Complexation of Cu,Zn and Cd by metabolites excreted from marine diatoms

The excretion of photosynthetically fixed carbon from cultured marine diatoms and its influence on Cu, Zn and Cd complexation in seawater was studied for three species. For each species, an isolate from oligotrophic waters was compared with an estuarine isolate. Complexation of metal was determined with the use of differential pulse anodic stripping voltammetry. Excreted material from cells in log-phase growth complexed Cu > Zn > Cd, while material derived from senescent cells complexed only Zn. The filtrates of all cultures complexed these metals comparably with natural coastal seawater. There were no appreciable differences in complexing ability within or among species, suggesting that no excretion-complexation ‘strategy’ peculiar to each ecosystem exists among these species.     

Measurements of the initial radii of the ionization columns of bright meteors

A multi-wavelength radar backscatter study of the echo characteristics of radio-meteors has yielded measurements of the height dependence of the radii, r_i, of overdense plasma meteor columns. For electron line densities α ～ 10¹⁵ m^?1 it is found that r_i ∝ ?^?0.63 (? atmospheric density) with r_i = 5 m at a height of 100 km.     

Laser sand detector

Laboratory measurements are presented showing how a laser sand detector (LSD) can be used to discriminate between bubbles and sand, because sand depolarizes light, whereas bubbles do not.     

Reducing emissions from deforestation—The “combined incentives” mechanism and empirical simulations

Despite accounting for 17–25% of anthropogenic emissions, deforestation was not included in the Kyoto Protocol. The UN Convention on Climate Change is considering its inclusion in future agreements and asked its scientific board to study methodological and scientific issues related to positive incentives to reduce emissions from deforestation. Here we present an empirically derived mechanism that offers a mix of incentives to developing countries to reduce emissions from deforestation, conserve and possibly enhance their ecosystem's carbon stocks. We also use recent data to model its effects on the 20 most forested developing countries. Results show that at low CO₂ prices (～US$ 8/t CO₂) a successful mechanism could reduce more than 90% of global deforestation at an annual cost of US$ 30 billion.     

A thermomechanical wedge model of Taiwan constrained by fission-track thermochronometry

We present 31 new apatite fission-track (AFT) ages for the island of Taiwan that, when combined with existing AFT and zircon fission-track (ZFT) data, provide regional spatial coverage of the island with respect to low-temperature thermochronometry. The overall pattern of ZFT and AFT ages in Taiwan exhibits unreset ages in the southern and western portions of the island and reset ages predominantly in the Central Range and eastern Taiwan. This pattern supports interpretations of the orogen kinematics as reflecting a crustal scale wedge with a southward propagating collision zone. In this model, new material is accreted to the wedge from the west and is transferred to the east with the greatest exhumation occurring along the eastern margin as recorded in the reset ages in the east and unreset ages in the west. The southward propagating collision is consistent with reset ages in the north, where erosional exhumation has been ongoing for longer, and unreset ages in the south, where the younger collision implies less time for erosional exhumation. Despite the variation in the age of the collision along the strike of the island, the widths of the AFT and ZFT reset age zones remain nearly constant between 23° 00′N to  24° 00′N and 23° 20′N to  24° 00′N, respectively, suggesting that the orogen is in an exhumational steady state over these regions with respect to the AFT and ZFT thermochronometers. We use the fission-track data in conjunction with observations of crustal structure, crustal fabric, and heat flow measurements to constrain a time-dependent, two-dimensional, thermomechanical model of orogen evolution. By accounting for the heat transfer, tectonic and erosion processes needed to predict AFT and ZFT ages, we are able to investigate the relationship between the measured ages and the tectonic characteristics of the orogen. With our model we conclude that: (1) roughly half of the material accretion in Taiwan occurs through underplating over an approximately 40 km wide region, (2) current average erosion rates are  3.3 mm/yr in the eastern Central Range and  2.3 mm/yr over the whole island, (3) the collision has been propagating southward at a rate between 20 and 51 km/Ma over the past 2–3 Ma, and (4) central Taiwan is in a topographic, thermal and exhumational steady state.     

Volatile Organic Compounds in the Mouth Areas of Small Rivers in Tatar Strait during Under-Ice Period

Water Resources - The distribution of volatile organic compounds was studied in water and bottom sediments of estuaries of small tidal rivers. In the under-ice period, water showed high...     

Natural and anthropogenic controls on sediment rating curves in northern California coastal watersheds

The watersheds along the north coast of California span a wide range of geologic settings, tectonic uplift rates, and historic timber harvest activity. Known trends in how each of these factors influence erosion rates provides an opportunity to examine their relative importance. We analyzed 71 watersheds within nine larger river basins, investigated the factors influencing suspended sediment rating curves (SRCs), investigated how SRCs varied among our study watersheds, and used Random Forest modeling (RFM) to determine which environmental characteristics and land management metrics influence SRC shapes, vertical offsets, and slopes. While SRCs typically take the form of a power function, they also can exhibit threshold or peak relationships. First, we found both power and threshold relationships for the SRCs within our study watersheds. Second, the SRC offsets and slopes systematically varied with regional tectonic uplift. Third, SRC offsets increased in several watersheds following intensive timber harvest events and SRC slopes decreased due to a greater relative increase in suspended sediment concentration at lower flows than higher flows. Our RFM correctly classified 96% of the SRC shapes using two near-channel metrics; near-channel precipitation-sensitive deep-seated landslide susceptibility and near-channel soil erodibility. Our RFM models also showed that timber harvest activity and near-channel local relief can explain 40% of the variability in SRC offsets, whereas tectonic uplift rates, millennial-scale erosion rates, and precipitation patterns explain 40% of the variability in SRC slopes.     

Radiative Cooling in MHD Models of the Quiet Sun Convection Zone and Corona

We present a series of numerical simulations of the quiet-Sun plasma threaded by magnetic fields that extend from the upper convection zone into the low corona. We discuss an efficient, simplified approximation to the physics of optically thick radiative transport through the surface layers, and investigate the effects of convective turbulence on the magnetic structure of the Sun’s atmosphere in an initially unipolar (open field) region. We find that the net Poynting flux below the surface is on average directed toward the interior, while in the photosphere and chromosphere the net flow of electromagnetic energy is outward into the solar corona. Overturning convective motions between these layers driven by rapid radiative cooling appears to be the source of energy for the oppositely directed fluxes of electromagnetic energy.