Characterization of flow and transport processes within the unsaturated zone of Yucca Mountain, Nevada, under current and future climates

This paper presents a large-scale modeling study characterizing fluid flow and tracer transport in the unsaturated zone of Yucca Mountain, Nevada, a potential repository site for storing high-level radioactive waste. The study has been conducted using a three-dimensional numerical model, which incorporates a wide variety of field data and takes into account the coupled processes of flow and transport in the highly heterogeneous, unsaturated fractured porous rock. The modeling approach is based on a dual-continuum formulation of coupled multiphase fluid and tracer transport through fractured porous rock. Various scenarios of current and future climate conditions and their effects on the unsaturated zone are evaluated to aid in the assessment of the proposed repository's system performance using different conceptual models. These models are calibrated against field-measured data. Model-predicted flow and transport processes under current and future climates are discussed.     

Patterns of development and succession of vegetated hummocks in slacks of the Alexandria coastal dune field, South Africa

Dune hummocks (small aeolian dunes formed by sand deposition in and around pioneer plants) are the smallest vegetated dune unit; they occur along the entire South African coastline but are poorly studied. Structural properties and distribution of the two main hummock-forming plants:Arctotheca populifolia (a pioneer species with fast growth rate and rapid turnover) andGazania rigens (a later colonizer with slower growth) were investigated. A marked vegetation succession exists across the floor of the slack as a result of the migration of transverse dune ridges across the slack.Arctotheca hummocks were initiated on the newly exposed eastern margin of the slack, and were replaced about midway across the width of the slack byGazania hummocks. Hummocks increased in size with distance from the eastern side of the slack.Gazania hummocks attain a greater vegetation height, support a greater vegetation complexity and mass, and attain a larger maximum size thanArctotheca hummocks. Succession, defined as both the replacement of plant species as well as site modification within the plants over time, was evident. Since the growth form and dynamics determine (1) the ability of plants to trap wind-borne soil and detritus, (2) the shape of the hummocks, and (3) the habitat complexity available to spiders and insects, the ecology of the hummocks is probably determined largely by the vegetation characteristics of the hummock-forming plants.     

Discharge From the Edwards Aquifer Through the Leona River Floodplain,Uvalde, Texas1

Abstract: Analysis of results from an electrical resistivity survey, a magnetic survey, and an aquifer test performed on the Leona River floodplain in south‐central Texas indicates that ground‐water discharge from the Edwards Aquifer through the Leona River floodplain may be as great as 91.7 Mm³/year. When combined with an estimate of 8.8 Mm³/year for surface flow in the Leona River, as much as 100.5 Mm³/year could be discharged from the Edwards Aquifer through the Leona River floodplain. A value of 11,200 acre‐ft/year (13.82 Mm³/year) has been used as the calibration target in existing ground‐water models for total discharge from Leona Springs and the Leona River. Including ground water or underflow discharge would significantly increase the calibration target in future models. This refinement would improve the conceptualization of ground‐water flow in the western portion of the San Antonio segment of the Edwards Aquifer and would thereby allow for more accurate assessment and management of the ground‐water resources provided by the Edwards Aquifer.     

镉和铁及其交互作用对植物生长的影响

镉是植物的非必需元素，而铁是植物生长发育过程中必不可少的元素。虽然这两种元素对植物的作用是截然相反的，但是它们在植物体内存在着交互作用关系，相互影响着对方功能的发挥。供给植物足够的铁可极大地缓解植物的镉污染毒害，利于植物合成更多的叶绿素，促进光合作用进行，降低镉对氨基酸、蛋白质合成以及酶活性的影响。相反，镉污染将诱导植物的铁营养缺乏。渍水植物根表形成的铁氧化物胶膜可促进植物对镉的吸收。     

An investigation into the energy use in relation to yield of rice (Oryza sativa) in Assam, India

Energy use scenario and resulting rice yield of 576 farms belonging to six agroclimatic zones of Assam, India were investigated. Input energy from eight distinct sources, viz., human, animal, diesel, commercial chemical fertilizer, farm yard manure (FYM), seed, pesticide chemical and machinery were determined on the basis of collected data and using standard procedure. Based on the power sources used and application of commercial chemical fertilizer, four categories of farms were delineated: (i) animal power without commercial fertilizer (APNF), (ii) animal power with commercial fertilizer (APF), (iii) mechanical power without commercial fertilizer (MPNF) and (iv) mechanical power with commercial fertilizer (MPF). The best-fit curve of energy versus yield indicated that use of commercial chemical fertilizer and mechanical power resulted in higher rice yield at higher level of input energy. Moreover, as the use of energy increased the yield increased up to maxima and then declined at higher levels of energy. This was observed in all four categories of farms with variation in yield–energy values. The average values of energy input (MJ ha⁻¹) and corresponding yield (kg ha⁻¹) for the APNF, APF, MPNF and MPF type of farms were (5220, 1980); (9050, 3170); (5100, 2360) and (8320, 3800), respectively. Renewable energy dominated the rice cultivation in Assam contributing more than 50% of the total input energy with the exception of MPF category of farm where share of renewable and non-renewable were found to be almost equal. Among the farm operations, tillage was the highest energy consuming operation followed by threshing, harvesting and transplanting for all four categories of farms. However, it was observed that rice yield was not positively correlated with tillage energy.     

