Reference conditions for phosphorus runoff from forested areas with arable soil properties (218902)

The main goal of the background runoff project is to estimate reference values of phosphorus concentrations in stream water in catchments with marine clay deposits. The project is using several approaches: 1. P-losses from small, forested catchments We have monitored (2013-2016) water quality in two watersheds with predominantly natural woodland, and a high coverage of marine clay sediments (Lund Catchments North and South). The results reveal that the water in the two creeks contain high amounts of phosphorus and sediments, and we have found high turbidity values. We have also found a good correlation between average phosphorus concentration and the proportion of marine clay coverage in the sub-catchments. There is also a correlation between phosphorus and slope. Both catchments have steep topography, especially in the lower parts, and eroded soil is assumed to be the origin of a considerable part of the phosphorus in the creeks. A multi-parameter comparison of phosphorus concentration compared to about 20 different catchment properties has been carried out based on data from 50 Norwegian catchments. The results showed that the proportion of catchment area covered with marine clay was the most important explanation for phosphorus concentrations in forested creeks. During the winter 2016/2017, a Master student at the University of Life Sciences at Ås, Norway, finished her exam and Master Thesis on "Episodic changes in water chemistry in a clay affected watershed" (Elisabeth Fremming). Her work demonstrates how the chemistry in the Northern Lund Creek changes downstream during episodic events (snowmelt, rainstorms). 2. P-levels in soil Marine clay comprises high amounts of phosphorus in the form of apatite-P. In this part of the project, the phosphorus content in the soil in Lund has been mapped. The purpose has been to investigate the availability of the phosphorus for plant and biota in uncultivated soil. The soils in the Lund catchments consist partly of marine clay, and partly of moraine deposits with a high amount of sand. Soil samples have been collected in a grid covering the entire catchment area. The results reveal that the average content of P-AL phosphorus (a fraction of phosphorus available for plants) in the marine clay is considerably higher (19 mg P-AL/kg) than in the sandy soil (11 mg P-AL/kg). The average content of total phosphorus is also higher in the marine clay than in the sandy soil. On the other hand, the water soluble fraction of the phosphorus is less in marine clay (0.5 mg/kg) than in the sandy soil (0.9 mg/kg). This means that the phosphorus in the marine clay was more strongly attached to the particles than the phosphorus in sandy soil. The effect of phosphorus on eutrophication is higher the higher proportion of the phosphorus that is bioavailable. Analyses of different phosphorus fractions in cultivated soil has shown a good correlation between bioavailable phophorus (P-AL) and water soluble phosphorus. The soil?s contents of the P-AL-fraction may therefore be a good estimate on the bioavailability of phosphorus from cultivated soil. The same correlation is not found in subsoil and in the soils from forested areas. The soil?s P-AL-content would therefore be less suited to describe the bioavailability of phosphorus from forested areas and subsoils. Hence, this study has demonstrated that the phosphorus from marine clay areas in these forests has a low bioavailability. Work on a scientific publication is started. 3. Palaeo limnology Sediment cores have been collected for palaeolimnological analyses. The cores have been examined for pollen residues and fragments from living organisms and fossilized plants and animals. The cores are taken in a pond, Vastadtjern, in the Municipality of Vestby. This is a lake that has 96% of the catchment area covered with marine clays. We employ physical, chemical, geological and biological data to reconstruct the history of the lake. The deepest of the sediment cores was more than 6.5 meters deep, and the lower parts are dated to 16,700 BP. The lower levels of the core reflects a marine environment, and the sediments that have been deposited in these layers seem to have been disturbed by land slides. Analyses of these cores are done in cooperation with the University College London. 4. Synthesis and recommendations The project has suggested new reference values and environmental goals (good-moderate threshold) for both total phosphorus and orthophosphate in rivers draining marine clay. The criteria for total phosphorus are strongly linked to the proportion of marin eclay in the catchments. The recommendations have been sent to the Norwegian Environment Agency.

The main objective of this project is to develop a methodology to assess the contribution of phosphorus runoff from clay-rich soils at reference conditions, for use as a management tool in the implementation of the European Water Framework Directive (WFD) in agricultural river basins. Sub-objectives; - Estimate levels of P losses from forested arable areas with clay-rich soils. - Estimate the bioavailability of P in runoff from clay-rich soils, soil-water/ground water, and surface water in forested areas. - Evaluate reference conditions in areas dominated by clay-rich soils based on palaeolimnological studies. - Develop an improved methodology and management tool for estimating background contributions of P in areas dominated by clay-rich soils. Although the WFD focuses on ecological aspects, nutrient concentrations are still important when designing appropriate abatement plans. In Norway large agricultural areas consist of marine clays with apatite-phosphorus. Waters in these areas are expected to have h igher reference levels of total phosphorus (TP). Several abatement plans to reduce TP from agricultural streams have pointed out that the presently assumed reference conditions are based on insufficient knowledge. The result may be too strict goals, with subsequent requirements for abatement measures and, thus, negative economical consequences for the agricultural sector. The project will seek to assess reference conditions of phosphorus through more than one approach to develop a robust methodology and m anagement tool for finding reference conditions. It is expected that this will have implications for the implementing of the WFD in Norway, and also be of interest in other European countries. The project will result in at least four peer reviewed scienti fic papers, and popularized information will also be prioritized so that management and stakeholders will be informed about the project through several info channels. The project will also result in a Ph.D. thesis.