Radio-acoustic positioning as a tool for studying site-specific behavior of the white shark and other large marine species

We describe a method, radio-acoustic-positioning (RAP), for continuously monitoring the movements and behavior of large marine animals. An ultrasonic transmitter on the animal can be localized with high spatial accuracy (2 to 10?m) within an area of 1?km², based on when the same pulse arrives at three hydrophones on sonobuoys aligned in a triangular array. Radio transceivers communicate with the base station, where the x and y coordinates of the subject are calculated using hyperbolic equations. The base station plots the individual's position and displays information from the tag's sensors in real time on a computer monitor before saving the data on a disk. The base station must be situated either on land or on a vessel within the reception range of the three buoys. We used a RAP system to monitor the movements and behavior of white sharks (Carcharodon carcharias) near the elephant seal rookery at Año Nuevo Island in central California. This type of system is an ideal tool to study the predatory behavior of the white shark because individuals patrol for seal prey within a zone <1300?m from shore. We describe the operation of the system, including acoustic triangulation, range of detection and positioning, data acquisition and analysis, and positional accuracy. We illustrate the implementation of the method and its advantages and disadvantages by describing an ongoing study of white shark hunting-behavior. Sample data from this study are presented to illustrate specific points. We describe the movements of five sharks within the receiving range and their behavior relative to each other. The RAP system is compared to other complementary tracking methods. We conclude that this system has great potential for monitoring the movements and behavior of large marine animals within a relatively small zone, where feeding or reproduction takes place.     

The hunting strategy of white sharks (Carcharodon carcharias) near a seal colony

The degree to which white sharks, Carcharodon carcharias, are social while hunting is unclear. Our aim was to describe the behavior and interactions among white sharks hunting seals near a seal colony. We attached ultrasonic beacons to five adult white sharks, 4.5–5.2?m long, and recorded their movements and behavior toward each other over a 15-day period in October 1997 at Año Nuevo Island, California. This site is home to colonies of four species of seals and sea lions. Two additional sharks, females 5.5 and 4.7?m in length, were later tracked intensively during periods of 12 and 3?days during October 1998 and November 1999, respectively. We recorded stomach temperature (indicative of feeding on warm-bodied seals) and swimming depths from the 5.5-m female, swimming speed and depth from the 4.7-m female. We monitored the movements and behavior of these sharks using an array of sonobuoys moored near the island; the receptive field measured 1?km². Our principal findings were: (1) the sharks spent a mean time of 39.5% of each day patrolling within the receptive field; (2) no shark ever moved far out of it; (3) the sharks spent an equal amount of time and activity in the receptive field at all times of the day, daytime, twilight, and nighttime; (4) movements with respect to the island rookery were most often back and forth parallel to the shoreline, (5) tracks of three sharks, tagged at the same time and place, overlapped more often than those of the other two sharks; and (6) some sharks patrolled certain areas in the field preferentially, but there was no conclusive evidence that they defended these areas as territories. Feeding appeared to be infrequent: only two likely feeding bouts occurred during a cumulative 78-day/shark period that individuals were monitored at Año Nuevo Island. The behavior and movements of the sharks were consistent with a hunting strategy, in which individuals search for prey independently but, at the same time, remain close enough to each other to “sense” and exploit a kill by any one of them by joining in on the kill to feed.     

Design and Testing of a Turbulence Probe for Harsh Flows

The force of wind on the ground created by turbulent eddies is commonly used to describe the horizontal flux of material during wind erosion. Here we present the Murdoch Turbulence Probe, an instrument for use in both clean and eroding flows which uses pressure differences to measure the three components of wind velocity. Correlation techniques calculate the forces near the ground and turbulence statistics in nearly real time, including turbulent velocity fluctuations from less than 0.1 Hz to 200 Hz, mean flow velocities, Reynolds stresses as well as the integral length and time scales. In the portable wind-tunnel used by Agriculture Western Australia, turbulence statistics were recorded over stable surfaces and in blowing sand from the initiation of erosion up to the time the sand supply was exhausted. Estimates of the friction velocity derived from the turbulence probe were compared with estimates obtained from the wind speed profile measured with a rake of pitot and static tubes. The Murdoch Turbulence Probe appears to work well in sandblasting conditions. Relative turbulence intensities ranged from 0.11 to 0.2 and are in close agreement with values in the literature. The ratio of the turbulence to the friction velocity (3 to 3.2) is at the high end of the reported range. The Reynolds stress measurements agree closely with predictions of the threshold friction velocities of the sand and estimates from the wind speed profile with a von Kármán constant of about 0.3, lower than the commonly accepted value of 0.4. We suggest that the wind-tunnel profile represents the `outer layer' of the boundary-layer that may best be described by a `Wake Law' or `Defect Law'. At about 54 mm above the surface, the friction velocity decreases from 0.64 m/s to 0.39 m/s and the mean velocity increases from 9.6 m/s to 11.6 m/s as the supply of sand is depleted. In addition to the friction velocity, other scales may be necessary to characterise the overriding effect of the wind and in extending wind-tunnel results to the field.     

