Modelling of physical and reactive processes during biodegradation of a hydrocarbon plume under transient groundwater flow conditions

Numerical experiments of non-reactive and reactive transport were carried out to quantify the influence of a seasonally varying, transient flow field on transport and natural attenuation at a hydrocarbon-contaminated field site. Different numerical schemes for solving advective transport were compared to assess their capability to model low transversal dispersivities in transient flow fields. For the field site, it is shown that vertical plume spreading is largely inhibited, particularly if sorption is taken into account. For the reactive simulations, a biodegradation reaction module for the geochemical transport model PHT3D was developed. Results of the reactive transport simulations show that under the site-specific conditions the temporal variations in groundwater flow do, to a modest extent, affect average biodegradation rates and average total (dissolved) contaminant mass in the aquifer. The model simulations demonstrate that the seasonal variability in groundwater flow only results in significantly enhanced biodegradation rates when a differential sorption of electron donor (toluene) and electron acceptor (sulfate) is assumed.     

The effect of low molecular weight chelators on iron chelation and free radical generation as studied by ESR measurement

The purpose of this work was to improve our current knowledge of the non-enzymatic mechanisms involved in brown rot fungal decay of wood, but also to improve our understanding of chelator-mediated reactions that may occur in other biological systems where low pH conditions may prevail. Several key steps (iron chelation and reduction) during early non-enzymatic wood decay processes have been studied by using electron spin resonance (ESR). It has been proposed that low molecular weight chelators as well as Fenton reagents are involved in brown rot decay, at least in early non-enzymatic stages. In this work, the binding between a catecholate model chelator and ferric iron was studied by ESR spectroscopy. The effects of the model chelator, Fenton reagents, as well as the reaction conditions on free radical generation were also studied using ESR spin-trapping techniques. The results indicate: (1) The relative quantity of the chelator-iron complex can be determined by measurement of the intensities of the characteristic g = 4.3 ESR signal. (2) The effects of the chelator:iron ratio, the pH, and other reaction parameters on the hydroxyl radical generation in a Fenton type system can be determined using ESR spin-trapping techniques. (3) Data support the hypothesis that superoxide radicals are involved in chelator-mediated Fenton processes.     

Multiple paternity in a wild population of northern water snakes,Nerodia sipedon

Summary For most animal species, a single mating is sufficient to fertilize all of a female's offspring. As a result, females do not usually increase their reproductive success with successive matings. However, multiple paternity has been discovered in many animal taxa. We demonstrate that the majority of female water snakes in a wild population mate with more than one male for each litter. Field observations indicated that a highly skewed operational sex ratio (3.6:1 M : F) during the breeding season, while not necessary for multiple paternity to occur, created ample opportunity for females to mate multiply. Protein electrophoretic analysis showed that at least 12 of 14 litters from naturally mated females had more than one father. Since male snakes can not force copulations, multiple matings seem likely to be the result of female choice. Offprint requests to: F.E. Barry     

Provisioning rules and chick competition in asynchronously hatching common terns (Sterna hirundo)

Interactions between nestling birds and their parents are models for examining parent–offspring communication and sibling competition. Most studies have focused on species where young are restricted to a nest. However, offspring of many species are mobile and fed by parents for an extended period post-hatch. These chicks mobility may provide an opportunity to examine the role of signalling and physical competition on parental feeding decisions. We examined parental provisioning rules in relation to offspring behaviour and hatching order (i.e., competitive ability) in a species with mobile young, the common tern. We determined that about 95% of feedings were directed to the first chick to reach the parent when it landed with food. We developed a probabilistic model to predict the likelihood of a chick reaching the parent first, and thus receiving food. Our model showed that begging intensity, feeding history, and the interaction between begging intensity and relative proximity to the parent best predicted which chick would arrive first. Increased begging was associated with arriving first significantly more when a chick was relatively further from the parent than when it was closer than its siblings. Independently of these factors, larger, earlier-hatched chicks were more likely to be fed than smaller, later-hatched chicks. Additional analyses showed that parents landed closer to more intensively begging chicks, however, increased begging did not explain the advantage of earlier-hatched chicks because begging intensity did not vary with hatching order. Instead, earlier-hatched chicks were more likely to outrun later-hatched siblings and reach the parent first.     

2007—2016年嘉峪关市城市绿地生态评价及障碍因子分析

对城市绿地进行科学评价有助于人们正确认识和改造城市绿地建设,为城市绿地规划和管理提供参考。以2007—2016年嘉峪关市城市绿地为研究对象,从数量、结构、功能三个方面构建评价指标体系,通过障碍度模型,识别影响城市绿地生态水平的障碍因子。结果表明：（1）10 a来嘉峪关市城市绿地生态水平整体呈波动上升趋势,级别由较低等级提高到高等级,但目前城市绿地生态水平属于低层次、不稳定的高等级阶段,城市绿地建设工作压力还很大。（2）从准则层看,嘉峪关市城市绿地生态水平的主要威胁变化较为明显,数量指标和结构指标是主要障碍因子;从指标层看,各年份主要障碍因子不尽相同,最大障碍因子历经了从人均公园绿地面积、树种丰富度到净化空气能力的演变。     

In‐well sediment incubators to evaluate microbial community stability and dynamics following bioimmobilization of uranium

An in‐well sediment incubator (ISI) was developed to investigate the stability and dynamics of sediment‐associated microbial communities to prevailing subsurface oxidizing or reducing conditions. Herein we describe the use of these devices at the Old Rifle Uranium Mill Tailings Remedial Action (UMTRA) site. During a seven‐month period in which oxidized Rifle Aquifer background sediment (RABS) were deployed in previously biostimulated wells under iron‐reducing conditions, cell densities of known iron‐reducing bacteria, including Geobacteraceae, increased significantly, showing the microbial community response to local subsurface conditions. Phospholipid fatty acid (PLFA) profiles of RABS following in situ deployment were strikingly similar to those of adjacent sediment cores, suggesting ISI results could be extrapolated to the native material of the test plots. Results for ISI deployment with laboratory‐reduced sediments showed only slight changes in community composition and pointed toward the ability of the ISI to monitor microbial community stability and response to subsurface conditions. © 2009 Wiley Periodicals, Inc.     

