Trends in hydrometeorological conditions and stream water organic carbon in boreal forested catchments

Temporal trends in stream water total organic carbon (TOC) concentration and export were studied in 8 forested headwater catchments situated in eastern Finland. The Seasonal Kendall test was conducted to identify the trends and a mixed model regression analysis was used to describe how catchment characteristics and hydrometeorological variables (e.g. precipitation, air and stream water temperatures, and atmospheric deposition) related to the variation in the concentration and export of stream water TOC. The 8 catchments varied in size from 29 to 494 ha and in the proportion of peatland they contained, from 8 to 70%. Runoff and TOC concentration were monitored for 15-29 years (1979-2006). Trends and variation in TOC levels were analysed from annual and seasonal time series. Mean annual TOC concentration increased significantly in seven of the eight catchments. The trends were the strongest in spring and most apparent during the last decade of the study period. The slopes of the trends were generally smaller than the variation in TOC concentration between years and seasons and between catchments. The annual TOC export showed no clear trends and values were largely determined by the temporal variability in runoff. Annual runoff showed a decreasing trend in two of the eight catchments. Mean annual air and stream water temperatures showed increasing trends, most clearly seen in the summer and autumn series. According to our modeling results, stream water temperature, precipitation and peatland percentage were the most important variables explaining annual and most seasonal TOC concentrations. The atmospheric deposition of SO₄, NH₄, and NO₃ decreased significantly over the study period, but no significant link with TOC concentration was found. Precipitation was the main hydrometeorological driver of the TOC export. We concluded that stream water TOC concentrations and exports are mainly driven by catchment characteristics and hydrometeorological factors rather than trends in atmospheric acid deposition.     

Variation in river water temperatures in an upland stream over a 30-year period

Stream water temperature data from the Girnock burn, a 30-km2 catchment in Scotland were examined for systematic variation across 30 years of record (1968-1997). The data suggest that there has been no change in mean annual temperature with time, but at a seasonal level there is some indication of an increase in mean daily maximum temperatures during the winter (December to February) and spring (March to May) seasons. For the spring season, there is also evidence that mean temperature has increased. There are no apparent or obvious changes in stream flow to account for this. The strong relationship between air and stream temperatures (r2 = 0.96) implies that changes in the stream are the result of changes in the climate. It is possible that this may occur as a result of the effect of increasing air temperatures which may have also reduced the influence of snow and snowmelt on the catchment during the winter and spring seasons.     

Link between DOC in near surface peat and stream water in an upland catchment

Hydrologic transport of dissolved organic carbon (DOC) from peat soils may differ to organo-mineral soils in how they responded to changes in flow, because of differences in soil profile and hydrology. In well-drained organo-mineral soils, low flow is through the lower mineral layer where DOC is absorbed and high flow is through the upper organic layer where DOC is produced. DOC concentrations in streams draining organo-mineral soils typically increase with flow. In saturated peat soils, both high and low flows are through an organic layer where DOC is produced. Therefore, DOC in stream water draining peat may not increase in response to changes in flow as there is no switch in flow path between a mineral and organic layer. To verify this, we conducted a high-resolution monitoring study of soil and stream water at an upland peat catchment in northern England. Our data showed a strong positive correlation between DOC concentrations at -1 and -5 cm depth and stream water, and weaker correlations between concentrations at -20 to -50 cm depth and stream water. Although near surface organic material appears to be the key source of stream water DOC in both peat and organo-mineral soils, we observed a negative correlation between stream flow and DOC concentrations instead of a positive correlation as DOC released from organic layers during low and high flow was diluted by rainfall. The differences in DOC transport processes between peat and organo-mineral soils have different implications for our understanding of long-term changes in DOC exports. While increased rainfall may cause an increase in DOC flux from peat due to an increase in water volume, it may cause a decrease in concentrations. This response is contrary to expected changes in DOC exports from organo-mineral soils, where increase rainfall is likely to result in an increase in flux and concentration.     

Management of optimum water quality in a stream

An optimal waste discharge policy along a stream is investigated based on a program of minimizing the total cost benefit function on a regional basis. The system consists of a stream along which are located several inputs of waste and intakes of water. The cost benefit function comprises of the sum of the cost of waste treatment and the cost of water treatment minus the benefits derived from maintaining a certain water quality in the stream. The biochemical oxygen demand and the dissolved oxygen are considered to be the primary indicators of water quality. A steady state dispersion model is employed to predict the BOD and DO concentrations along the stream.     

