Per Sandén

Spatial patterns of organic chlorine and chloride in Swedish forest soil.

The concentration of organic carbon, organic chlorine and chloride was determined in Swedish forest soil in the southern part of Sweden and the spatial distribution of the variables were studied. The concentration of organically bound chlorine was positively correlated to the organic carbon content, which is in line with previous studies. However, the spatial distribution patterns strongly indicate that some other variable adds structure to the spatial distribution of organic chlorine. The distribution patterns for chloride strongly resembled the distribution of organic chlorine. The spatial distribution of chloride in soil depends on the deposition pattern which in turn depends on prevailing wind-direction, amount of precipitation and the distance from the sea. This suggests that the occurrence of organic chlorine in soil is influenced by the deposition of chloride or some variable that co-varies with chloride. Two clearly confined strata were found in the area: the concentrations of organic chlorine and chloride in the western area were significantly higher than in the eastern area. No such difference among the two areas was seen regarding the carbon content.

Chloride imbalances in soil lysimeters.

The assumption that soil neither acts as a source or a sink of chloride is evaluated by incubating soil cores in lysimeters in a climate chamber under controlled conditions. Some of the lysimeters acted as a sink while others acted as a source of chloride. Considerable amounts of organic chlorine were lost by leaching. The loss by leaching of organic chlorine could only explain part of the discrepancy in the lysimeters where the soil acted as a sink and it could certainly not explain the cases where the soil acted as a source. The storage of organic chlorine was four times larger than the storage of chloride and comparably small changes in the organic chlorine storage will thus have a considerable influence on the chloride budget. However, the soil was too heterogeneous to determine whether a change in the storage had taken place or not. It is concluded that the observed chloride surplus and also, at least to some extent, the observed chloride deficit, most likely was caused by net-changes in the storage of organic chlorine in soil. An inverse correlation was found between the initial chloride content of the soil and the imbalance in the chloride budget.Dry deposition of chloride is generally assumed to equal the run-off minus the wet deposition. Extrapolation to the field situation suggests that the output of organic chlorine by soil leachate is at risk to cause an underestimation of the dry deposition by about 25%.

Organic and inorganic chlorine in Swedish spruce forest soil : influence of nitrogen

Concentrations of organic and inorganic chlorine were estimated in samples collected in forest soils in the southern part of Sweden, and changes were observed after the addition of nitrogen in incu ...

Organic chlorine in deciduous and coniferous forest soils in southern Sweden

The concentration of organic chlorine (Clorg) was determined in soil samples collected in the O-horizon in forest soils in southern Sweden to describe differences among stand types and elucidate the influence of chloride (Clinorg), pH, and organic carbon. The samples were collected within the Swedish National Survey of Forest Soils and Vegetation, with moraine as the dominating soil type and with granite and gneiss as bedrock. The concentration of organic chlorine (Clorg) found in the deciduous forest soils was significantly lower than that in the coniferous forest soils. The Clorg increased with Clinorg, organic carbon content, and decreasing pH but was most strongly correlated to Clinorg. Crosswise comparisons among the variables showed that the influence of Clinorg overrode the influence of pH and organic carbon. We concluded that the major driving force in the formation of Clorg in soils is deposition of Clinorg and that the difference among deciduous and coniferous stands is due primarily to a higher input of Clinorg in the canopy of coniferous trees as a result of a larger wet and dry deposition in coniferous compared with deciduous forests. The concentration of Clorg decreased significantly from June to August. This follows the pattern of chloride deposition in the region and gives further evidence that Clinorg is a driving force in the formation of Clorg in soil. The results of the present study gives further evidence that the turnover of Clorg is closely related to the turnover of Clinorg and that it is necessary to include Clorg in the assessment of the biogeochemical cycling of chlorine in the environment.

Organic matter chlorination rates in different boreal soils: the role of soil organic matter content.

Transformation of chloride (Cl(-)) to organic chlorine (Cl(org)) occurs naturally in soil but it is poorly understood how and why transformation rates vary among environments. There are still few measurements of chlorination rates in soils, even though formation of Cl(org) has been known for two decades. In the present study, we compare organic matter (OM) chlorination rates, measured by (36)Cl tracer experiments, in soils from eleven different locations (coniferous forest soils, pasture soils and agricultural soils) and discuss how various environmental factors effect chlorination. Chlorination rates were highest in the forest soils and strong correlations were seen with environmental variables such as soil OM content and Cl(-) concentration. Data presented support the hypothesis that OM levels give the framework for the soil chlorine cycling and that chlorination in more organic soils over time leads to a larger Cl(org) pool and in turn to a high internal supply of Cl(-) upon dechlorination. This provides unexpected indications that pore water Cl(-) levels may be controlled by supply from dechlorination processes and can explain why soil Cl(-) locally can be more closely related to soil OM content and the amount organically bound chlorine than to Cl(-) deposition.

Spatial properties of nutrient concentrations in the Baltic Sea.

