Bioaccumulation and histopathological effects of oil on a stony coral

Colonies of the shallow-water Caribbean coral Manicina areolata incorporated petroleum hydrocarbons into their tissues during exposure to water accommodated fractions of No. 2 fuel oil for three months. This contamination was not removed after depuration periods of up to two weeks. Although these corals remained alive, evidence of pathological responses was found which included impaired development of reproductive tissues, degeneration and loss of symbiotic zooxanthellae, and atrophy of mucous secretory cells and muscle bundles.     

Generating MODFLOW grids from boundary representation solid models

Complex stratigraphy can be difficult to simulate in MODFLOW models. MODFLOW uses a structured grid that requires that each grid layer be continuous throughout the model domain. This makes it difficult to explicitly represent common features such as pinchouts and embedded seams in a MODFLOW model. In this paper, we describe a method for automatically generating MODFLOW-compatible grids from boundary-representation solid models. Solid models are data structures developed originally for computer-aided design applications that define the geometry of three-dimensional objects. Solid models can be used to represent arbitrarily complex stratigraphy. The elevations defined by the solids are then extracted from the solids in a manner that preserves the continuous-layer requirement imposed by MODFLOW. Two basic approaches are described: The first method adjusts the MODFLOW grid dimensions (layer elevations) to fit the solid model boundaries, and the second method creates a regular MODFLOW grid and adjusts the material properties to match the changes in stratigraphy. One of the main benefits of using solid models to define stratigraphy for MODFLOW models is that it provides a grid-independent definition of the layer elevations that can be used to immediately re-create the MODFLOW grid geometry after any change to the grid resolution.     

From the Hagedoorn imaging technique to Kirchhoff migration and inversion

The seminal 1954 paper by J.G. Hagedoorn introduced a heuristic for seismic reflector imaging. That heuristic was a construction technique – a 'string construction' or 'ruler and compass' method – for finding reflectors as an envelope of equal traveltime curves defined by events on a seismic trace. Later, Kirchhoff migration was developed. This method is based on an integral representation of the solution of the wave equation. For decades Kirchhoff migration has been one of the most popular methods for imaging seismic data. Parallel with the development of Kirchhoff wave-equation migration has been that of Kirchhoff inversion, which has as its objectives both structural imaging and the recovery of angle-dependent reflection coefficients. The relationship between Kirchhoff migration/inversion and Hagedoorn's constructive technique has only recently been explored. This paper addresses this relationship, presenting the mathematical structure that the Kirchhoff approach adds to Hagedoorn's constructive method and showing the relationship between the two.     

Effects of urbanization on streamflow in the Atlanta area (Georgia,USA): a comparative hydrological approach

For the period from 1958 to 1996, streamflow characteristics of a highly urbanized watershed were compared with less‐urbanized and non‐urbanized watersheds within a 20 000 km² region in the vicinity of Atlanta, Georgia: in the Piedmont and Blue Ridge physiographic provinces of the southeastern USA. Water levels in several wells completed in surficial and crystalline‐rock aquifers were also evaluated. Data were analysed for seven US Geological Survey (USGS) stream gauges, 17 National Weather Service rain gauges, and five USGS monitoring wells. Annual runoff coefficients (RCs; runoff as a fractional percentage of precipitation) for the urban stream (Peachtree Creek) were not significantly greater than for the less‐urbanized watersheds. The RCs for some streams were similar to others and the similar streams were grouped according to location. The RCs decreased from the higher elevation and higher relief watersheds to the lower elevation and lower relief watersheds: values were 0·54 for the two Blue Ridge streams, 0·37 for the four middle Piedmont streams (near Atlanta), and 0·28 for a southern Piedmont stream. For the 25 largest stormflows, the peak flows for Peachtree Creek were 30% to 100% greater than peak flows for the other streams. The storm recession period for the urban stream was 1–2 days less than that for the other streams and the recession was characterized by a 2‐day storm recession constant that was, on average, 40 to 100% greater, i.e. streamflow decreased more rapidly than for the other streams. Baseflow recession constants ranged from 35 to 40% lower for Peachtree Creek than for the other streams; this is attributed to lower evapotranspiration losses, which result in a smaller change in groundwater storage than in the less‐urbanized watersheds. Low flow of Peachtree Creek ranged from 25 to 35% less than the other streams, possibly the result of decreased infiltration caused by the more efficient routing of stormwater and the paving of groundwater recharge areas. The timing of daily or monthly groundwater‐level fluctuations was similar annually in each well, reflecting the seasonal recharge. Although water‐level monitoring only began in the 1980s for the two urban wells, water levels displayed a notable decline compared with non‐urban wells since then; this is attributed to decreased groundwater recharge in the urban watersheds due to increased imperviousness and related rapid storm runoff. Copyright © 2001 John Wiley & Sons, Ltd.     