A GIS tool to estimate West Nile virus risk based on a degree-day model

West Nile virus (Flaviviridae: Flavivirus) is a serious infectious disease that recently spread across the North America continent. A spatial analysis tool was developed on the ArcMap 9.x platform to estimate potential West Nile virus activity using a spatially explicit degree-day model. The model identifies when the virus Extrinsic Incubation Period (EIP) is completed within the vector longevity during mid-summer months. The EIP is treated as a threshold indicator of the potential for virus emergence and activity. Comparing the number of West Nile virus cases in Wyoming reported from 2003 to 2005 with model results, actual cases and predicted events of West Nile virus activity match relatively well. The model represents a useful method for estimating potential West Nile virus activity in a large spatial scale.     

The municipal solid waste system and solid waste characterization at the municipality of Veles, Macedonia

A short-term study to characterize the solid waste stream in the Municipality of Veles, Macedonia, was performed during a 1 week period in the summer of 2002. In this study, several important parameters of the municipal solid waste stream were assessed. It was estimated that the average daily generation rate is 1.06+/-0.56 kg/cap/day, while the specific weights of the uncompacted and compacted solid waste are approximately 140.5 kg/m3 and 223 kg/m3, respectively. Furthermore, it was estimated that the daily generated volume of uncompacted waste is 7.5+/-4 L/cap/day. Although the short-term study is characterized by numerous limitations, in the absence of other existing data, such a study with direct measurements could significantly contribute to the development of an efficient solid waste management system in countries with economies in transition like Macedonia.     

Arsenic speciation in arsenic-rich Brazilian soils from gold mining sites under anaerobic incubation

BACKGROUND: Arsenic speciation in environmental samples is essential for studying toxicity, mobility and bio-transformation of As in aquatic and terrestrial environments. Although the inorganic species As(III) and As(V) have been considered dominant in soils and sediments, organisms are able to metabolize inorganic forms of arsenic into organo-arsenic compounds. Arsenosugars and methylated As compounds can be found in terrestrial organisms, but they generally occur only as minor constituents. We investigated the dynamics of arsenic species under anaerobic conditions in soils surrounding gold mining areas from Minas Gerais State, Brazil to elucidate the arsenic biogeochemical cycle and water contamination mechanisms. METHODS: Surface soil samples were collected at those sites, namely Paracatu Formation, Banded Iron Formation and Riacho dos Machados Sequence, and incubated in CaCl2 2.5 mmol L(-1) suspensions under anaerobic conditions for 1, 28, 56 and 112 days. After that, suspensions were centrifuged and supernatants analyzed for soluble As species by IC-ICPMS and HPLC-ICPMS. RESULTS: Easily exchangeable As was mainly arsenite, except when reducible manganese was present. Arsenate was mainly responsible for the increase in soluble arsenic due to the reductive dissolution of either iron or manganese in samples from the Paracatu Formation and Riacho dos Machados Sequence. On the other hand, organic species of As dominated in samples from the Banded Iron Formation during anaerobic incubation. DISCUSSION: Results are contrary to the expectation that, in anaerobic environments, As release due to the reductive dissolution of Fe is followed by As(V) reduction to As(III). The occurrence of organo-arsenic species was also found to be significant to the dynamics of soluble arsenic, mainly in soils from the Banded Iron Formation (BIF), under our experimental conditions. CONCLUSIONS: In general, As(V) and organic As were the dominant species in solution, which is surprising under anaerobic conditions in terrestrial environments. The unexpected occurrence of organic species of As was attributed to enrollment of ternary organic complexes or living organisms such as algae or cyanobacteria. PERSPECTIVES: These findings are believed to be useful for remediation strategies in mine-affected regions, as the organic As species are in general considered to be less toxic than inorganic ones and even As(V) is considered less mobile and toxic than As(III).     

