Size-fractionated particulate trace element concentrations from the Irminger Basin Iron Study in 2010
Description
The particulate element data in this dataset were determined from samples collected by in-situ pumps from the upper water column during three research cruises in May (D350, D351) and July-August (D354) 2010. All three research cruises were part of a project to study seasonal iron limitation in the high latitude North Atlantic (HLNA), notably in the Irminger Basin and the Iceland Basin. Research cruises D350 and D351 coincided with the April/May 2010 eruption of the Eyjafjallajökull volcano in southern Iceland, which led to significant deposition of volcanic ash over the study region and perturbation of local iron biogeochemistry, and the influence of this volcanic material is evident in several of the springtime samples in this dataset. Data from the summertime research cruise (D354) also suggest more localized influence from volcanic ash that may have been resuspended from deposits in southern Iceland by wind events and transported over the Iceland Basin. The data are presented here in three worksheets. The first (“1. Total element amounts”) gives total ng amounts measured in each sample following a leach and digest treatment and accounting for material lost to the rinse when material was rinsed from the SAPS filters. Also included is the total mass of material (mg) rinsed from each filter (to calculate ng/mg elemental content of the material) and the volume of seawater filtered through each in situ pump (to calculate concentrations in ng/L). The worksheet also displays for each element the percentage that was refractory in nature for each sample (i.e. accessed by a strong acid digestion). The second worksheet (“2. Leach and digest values”) lists separately the filter blank corrected amounts of each element in the acetic acid leach and the strong acid digest, with uncertainties propagated from filter blank corrections and uncertainties in filter mass measurements. The third worksheet (“3. Rinse loss percentages”) summarizes losses of each element lost from the particulate material as it was rinsed off the large SAPS filters onto smaller filters. A subset of 13 rinse samples for each size fraction were analyzed by ICPMS and the element concentrations were used to calculate the mean and standard deviation of the “rinse loss” as a percentage of the total element load associated with particulate material.
Files
Steps to reproduce
Each pump (Challenger Oceanic Stand Alone Pump System; SAPS) was fitted with two large filters (~300 mm diameter) arranged in-line inside a filter housing to collect particulate material in two size fractions (>53 μm and 1-53 μm). Nylon monofilament mesh (Sefar Nitex) was used for the >53 μm size fraction and either a smaller Nitex mesh or a 293 mm diameter polycarbonate 1 μm membrane (Sterlitech) was used for the small size fraction. At the designated depth, several hundred liters of seawater were pumped through the two filters inside each SAPS over a period of 1.5-2 hours. Upon recovery, the filters were removed, folded and stored frozen in resealable plastic bags until further processing on shore. The collected particulate material was later rinsed off each filter with ultrapure water adjusted to pH 8.3, and collected onto smaller preweighed polycarbonate filters (47 mm Whatman Nuclepore, 0.4 μm). After drying, these filters were reweighed to calculate the mass of material collected on the filter. Each 47 mm filter was treated with a 2 hour room temperature leach in 25% acetic acid leach. Then the leachate was separated from the filter and the filter was treated to a strong acid digest. For this, the filter was heated at 130°C in a sealed Teflon vial for 4 hours with 2.5ml of concentrated nitric acid and 0.5 mL concentrated hydrofluoric acid, dried down, then heated at 130°C for a further 2 hours with 1.5ml concentrated nitric acid. All leach and digest solutions were dried down and the residues redissolved in 2% nitric acid for analysis of Al, P, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Cd and Pb by Inductively Coupled Plasma Mass Spectrometry (ThermoFisher Scientific Element II XR). Filter blanks were subjected to the same procedures and the average leach filter blank and digest filter blank subtracted from leach and digest sample data respectively. For a subset of samples, the water used to rinse material off the large filters was collected after passing through the smaller filters and also analyzed by ICPMS. From this the average percentage of material lost to the rinse was calculated for each size fraction. Thus the total ng of each element for samples (worksheet 1) is determined by measurements of the leach and digest for that sample (worksheet 2) and adjusted using the mean percentage of material lost to the rinse (worksheet 3). The uncertainties presented for each element are propagated from the standard deviations of the filter blank correction and the rinse contribution. In most cases the latter makes the greatest contribution to propagated uncertainty. Uncertainties associated with the particle mass arise from propagation of standard deviations of mass measurements before and after material was collected on the filter. The digest contribution to the total for each element was calculated as a percentage (worksheet 1) by dividing the amount measured in the acid digest of filter and particles by the total amount in rinse, leach and digest.