increase in pollen of woody taxa; during interstadial 20 (correlated with PAZ 17a), biogenic silica values show a strong peak (Fig. 3d) while pollen of woody taxa is similar in abundance to that in interstadial 19 (Fig. 3e). Environmentally, the two interstadials were apparently equally moist, but whereas interstadial 19 was warmer in winter than interstadial 20, the latter had a higher annual temperature sum than the former; such differences almost certainly re¯ect differing atmospheric circulation patterns during the two events. Characteristics of the additional environmental¯uctuations can also be inferred. Thus during interstadial 21, corresponding to PAZs 17e±c, the decrease in abundance of pollen of woody taxa during PAZ 17d and the corresponding period of lower lake productivity indicate conditions comparable to those during later stadials. This event is recorded as an increase in d 18 O of planktonic foraminiferans in core M25/4-11 ( Fig. 3i), but has no correlate in the GISP2 record. PAZ 18, a period of rapid environmental¯uctuations at Monticchio, is represented in the GISP2 record by a decrease in d 18 O values between interstadials 22 and 21 and in DSDP-609 by increased, and to some extent¯uctuating, relative abundance of N. pachyderma (s.) (Fig. 3k).Our record from Monticchio demonstrates the capability of late Quaternary lake sediments to provide sensitive, high-resolution records of rapid (centennial±millennial) environmental¯uctuations comparable to those obtained from ice cores. It also reveals that the biosphere was a full participant in these rapid¯uctuations, contrary to widely held views that vegetation is unable to change with such rapidity. The opportunity to develop an independent calendar-year chronology (Fig. 1) allows comparison to precisely dated records from other realms without relying on correlating their principal features (`wiggle matching'); this allows us to quantify, for example, the much shorter duration in terrestrial records of the stadial event correlated with marine oxygen-isotope substage 5b 15 . Lake sediments also have the advantage of recording many proxies of past environments, allowing seasonal climate characteristics to be reconstructed. The Monticchio record demonstrates that the closely coupled Northern Hemisphere ocean±atmosphere system of the last glacial period 4 extended its in¯uence beyond the North Atlantic and Greenland, at least as far as the central Mediterranean region. In addition, the multiple proxies reveal differences in the character of the climate during successive interstadials, as well as revealing additional climate¯uctuations before 65 kyr ago not evident in records from other archives, most probably because of limitations of the ice cores in particular. Although, given predominant midlatitude atmospheric circulation patterns, the linkage of the Mediterranean and North Atlantic regions during the last glacial should come as no surprise, the new information about the varying character and expression of¯uctuations in the Mediterranean region prov...

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[ 1994] are compared with field measurements using nine scenarios. Heterogeneous oxidation of SO2 in cloud droplets and sea-salt particles is also simulated. A sensitivity analysis is performed to evaluate which atmospheric parameters require the greatest attention in future field studies. Results indicate that the variations among the gas phase mechanisms are small with the parameterized mechanisms performing as accurately as the comprehensive ones. Among the nine scenarios tested, nss-sulfate is predicted without bias. Predicted MSA and SO2 concentrations depend more on the gas phase mechanism, with the mechanisms tending to underpredict SO2 concentrations. Compared to differences in MSA and SO2 predictions, DMSO, MSEA, and DMSO2 predictions by the various mechanisms are similar. Sulfate predictions are sensitive to the uncertain parameterizations of heterogeneous processes. The interaction of the marine boundary layer with the free troposphere can explain much of the discrepancy between the model predictions and measurements.

Abstract. To evaluate the impact of aerosols on climate we must consider the aerosol dynamics of the remote marine atmosphere. Marine aerosols are subject to losses due to precipitation, dry deposition, and coagulation; yet, observed remote marine aerosol concentrations and size distributions are relatively constant. This maintenance of the aerosol distribution requires a particle source. This work focuses on the potential of H2SO4 nucleation within the marine boundary layer (MBL) to supply these particles. Spatial and temporal variability in meteorology and species concentrations are considered in a mathematical model to evaluate the effect of natural deviations from average MBL conditions on the highly nonlinear aerosol system. A dynamic, vertically dimensioned, size-resolved aerosol model is used with parameterized heterogeneous chemical processes. The results suggest that MBL nucleation may be an important source of new particle number in the remote MBL. However, though our model shows that typical remote MBL aerosol distributions can on average be maintained by MBL nucleation and sea-salt emissions, large oscillations in particle number concentration occur. Because such oscillations are only occasionally reported in measurements, MBL nucleation may not be the dominant source of new particles in the remote MBL. The nucleation events, which cause these oscillations, are predicted to occur at the top of the MBL after rain and/or entrainment of clean free tropospheric air. Predictions are particularly sensitive to the H2SO4 accommodation coefficient, nucleation tuner, and washout efficiency. Reduction of the accommodation coefficient is shown to increase the predicted accumulation mode concentration because the nucleation rate is enhanced. Entrainment of clean free tropospheric air is shown to increase the frequency of nucleation events within the MBL and may help to explain the observed correlation between subsidence and MBL small particles. A small constant addition of particles from the free troposphere, ocean, etc. suppresses H2SO 4 nucleation and can lead to a reduction in total predicted aerosol number. This is because nucleation events require low total aerosol surface area and the constant addition of particles reduces the severity of aerosol surface area minimums. Larger external aerosol sources can maintain the observed remote MBL aerosol distribution. However, the temporal and spatial variability of such sources could have a large impact on aerosol concentrations and requires further investigation.

Paraffins are linear and branched aliphatic molecules (ϾC18) present within crude oil. As crude oil cools upon exiting a well, the paraffins can gel or precipitate and ultimately cause pipelines to plug. The result is costly downtime in production as the pipelines are cleaned or repaired. One solution to address this challenge is chemical prevention, namely the use of wax inhibitors and pour point depressants.Traditionally wax inhibitors and pour point depressants are organic solvent-based materials that contain a low concentration of active inhibitor (approximately 5% active in a solvent such as toluene). In this work, newly developed high concentration (Ͼ30% active) aqueous-based wax inhibitors and pour point depressants will be discussed.These formulations are stable dispersions of active copolymers in water and can be freeze-protected to Ϫ40°C, enabling their use in arctic environments. There is also an advantage of reduced logistics costs, decreased storage space and the absence of flammable solvents. Additionally, the replacement of organic solvent with water makes these materials more environmentally friendly and less expensive to dilute during application. The physical properties and stability of these materials throughout a broad temperature range from Ϫ40°C to 125°C will be discussed. The performance of these innovative materials on various crude oils will also be presented. Up to a 30°C reduction in the pour point temperature was observed. This unique combination of properties and significant reduction in pour point temperatures is a novel advancement in flow assurance technology.

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