Using existing monitoring data, the present study attempts to characterize spatial patterns of surface water nutrients in the Baltic Sea. The analysis was made for two different spatial scales, differences between and within sub-basins.Non-parametric methods were chosen to reduce problems with the distributional properties of the data. By dividing the data into four seasons care was taken as to seasonality. To avoid bias due to different laboratory analysis, only data from Nordic countries were used, whose results did not apparently depart from each other. Bias due to different sampling frequency was another problem. This was reduced by using only the last observation in each season for every station and year.The results suggested differences in the nutrient concentrations between basins. The two northernmost basins (Bothnian Bay and Bothnian Sea) had lower phosphate concentrations and higher silicate concentrations compared to the rest of the Sea. Bothnian Bay and the Gulf of Finland had higher nitrate concentrations.The concentration structure within basins was studied using transects in both latitudinal and longitudinal direction. A gradient for phosphate and nitrate was found in the Gulf of Finland, with lower concentrations at the mouth. The Bothnian Sea showed lower concentrations in the middle of the basin compared to the coasts. The highest concentrations of phosphate were found close to the Finnish coast and for silicate the highest concentrations were located near the Swedish coast. It was not possible to study variation in the west-east direction within the Baltic proper, due to data shortage. For the transects in the north-south direction no differences were detected for nitrate and silicate. Phosphate gave one significant result during autumn for the transect in the eastern part of the Baltic proper.This study revealed several problems associated with the data available. Uneven sampling in space and time put severe constraints on the study. A better design of the monitoring program is suggested, where spatial properties are considered explicitly. Revision of the program in this direction is needed for reasonable calculation of total amounts and concentrations representative for a basin.

Acidification trends in Sweden

A Swedish hydrochemical monitoring program, which was started during the International Hydrological Decade (1965–1975), has been evaluated with respect to trends and regional differences in acidic deposition and stream water quality. Despite the more than twofold decrease in S emissions in Sweden since the early 1970s, there was only a marginal decrease in sulphate level in precipitation, indicating that long-range transport dominates precipitation chemistry. Trend analyses of stream water data gave practically no evidence that surface water quality had been changing since the late 1960s, i.e., no time lagged or accumulating effects of acidic deposition during past decades could be demonstrated. The difference between the wet deposition of S in southern and northern parts of Sweden was found to be smaller than previously reported. In the northern catchment areas, the input of S was considerably larger than the output. The statistical uncertainty of the trend estimates raises questions about the effectivity of present hydrochemical monitoring programs in detecting environmental changes.

Temporal changes in concentration, composition and size distribution of the colloidal phase in Lake Risten, Sweden

The concentration and size distribution of colloidal matter ( < 1.2 μm) at different depths in the oligotrophic Lake Risten, Sweden, as well as in its main tributary were studied with light scattering in combination with photon correlation spectroscopy at least 4 times/year during 3 consecutive years. Qualitative information on the composition of the colloidal phase was obtained from estimations of the colloidal fraction of Al, Fe, Mn and organic carbon as well as by a sequential leaching procedure. The concentration of colloidal matter varied within a broad range (1.4–100 mg/l) in the stream, while the measurements in the lake indicated minor changes (range 0.8-3.3 mg/l) between the different sampling occasions as well as locations (both vertically and longitudinally). Annual variations in the size ranges of the colloids (spring 120–340 nm; summer 280–700 nm; winter 200–500 nm) were observed. The changes in the average diameters of the colloidal population showed no correlation with changes in any general hydrochemical parameters, but the estimates of the fraction of colloidal organic carbon (COC) indicated increased concentrations with increasing diameters.

Oxygen saturation trends in the Baltic Sea : Problems with statistical inference of marine environmental data.

Marine monitoring programmes are seldom planned and realized to fulfil the requirements of the statistical methods used. The shortcomings of these methods are rarely discussed in the literature. In this work two different methods for trend analysis are applied to a real case and attention is given to the possible violation of the underlying assumptions. Long-term changes in oxygen supersaturation in the Baltic Sea are the object of the study. Linear regression and non-parametric methods are those chosen. The linear regression gave significantly increasing trends of oxygen saturation in Arkona, Eastern Gotland basin and in the Bothnian Sea, but the tested assumptions turned out to be violated. The corresponding non-parametric trend test only confirmed the increasing trend in Arkona. It is suggested that non-parametric methods, like the one used in this work, should be favoured in the future for similar types of marine environmental data.

Oxygen saturation trends in the Baltic Sea

Marine monitoring programmes are seldom planned and realized to fulfil the requirements of the statistical methods used. The shortcomings of these methods are rarely discussed in the literature. In this work two different methods for trend analysis are applied to a real case and attention is given to the possible violation of the underlying assumptions. Long-term changes in oxygen supersaturation in the Baltic Sea are the object of the study. Linear regression and non-parametric methods are those chosen. The linear regression gave significantly increasing trends of oxygen saturation in Arkona, Eastern Gotland basin and in the Bothnian Sea, but the tested assumptions turned out to be violated. The corresponding non-parametric trend test only confirmed the increasing trend in Arkona. It is suggested that non-parametric methods, like the one used in this work, should be favoured in the future for similar types of marine environmental data.