth of legionellae in circulating warm water. The results showed that it is more difficult to eradicate legionellae from taps and showers: these points were colonized by a small number of legionellae after the metal ion concentrations were increased in the circulating water. A regular use of water eradicated legionellae from the shower. One tap was still used irregularly, and this may be a reason why it still contained small concentrations of legionellae also in the last years of the study. Mycobacteria were occasionally isolated from the circulating water and repeatedly from the shower, even when the metal concentrations were high. To control legionella bacteria in warm water systems, silver concentrations of only 3 microg/l are needed if all taps and showers of the system are regularly used. Such low copper and silver concentrations, however, are not efficient against nontuberculous mycobacteria or other heterotrophic bacteria.

Physiology and taxonomy of thiobacillus strain TJ330, which oxidizes carbon disulphide (CS2).

A bacterium (strain TJ330) capable of using carbon disulphide (CS2) as its sole energy source in an acidic environment was isolated from a peat biofilter used in experiments to remove CS2 and hydrogen sulphide (H2S) from air. Its physiology and taxonomy are described here. The strain oxidized CS2, H2S and elemental sulphur to sulphate chemolithotrophically. The rate of sulphate production was highest at pH 2. The maximum growth rate constant (micromax) using CS2 as a substrate was 3.9 x 10(-2) h(-1) (generation time 18 h) and the Monod constant (Ks) was 0.97-2.6 micromol l(-1) CS2 (74-198 microg l(-1)), corresponding to an equilibrium with 15-40 ppm CS2 in the headspace. The optimum growth temperature using elemental sulphur as a substrate was 28 degrees C. The strain bears morphological and physiological similarities to Thiobacillus thiooxidans, but the latter is incapable of oxidizing CS2. The strain TJ330 (DSM 8985) showed only 44.2 + 11.8% DNA homology with the type strain T. thiooxidans ATCC 19377, while its homology with T. ferrooxidans ATCC 23270 was 17.1 + 3.4%. The strain TJ 330 represents a high-affinity bacterium which can effectively remove low CS2 concentrations in an acid environment. These properties can be utilized in biotechnological purification applications.

Environmental factors affecting the occurrence of mycobacteria in brook sediments.

The occurrence of mycobacteria was studied in aerobic brook sediments from 39 drainage areas in Finland. The culturable counts of mycobacteria were related to climatic conditions, characteristics of the drainage area, chemical characteristics of the sediment and water, culturable counts of other heterotrophic bacteria, and microbial respiration rate in the sediment. The counts of mycobacteria varied from 1.1 x 10(2) to 1.5 x 10(4) cfu g-1 dry weight of sediment. They correlated positively with the proportion of the drainage area consisting of peatland, total content of C, content of Pb, microbial respiration rate in the sediment, and chemical oxygen demand of the water. The correlations of the mycobacterial counts with pH of sediment and alkalinity of water were negative. The results of the present sediment study and of the forest soil study published earlier strongly suggest that an increase in acidity increases the counts of mycobacteria and decreases the counts and activity of other heterotrophic bacteria. Mycobacterial counts were more than 100 times higher (per dry weight) in forest soils with pH 3.5-4.3 than in sediments with pH 4.5-6.3.

Mutagenicity and amount of chloroform after chlorination of bank filtered lake water.

Chlorinated drinking waters produced from humus-rich waters often have a high content of halogenated organic by-products which increases the mutagenicity of drinking water. With in vitro chlorination experiments we studied the formation of chloroform (CHCl3) and mutagenicity of artificially recharged ground water samples. The water samples where obtained from an artificial ground water plant which infiltrates humus-rich lake water through an esker island. The chlorination experiments showed that bank filtration reduced strongly the formation of chloroform and mutagenicity of chlorinated water. Reduction in the amount of chloroform and mutagenicity in chlorinated waters was strongly associated with the decrease in the total content of organic carbon and with the decrease in molecular weight of organic matter during bank filtration.

Physicochemical quality of drinking and hot waters in Finnish buildings originated from groundwater or surface water plants.

The physicochemical quality of drinking and hot waters of 67 buildings in different parts of Finland was studied. Some of the buildings used processed groundwater and some processed surface water. Drinking water samples were taken from the first tap after the water was led into the building. Hot water samples were taken from taps and showers and from circulating hot water systems. Thy physicochemical quality of drinking water was affected by the origin of raw water used in the water plants. Drinking water from surface water plants contained more organic matter and less metals than water from groundwater plants. The quality goal for total organic carbon (TOC; < 2 mg l-1) was exceeded by all drinking water samples. In groundwaters, the variation in the content of non-purgeable organic carbon (NPOC) was great, probably because artificial groundwaters processed from surface waters were included in this group. Unlike in natural waters, the correlation between KMnO4-number and NPOC in the processed waters was weak. This result shows that KMnO4-number is an inaccurate estimate for organic carbon in processed waters. Corrosion of pipe materials was seen as elevated concentrations of iron and copper. In general, the physicochemical quality of drinking and hot waters in the buildings was rather similar.

Phosphorus and bacterial growth in drinking water.

The availability of organic carbon is considered the key factor to regulate microbial regrowth in drinking water network. However, boreal regions (northern Europe, Russia, and North America) contain a large amount of organic carbon in forests and peatlands. Therefore, natural waters (lakes, rivers, and groundwater) in the northern hemisphere generally have a high content of organic carbon. We found that microbial growth in drinking water in Finland is highly regulated not only by organic carbon but also by the availability of phosphorus. Microbial growth increased up to a phosphate concentration of 10 micrograms of PO4-P liter-1. Inorganic elements other than phosphorus did not affect microbial growth in drinking water. This observation offers novel possibilities to restrict microbial growth in water distribution systems by developing technologies to remove phosphorus efficiently from drinking water.

Efficacy of three prevention strategies against legionella in cooling water systems.

The efficacy of three different prevention strategies on legionella in cooling systems was studied. The strategies were as follows: (1) water temperature was lowered; (2) water quality was improved; or (3) the system as disinfected with polyhexamethylene biguanidechloride (PHMB) biocide or with 2-bromo-2-nitropropane-1,3-diol (BNPD) biocide. Lowering of water temperature was the most effective method to reduce the concentration of legionella in cooling systems. Improving of water quality resulted in a transitory disinfection effect. The additions of PHMB or BNPD decreased the concentrations of both legionella and heterotrophic bacteria in cooling water. The effect of biocides, however, lasted at the most only a few months. If possible, lowering water temperature and improving the water quality should be the primary practices for controlling bacterial growth in cooling systems. Regular biocide treatments should be incorporated into the maintenance procedures if technical improvements cannot be done or if their efficiency is too low.