Profiling the antibiotic resistome in soils between pristine and human-affected sites on the Tibetan Plateau

With increasing pressure from anthropogenic activity in pristine environments, the comprehensive profiling of antibiotic resistance genes(ARGs) is essential to evaluate the potential risks from human-induced antibiotic resistance in these under-studied places. Here, we characterized the microbial resistome in relatively pristine soil samples collected from four distinct habitats on the Tibetan Plateau, using a Smart chip based high-throughput q PCR approach. We compared these to soils from the s...     

Interspecific interactions of amphipods <Emphasis Type="Italic">Gammarus lacustris</Emphasis> and <Emphasis Type="Italic">Gmelinoides fasciatus</Emphasis>

Experimental studies of interactions between two amphipod species (Gmelinoides fasciatus and Gammarus lacustris) showed that predation is the basic mechanism accounting for their mutual exclusion in nature. Mortality from predation among similar-sized specimens of both species at an equal abundance ratio was similar (24–25% in G. lacustris and 27–30% in G. fasciatus). The displacement of G. lacustris by G. fasciatus was observed when the latter was dominant. Adult G. fasciatus and G. lacustris successfully preyed on juveniles of their competitors and did not differ significantly in daily food consumption as a percentage of body weight: 6–24% at a fresh body weight of 18–24 mg in both species. The potential for rapid population growth under new conditions contributed to the success of the invasive Baikal species G. fasciatus in displacing G. lacustris from many water bodies of Russia.     

Preventing behavioural interactions with a male facilitates sex change in female bluebanded gobies, Lythrypnus dalli

Sex change in marine teleost fishes is commonly regulated by social factors. In species that exhibit protogynous sex change, such as the bluebanded goby Lythrypnus dalli, the most dominant female typically initiates sex change when a male is removed from the social group. Females can use visual, chemical or tactile cues to assess the presence or absence of a male. The primary goal of our study was to determine whether the olfactory and visual presence of a male versus its behavioural interactions with females were important for mediating sex change. We exposed females to three different treatments: absence of a male, presence of a male that could physically interact with her and presence of a male behind a barrier that allowed visual and olfactory interactions but prohibited physical interactions. Sex change occurred in the absence of a male but not in the presence of a male that could physically interact with the female. The presence of a male behind the barrier did not prevent sex change but affected the timing of sex change. Season appeared to affect the latency to initiate male typical courtship, with a delay at the end of the reproductive season only when the male was present behind the barrier. We discuss the seasonal results in terms of L. dalli life history and the potential benefits and costs of changing sex late in the season in the presence or absence of aggressive reinforcement by the male. Our results identify direct behavioural interactions as an important proximate mechanism in the social regulation of sex change in L. dalli.     

Constitutive or induced defences - how does <Emphasis Type="Italic">Eucalyptus globulus</Emphasis> defend itself from larval feeding?

Summary. Following herbivory, induced responses involving plant secondary metabolites have been reported in a number of tree species. Although a wide range of plant secondary metabolites appear to operate as constitutive plant defences in trees belonging to the Eucalyptus genus, no induced responses have as yet been reported following foliar-chewing insect damage. We empirically tested whether branch defoliation (artificial and larval) of 2-year-old Eucalyptus globulus Labill. trees altered the abundance of specific plant secondary metabolites immediately (3 months after initial larval feeding) and 8 months after the cessation of larval feeding. Metabolites assayed, included essential oils, polyphenolic groups and foliar wax compounds and in all cases their abundance was not significantly altered by defoliation. However, the level of foliar tannins after 3 months of larval feeding did display a trend that suggested elevated levels as the result of defoliation, though this trend was not evident 8 months later, indicating that, if real, the response was a rapid and not a delayed induced response. The level of foliar tannins was also negatively correlated to both average larval survival and average percentage branch defoliation, suggesting that foliar tannins may operate as toxins and/or anti-feedants to M. privata larval feeding.     

畜粪污染处理与利用研究

国内外对于粪便固体物的处理主要采用焚烧法、干燥法和堆肥法等，在粪便污水处理方面主要采用厌氧消化法，它将治污、产气和综合利用相结合，使废物资源化，达到环境效益、经济效益和社会效益相统一。