Atmospheric Deposition Connected with Marine Primary Production,Nitrogen Cycle: A Review

Atmospheric Deposition (AD) provides external nutrients such as nitrogen (N), phosphorus (P) and iron (Fe) supporting the growth of phytoplankton in oceans and thereby exerts obvious impacts on carbon and nitrogen cycles and climate change associated. Specifically, the external nutrients derived from atmospheric deposition can promote the marine primary production and nitrogen fixation that enhance the ocean capacity in absorbing CO₂; AD may also change a few pathways of carbon and nitrogen cycles in oceans and increase the emissions of biogenic aerosol and radioactive gases such as N₂O, DMS, etc. Due to the underlying important impacts on climate and environmental change, AD and processes related have become the hot topics of multidisciplinary studies in the areas of ocean and atmospheric sciences, and the focus of some international core projects such as Surface Ocean Lower Atmosphere Study (SOLAS), an International Study of Marine Biogeochemical Cycles of Trace Elements and Their Isotopes (GEOTRACES) and Integrated Marine Biogeochemistry and Ecosystem Research (IMBER). With the severe air pollution and high frequencies of Asian dust events, as the downwind areas of big cities and dust sources, the East China Sea and adjacent North Pacific have received increasing influences of AD. Limited studies showed that the increase of AD indeed caused significant influence on carbon and nitrogen cycles in these immediately related oceanic areas and the study there would have a signature effect on global oceans. A multidisciplinary study on the impacts of AD in oceans, e.g., combing molecular biology and experimental ecology techniques to study primary production processes, utilizing isotopic techniques to trace the change of the nitrogen cycle, new evidences of ocean-biogenic aerosol emissions, etc. would be the focus in the future.     

Erosion-driven drawdown of atmospheric carbon dioxide: The organic pathway

Rapidly eroding, coastal mountain belts, where steep rivers and submarine channels connect upland sources to nearby marine sinks are hotspots of organic carbon transfer from life biomass, soil and exhumed bedrock into geological storage. Using observations from the Southern Alps of New Zealand, and Taiwan, we have mapped this organic pathway to geological carbon sequestration, and can evaluate the magnitude and efficiency of transfers between sources and sinks. We demonstrate that POC is harvested by landsliding, but importantly also by common and widespread surface runoff on steep hillslopes. Although terrestrially sourced POC is found in many sedimentary environments associated with mountain belts and frontier basins, it appears to be most abundantly trapped and preserved in marine turbidites. The loss of all forms of POC in onward transport through short, steep routing systems to this repository is limited. This is in marked contrast to larger routing systems, in which only the most resilient forms of POC survive into long-term deposition.     

Assessment of Radar Waveform Retracked Jason-2 Altimetry Sea Surface Heights Near Taiwan Coastal Ocean

This study focuses on assessing the accuracy of 20-Hz waveform retracked Jason-2 (J-2) altimetry sea surface heights (SSHs) in the vicinity of Taiwan by comparisons with the TOPEX/Poseidon (T/P) 10-Hz SSHs and sea level data from the Anping tide gauge. The study areas exhibit high, medium, and low amplitudes of ocean tides and contain diverse bathymetries with depths of 0–4000 m. The performance of Offset Center of Gravity (OCOG), threshold, modified threshold, and ice retrackers was examined by comparing the retracked SSHs with Earth Gravitational Model 2008 (EGM08) geoid via the use of the improvement percentages (IMPs). The results indicate that both altimetry measurements are significantly improved by waveform retracking techniques, with a maximum IMP of 46.6% for T/P and 82.0% for J-2, and the optimal achievement of retrackers is influenced by the characteristics of the study areas. In addition, valid retracked J-2 SSHs are much closer to shorelines than T/P. A comparison of retracked J-2 data with Anping tide gauge records reveals that applying the optimal retracking algorithms reduces the root mean squares of differences and increases the number of valid measurements.     

Field investigation of the natural attenuation and intrinsic biodegradation rates at an underground storage tank site

 Contamination of groundwater by petroleum-hydrocarbons is a widespread environmental problem. Natural attenuation is a passive remedial approach to degrade and dissipate contaminants in soil and groundwater. In this study, a mass flux approach was used to calculate the contaminant mass reduction and field-scale decay rate at a gasoline spill site. The mass flux technique is accomplished using the differences in total contaminant mass flux across two cross sections of the contaminant plume. The mass flux calculation shows that up to 88% of the dissolved BTEX (benzene, toluene, ethylbenzene, and xylene isomers) removal was observed by natural attenuation processes. The efficiency of intrinsic biodegradation was evaluated by the in situ tracer method. A first-order decay model was applied for the natural attenuation and intrinsic biodegradation rate calculation. Results reveal that intrinsic biodegradation process was the major cause of the BTEX reduction among the natural attenuation mechanisms, and iron reduction was the dominant biodegradation pattern within the plume. Approximately 87% of the BTEX removal was caused by intrinsic biodegradation processes. The calculated BTEX natural attenuation and intrinsic biodegradation rates were 0.24 and 0.16% l/day, respectively. Results suggest that natural attenuation mechanisms can effectively contain the plume, and the mass flux method is useful in assessing the efficiency of the natural attenuation. Received: 6 December 1999 · Accepted: 11 July 2000     

