Improved direct push technologies: Quicker and cheaper on-site methods for sampling and monitoring

Cost-effective remedial action is dependent on clear identification of site conditions and accurate delineation of contamination. Many site cleanups have been hampered by complex subsurface conditions. Standard drilling and monitoring well installations have proven to be costly and time-consuming. Improved direct push technologies, however, are being developed to perform quicker and less expensive on-site sampling and testing. This article describes the benefits of improved direct push technologies.     

The investment climate for gold mining

This analysis compares the gold mining industry investment climate in the USA to the investment climate in Australia. These two major gold producing nation's industries share many similarities; in both the USA and Australia, there is evidence of a maturing gold mining industry. Each country has experienced a dramatic increase in gold production and, more recently, greater mining of refractory ore and development of more underground operations. In the 1980s both nations experienced a pronounced rationalization trend that consolidated some gold producing operations and eliminated others. Each country commands a disproportionately large share of exploration expenditures. Land access, a major concern in the USA, has also become a critical issue in Australia as well. For all their similarities, however, the two countries have differences that are significant enough to influence mining company investment decisions. This paper explores those differences and how they may affect the future course of these nations' gold mining industries. Both effective government policy making and corporate strategic planning will occupy a major role in the future course of the two nations' gold mining industries .     

Search costs influence the spatial distribution,but not the level,of extra-pair mating in tree swallows

Costs of searching for a mate are an important component of models of sexual selection, yet they have rarely been examined in wild populations of vertebrates. In this paper, we report an experiment in which we handicapped female tree swallows by clipping some flight feathers. This manipulation increased the costs of flight and searching for extra-pair mates. Despite these costs, handicapped females had the same level of extra-pair mating (percentage of extra-pair young, percentage of broods with extra-pair young, and the number of extra-pair sires per brood) as control females. However, handicapped females were more likely to have young sired by extra-pair males that lived closer to her nest than control females. This change in the distribution of extra-pair mating was most likely due to female choice rather than male coercion, and it suggests that extra-pair mating has significant benefits to females. One important implication of our study is that ecological and social factors that influence search costs could affect the spatial distribution of extra-pair sires and, consequently, the intensity of sexual selection. These effects may have been overlooked in previous studies that did not identify extra-pair sires.     

Trade-offs in foraging success and predation risk with spatial position in colonial spiders

Summary Colonial web-building spiders respond to trade-offs between selective forces relative to spatial position within colonies and thus provide support for the selfish herd theory. The size distribution of spiders within colonies of Metepeira incrassata, a colonial orb-weaver (Araneae: Araneidae) from tropical Mexico is nonrandom; larger (mature) spiders and females guarding eggsacs are more prevalent in the center, whereas more small (immature) spiders are found on the periphery. Experimental field studies with spiders of selected size classes show that larger spiders actively and aggressively seek protected positions in the center of the colony webbing, even though prey availability and capture rates are significantly higher on the periphery. Attacks by predatory wasps, other spiders, and hummingbirds are more frequent on the periphery than in the core of the colony. Reproductive females on the periphery are at greater risk because they are captured more often than smaller spiders, and if their egg sacs consequently remain unguarded, chances of cocoon parasitism are increased. As a result, spiders in the core of the colony have greater reproductive success, producing more egg sacs with greater hatching frequency. Colonial spiders thus appear to be making a trade-off between foraging and protection from predation and show a spatial organization predicted by the selfish herd theory. The influence of such trade-offs on individual fitness and the structure of colonies is discussed. Offprint requests to: G.W. Uetz     

The effects of feeding by the black bean aphidAphis fabae Scop. (Homoptera: Aphididae) on copper and cadmium accumulation in broad bean (Vicia faba L.)

Broad beans (Vicia faba L.), cultured hydroponically were supplied with 100 g mL^–1 copper or 50 g mL^–1 cadmium in nutrient solution. Samples of plant material from both nutrient regimes were analysed before and after infestation by the black bean aphid (Aphis fabae Scop.). Heavy aphid infestation resulted in a significant reduction in copper content of shoots in comparison with uninfested plants. A similar, but less well- defined, situation occurred in the case of cadmium.Further investigations examined the effects of different levels of aphid infestation on the above phenomena. In all cases the presence of feeding aphids reduced elemental accumulation in plant shoots. Long term infestation with population densities as low as three adult aphids showed a reduction in shoot copper and cadmium content.     

