Improvement in the quality of data on nutrient inputs with a focus on transboundary loads

The report describes the results of pilot project aimed at improving the quality of data on transboundary nutrient loads, in particular, in the rivers Daugava and Nemunas. Two sampling rounds (in May and November 2013) were organised and executed by the Finnish Environment Institute (SYKE) in close cooperation with representatives from the participating countries, one laboratory from Latvia, two from Lithuania, three from Belarus and one from Finland. The results from the total nitrogen analyses of the different laboratories were in general comparable, while the total phosphorus results varied between the laboratories. One explanation might be that the analytical methods applied were not fully comparable; for example, the filtration of the samples before analysis of total phosphorus may have affected the results. Highest concentrations were observed at the Belarusian border. Both absolutely and relatively high concentrations of dissolved phosphorus in the rivers give an indication of a clear anthropogenic influence. A key finding of the project was that a reasonably good consensus and comparability has been reached on the phosphorus and nitrogen loads originating in the upstream catchment area and flowing into Latvia and Lithuania – even if the results were produced through separate data sets and by partly different methods. This is a good starting point for the efforts to further estimate the retention in the lower reaches in the Latvian and Lithuanian territories of the two rivers and the percentage of the transboundary nutrient loads which finally enter into the Baltic Sea. An equally important result of the project is the ability to now present – in connection with the data on the total riverine loads measured at the mouth of the rivers Daugava and Nemunas – complete data sets on nutrient loads at the border between Latvia or Lithuania and Belarus. This data also sup-ports the assessment of transboundary nutrient loads originating in the territory of Belarus (and Russia) in the catchment area of these two rivers.