Use of the electrical aerosol detector as an indicator of the surface area of fine particles deposited in the lung

Because of recent concerns about the health effects of ultrafine particles and the indication that particle toxicity is related to surface area, we have been examining techniques for measuring parameters related to the surface area of fine particles, especially in the 0.003- to 0.5-microm size range. In an earlier study, we suggested that the charge attached to particles, as measured by a prototype of the Electrical Aerosol Detector (EAD, TSI Inc., Model 3070), was related to the 1.16 power of the mobility diameter. An inspection of the pattern of particle deposition in the lung as a function of particle size suggested that the EAD measurement might be a useful indicator of the surface area of particles deposited in the lung. In this study, we calculate the particle surface area (micrometer squared) deposited in the lung per cubic centimeter of air inhaled as a function of particle size using atmospheric particle size distributions measured in Minneapolis, MN, and East St. Louis, IL. The correlations of powers of the mobility diameter, Dx, were highest for X = 1.1-1.6 for the deposited surface area and for X = 1.25 with the EAD signal. This overlap suggested a correspondence between the EAD signal and the deposited surface area. The correlation coefficients of the EAD signal and particle surface area deposited in the alveolar and tracheobronchial regions of the lung for three breathing patterns are in the range of Pearson's r = 0.91-0.95 (coefficient of determination, R2 = 0.82-0.90). These statistical relationships suggest that the EAD could serve as a useful indicator of particle surface area deposited in the lung in exposure and epidemiologic studies of the human health effects of atmospheric particles and as a measure of the potential surface area dose for the characterization of occupational environments.     

Evaluating landfill disposal of chromated copper arsenate (CCA) treated wood and potential effects on groundwater: evidence from Florida

Chromated copper arsenate (CCA) treated wood has been used for more than 50 years. Recent attention has been focused on appropriate disposal of CCA-treated wood when its service life ends. Groups in the US and Europe concerned with the possibility of arsenic migration to groundwater from disposed CCA-treated wood have proposed that consumers be required to dispose of the wood as a hazardous waste, in the most protective of landfills. We examined available data for evidence of arsenic migration from unlined construction and demolition (C&D) debris landfills in Florida, where CCA-treated wood is disposed. Florida was chosen because soil, groundwater, landfill design, weather, and levels of CCA-treated wood use make the state a uniquely sensitive indicator for observing arsenic migration from CCA-treated wood disposal sites, should it occur. We developed and quality-checked a CCA-treated wood disposal model to estimate the amount of wood and associated arsenic disposed. By 2000, an estimated 13 million kg of arsenic in CCA-treated wood was disposed in Florida; however, groundwater monitoring data do not indicate that arsenic is migrating from unlined C&D landfills. Our results provide evidence that highly stringent regulation of CCA-treated wood disposal, such as treatment as a hazardous waste, is unnecessary.     

A reaction-based paradigm to model reactive chemical transport in groundwater with general kinetic and equilibrium reactions

This paper presents a reaction-based water quality transport model in subsurface flow systems. Transport of chemical species with a variety of chemical and physical processes is mathematically described by M partial differential equations (PDEs). Decomposition via Gauss-Jordan column reduction of the reaction network transforms M species reactive transport equations into two sets of equations: a set of thermodynamic equilibrium equations representing N(E) equilibrium reactions and a set of reactive transport equations of M-N(E) kinetic-variables involving no equilibrium reactions (a kinetic-variable is a linear combination of species). The elimination of equilibrium reactions from reactive transport equations allows robust and efficient numerical integration. The model solves the PDEs of kinetic-variables rather than individual chemical species, which reduces the number of reactive transport equations and simplifies the reaction terms in the equations. A variety of numerical methods are investigated for solving the coupled transport and reaction equations. Simulation comparisons with exact solutions were performed to verify numerical accuracy and assess the effectiveness of various numerical strategies to deal with different application circumstances. Two validation examples involving simulations of uranium transport in soil columns are presented to evaluate the ability of the model to simulate reactive transport with complex reaction networks involving both kinetic and equilibrium reactions.