Nutrient loads from agricultural and forested areas in Finland from 1981 up to 2010-can the efficiency of undertaken water protection measures seen?

Long-term data from a network of intensively monitored research catchments in Finland was analysed. We studied temporal (1981-2010) and spatial variability in nitrogen (N) and phosphorus (P), from 1987 losses, both from agricultural and forestry land. Based on trend analysis, total nitrogen (TN) concentrations increased in two of the four agricultural sites and in most of the forested sites. In agricultural catchments, the total phosphorus (TP) trends were decreasing in two of the four catchments studied. Dissolved P (DRP) concentrations increased in two catchments and decreased in one. The increase in DRP concentration can be a result of reducing erosion by increased non-plough cultivation and direct sowing. In forested catchments, the TP trends in 1987-2011 were significantly decreasing in three of the six catchments, while DRP concentrations decreased significantly in all sites. At the same time, P fertilisation in Finnish forests has decreased significantly, thus contributing to these changes. The mean annual specific loss for agricultural land was on average 15.5 kg ha-1 year-1 for N and 1.1 kg ha-1 year-1 for P. In the national scale, total TN loading from agriculture varied between 34,000-37,000 t year-1 and total P loading 2400-2700 t year-1. These new load estimates are of the same order than those reported earlier, emphasising the need for more efforts with wide-ranging and carefully targeted implementation of water protection measures.

Suspended solids and total phosphorus loads and their spatial differences in a lake-rich river basin as determined by automatic monitoring network.

Turbidity datasets recorded by sensors during 2009-2012 were collected in five observation sites in the 2046-km2 Karjaanjoki River Basin in southern Finland. From these and water sample-based data, total phosphorus (TP) and total suspended solids (TSS) fluxes were determined. Based on calculations made with combined sensor- and water sample-based dataset, the annual loading from the Karjaanjoki Basin in 2009-2012 varied between 11,300 and 23,900[corrected] kg of TP and 3300-8400 t of TSS. As compared with two other river basins discharging into the Baltic Sea in southern Finland, the TP loading from Karjaanjoki was low because the summed retention in the two major lakes Hiidenvesi and Lohjanjärvi was high: 48 and 49% of the TSS and TP loadings generated in their upstream catchments, respectively. Depending on how water sampling took place in relation to peak flow events, differences of annual fluxes as determined by "water samples only" vs. "sensors and water samples" data varied between -22 and 26 for TP and -31 and 39% for TSS. This study proved automatic monitoring being useful when spatial differences and lake retention of riverine fluxes are explored. Moreover, the loading estimates calculated on the base of well-functioning and well-maintained automatic monitoring system, supported with water sampling during periods when devices were off, are undoubtedly more accurate than those based on manual grab water sampling only. The findings of this study were in line with, and well contribute to, earlier Finnish and international research on automatic water quality monitoring.

How effective are River Basin Management Plans in reaching the nutrient load reduction targets?

Riverine nutrient loads are among the major causes of eutrophication of the Baltic Sea. This study applied the Soil & Water Assessment Tool (SWAT) in three catchments flowing to the Baltic Sea, namely Vantaanjoki (Finland), Fyrisån (Sweden), and Slupia (Poland), to simulate the effectiveness of nutrient control measures included in the EU's Water Framework Directive River Basin Management Plans (RBMPs). Moreover, we identified similar, coastal, middle-sized catchments to which conclusions from this study could be applicable. The first modelling scenario based on extrapolation of the existing trends affected the modelled nutrient loads by less than 5%. In the second scenario, measures included in RBMPs showed variable effectiveness, ranging from negligible for Slupia to 28% total P load reduction in Vantaanjoki. Adding spatially targeted measures to RBMPs (third scenario) would considerably improve their effectiveness in all three catchments for both total N and P, suggesting a need to adopt targeting more widely in the Baltic Sea countries.

Wireless in-situ Sensor Network for Agriculture and Water Monitoring on a River Basin Scale in Southern Finland: Evaluation from a Data User's Perspective.

