Belowground decomposition of mangrove roots in Florida coastal everglades

Mangrove root decomposition rates were measured by distributing mesh bags containing fine root material across six sites with different soil fertility and hydroperiod to compare ambient differences to substrate quality. Roots from a site with lower soil phosphorus concentration were used as a reference and compared to ambient roots at five other sites with increased phosphorus concentration. Four mesh bags of each root type (ambient versus reference), separated into four 10-cm replicate intervals, were buried up to 42 cm depth at each site and incubated for 250 d (initiation in May 2004). Mass loss of ambient mangrove roots was significant at all study sites and ranged from 17% to 54%; there was no significant difference with depth at any one site. Reference decomposition constants (−k) ranged from 0.0012 to 0.0018 d⁻¹ among Taylor Slough sites compared to 0.0023–0.0028 d⁻¹ among Shark River sites, indicating slower decomposition rates associated with lower soil phosphorous and longer flood duration. Reference roots had similar decomposition rates as ambient roots in four of the six sites, and there were no significant correlations between indices of root substrate quality and decomposition rates. Among these distinct landscape gradients of south Florida mangroves, soil environmental conditions have a greater effect on belowground root decomposition than root substrate quality.     

A regional strategy for geothermal exploration with emphasis on gravity and magnetotellurics

As part of the resource evaluation and exploration program conducted by Los Alamos Scientific Laboratory for the national Hot Dry Rock (HDR) Geothermal Program, a regional magnetotelluric (MT) survey of New Mexico and Arizona is being performed. The MT lines are being located in areas where the results of analysis of residual gravity anomaly maps of Arizona and New Mexico, integrated with other geologic and geophysical studies indicate the greatest potential for HDR resources.The residual gravity anomalies are derived by applying the concept of predicting gravity anomalies from topography. This can be accomplished by employing reductions similar to those used in some isostatic investigations, in which a regional topographic surface is used as the Bouguer reduction datum. The datum is derived by comparison of various harmonics of Bouguer anomalies and elevations of stations. Topography can be used to predict Bouguer anomalies because of isostatic compensation; the resultant anomalies can be considered high frequency residual anomalies or isostatic anomalies corrected for regional compensation. Such maps have been produced for Arizona, New Mexico, west Texas, and Chihuahua, Mexico.The main objective of the MT project is to produce a regional geoelectric contour map of the pervasive deep electrical conductor within the crust and/or upper mantle beneath the Colorado Plateau and the adjacent Basin and Range Province and Rio Grande Rift. The MT survey consists of 200 sites along several long profiles with site spacing of 15–20 km. Pre-existing available MT data are being integrated with the new data. After the data are processed, a one-dimensional inversion is applied to the sounding curve and used as a starting point for 2-D modeling. Such a project and ultimate map will be of major value in studying the regional geophysics and tectonics of the southwest United States as they now apply to HDR resources in particular and geothermal resources in general.Electrical conductivity anomalies of large areal extent are of particular interest in geothermal exploration. Correlation analysis of large conductive anomalies with other geophysical, geological, and geotectonic data is being performed. Preliminary analysis of the data has suggested several major regions of anomalously shallow high electrical conductivity. Among these is the Aquarius area of northwest Arizona which is the site of a longwavelength residual anomaly low, which when modeled and correlated with other geophysical data can be shown to be possibly related to low density and high temperature in the crust at depths of 20 km or less. Preliminary analysis of MT data indicates the possible existence of a mid-crustal high electrical conductivity anomaly in this same region.     

Radial velocities in the open cluster IC 2391

We have determined radial velocities for 31 stars in the field of the open cluster IC 2391, and derived the percentage of probable radial-velocity variables. We improved the orbit of one previously known spectroscopic binary, and confirmed the existence of two double-line binaries. We discussed with such data the membership to the cluster, the average cluster radial velocity and compared the incidence of short-period binaries among the Main-Sequence members of IC 2391 with the incidence for other clusters with similar average axial rotation of its members.Member of the Carrera del Investigador Científico del Consejo Nacional de Investigaciones Científicas y Técnicas de la República ArgentinaVisiting Astronomer, Cerro Tololo Inter-American Observatory, operated by AURA, Inc. under contract with the National Science Foundation.     

Multi-criteria analysis for the identification of waste disposal areas

The municipality of Cachoeiro de Itapemirim (ES) is currently the largest domestic producer and exporter of marble and granite in Brazil. The processing of the rock, especially the sawing results in a large volume of waste, including the abrasives used during sawing and the off-cut pieces. Presently these waste products are disposed of without proper environmental protection and cause pollution to surface water and groundwater resources, including silting, an increase in hardness and increased aluminium values in the groundwater. In order to minimize the harmful effects of these practices on the environment, a research project was undertaken to identify potential disposal sites for the generated waste. A multi-criteria approach was followed during which a database was compiled of all the companies generating waste products and also including a baseline environmental study of the region, integrated analysis (multi-criteria analysis) of the restriction factors and the preliminary identification of possible disposal sites. This revised version was published online in July 2006 with corrections to the Cover Date.     

Experimental investigation of the effect of dissolution on sandstone permeability, porosity, and reactive surface area

The temporal permeability, porosity, and reactive surface area evolution during dissolution of nonfractured/clay-free Fontainebleau sandstone cores was measured using a flow through percolation reactor. Four core dissolution experiments, each of ∼1000 h duration, were performed on sandstone cores having initial porosities ranging from 5.1 to 16.6%. All experiments were performed at 80°C and at far from equilibrium conditions using a 0.1 M NaOH input solution with a calculated in situ pH of 11.4. Permeability evolution was determined using Darcy’s law together with in situ measured differential pressures. Reactive surface area and porosity evolution were quantified from the mass of Si leaving the core during the experiments. The 5.1 and 8.9% initial porosity sandstone cores experienced porosity increases of 1.2 and 1.4 percent, respectively, during the experiments. These cores experienced a corresponding permeability increase from 0.27 to 0.74 mD and 0.57 to 0.87 mD, respectively. In contrast, the 10.6 and 16.6% initial porosity sandstone cores had permeabilities that were essentially constant during the dissolution experiments despite porosity increases of 6.3 and 2.5%, respectively. Only the 5.1% initial porosity core experienced a permeability evolution roughly consistent with a cubic law dependence on porosity. Reactive surface areas increased during the experiments for all cores; those for the 5.1, 10.6, and 16.6% initial porosity cores increased by 21±6% for each percent porosity increase. The reactive surface area of the 8.9% initial porosity core, however, increased by 148% for each percent porosity increase. These results suggest that dissolution of the 8.9% initial porosity core opened a substantial number of isolated pores, exposing new quartz grain surfaces to dissolution.     

Evidence of direct particle trapping by a tropical seagrass meadow

The capacity of seagrass canopies to directly retain sestonic particles was tested by quantifying the rate at which suspended fluorescent tracer particles were retained within a tropical Philippine seagrass meadow and by examining whether the test particles lost from the water column were later bound to seagrass leaves or inside epibionts. The particle loss rates in the presence of seagrass canopies were up to 4 times higher than those in unvegetated and plankton controls. The seagrass canopies trapped particles with a maximum rate of 0.73 (±0.24) h^?1. As much as 5% of the particles trapped by the seagrass leaves were physically adhered to the leaf surfaces following rinsing. Particles were also observed to be ingested by protozoa (ciliates and amoeba-like organisms), residing on the surface of the leaves, and may be the dominant particle trapping mechanism by seagrass leaves. These processes should provide an efficient mechanism for the transfer of planktonic production to the benthos, adding to the high organic carbon input maintained by the high production of the seagrass themselves.