Provisions in design and maintenance to protect water quality from roof catchments

An analytical model has been developed to study time‐dependent atmospheric diffusion in the protected zone a ≥ z ≥ h, considering heavy admixture's concentration, where h is the height of the surface layer, a is the height of the mixing layer and z is the the vertical coordinate. This model takes care of the variation of surface and mixing layer heights on thermal stratification, geostrophic drag by terrain and several other meteorological parameters. Pollutants are emitted from two sources. One is continuous in the surface layer 0 ≤ z ≤ h and the other is instantaneous above the surface layer h ≤ z ≤ a. We have used an appropriate boundary condition at the surface layer height to model the effect of surface layer source, effect of terrain and settling of larger particles. Results have been analysed for the case of stable and neutral atmospheric conditions. It is found that the effect of settling of larger particles is to reduce concentration throughout the protected zone for large settling velocities. For smaller values of settling velocity there will be an increase in concentration in the lower part and decrease in the upper part. It is also found that the concentration in the lower part of the protected zone is higher in the stable case compared to the neutral case at large travel time. The effect of settling of larger particles is to reduce the concentration significantly in a stable atmospheric layer compared to the neutral case. The effect of roughness of terrain, ground absorption and geostrophic wind have also been discussed.     

Integrated analysis of water quality parameters for cost-effective faecal pollution management in river catchments

In many parts of the world, microbial contamination of surface waters used for drinking, recreation, and shellfishery remains a pervasive risk to human health, especially in Less Economically Developed Countries (LEDC). However, the capacity to provide effective management strategies to break the waterborne route to human infection is often thwarted by our inability to identify the source of microbial contamination. Microbial Source Tracking (MST) has potential to improve water quality management in complex river catchments that are either routinely, or intermittently contaminated by faecal material from one or more sources, by attributing faecal loads to their human or non-human sources, and thereby supporting more rational approaches to microbial risk assessment. The River Ouse catchment in southeast England (U.K.) was used as a model with which to investigate the integration and application of a novel and simple MST approach to monitor microbial water quality over one calendar year, thereby encompassing a range of meteorological conditions. A key objective of the work was to develop simple low-cost protocols that could be easily replicated. Bacteriophages (viruses) capable of infecting a human specific strain of Bacteroides GB-124, and their correlation with presumptive Escherichia coli, were used to distinguish sources of faecal pollution. The results reported here suggest that in this river catchment the principal source of faecal pollution in most instances was non-human in origin. During storm events, presumptive E. coli and presumptive intestinal enterococci levels were 1.1-1.2 logs higher than during dry weather conditions, and levels of the faecal indicator organisms (FIOs) were closely associated with increased turbidity levels (presumptive E. coli and turbidity, r = 0.43). Spatio-temporal variation in microbial water quality parameters was accounted for by three principal components (67.6%). Cluster Analysis, reduced the fourteen monitoring sites to six representative ‘sentinel’ sites. The correlation coefficient between presumptive E. coli and phages of Bacteroides GB-124 was very small (r = 0.05) whilst that between turbidity and suspended solids was high (r = 0.62). Variations in climate, animal and anthropogenic interferences were all, either directly or indirectly, related to faecal contamination. The findings show the importance of meteorological conditions, such as storm events, on microbial water quality, and suggest that any future increases in the frequency of storm events (associated with climate change) are likely to result in a greater incidence of FIO/pathogen loads. This low-cost approach could help to predict spatio-temporal ‘hotspots’ of elevated waterborne disease risk. The work also represents an important step towards integrating novel MST tools into river catchment modelling.     

Observations on the changes in nitrate concentrations along streams in seven upland moorland catchments in Northeast Scotland

River water has been sampled under baseflow conditions in both summer and winter at c. 250-m intervals along the length of each of seven rivers in northeast Scotland, and the nitrate contents have been determined. The resultant data have been examined in the context of the nitrogen saturation hypothesis. Capacity of the catchment soils to retain nitrate was generally minimal in winter. Although biological uptake of nitrate was evident in summer, in the upper part of each catchment substantial nitrate leaching still occurred. The phenomenon was most marked in water draining from hill peats, except where these were conspicuously waterlogged. The results are discussed in the context of possible nitrogen saturation effects on upper catchment slopes.     

An investigation into the effects of forestry plantations on the water quality of upland reservoirs in northern ireland

A study was made of a wide range of Northern Ireland lakes to determine the effect of the fertilisation of forestry plantations. Lakes with fertilised forest catchments contained very high phosphorus levels. Bioassay with Selenastrum suggested that nitrogen and phosphorus were the only elements limiting growth and the supply of iron and trace metals was sufficient for large crops in nearly all cases.     