Radiocarbon and Luminescence Age Determinations on Mounds at Crystal River and Roberts Island,Florida, USA

Optically stimulated luminescence (OSL) has been employed successfully to determine the ages of palaeosols from earthen mounds in the southeastern USA, providing archaeologists with a means of dating monument construction in the absence of carbonaceous materials and geologists with a setting for understanding factors that can affect the luminescence intensity (i.e., burial dose) of soils. However, OSL dating has not been adequately tested on mounds whose principal component is sand, shell, or a combination of these two, despite the fact that monuments composed of such materials are common to the coasts and interior coastal plains of the region. Radiocarbon dating of bone collagen and soil‐carbon and OSL dating of quartz grains extracted from the fill of mounds at the Crystal River and Roberts Island sites on the west‐central coast of Florida, USA are used to determine the timing and history of mound construction at the sites. Comparison of OSL and radiocarbon ages on materials from the same or closely related contexts provides insight into factors influencing age determinations in mound fill deposits, particularly the type of construction material (sand or shell) and the manner in which these were deposited. The results contribute to the understanding of the temporal context of platform mound construction in southeastern USA.     

Land‐use Effects on Anion‐associated Cation Leaching in Response to Above‐normal Precipitation

Fertilizers and liming agents are generally used to achieve optimal economic yields. However, several negative effects of long‐term annual fertilization of nitrogen (N) in particular have been observed, such as reduced cation exchange capacity and decreased base saturation, which may stimulate accelerated leaching loss of other nutrients. Equilibrium‐tension lysimeters installed at a depth of 1.4 m were used to evaluate leaching of soil‐solution ionic constituents from a tallgrass prairie restoration and optimally and deficiently N‐fertilized, no‐tillage (NT) and chisel‐plowed (CP) maize (Zea mays L.) agroecosystems on Plano silt loam soil (fine‐silty, mixed, superactive, mesic Typic Argiudoll). This study was conducted in south‐central Wisconsin, USA during a 1‐year period of above‐normal precipitation between January 2000 and January 2001. The loss of soluble constituents added to agroecosystems to maintain adequate soil fertility and pH, such as N, phosphorus, potassium, calcium, and magnesium, was generally numerically smaller from the natural prairie 25 years after conversion from cultivated agriculture than from optimally and deficiently N‐fertilized, NT and CP maize agroecosystems, though the differences were not significant. Tillage and fertilizer N‐rate generally did not significantly affect drainage, ionic concentrations, or their leaching losses in the maize agroecosystems, though all parameters evaluated tended to be numerically smaller in the deficiently than optimally N‐fertilized maize agroecosystems. Nitrate‐N leaching losses were generally significantly positively correlated with leaching losses of K, Ca, Mg, and Na in the maize agroecosystems, but not for the prairie, indicating that nitrate‐N leaching plays a significant role in the concomitant loss of cations to maintain soil‐solution charge balance in N‐fertilized maize agroecosystems in a temperate environment.     

