Multielement data of sediment samples from the Kvarken Archipelago, eastern Gulf of Bothnia, impacted by metal loading from acid sulphate soils
2020
Virtasalo, Joonas J | Åström, Mats E | Österholm, Peter | Kotilainen, Aarno T
This dataset includes contents of 55 elements, determined for 1-cm sediment slices of 9 short gravity-cores from the Kvarken Archipelago, eastern Gulf of Bothnia, northern Baltic Sea. Geochronology of the cores is constrained by the measurements of Cs-137 activity content. The sediments represent organic-rich brackish-water muds. The sea area receives large amounts of trace metals (e.g. Al, Cd, Co, Cu, La, Mn, Ni and Zn) from rivers draining the acid sulphate soils of western Finland. The metal contents in the cores increase during the 1960s and 1970s, and stay at the high level afterwards. The enrichment is visible more than 25 km out from the river mouths. The sample slices were sieved through a 63 μm mesh, and 0.2 g of the passed-through fraction was digested in a four-acid mixture of hydrofluoric acid, perchloric acid, hydrochloric acid and nitric acid (USGS Methods T01 and T20). After evaporation of the acids at 160 °C, the resulting gel was dissolved to 1 M nitric acid, and analysed for element concentrations by inductively coupled plasma-mass spectrometry (ICP-MS), or inductively coupled plasma-optical emission spectrometry (ICP-OES), depending on the element. The commercial sediment reference materials QCGBMS304-6, QCMESS-4, QCNIST8704, CO153B and in-house standards were used for assessing measurement accuracy. Element concentrations for all reference materials measured with each sample batch fell well within ±10 % of the certified values. Mercury was measured separately by nitric acid leach of 0.2 g samples through thermal decomposition, amalgamation and atomic absorption spectrometry (US EPA Method 7473). Solid-phase contents of carbon and nitrogen in the samples were analyzed by thermal combustion elemental analysis. The pools of inorganic C and N are negligible in this setting, hence the total contents are considered equal to organic C and N.
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