A Comparative Study of Distribution of Heavy Metal Concentrations in the Pomacea insularum Collected from Polluted and Unpolluted Sites of the Freshwater Ecosystem in Malaysia

The snails (Pomacea insularum) were collected from polluted and unpolluted sites at Juru River and the Universiti Putra Malaysia Lake, respectively. Besides the shells, the soft tissues of snails were dissected into 6 different parts: intestine, operculum, foot, pennial sac, lung sac and the remainder. They were analyzed for the concentrations of Cu, Cd, Zn, Pb, Ni and Fe. The present study found 6 interesting points. First, all the metal levels found in the different parts of P. insularum collected from Juru River were significantly (p<0.05) higher than those in the snails of unpolluted lake. These results were also supported by the sediment data in which the Juru River sediment had significantly (p<0.05) higher levels of metal than those in the unpolluted lake. Second, the high levels of Cd and Pb were found in the shell of P. insularum, indicating that it is a potential biomonitoring material for these metals. Third, intestine accumulated elevated levels of Zn, Ni and Fe and thus is a potential biomonitoring organ for the 3 metals. Fourth, high levels of Cu were found in the lung sac and this phenomenon could be related to this metal binding to metallothionein in this organ. Fifth, elevated level of Pb found in the soft tissues of P. insularum indicated that this snail is not suitable for human consumption since its pollution level was higher than the food safety guideline for Pb. Sixth, there was no significant difference (p>0.05) between the different sizes (small sizes: 30.5-33.2 mm; large sizes: 37.7-40.4 mm) of P. insularum. The first 5 points supported the use of different soft tissues of P. insularum as biomonitoring organs of heavy metal pollution in the freshwater ecosystem in Malaysia although further validation is required.     

Geophysical greenfield exploration in the permo‐carboniferous Saar–Nahe basin—The Wiesbaden Geothermal Project,Germany

Structurally bound upwelling and outflowing hot fluids in the city of Wiesbaden suggest an interesting geothermal potential at the northern margin of the permo‐carboniferous Saar–Nahe basin, Germany. The Saar–Nahe basin in the Wiesbaden area was previously not a target for intensive geophysical prospecting of the deep underground. We present an exploration concept to investigate potential geothermal reservoirs near Wiesbaden for heat and power production. The acquired geophysical exploration data give new insights into the local geometry and internal structure of the Saar–Nahe basin. The exploration combines a wide range of methods, including the analysis of data, a dense grid gravity survey, as well as two‐dimensional and three‐dimensional seismic surveys. The resulting data, which for the first time reveal the deep structure of the Mainz and Saar–Nahe basins near Wiesbaden down to a depth of c. 4,000 m, show that the Saar–Nahe basin is strongly segmented and contains deep‐reaching active faults. Combining these information with numerical models of the stresses in the fault system and of the temperature distribution in the exploration area, a promising drilling target has been identified, which promise high permeability at a low risk of induced or triggered seismicity.     

Numerical Modeling of Methane Leakage from a Faulty Natural Gas Well into Fractured Tight Formations

Horizontal drilling and hydraulic fracturing have enabled hydrocarbon recovery from unconventional reservoirs, but led to natural gas contamination of shallow groundwaters. We describe and apply numerical models of gas‐phase migration associated with leaking natural gas wells. Three leakage scenarios are simulated: (1) high‐pressure natural gas pulse released into a fractured aquifer; (2) continuous slow leakage into a tilted fractured formation; and (3) continuous slow leakage into an unfractured aquifer with fluvial channels, to facilitate a generalized evaluation of natural gas transport from faulty natural gas wells. High‐pressure pulses of gas leakage into sparsely fractured media are needed to produce the extensive and rapid lateral spreading of free gas previously observed in field studies. Transport in fractures explains how methane can travel vastly different distances and directions laterally away from a leaking well, which leads to variable levels of methane contamination in nearby groundwater wells. Lower rates of methane leakage (≤1 Mcf/day) produce shorter length scales of gas transport than determined by the high‐pressure scenario or field studies, unless aquifers have low vertical permeabilities (≤1 millidarcy) and fractures and bedding planes have sufficient tilt (～10°) to allow a lateral buoyancy component. Similarly, in fractured rock aquifers or where permeability is controlled by channelized fluvial deposits, lateral flow is not sufficiently developed to explain fast‐developing gas contamination (0‐3 months) or large length scales (～1 km) documented in field studies. Thus, current efforts to evaluate the frequency, mechanism, and impacts of natural gas leakage from faulty natural gas wells likely underestimate contributions from small‐volume, low‐pressure leakage events.     

Naïve Simplicity: The Overlooked Piece of the Complexity‐Simplicity Paradigm

Concepts of simplicity and complexity in modeling have been explored in papers, editorials, and talks. The concept is not well understood because there are at least two flavors of simplicity. Modelers envision simplicity (i.e., elegant simplicity) as the sought‐after goal in modeling, but naïve simplicity, which is the focus of this paper, is commonly unrecognized and dangerous. The problem is that naïve or simple ideas are often mistaken for settled science and come with the prospect of being more wrong than right. The concept of the so‐called simplicity cycle, in relation to classical problems of carbon‐14 age and salinity in closed‐basin lakes, is used to illustrate these points. The emerging problems of water‐mosquitoes‐diseases show the value of mapping new problems to the simplicity cycle. Researchers can “know what they do not know” and avoid the dangers of naïve simplicity.     

