Ingemar Cato

Spatial clustering of metals in the sediments of the Skagerrak/Kattegat

The present work attempts to describe the spatial distribution of heavy metals in the surficial sediments of the Kattegat and Skagerrak. It is based on multivariate statistical analyses. Principal Component Analysis is used to gain information on the chemical characteristics of the metals as a group. Cluster analysis is used to classify the sampling stations into groups regarding the principal components. In addition, cluster analysis is adopted directly on the metals. Together these enable an interpretation of the processes involved in the formation of these coastal sediments. It is seen that the main factors controlling the composition of the clusters are the chemical characteristics of the data and not the sources. A few exceptions are found though, where direct point sources are identified.

Marine environment quality assessment of the Skagerrak-Kattegat

Abstract This quality assessment of the Skagerrak-Kattegat is mainly based on recent results obtained within the framework of the Swedish multidisciplinary research projekt ‘Large-scale environmental effects and ecological processes in the Skagerrak-Kattegat’ completed with relevant data from other research publications. The results show that the North Sea has a significant impact on the marine ecosystem in the Skagerrak and the northern Kattegat. Among environmental changes recently documented for some of these areas are: increased nutrient concentrations, increased occurrence of fast-growing filamentous algae in coastal areas affecting nursery and feeding conditions for fish, declining bottom water oxygen concentrations with negative effects on benthic fauna, and sediment toxicity to invertebrates also causing physiological responses in fish. It is concluded that, due to eutrophication and toxic substances, large-scale environmental changes and effects occur in the Skagerrak-Kattegat area.

The relationship between annual varve thickness and maximum annual discharge (1909-1971)

Annually laminated (varved) sediments from the River Angermanalven, mid-central Sweden, have been used to construct an annual 2000-year long record of varve thickness. Maximum daily annual discharge and mean varve thickness for the years 1909-1971 are significantly correlated (r = 0.87). A relationship between maximum daily annual discharge for the observed period (1909-1971) and varve thickness was determined. The return time of two exceptionally thick varves in the 2000-year long record at the years 658 and 492 AD were estimated and their likelihood estimated based on a Gumbel frequency analysis

The climatic significance of clastic varves in the Ångermanälven Estuary, northern Sweden, AD 1860 to 1950

Multiple regression analyses were applied to decipher the correlation between monthly discharge, precipitation and temperature records and annual varve-thickness data from river Ångermanälven north-central Sweden between 1860 and 1950. Over the whole 90-year period we found generally a strong correlation between spring/summer precipitation and annual varve thickness. However, there are clear indications that precipitation during the months of January and March–May was more important for the formation of varves in the early part of the twentieth century, while January, March, April and June seem to have been more significant during the later part of the nineteenth century. Monthly temperatures and annual varve thickness, on the other hand, did not show any significant correlations over the whole 90-year period, but, when split into 30-year periods, a dependence of varve thickness on October (1862–90) and March (1919–50) temperatures could be observed. Our results show that it is important to test each specific varve record against instrumental data sets before any conclusions can be drawn in terms of precipitation and/or temperature dependence. They also emphasize the necessity to correlate varve-thickness records against long instrumental series in order to detect any changing forcing mechanisms.

Temporal trends of PCDD/Fs in Baltic Sea sediment cores covering the 20th century.

