This review provides an assessment of sediment trap accuracy issues by gathering data to address trap hydrodynamics, the problem of zooplankton "swimmers," and the solubilization of material after collection. For each topic, the problem is identified, its magnitude and causes reviewed using selected examples, and an update on methods to correct for the potential bias or minimize the problem using new technologies is presented. To minimize hydrodynamic biases due to flow over the trap mouth, the use of neutrally buoyant sediment traps is encouraged. The influence of swimmers is best minimized using traps that limit zooplankton access to the sample collection chamber. New data on the impact of different swimmer removal protocols at the US time-series sites HOT and BATS are compared and shown to be important. Recent data on solubilization are compiled and assessed suggesting selective losses from sinking particles to the trap supernatant after collection, which may alter both fluxes and ratios of elements in long term and typically deeper trap deployments. Different methods are needed to assess shallow and short-term trap solubilization effects, but thus far new incubation experiments suggest these impacts to be small for most elements. A discussion of trap calibration methods reviews independent assessments of flux, including elemental budgets, particle abundance and flux modeling, and emphasizes the utility of U-Th radionuclide calibration methods.
[1] The global tropospheric budget of gaseous and particulate non-methane organic matter (OM) is re-examined to provide a holistic view of the role that OM plays in transporting the essential nutrients nitrogen and phosphorus to the ocean. A global 3-dimensional chemistry-transport model was used to construct the first global picture of atmospheric transport and deposition of the organic nitrogen (ON) and organic phosphorus (OP) that are associated with OM, focusing on the soluble fractions of these nutrients. Model simulations agree with observations within an order of magnitude. Depending on location, the observed water soluble ON fraction ranges from $3% to 90% (median of $35%) of total soluble N in rainwater; soluble OP ranges from $20-83% (median of $35%) of total soluble phosphorus. The simulations suggest that the global ON cycle has a strong anthropogenic component with $45% of the overall atmospheric source (primary and secondary) associated with anthropogenic activities. In contrast, only 10% of atmospheric OP is emitted from human activities. The model-derived present-day soluble ON and OP deposition to the global ocean is estimated to be $16 Tg-N/yr and $0.35 Tg-P/yr respectively with an order of magnitude uncertainty. Of these amounts $40% and $6%, respectively, are associated with anthropogenic activities, and 33% and 90% are recycled oceanic materials. Therefore, anthropogenic emissions are having a greater impact on the ON cycle than the OP cycle; consequently increasing emissions may increase P-limitation in the oligotrophic regions of the world's ocean that rely on atmospheric deposition as an important nutrient source.Citation: Kanakidou, M., et al. (2012), Atmospheric fluxes of organic N and P to the global ocean, Global Biogeochem. Cycles, 26, GB3026,
[1] Synchronous sampling of bulk-aerosols, carried out during wintertime from the two strategically located sites in North India, reveals that total suspended particulates (TSP) over an urban site (Hisar: 29.2°N 75.7°E; 219 m asl) ranged from 67 to 396 mg m À3 ; in contrast, TSP at Manora Peak (a high-altitude station: 29.4°N 79.5°E; 1950 m asl) was relatively low (range: 13.7 to 42.7 mg m À3 ). At Hisar, on average, water-soluble ionic species (WSIS, range: 14.1 to 78.3 mg m À3 ) contribute nearly one-fourth by weight to TSP, with dominant contribution from SO 4 2À , NO 3 À and NH 4 + . The time series analysis over a span of 30 days shows somewhat uniform distribution of organic carbon/elemental carbon (OC/EC) ratio centering around 8.5 ± 2.2 at this urban site; and the water-soluble organic components (WSOC range: 6.7 to 42.0 mg m À3 ) account for 11.5 % to the TSP concentration. Both WSOC and OC exhibit significant positive correlation with water-soluble K + (r = 0.88 and 0.79 respectively), suggesting their dominant contribution from biomass burning. At Manora Peak, the chemical composition of ambient aerosols show characteristically lower abundances of WSIS (range: 2.0 to 9.9 mg m À3 ) and WSOC (range: 1.4 to 6.0 mg m À3 ); together they account for one-third of the TSP. The characteristic low abundances of OC (range: 2.8 to 6.9 mg C m À3 ) and EC (range: 0.34 to 1.4 mg C m À3 ) at this high-altitude site and their significant correlation with K + and SO 4 2À suggest contribution from long-range transport of anthropogenic species. This study represents a first comprehensive data set for documenting the chemical characteristics of ambient aerosols and source apportionment of EC, OC, WSIS and mineral dust over urban and high-altitude sites in north India, an important data set required for the south Asian region. If the observed OC/EC ratios far greater than $2 (unlike reported values in the literature for urban sites) and the semi-empirical estimates of secondary OC are typical of the annual average abundances in the ambient aerosols over north India, then the temporal and regional analyses of primary and secondary OC using the existing emission models require reassessment for this region.Citation: Rengarajan, R., M. M. Sarin, and A. K. Sudheer (2007), Carbonaceous and inorganic species in atmospheric aerosols during wintertime over urban and high-altitude sites in North India,
) data set on the chemical composition of ambient aerosols collected from an urban location (Kanpur) in the Indo-Gangetic Plain (IGP) and suggests that the varying strength of the regional emission sources, boundary layer dynamics, and formation of secondary aerosols all contribute significantly to the temporal variability in the mass concentrations of elemental carbon (EC), organic carbon (OC), and water-soluble OC (WSOC). On average, carbonaceous aerosols contribute nearly one third of the PM 10 mass during winter, whereas their fractional mass is only ∼10% during summer. A three-to four-fold increase in the OC and K + concentrations during winter and a significant linear relation between them suggest biomass burning (wood fuel and agricultural waste) emission as a dominant source. The relatively high OC/EC ratio (average: 7.4 ± 3.5 for n = 66) also supports that emissions from biomass burning are overwhelming for the particulate OC in the IGP. The WSOC/OC ratios vary from 0.21 to 0.70 over the annual seasonal cycle with relatively high ratios in the summer, suggesting the significance of secondary organic aerosols. The long-range transport of mineral aerosols from Iran, Afghanistan, and the Thar Desert (western India) is pronounced during summer months. The temporal variability in the concentrations of selected inorganic constituents and neutralization of acidic species (SO 4 2− and NO 3 − ) by NH 4 + (dominant during winter) and Ca 2+ (in summer) reflect conspicuous changes in the source strength of anthropogenic emissions.Citation: Ram, K., M. M. Sarin, and S. N. Tripathi (2010), A 1 year record of carbonaceous aerosols from an urban site in the Indo-Gangetic Plain: Characterization, sources, and temporal variability,
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