Sensor networks are increasingly being implemented for environmental monitoring and agriculture to provide spatially accurate and continuous environmental information and (near) real-time applications. These networks provide a large amount of data which poses challenges for ensuring data quality and extracting relevant information. In the present paper we describe a river basin scale wireless sensor network for agriculture and water monitoring. The network, called SoilWeather, is unique and the first of this type in Finland. The performance of the network is assessed from the user and maintainer perspectives, concentrating on data quality, network maintenance and applications. The results showed that the SoilWeather network has been functioning in a relatively reliable way, but also that the maintenance and data quality assurance by automatic algorithms and calibration samples requires a lot of effort, especially in continuous water monitoring over large areas. We see great benefits on sensor networks enabling continuous, real-time monitoring, while data quality control and maintenance efforts highlight the need for tight collaboration between sensor and sensor network owners to decrease costs and increase the quality of the sensor data in large scale applications.

Phosphorus removal in a wetland constructed on former arable land.

Phosphorus in surface runoff water may cause eutrophication of recipient water. This study clarifies the mechanisms of P removal in the wetland of Hovi, Finland, constructed on arable land in 1998. Before the construction, the surface soil (removed in the construction) and subsoil (the current wetland bottom) were analyzed for Al and Fe oxides (Al(ox) and Fe(ox)) reactive in P sorption, and for the distribution of P between various pools as well as for P exchange properties. Retention of P from runoff water within the wetland was studied from 1999 to 2001 in situ and factors affecting the P removal (O2 availability and P concentration in water) were investigated in a laboratory microcosm. The processes taking place in the wetland diminished by 68% the total P load and by 49% the dissolved reactive P load. Desorption-sorption tests indicated that without removal of the surface soil, there would have been a risk of the wetland being a source of P, since the equilibrium P concentration of the soil removed was high compared with the mean P concentration of the inflowing water. The subsoil contained less P and high amounts of reactive oxides, which could bind P. Evidently, the P sorption by Al(ox) played an important role in a first phase removal of P, since the wetland retained P efficiently even under anoxic conditions, where Fe tends to be reduced. Fine-textured, mineral soil on the bottom of the wetland (subsoil of the former arable land) seemed to be very efficient in retaining P from agricultural runoff.

Function and potential of constructed wetlands for the control of N and P transport from agriculture and peat production in boreal climate.

The use of constructed wetlands (CWs) for the treatment of the runoff waters from field cultivation and peat production in boreal climate is reviewed on the base of the authors' own research experiences and a literature study. The main water purifying mechanisms are presented, and the effectiveness of different types of CWs as well as the design and dimensioning parameters at the bottom of the effectiveness are discussed. In our view, CW area in relation to its catchment and hydraulically efficient CW shape are the main issues that a CW designer should focus on. This is because water purifying processes need time for efficient functioning, and both of these factors increase the actual residence time of water in a CW. Although both these factors stand up to as general guidelines, drawing conclusions from direct comparison of CWs in different locations is often misleading because of the differences in climate, catchment properties etc that highly effect the retention performance. Landscape improvement and increased birdlife are raised as examples of the ancillary benefits of CWs. The potential significance of CWs in water protection is dealt with at catchment scale. Comprehensive catchment management with variety of pollution control measures is needed if sustainable water quality improvement is aspired. When designed and located appropriately, CWs can make a useful contribution to this.

Convective oxygen transport in a constructed wetland pond: mechanism, measurements and modelling by multilayer perceptrons.

The study presented here found evidence for the presence and importance of convective flows and associated oxygen transport in a constructed wetland pond in southern Finland. These flows are triggered by nightly cooling of the water at the surface, which may then become denser than the water lower down in the pond. The resulting layering (heavier water overlying less dense one) is hydromechanically unstable and--almost immediately--starts driving convective motion. This flow takes oxygen enriched water from the surface to the bottom of the wetland, where a distinct rise in oxygen saturation is recorded after some time lag. The process described can be modelled successfully by means of so-called Multilayer Perceptrons (MLPs), a class of Artificial Neural Networks. As explored in this study, these models are well suited to "learn" the mechanism of convective transport, which results in their ability to forecast oxygen saturation near the wetland bottom at a satisfactory level of accuracy.