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The adverse impacts of the inorganic labile monomeric Al (Al-i) fraction on aquatic organisms have meant that Al (Al-tot) determination and even speciation has become a routine part of environmenta ...

Whole catchment liming or forest liming has been proposed and implemented as a countermeasure to the effects of elevated sulphur deposition. Since the end of the 1980s the Swedish Forest Agency has undertaken experimental forest liming experiments in selected catchments in southern Sweden. These studies were with low doses (3 tonnes ha−1) of lime (CaCO3) and dolomite (CaMg(CO3)2). Data from both soil samples and stream water samples have been collected for the 16 years following treatment. The stream data has been complemented with data from untreated catchments, from the Swedish monitoring stream network. Significant differences due to treatment were seen for Ca, cation exchange capacity (CEC) and base saturation (BS) in the humus layer, none of these variables showed a statistically significant change in the mineral soil due to treatment alone. Soil samples from both the treated and untreated sites showed temporal changes in both the humus layer and the mineral soils with increases in pH, Ca and CEC and decreases in BS and Al which were independent of treatment. A combination of treatment and time, gave significant changes in BS and TA down to 10 cm in the mineral soil. In the stream water samples no statistically significant differences were observed between treated and untreated sites. Regardless of treatment, the streams exhibited a general pattern of declining concentrations of SO4, Ca, sum of base cations (BC) and increasing acid neutralizing capacity (ANC). In summary, the application of a low dose of lime (3 tonnes ha−1) did not result in significant changes in surface water chemistry in the study catchments and changes in soil chemistry were mainly restricted to the humus layer during the 16 years following treatment. The natural recovery, as a result of reductions in sulphur deposition, dominated the effects and was clearly seen in both the treated and untreated study sites. MAGIC simulations indicate that this recovery will continue in the coming decades.

The negative effects of elevated concentrations of inorganic aluminium on aquatic organisms are well documented. Acid deposition is often cited as a main driver behind the mobilisation and speciation of aluminium in soils and surface waters. In the study, we tested the hypothesis that sulphur deposition is the main driver for elevated concentrations of inorganic aluminium in 114 base poor, boreal Swedish streams. However, the deposition of anthropogenic sulphate has decreased substantially since it peaked in the 1970s, and at the current deposition levels, we hypothesise that local site parameters play an important role in determining vulnerability to elevated concentrations of inorganic aluminium in boreal stream waters. Presented here are the results of a principal components analysis of stream water chemistry, acid deposition data and local site variables, including forest composition and stem volume. It is shown that the concentrations of both organic and inorganic aluminium are not explained by either historical or current acid deposition, but are instead explained by a combination of local site characteristics. Sites with elevated concentrations of inorganic aluminium were characterised by small catchments (

Due to the varying toxicity of different Al species, information about Al concentration and speciation is important when assessing water quality. Modelling Al speciation can support operational mon ...

[1] In this study, we examine the impact of increasing concentrations of dissolved organic carbon (DOC) on the recovery from acidification for 66 lakes in Southern Sweden. The lakes are small, weakly buffered, and have all been affected by acidifying deposition. A majority of the lakes (∼75%) showed an increase in DOC concentrations between 1990 and 2008. The method used in this study was to model pH in 2008 from DOC, acid neutralizing capacity, pCO2 (partial carbon dioxide pressure), and Al speciation, using both the DOC observed in 2008 and the “unelevated” DOC of 1990. Furthermore, we consider the indirect effects of increasing DOC on acidity, i.e., the ancillary effects from DOC on pCO2, Al transport and speciation, and release of base cations (BCs). Our results indicate that the DOC increase in the latest decades has retarded the recovery from acidification by 0.13 pH units (median for all lakes) and by more than 1 unit for individual lakes. The effects of elevated pCO2 and BC concentrations accompanying the DOC increase compensated for each other for the average lake, whereas the effects of higher Al transport on pH were minor. The estimate of the amount of BCs released with the organic anions is however uncertain, and further studies on this topic are needed.