Warfare in Biodiversity Hotspots

Abstract:  Conservation efforts are only as sustainable as the social and political context within which they take place. The weakening or collapse of sociopolitical frameworks during wartime can lead to habitat destruction and the erosion of conservation policies, but in some cases, may also confer ecological benefits through altered settlement patterns and reduced resource exploitation. Over 90% of the major armed conflicts between 1950 and 2000 occurred within countries containing biodiversity hotspots, and more than 80% took place directly within hotspot areas. Less than one-third of the 34 recognized hotspots escaped significant conflict during this period, and most suffered repeated episodes of violence. This pattern was remarkably consistent over these 5 decades. Evidence from the war-torn Eastern Afromontane hotspot suggests that biodiversity conservation is improved when international nongovernmental organizations support local protected area staff and remain engaged throughout the conflict. With biodiversity hotspots concentrated in politically volatile regions, the conservation community must maintain continuous involvement during periods of war, and biodiversity conservation should be incorporated into military, reconstruction, and humanitarian programs in the world's conflict zones.     

Studies on Soil Microarthropods Associated With Mechanic Workshops in Benin City

This study assessed the abundance of soil microarthropods in the soil in proximity to three auto mechanic workshops in Benin City, Nigeria, to determine the effect of petroleum hydrocarbon wastes on these organisms. A Berlese funnel was used to collect the microarthropods from soil samples collected from one mechanic workshop located in each of the three local government areas within Benin City: Oredo (site 1), Egor (site 2), and Ikpoba‐Okha (site 3). A Control Site soil sample was also collected from an area where no mechanic workshops were present. Inspection of the soil samples revealed a total number of 198 soil microarthropods belonging to two classes (Insecta and Acarina), eight families, and 10 species: Achegozetes longisetosus, Dermatophagoides pteronyssinus, Eremaeus columbianus, Eremaeus oblongus, Euzetes globules, Isotomurus palustris, Phlebotomus duboscqi, Solenopsis invicta, Hydrachna magnicutata, and an unidentified species were recorded. S. invicta was the most abundant, whereas the least abundant were E. columbianus, E. oblongus, and E. globules. Although there were no significant differences (p > 0.05) in mean temperature, pH, or soil moisture content across the study sites, there was a significant difference (p < 0.01) in the mean total hydrocarbon content (THC) measurements for sites 1, 2, 3, and the Control Site (48.62 ± 6.19, 51.70 ± 4.86, 52.69 ± 4.58, and 0.05 ± 0.01, respectively). Furthermore, soil microarthropod abundance and physiochemical parameters were evenly distributed from month to month. We observed a negative correlation of THC with soil microarthropod abundance across sites, although the microarthropods abundance was independent of the THC concentrations (expressed in parts per million [ppm]). In addition, although our analysis revealed no significant difference (p > 0.05) in microarthropod abundance across sites 1 through 3, abundance varied significantly (p < 0.05) between sites 1 through 3 collectively when compared with the abundance observed in samples from the Control Site. The implication of this survey is that the indiscriminate dumping of spent oils onto the soil has adverse effects on both the environment and the abundance of soil microarthropods.     

Atmospheric oxidation capacity in the summer of Houston 2006: Comparison with summer measurements in other metropolitan studies

Both similarities and differences in summertime atmospheric photochemical oxidation appear in the comparison of four field studies: TEXAQS2000 (Houston, 2000), NYC2001 (New York City, 2001), MCMA2003 (Mexico City, 2003), and TRAMP2006 (Houston, 2006). The compared photochemical indicators are OH and HO₂ abundances, OH reactivity (the inverse of the OH lifetime), HO_x budget, OH chain length (ratio of OH cycling to OH loss), calculated ozone production, and ozone sensitivity. In terms of photochemical activity, Houston is much more like Mexico City than New York City. These relationships result from the ratio of volatile organic compounds (VOCs) to nitrogen oxides (NO_x), which are comparable in Houston and Mexico City, but much lower in New York City. Compared to New York City, Houston and Mexico City also have higher levels of OH and HO₂, longer OH chain lengths, a smaller contribution of reactions with NO_x to the OH reactivity, and NO_x-sensitivity for ozone production during the day. In all four studies, the photolysis of nitrous acid (HONO) and formaldehyde (HCHO) are significant, if not dominant, HO_x sources. A problematic result in all four studies is the greater OH production than OH loss during morning rush hour, even though OH production and loss are expected to always be in balance because of the short OH lifetime. The cause of this discrepancy is not understood, but may be related to the under-predicted HO₂ in high NO_x conditions, which could have implications for ozone production. Three photochemical indicators show particularly high photochemical activity in Houston during the TRAMP2006 study: the long portion of the day for which ozone production was NO_x-sensitive, the calculated ozone production rate that was second only to Mexico City's, and the OH chain length that was twice that of any other location. These results on photochemical activity provide additional support for regulatory actions to reduce reactive VOCs in Houston in order to reduce ozone and other pollutants.