Indoor Air: the first 10 years

This paper recounts the first 10 years of the Indoor Air journal from the perspective of the founding editor. It represents personal recollections of the journal's founding and initial publication. It describes some of the amazing changes that have occurred since the decade of the 1990s when it was first published. PRACTICAL IMPLICATIONS: It is useful to reflect back periodically to earlier times when the Indoor Air journal was just beginning to understand the conditions that led to its founding. Wise people have contributed much to create this outstanding journal. Their contributions should not be forgotten.     

Impacts of agricultural phosphorus use in catchments on shallow lake water quality: About buffers, time delays and equilibria

Phosphorus (P) losses caused by intensive agriculture are known to have potentially large negative effects on the water quality of lakes. However, due to the buffering capacity of soils and lake ecosystems, such effects may appear long after intensive agriculture started. Here we present the study of a coupled shallow lake catchment model, which allows a glimpse of the magnitude of these buffer-related time delays. Results show that the buffering capacity of the lake water was negligible whereas buffering in the lake sediment postponed the final lake equilibrium for several decades. The surface soil layer in contact with runoff water was accountable for a delay of 5-50 years. The most important buffer, however, was the percolation soil layer that may cause a delay of 150-1700 years depending on agricultural P surplus levels. Although the buffers could postpone final lake equilibria for a considerable time, current and target agricultural surplus levels eventually led to very turbid conditions with total P concentrations of 2.0 and 0.6 mg L(-1) respectively. To secure permanent clear water states the current agricultural P surplus of 15 kg P ha(-1) yr(-1) should drop to 0.7 kg P ha(-1) yr(-1). We present several simple equations that can be used to estimate the sustainable P surplus levels, buffer related time delays and equilibrium P concentrations in other catchment-lake systems.     

Environmental impact of mining activities on the surface water quality in Tibet: Gyama valley

Nearly 20 years of industrial scale metal mining operations in Tibet have caused an impact on the region's surface water quality. However, no information with respect to the pollution has been provided to the public. The aim of this work was to evaluate the chemical quality of the stream water and to assess the present and future potential risks of acid mine drainage to the regional and downstream environments.This study, based on data collected in 2006, 2007 and 2008 in the Gyama valley, using the Environmental Risk Index (I_ER) documents that elevated concentrations of Cu, Pb, Zn, Mn, Fe and Al in the surface water and streambed at the upper/middle part of the valley pose a considerably high risk to the local environment. In contrast, the risk level at the stream source area is zero and only minor risk at the lower reaches. The iron and copper contamination of the upper/middle part of the river appears to be both natural and accelerated by the mining activities. The level of dissolved contaminants in the water decreases within short distance downstream due to precipitation and sorption to the streambed and strong dilution by a tributary stream and eventually by the Lhasa River.A high content of heavy metals in the stream sediments as well as in a number of tailings with gangue and material from the ore processing, poses a great potential threat to the downstream water users. Environmental changes such as global warming or increased mining activity may increase the mobility of these pools of heavy metals.     

Predicting the long-term variations in stream and lake inorganic aluminium concentrations for acidic and acid sensitive catchments

A modification to the one-box version of the MAGIC model of stream and lake acidification is given which presents a new hypothesis for describing inorganic aluminium controls in streams draining acidic catchments. This modification entails the removal of any assumption of Al(OH)₃ solubility control in the stream. Success of this modification is demonstrated for data collected from a regional survey of Welsh streams and lakes. The modified model is used with data from the acidic and acid impacted Dargall Lane catchment of the Galloway region of South West Scotland to provide an example of the long-term changes in stream acidity and inorganic aluminium concentration.     

铁锰超标对天然河床潜流水水质影响及处理

研究了铁锰离子超标对天然河床潜流水水质的影响及相应的处理技术,分析了潜流水中铁锰的危害及迁移富集规律,通过对除铁锰技术进行比选,得出接触氧化法是去除潜流水中铁锰的最佳方法,并对其工艺流程作了具体介绍,以期指导实践。     

The effect of a wildfire on stream water quality and catchment water yield in a tropical savanna excluded from fire for 10 years (Kakadu National Park, North Australia)

The wet/dry tropics of the Australian savannas are particularly prone to fire due to the highly seasonal rainfall and accumulation of grassy fuels. The effect of an early dry season wildfire (May, 1998) on the water quality of a seasonally flowing stream (December-June) was examined for a lowland savanna forest in Kakadu National Park (northern Australia) which had remained unburnt for 10 years. The water quality variables assessed were: total and volatile suspended sediment, phosphorus, nitrogen, iron and manganese. Compared to three years of pre-fire water quality data and 5 years of stream flow data, there was no detectable impact of the wildfire on the volume of stream flow, mean concentrations and the total mass transported by the stream for each water quality variable, except possibly nitrogen. The limited effect on water quality is attributed primarily to the timing of the wildfire and the low intensity relative to fires later in the dry season (September). The retention of canopy cover and the accumulation of leaf litter following the wildfire, and the catchment's gently undulating terrain all contributed to the negligible impact on water quality. Early dry season fires appear to be a viable management option for reducing accumulated fuel loads and hence reducing the risk of destructive wildfires later in the dry season.     