Global Climate Change: Why U.S. Insurers Care

The number of natural catastrophes in this decade is four times greater than in the 1960s; economic losses are eight times greater; and insured losses are 15 times greater. The insurance industry's financial interest is inter-dependent with climate and weather. Natural events drive the demand for insurance coverage and can threaten the viability of an insurer if it is over-exposed in high risk areas. Early in the 1990s, the industry began to recognize that historical data were potentially misleading with respect to future natural catastrophe exposure. The U.S. insurance industry is pursuing a variety of new approaches including: the use of catastrophe computer models to integrate the natural knowledge about extreme events taken from the sciences into the actuarial sciences. The evaluation of building codes and building code enforcement in every community in the country enhanced its support for hazard mitigation.     

A paleoclimate record for the past 250,000 years from Summer Lake, Oregon, USA. 1. chronology and magnetic proxies for lake level

This study presents the age control and environmental magnetism components of a new, late Pleistocene paleoclimate record for the Great Basin of western North America. Two new cores from the Summer Lake sub-basin of pluvial Lake Chewaucan, Oregon, USA are correlated to basin margin outcrops on the basis of tephrochronology, lithostratigraphy, sediment magnetism and paleomagnetic secular variation. Eleven tephra layers were found in the cores that correlate to tephra identified previously in the outcrop. The Olema ash was also found in one of the cores; its stratigraphic position, relative to 3 dated tephra layers, indicates that its age is 50-55 ka, somewhat younger than has been previously reported. The Summer Lake sediments are divided into deep and shallow lake lithosomes based on sedimentary features. The stratigraphic position of these lithosomes support the tephra-based correlations between the outcrop and the cores. These sediments contain a well resolved record of the Mono Lake Excursion (MLE) and an earlier paleomagnetic excursion as well as a high quality replication of the paleosecular variation immediately above the MLE.Relative sedimentation rates increased dramatically toward the depocenter during intervals of low-lake level. In contrast, during intervals of high-lake level, relative sedimentation rates were comparable along the basin axis from the basin margin to the depocenter. The magnetic mineralogy of the Summer Lake sediments is dominated by pseudo-single domain (titano)magnetite and intervals of high/low magnetite concentration coincide with lithosomes that indicate high/low lake levels. Magnetic grain size also varies in accord with bulk sediment grain size as indicated by the silt/clay ratio. To a first order, variations in magnetic parameters, especially those attributable to the concentration of magnetic minerals, correlate well with global glacial/interglacial oscillations as indicated by marine oxygen isotope stages. This relationship can be explained by increased dissolution of (titano)magnetite minerals as lake level dropped and the lake became more productive biologically. This inference is supported by a correspondence between lower concentrations of magnetite with higher levels of total organic carbon and vice-versa.     

Dissolved oxygen criteria for freshwater fish in New Zealand: a revised approach

Maintenance of suitable conditions in lowland rivers for both fish passage and resident species is crucial to ensuring the long-term sustainability of fish populations. The dissolved oxygen concentration of water is a key factor controlling habitat quality for fish and a critical measure of stream health. Continued land use intensification and greater exploitation of water resources has contributed towards increasing the frequency and duration of low dissolved oxygen events in lowland rivers and the associated risk of adverse effects on fish communities. Revised guidelines are therefore proposed to support setting of biologically relevant dissolved oxygen limits for the protection of New Zealand freshwater fish communities. These guidelines account for both event magnitude and duration, identify different protection levels based on the risk of negative impacts and are based on current scientific knowledge on the tolerances of New Zealand fish species.     

Field and geochemical characteristics of the Coolac Ophiolite suite and its possible origin in a marginal sea

Geological and geochemical data from the Coolac Serpentinite Belt, North Mooney Complex and Honeysuckle Beds in southern New South Wales indicate that the association represents a partially dismembered ophiolite suite. All the ideal ophiolite units are present, although the sheeted dyke unit is apparently of limited extent. Major and trace element (including rare‐earth) results, relationships of mafic volcanics and dolerite to massive and layered gabbroic and ultramafic intrusives, the occurrence of tectonised harzburgite with podiform chromitite, and the nature of pyritic sulphide occurrences, are consistent with a marginal sea or back‐arc environment for the generation of the ophiolite suite.     

Mangrove litter fall: Extrapolation from traps to a large tropical macrotidal harbour

Mangrove litter is a major source of organic matter for detrital food chains in many tropical coastal ecosystems, but scant attention has been paid to the substantial challenges in sampling and extrapolation of rates of litter fall. The challenges arise due to within-stand heterogeneity including incomplete canopy cover, and canopy that is below the high tide mark. We sampled litter monthly for three years at 35 sites across eight mapped communities in the macrotidal Darwin Harbour, northern Australia. Totals were adjusted for mean community canopy cover and the occurrence of canopy below the high tide mark. The mangroves of Darwin Harbour generate an estimated average of 5.0 t ha⁻¹ yr⁻¹ of litter. This amount would have been overestimated by 32% had we not corrected for limited canopy cover and underestimated by 11% had we not corrected for foliage that is below the high tide mark. Had we made neither correction, we would have overestimated litter fall by 17%. Among communities, rates varied 2.6-fold per unit area of canopy, and 3.9-fold among unit area of community. Seaward fringe mangroves were the most productive per unit of canopy area but the canopy was relatively open; Tidal creek forest was the most productive per unit area of community. Litter fall varied 1.1-fold among years and 2.0-fold among months though communities exhibited a range of seasonalities. Our study may be the most extensively stratified and sampled evaluation of mangrove litter fall in a tropical estuary. We believe our study is also the first such assessment to explicitly deal with canopy discontinuities and demonstrates that failure to do so can result in considerable overestimation of mangrove productivity.