Characteristics and Seasonal Variation of Sediments in Lake Junttiselkä, Pyhäsalmi, Finland

Abstract

Lake Junttiselkä, located in central Finland, has been loaded by effluents from Pyhäsalmi Zn-Cu mine since 1962 and also receives Pyhäsalmi municipal effluent. A total of 32 top sediment samples (0-2, 2-4, and 4-6 cm) were collected in October 2005 and March 2006 to examine the seasonal variation in sediment composition. Furthermore, two sediment cores of 1 m were taken from the northern and southern parts of the lake (Junttiselkä_N, Junttiselkä_S) to investigate the sedimentation history. Electrical conductivity (EC) was measured from the sediment in situ, and sediment pH, redox values, and EC were measured in the winter from the top samples. The sediment samples were freeze-dried and multi-element determinations were performed using ICP-MS on nitric acid extracts (EPA 3051, acid soluble fraction, AF) and on ammonium acetate extracts (bioavailable fraction, BF). The composition of crystalline and semi-crystalline fractions (CF) was calculated by the formula C CF = C AF -C BF . Due to the high clay content of till in the catchment area, the Al, K, and Mg concentrations in the natural lake sediments ([49 cm) are greater than the average level in lake sediments of Finland (AF). Soil cultivation has increased the sedimentation of fines, which has further increased Al, K, and Mg concentrations in the lake sediments (49-19 cm). Mine effluents have had the greatest impact on sediment concentrations of Cu and Zn, with the recorded levels of 166 mg/kg and 434 mg/kg (\19 cm), respectively, being nine-and threefold greater than the natural concentration level. Also, Ca and S concentrations are elevated. The electric conductivity of pore water was elevated at a depth of 1 m. Seasonal variation in the composition of Junttiselkä top sediments is linked to the oxic/anoxic conditions in the water column during the autumn to winter period. The greatest variation was recorded in the 0-2 cm layer in Junttiselkä_S, where Ca BF and S BF concentrations were three and sixfold higher in the winter than in the autumn. decreased. The seasonal variation in composition was less for CF than for BF, and was also partially different. The most significant difference was an increase in Ca CF and S CF concentrations in the winter in Junttiselkä_S, with the reverse situation being observed in Junttiselkä_N. Furthermore, the Fe CF concentration increased in Junttiselkä_N. Equimolar variations in Ca and S suggest that the precipitation and dissolution of gypsum is the most notable seasonal process in the top sediment layer. The seasonally precipitated S corresponds to only 1.4% of the total load of S from the mine effluents.

Ecological risk assessment of boreal sediments affected by metal mining: Metal geochemistry, seasonality, and comparison of several risk assessment methods

“…Finally, the sediment sample (0-6 cm top layer) was collected with a plastic spoon and stored in a resealable plastic bag. A depth of 6 cm was chosen because this was assumed to be the most biologically active part of the sediment, representing current conditions (M€ akinen and Lerssi 2007). The samples were stored in cold (þ4°C) and dark conditions until analysis.…”

“…Metal emissions to water bodies are monitored, but because of the tendency of these contaminants to sink into the sediment, sediment contamination should be seen as an equally important factor affecting the ecological status of aquatic systems. When environmental conditions (e.g., pH, O 2 status, SO 4 ) change, the bioavailable metal fraction may be released back into the water via a biogeochemical exchange with the overlying water (Mäkinen and Lerssi ; EC ; EU ). In boreal ecosystems, environmental conditions vary due to seasonality, making risk assessment for sediments challenging.…”

“…Lakes are covered by an ice cap during the winter, which contributes to stratification and changes in water chemistry. The O 2 levels at the lake bottom often decline at the end of the winter, due to high biological productivity and restricted water exchange, enhanced by eutrophication and heat accumulation from sediment to the overlying water (Borsuk et al ; Mäkinen and Lerssi ; Pulkkanen ).…”

Mine Wastes

“…If mine waters are released into local stream systems, the environmental impact will depend on the quality of the released effluent. This may cause soils as well as floodplain, stream and lake sediments to become contaminated with metals, metalloids, and salts (Juracek 2008;Mäkinen and Lerssi 2007;Roychoudhury and Starke 2006). 3.20) ).…”

Lumbriculus variegatus (Annelida) biological responses and sediment sequential extractions indicate ecotoxicity of lake sediments contaminated by biomining

“…Metals are often released to the environment from mining sites because of accidents, such as leakages from wastewater ponds or the breaking of tailings dams, and effluents that comply with environmental permission procedures. Effluents and leachates from mining sites are often heterogeneous and their characteristics such as pH, metal composition and conductivity can fluctuate considerably over time (Dudka and Adriano 1997, Mäkinen and Lerssi 2007, Nieto et al 2013). In addition to metals, mining effluents may contain other chemicals used in the mining processes.…”