The Lagrangian governing equations of a rotating,compressible, viscous atmosphere

In this paper, the Lagrangian equations of motion, thermodynamics, continuity and diffusion of a rotating, compressible, viscous atmosphere are derived. It is shown that the pressure force and Laplacian terms involving velocity, temperature and concentration in the Eulerian system become nonlinear in the Lagrangian system. In the case that these Laplacian terms can be neglected, the governing equations in the Lagrangian system can be greatly simplified, and particle dynamics and dispersion can be investigated.     

An analysis of the topographical effect on turbulence and diffusion in the atmosphere's boundary layer

An analysis of the wind data recorded at the fifteen stations in the Salt Lake Valley indicates that the distributions of the kinetic energy of the mean and turbulent motions in the valley are generally inhomogeneous and nonstationary. The mean motion in the valley, which is strongly affected by the mountain-valley winds, shows a southeasterly flow in the evening and early morning, a northwesterly flow in the afternoon, and a transitional flow in the late morning and after sunset. The mountain winds generally associate with a horizontally convergent flow, whereas the valley winds associate with a horizontally divergent flow. The distributions of the kinetic energy of the mean and turbulent motions show a maximum occurring in the central part of the valley and two minimums, one in the northern and one in the southern part of the valley. In the afternoon, both the mean and turbulent motions increase their intensities, particularly in the western part of the valley. An analysis of the dispersion characteristics indicates that the rate of diffusion in the valley changes with time and space, with a maximum occurring in the early afternoon and minimum in the early morning.     

Mountain effect on the motion in the atmosphere's boundary layer

An analysis of 3 years' (1967–70) radiosonde wind data on the windward (Salt Lake City, Utah) and lee (Denver, Colorado) sides of mountains indicates that at these two stations: (1) the distributions of the kinetic energy of the mean and turbulent motions are similar above the mountain top; (2) below the mountain top, on the windward side, mountains tend to divert the component of the mean motion normal to the mountains to that parallel to the mountains; (3) the meridional eddy transport of westerly momentum is affected by the presence of the mountains to a higher level to the lee of the mountains than upwind of them; (4) the production of turbulent energy is higher below the mountain top in the vicinity of mountains than it is for the zonal average; (5) high frequencies of the motion show a more pronounced contribution in the meridional motion in the windward side, but in the zonal motion in the lee of the mountains; (6) disturbances of 1–2 day periods can be maintained deep into the valley, whereas disturbances of longer periods reduce their amplitudes rapidly with decreasing height from the mountain top; (7) the cospectra of the wind velocities show that the southward/northward transport of westerly momentum results from a southward/northward contribution from most frequencies. The main contributions come from eddies with periods longer than two days.     

Estimation of fog deposition on epiphytic bryophytes in a subtropical montane forest ecosystem in northeastern Taiwan

The fog meteorology, fog chemistry and fog deposition on epiphytic bryophytes were investigated from July 2000 to June 2001 in the Yuanyang Lake forest ecosystem. The elevation of the site ranges from 1650 to 2420 m, at which the high frequency of fog occurrence throughout the year has been thought to be of benefit to the establishment of the primary Taiwan yellow cypress forest [Chamaecyparis obtusa var. formosana (Hayata) Rehder] and to the extensive growth of the epiphytic bryophytes. A weather station including a visibility sensor and an active fog collector was installed for fog meteorological and chemical study. The fog deposition rate on epiphytic bryophytes was estimated by measuring the increase rate in plant weight when exposed to fog. Average fog duration of 4.7 and 11.0 h per day was measured in summer months (June to August) and the rest of the year, respectively. November 2000 was the foggiest month in which the average fog duration reached 14.9 h per day. The ionic composition of fog water revealed that the area was less polluted than expected from literature data. The in situ exposure experiments done with the dominant epiphytic bryophytes showed an average fog deposition rate of 0.63 g H₂O g⁻¹ d. w. h⁻¹, which approximated 0.17 mm h⁻¹ at the stand scale. The nutrient fluxes estimated for February 2001 showed that for all ions, more than 50% of the ecosystem input was through fog deposition. These results demonstrate the importance of epiphytic bryophytes and fog deposition in nutrient cycling of this subtropical montane forest ecosystem. The incorporation of fog study in the long-term ecosystem research projects is necessary in this area.