Herbicide contamination and the potential impact to seagrass meadows in Hervey Bay, Queensland, Australia

Low concentrations of herbicides (up to 70 ng l(-1)), chiefly diuron (up to 50 ng l(-1)) were detected in surface waters associated with inter-tidal seagrass meadows of Zostera muelleri in Hervey Bay, south-east Queensland, Australia. Diuron and atrazine (up to 1.1 ng g(-1) dry weight of sediment) were detected in the sediments of these seagrass meadows. Concentration of the herbicides diuron, simazine and atrazine increased in surface waters associated with seagrass meadows during moderate river flow events indicating herbicides were washed from the catchment to the marine environment. Maximum herbicide concentration (sum of eight herbicides) in the Mary River during a moderate river flow event was 4260 ng l(-1). No photosynthetic stress was detected in seagrass in this study during low river flow. However, with moderate river flow events, nearshore seagrasses are at risk of being exposed to concentrations of herbicides that are known to inhibit photosynthesis.     

Effect of Bioremediation on the Microbial Community in Oiled Mangrove Sediments

Bioremediation was conducted in the field on a mature Rhizophora stylosa mangrove stand on land to be reclaimed near Fisherman’s Landing Wharf, Gladstone Australia. Gippsland crude oil was added to six large plots (>40 m²) and three plots were left untreated as controls. Bioremediation was used to treat three oiled plots and the remaining three were maintained as oiled only plots. The bioremediation strategy consisted of actively aerating the sediment and adding a slow-release fertilizer in order to promote oil biodegradation by indigenous micro-organisms. Oil addition stimulated the numbers of alkane-degrading bacteria slightly to levels of 10⁴–10⁵/g sediment. Bioremediation of the oiled sediment had a marked effect on the alkane-degrading population, increasing the population size by three orders of magnitude from 10⁵ to 10⁸ cells/g of sediment. An effect of bioremediation on the growth of aromatic-degraders was detected with numbers of aromatic-degraders increasing from 10⁴ to 10⁶ cells/g of sediment. Active aeration and nutrient addition significantly stimulated the growth of hydrocarbon-degraders in oiled mangrove sediment in the field.     

Implications of ozone depletion for surface-water photochemistry: Sensitivity of clear lakes

Increased ultraviolet-B radiation (UV-B) in aquatic ecosystems brought about by stratospheric ozone depletion may result in increased formation rates of photochemical reaction products in the surface waters of aquatic ecosystems. In this study, the potential impact of increases in lower wave-length radiation on the formation of hydrogen peroxide (H₂O₂) and singlet oxygen (¹O₂) was modelled for lakes over a range of dissolved organic carbon (DOC) concentrations. The impact of increased UV-B radiation on the production of carbon monoxide (CO) was also calculated for two humic stained systems. The relative increases of H₂O₂ and¹O₂ production were greater in the clear lakes (70% increase in photochemical reaction rates near the surface) than the coloured systems (25%). Production of CO in the study sites also increased under depleted ozone conditions implying increased DOC losses to the overlying atmosphere.     

N2-Ar-He systematics and source of ore-forming fluid in Changkeng Au-Ag deposit, central Guangdong, China*

Changkeng Au-Ag deposit is a newly-discovered new type precious metal deposit. N₂-Ar-He systematics studies and³He/⁴He and δD- δ¹⁸O composition analyses show that the ore-forming fluid of the deposit is composed mainly of formation water (sedimentary brine) but not of meteoric water, which was thought to be source of the ore-forming fluid by most previous researchers. The content of mantle-derived magmatic water in the ore-forming fluid is quite low, usually lower than 10%. According to the source of the ore-forming fluid, the Changkeng Au-Ag deposit should belong to sedimentary brine transformed deposits. From the Late Jurassic to the Early Cretaceous Period, with deposition and accumulation of thick sediments in Sanzhou Basin, the formation water in the sedimentary layers was expelled from the basin because of overburden pressure and increasing temperature. The expelled fluid moved laterally along sedimentary layers to the margin of the basin, and finally moved upward along a gently-dipping interlayer fault. Because of a decline in pressure and temperature, ore minerals were deposited in the fault. Project supported by the National Natural Science Foundation of China (Grant No. 495020291, the Natural Science Foundation of Zhongshan University, the Research Foundation of National Key Laboratory of Metallogenesis in Nanjing University (Grant No. 039704) and the Lingnan Foundation.