Egg removal and intraspecific brood parasitism in the European starling (Sturnus vulgaris)

Summary From 1983 to 1986 we monitored 284 European starling (Sturnus vulgaris) nests in New Jersey for evidence of intraspecific brood parasitism and egg removal during the laying period. Egg removal occurred significantly more often at nests where intraspecific brood parasitism was detected (12 of 35 nests, 34%) than at unparasitized nests (23 of 249 nests, 9%). Brood parasitism (92% of parasitized nests) and egg removal (74% of nests with egg removal) were most common at nests where egg laying began in April of each year (i.e., early nests). Egg removal occurred at 26 (19%) and brood parasitism at 32 (23%) of 138 early nests. Both brood parasitism and egg removal were concentrated during the first four days in the laying period when brood parasitism is most likely to be successful and when host nests are most vulnerable to parasitism (Romagnano 1987). Both parasitism and removal usually involved a single egg at each nest. We detected brood parasitism and egg removal on the same day at five of 12 nests (42%) where both were observed. Because starlings do not remove foreign eggs from their nests once they begin laying (Stouffer et al. 1987) we hypothesize that parasite females sometimes removed host eggs while parasitizing nests.     

Spatio-temporal Analysis of Acute Admissions for Ischemic Heart Disease in NSW,Australia

The recently funded Spatial Environmental Epidemiology in New South Wales (SEE NSW) project aims to use routinely collected data in NSW Australia to investigate risk factors for various chronic diseases. In this paper, we present a case study focused on the relationship between social disadvantage and ischemic heart disease to highlight some of the methodological challenges that are likely to arise.     

An improved activated carbon method to quantify dichlorodiphenyltrichloroethane (DDT) in surface water

Currently, South Africa is designing a strategy for surface water protection involving organic contaminants such as dichlorodiphenyltrichloroethane (DDT), which is currently used for malaria control in mosquito-infested areas. Here, we demonstrate the successful use of an improved activated carbon technique using dichloromethane instead of chloroform, and slower leaching rate of 15 mL/min to quantify DDT and its metabolites in surface water. The recovery tests for 2,4′DDT, 2,4′DDD, 2,4′DDE, and 4,4′DDT, 4,4′DDD, 4,4′DDE ranged from 75 to 84% and 87 to 96%, respectively (DDE: dichlorodiphenyldichloroethylene, DDD: dichlorodiphenyldichloroethane). The main advantages of this technique over conventional liquid–liquid extractions are reduced amount of organic solvent, little sample preparation, and larger sample throughput. Because activated charcoal is fairly cheap, the technique can be routinely used to quantify and monitor DDT and its metabolites in surface water samples.     

GC/MS分析20种纺织品和消费品中禁止使用的胺类致癌物和印染处理废水的环境监测中出现的胺类致癌物

一些偶氮染料用于纺织品和其它材料会产生胺类致癌物,这类物质从两个途径危害健康:一是消费者直接接触产品,二是印染厂产生的废水及污泥对环境水的污染.德国已经禁止某些含有这种超过规定浓度限量的胺类染料货物进口,使用质谱(MS)方法分析测定其含量.在德国规定用6890气相色谱仪/5973质谱检测器检测有关纺织品和其它消费品中有害物质的浓度限量,这一规定很适宜而且优于其它方法,例如,使用脉冲不分流进样和质谱的SIM模式检测方法,其检测限(LOD)是5ng·ml-1(ppb),这样低的检测限为分析人员提供了很大的方便:可以检测出浓度样品的低限,或者不要使用繁琐的样品处理方法,可以节约劳力从而增加分析样品的数量,而且,可以达到低的LOD并改善了数据处理的能力,适合环境样品的分析,用以检测印染厂废水中的污染物.利用能力卓越的MSD Productivity ChemStation,可以打印出符合用户需要的分析报告.     

Entrapment and dissolution of DNAPLs in heterogeneous porous media

Two-dimensional multiphase flow and transport simulators were refined and used to numerically investigate the entrapment and dissolution behavior of tetrachloroethylene (PCE) in heterogeneous porous media containing spatial variations in wettability. Measured hydraulic properties, residual saturations, and dissolution parameters were employed in these simulations. Entrapment was quantified using experimentally verified hydraulic property and residual saturation models that account for hysteresis and wettability variations. The nonequilibrium dissolution of PCE was modeled using independent estimates of the film mass transfer coefficient and interfacial area for entrapped and continuous (PCE pools or films) saturations. Flow simulations demonstrate that the spatial distribution of PCE is highly dependent on subsurface wettability characteristics that create differences in PCE retention mechanisms and the presence of subsurface capillary barriers. For a given soil texture, the maximum and minimum PCE infiltration depth was obtained when the sand had intermediate (an organic-wet mass fraction of 25%) and strong (water- or organic-wet) wettability conditions, respectively. In heterogeneous systems, subsurface wettability variations were also found to enhance or diminish the performance of soil texture-induced capillary barriers. The dissolution behavior of PCE was found to depend on the soil wettability and the spatial PCE distribution. Shorter dissolution times tended to occur when PCE was distributed over large regions due to an increased access of flowing water to the PCE. In heterogeneous systems, capillary barriers that produced high PCE saturations tended to exhibit longer dissolution times.