Carl Rolff

Predicting effects of different harvesting intensities with a model of nitrogen limited forest growth

The anticipated increasing utilisation of forest biomass necessitates improved understanding of its long-term consequences on forest productivity. We have used a model of carbon and nitrogen fluxes to predict effects of different management regimes in Norway spruce stands at three levels of fertility. Stands with high production are the least sensitive to intensified harvesting, partly because these stands occur in regions with high nitrogen deposition which compensates for the removal in nitrogen in harvests. Intensified thinning with stem-only removal is the management that affects productivity least followed by whole-tree harvesting at clear-fellings. Whole-tree thinnings are less beneficial and shortened rotation times the least desirable from a production point of view. Increases in total biomass harvests are at the expense of stem harvest, which can mean a conflict between volume and value. The importance of secondary vegetation as is also discussed.

Potential biomagnification of PCDD/Fs - new possibilities for quantitative assessment using stable isotope trophic position

Abstract The transport of PCDD/Fs in two Baltic food chains is studied with a new method which quantitatively estimates biomagnification. Metabolic fractionation of stable isotopes of nitrogen is used to numerically estimate the trophic position of organisms. An application of the method to PCDD/F data from two Baltic food chains indicates that summed whole body concentrations of 2378-substituted PCDD/Fs decrease with increasing trophic position. The sum of TEQs however increases with trophic position. The main reason for this is the decrease in OCDD concentrations and a selective biomagnification of the three most toxic isomers 2378-TCDD, 23478-PnCDF and 12378-PnCDD.

Concentrations and spatial variations of cyclodienes and other organochlorines in herring and perch from the Baltic Sea.

Herring (Clupea harengus) and perch (Perca fluviatilis) were collected in the northern and southern Baltic Sea and analyzed for the presence of the cyclodiene pesticides chlordane (CHL), heptachlor, aldrin, dieldrin, endrin, isodrin, endosulfan and mirex, as well as other organochlorine contaminants, hexachlorocyclohexanes (HCHs), DDTs, hexachlorobenzene (HCBz) and polychlorinated biphenyls (PCBs) in order to investigate concentrations, accumulation and differences in geographical distribution. In the northern part of the Baltic Sea, Gulf of Bothnia, herring were collected at two pelagic stations, one in the Bothnian Bay (BB) and the other in the Bothnian Sea (BS), respectively; perch were collected at four coastal locations along the Swedish coast. All these locations were selected to represent background areas except one in the vicinity of an industrialised and contaminated area. Both specimens were also caught in the southern part of the Baltic Sea, in the Gulf of Gdansk (GG), Poland, a potentially highly polluted area. From the eight cyclodiene pesticides analyzed, three were detected in herring and perch samples, including 12 different CHL-related compounds, dieldrin and mirex. To our knowledge, it is the first time that mirex has been detected in samples from the Baltic Sea. Neither heptachlor, aldrin, endrin, isodrin nor endosulfan were found. However, HCHs, DDTs, HCBz and PCBs were found in every sample investigated, and the concentrations ranged e.g. for the cyclodiene chemicals dieldrin and CHL-related compounds from 30 to 170 ng/g lipid and for PCBs from 360 to 5400 ng/g lipid, both fish species included. Differences in contamination burden between the sites can be seen, e.g. for herring the BB and GG locals were similar, and generally lower than BS for all chemicals except that of DDT where GG was the highest. For the perch samples the industrialised location had markedly higher concentrations of HCBz and PCBs than the other locations. This species also identifies GG as the most DDT contaminated site among the three studied areas.

Levels of PCBs in the aquatic environment of the Gulf of Bothnia : Benthic species and sediments

Levels of PCBs in the aquatic environment of the Gulf of Bothnia: Benthic species and sediments

Analysis of polychlorinated dibenzo-p-dioxins (PCDD) and polychlorinated dibenzofurans (PCDF) in soil and digested sewage sludge from Stockholm, Sweden

In this investigation the content of PCDDs and PCDFs in sewage sludge samples and top soil from fields situated in the County of Stockholm has been investigated. Further, the contribution of PCDDs and PCDFs to the fields from sewage sludge is compared with the contribution from two non-point emission sources i.e. road traffic and the urban area of the city of Stockholm. The mean concentration in four analyzed sludge samples is 79 pg TEQ/g (organic weight; o.w.). Soil samples taken close to major roads vary between 13 and 49 pg TEQ/g (o.w.) and soil samples (1b-4b) which were not taken close to major roads vary between 9 and 32 pg TEQ/g (o.w.). The results indicate that both road traffic and outlets from the urban area influence the PCDD and PCDF concentrations in the arable soil. Fertilization with sludge (1 tonne dry weight/hectare and year) raise the initial soil concentrations of PCDD and PCDF in the fields by approx. 2 – 3%.