The pollution trend of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) in the Baltic Sea region was studied based on depth profiles of PCDD/Fs in sediment cores collected from six offshore areas, eight coastal sites impacted by industrial/urban emissions, and one coastal reference site. A general trend was observed for the offshore and coastal reference sites with substantial increase in PCDD/F concentrations in the mid-late 1970s and peak levels during 1985-2002. The overall peak year for PCDD/Fs in Baltic Sea offshore areas was estimated (using spline-fit modeling) to 1994 ± 5 years, and a half-life in sediments was estimated at 29 ± 11 years. For the industrial/urban impacted coastal sites, the temporal trend was more variable with peak years occurring 1-2 decades earlier compared to offshore areas. The substantial reductions from peak levels (38 ± 11% and 81 ± 12% in offshore and coastal areas, respectively) reflect domestic and international actions taken for reduction of the release of PCDD/Fs to the environment. The modeled overall half-life and reductions of PCDD/Fs in offshore Baltic Sea sediment correspond well to both PCDD/F trends in European lakes without any known direct PCDD/F sources (half-lives 30 and 32 years), and previously modeled reduction in atmospheric deposition of PCDD/Fs to the Baltic Sea since 1990. These observations support previous findings of a common diffuse source, such as long-range air transport of atmospheric emissions, as the prime source of PCDD/Fs to the Baltic Sea region. The half-life of PCDD/Fs in Baltic Sea offshore sediments was estimated to be approximately 2 and 4-6 times longer than in semirural and urban European air, respectively. This study highlights the need for further international actions to reduce the levels of PCDD/Fs in Baltic Sea air specifically and in European air in general.

Historical trends in Hg, Pb and Zn sedimentation in the central shelf area of Portugal

Temporal records of excess 210Pb, and the determination of major (Al and Ca) and trace elements (Zn, Cr, Ni, Pb, Cu and Hg) in two sediment box-cores, collected in the central area of the Portuguese shelf of North of the Nazare canyon (offshore from the Lis River), allow evaluation of the deposition of various chemical elements normally associated with anthropogenic activities. In order to compensate for the natural sediment variability, heavy metal contents were normalised to Al. Temporal variations of Hg, Pb and Zn (Al-normalised) show an increasing trend since the beginning of the 1920’s, recording the development of industrial activities. Enrichment factors (EF) were calculated to estimate the level of contamination in these sediments. Mercury is the element with the highest average EF values (EF = 3), followed by Pb (EF = 1.5) and Zn (EF = 1.2). The results indicate that since 1991 64% of total Hg, 44% of total Pb and 24% of total Zn are derived from anthropogenic sources. The average anthropogenic fluxes of Hg, Pb and Zn (0.008, 3, 6 μg cm-2yr-1, respectively) for the last 40 years in a ca. 400 km2 deposition area represent a total accumulation of approximately 30, 12000 and 24400 kg per year of Hg, Pb and Zn, respectively. These results indicate that despite the high-energy conditions and the generally sandy nature of the Portuguese shelf sediments, it is possible to identify significant anthropogenic enrichments in some areas of sediment accumulation. These contaminants are not necessarily related to immediate sources but may instead indicate atmospheric and or marine transport from more distant sources.

Comparing spatial and temporal changes in metal trends (Cr, Ni, Pb and Zn) on the Portuguese shelf since the 1970s

Comparison between an archive dataset, collected during the 1970s (1974–1977), and samples taken during the PALEO1 cruise (2002) enabled evaluation of large-scale and long-term spatiotemporal changes in Al, Cr, Ni, Pb and Zn contents in bulk surface sediments in four areas of the Portuguese shelf. The so-called gradient method (GM) with normalisation to Al, a proxy for terrigenous clay content, was applied. The studied areas are distributed from north to south along the western margin, with the northernmost located off shore the Ave and Douro rivers, a central one located off shore the Lis River and a southern one located off shore the Mira River. One-way ANOVA and Kruskal-Wallis tests were used to identify differences among study areas and periods of sample collection. A comparison of metal contents in 2002 samples with the Portuguese classification scheme regulation for deposition of dredged materials in coastal areas indicates good environmental quality in terms of Cr, Ni, Pb and Zn levels. Nevertheless, the GM results suggest an increase in metal loadings relative to Al from the 1970s to the 2002 samples (except for Pb). The Algarve area on the southern shelf is characterised by having high number of sites with metal level on class 2. These high values have traditionally been explained by a substantial supply of natural metals from the Guadiana, Tinto and Odiel rivers that drain areas Iberian Pyrite Belt formations. This supply has probably been magnified by present and past mining activities. For quality evaluation of marine sediments, especially when using total metal contents, this study shows the importance of considering all possible sources of metal loading. The natural grain size and composition variability have also a crucial influence on the metal content, and the combined evaluation allows a more holistic perspective.