Environmental change, land use and water quality in Scotland: current issues and future prospects

An outline of both the scientific and management needs facing the future water quality issues of Scotland is discussed. The scientific needs are considered in terms of monitoring to increase the understanding of hydrochemical processes, issues of scaling, and the need for improved modelling under changing environmental processes. In terms of the management needs, the requirements highlighted relate to improving the ecological quality of Scottish rivers and the implementation of integrated river basin management plans.     

上海市人口发展的趋势、困境及调控策略

探讨了上海人口规模调控问题.认为在中国城镇化大背景之下,上海人口将继续保持快速增长势头,然而膨胀的城市规模将使城市交通难以承受,人口规模调控从长远考虑势在必行.但是,基于年龄结构与用地视角的分析却从另一方面揭示了调控的困难.面对必要性与困难并存的局面,研究认为从长远发展出发,必须坚持积极调控的方针,不可本末倒置;同时应注重策略的合理性,尽可能降低调控的不利影响,避免过度与失衡.面对如何调控的问题,研究认为关键在于城市职能的疏散.通过对上海市就业岗位、产业用地以及人口规模关系的分析,论证了以产业结构调整为着眼点,通过就业职能的疏解实现人口调控的可行性,进而明确人口规模调控的方向.     

A new method of monitoring water quality in a stream receiving sewage effluent, using chironomid pupal exuviae

The midge family Chironomidae (Diptera) are of prime importance in fresh waters, and have over 450 species in Great Britain. They live in all types and conditions of rivers and lakes, and occur in large numbers. Their great potential in biological assessment of water quality has been offset by taxonomic difficulties, and especially by problems of larval identification, and by the labour of sorting benthos samples.It is proposed that the chironomid fauna of a river may be adequately sampled by collecting the floating pupal exuviae which accumulate along the banks and against obstructions. This technique is simple, quick, and is applicable to large, deep rivers as well as to small, shallow streams. Such samples provide enough material for examining the percentage composition of species, and for calculating diversity indices. The pupal exuviae are much easier to identify to species or species group than are the larvae.An examination of the effect of a sewage discharge into a small stream in South West England is given as a practical example of the method.     

Evaluation of phosphorus concentrations in relation to annual and seasonal physico-chemical water quality parameters in a UK chalk stream

The aim of this paper was to examine historical physico-chemical water quality parameters (1990-1997) in the River Frome, East Stoke (NGR SY867868), in order to show both annual and seasonal (monthly) trends. EpCO2 (defined as the partial pressure of CO2 in natural water divided by the equilibrium partial pressure of CO2) levels ranged from mean values of 6.32+/-0.41 in spring/summer to 7.86+/-1.17 in autumn/winter. A decreasing trend in mean annual EpCO2 was also observed, with a high of 9.61 in 1990 and a low of 5.22 in 1996. The variations were attributed to changes in pH, which showed an inverse relationship with river discharge (r2=0.47). Both pH and EpCO2 levels were strongly linked to biological activity with increases caused by primary productivity. Filterable reactive phosphorus (FRP) and total phosphorus (TP) concentrations correlated with river discharge. The results showed that the majority of the phosphorus load was transported during storm events, which agrees with results from an export coefficient model predicting phosphorus loading in the Frome catchment. Recent River Frome monitoring campaigns using an in situ flow-injection (FI)-based monitor were in agreement with phosphorus concentration and related physico-chemical trends observed during historical sampling and laboratory analysis.     

Environmental radioactive contamination in Greenland: a 35 years retrospect

Environmental studies of anthropogenic radionuclides in Greenland over four decades are reported. The studies have comprised the marine as well as the terrestrial environments and emphasis has been laid on measurements of 90Sr and 137Cs. The temporal and the spatial trends of these radionuclides are described. The radiation exposure from consumption of locally produced diets has been calculated from consumption rates and the infinite time integrated levels of 90Sr and 137Cs concentrations in the various food products. Compared with most other Arctic people, the Greenlanders have received relatively low doses from anthropogenic radionuclides. There are several reasons for this, first of all, because of the relatively high consumption of marine products compared with terrestrial products. Secondly, because winter slaughtering of reindeer is less frequent in Greenland than in other Arctic countries and Greenland reindeer consume, in general, less lichen than most other Arctic reinder, and thirdly, because the transfer from deposition to lichen in Greenland seems lower than in other Arctic areas.