Modeling Flow Through a One-Dimensional Multi-Layered Soil Profile Using the Method of Lines

The vertical flow of water through horizontal layers of soil is considered using the Method of Lines. Continuity of mass principles are used to develop the interface boundary conditions, by introducing fictitious points at the interface, and the boundary conditions are handled using explicit and iterative approximations. Both the pressure based, and the water content based forms of Richards' equation are solved using the Method of Lines. The solutions obtained are compared with some particular analytic solutions obtained from the literature, and the results show that good accuracy can be achieved. It is also shown that the water content model can handle a large discontinuity at the interface when compared against the analytical solution. This result is also confirmed against a numerical example from the literature, and was effective for relatively dry initial conditions.     

Preparing future engineers for challenges of the 21st century: Sustainable engineering

The field of engineering is changing rapidly as the growing global population puts added demands on the earth's resources: engineering decisions must now account for limitations in materials and energy as well as the need to reduce discharges of wastes. This means educators must revise courses and curricula so engineering graduates are prepared for the new challenges as practicing engineers. The Center for Sustainable Engineering has been established to help faculty members accommodate such changes through workshops and new educational materials, including a free access website with peer-reviewed materials.     

Bioavailability to rats of bound [14C] pirimiphos-methyl in stored wheat.

Stored wheat treated with radiolabelled pirimiphos-methyl (0-2-diethyl-amino-6-methyl-pyrimidin-4-yl 0,0-dimethyl phosphorothioate) formed bound (nonextractable) 14C residues. Supercritical fluid extraction, gas chromatography and mass spectrometric techniques were used to identify and quantitate the 14C bound residues in wheat grains. The amount of bound 14C residues present after 28 weeks of storage was about 9.9% of the applied radioactivity. Pirimiphos-methyl accounted for 80% of the bound residue. Grain-bound residues were fed to rats for 5 days. After a total period of 8 days a substantially large percentage of the administered bound 14C residues (72.9%) was eliminated in urine while feces contained only 17.9%. Bound pirimiphos-methyl in wheat grain was metabolized in rats by processes involving hydrolysis, N-dealkylation and 0-demethylation. The results indicate that wheat-bound residues of pirimiphos-methyl are highly bioavailable to the rat and may possess a toxicological potential as manifested by a significant reduction in body weight gain.     

Evaluating colloidal phosphorus delivery to surface waters from diffuse agricultural sources

Colloid-facilitated phosphorus (P) delivery from agricultural soils in different hydrological pathways was investigated using a series of laboratory and field experiments. A soil colloidal P test was developed that yields information on the propensity of different soils to release P attached to soil colloids. The relationship between turbidity of soil extracts and total phosphorus (TP) was significant (r2 = 0.996, p < 0.001) across a range of agricultural soils, and a strong positive relationship (r2 = 0.86, p < 0.001) was found between "colloidal P" (H2O-CaCl2 extracts) and turbidity. Linear regression of the proportion of fine clay (<2 microm) for each soil type evaluated against the (H2O-CaCl2) colloidal P fraction gave a weak but positive relationship (r2 = 0.38, p = 0.082). The relative contribution of different particle-size fractions in transporting P in agricultural runoff from grassland soils was evaluated using a randomized plot experiment. A significant difference (p = 0.05) in both TP and reactive phosphorus (RP) in subsurface flow was recorded for different particle-size fractions, with most TP transferred either in association with the 2-microm fraction or with the 0.001-microm or smaller fractions. Total P concentrations in runoff were higher from plots receiving P amendments compared with the zero-P plots; however, these differences were only significant for the >0.45-microm particle-size fractions (p = 0.05), and may be evidence of surface applications of organic and inorganic fertilizers being transferred through the soil either as intact organic colloids or attached to mineral particles. Our results highlight the potential for drainage water to mobilize colloids and associated P during rainfall events.     

Temporal patterns and transport processes in recruitment of spiny lobster (Panulirus argus) postlarvae to south Florida

We used time-series analysis to identify weekly and annual patterns in the supply of spiny lobster, Panulirus argus (Latreille, 1804), postlarvae to the Florida Keys, USA, over an 8 yr period. We also investigated the relationship between postlarval influx and wind forcing as a transport mechanism using the complex vector-scalar correlation analysis. Postlarval supply had a lunar phase periodicity at 4.5 wk intervals, with postlarval abundance peaking between the new moon and first-quarter lunar phases. A distinct annual cycle of postlarval supply with two peak periods was also apparent. Cross-correlation analysis between relative postlarval abundance and a 12 mo cycle showed that the annual peak occurs in spring, centered around March. With the 12 mo periodicity removed, a smaller peak at 5 mo intervals was also well defined. Wind-forcing for 7 d prior to the time of postlarval collection was marginally correlated with postlarval abundance through the entire time-series; the association was strongest during the late fall to early spring months. The analysis indicated that postlarval supply was correlated with winds from the northeast (ca. 45°), which are associated with winter atmospheric fronts. In contrast to results reported for other spiny lobster populations, these patterns suggest that recruitment of lobster postlarvae to south Florida is predictable only at a gross level and is presumably affected by the temporally inconsistent structure of regional oceanic gyres and variability in the timing of lobster spawning in the Caribbean. Received: 24 January 1997 / Accepted: 4 March 1997     

The People and Landscape Model (PALM): Towards full integration of human decision-making and biophysical simulation models

A model for simulating resource flows in a rural subsistence community is described. The People and Landscape Model (PALM) consists of a number of agents representing households, the landscape, and livestock. The landscape is made up of a number of homogeneous land units, or ‘fields’, each represented by an object containing data, methods and properties relevant to the field. Each field object consists of a number of soil layer objects, each of which contains routines to calculate its water balance and carbon and nitrogen dynamics. Organic matter decomposition is simulated by a version of the CENTURY model, while water and nitrogen dynamics are simulated by versions of the routines in the DSSAT crop models. The soil processes are simulated continuously, and vegetation types (crops, weeds, trees) can come and go in a field depending on its management. Crop growth and development are simulated by a generic model based on the DSSAT crop models, and which can be parameterised for different crops. Similarly, livestock growth and resource use is simulated by a generic model which can be parameterised for buffalo, cows, goats, sheep, chickens and pigs.     

Screening the wetland plant species Alisma plantago-aquatica, Carex rostrata and Phalaris arundinacea for innate tolerance to zinc and comparison with Eriophorum angustifolium and Festuca rubra Merlin

Several wetland plant species appear to have constitutive metal tolerance. In previous studies, populations from contaminated and non-contaminated sites of the wetland plants Typha latifolia, Phragmites australis, Glyceria fluitans and Eriophorum angustifolium were found to be tolerant to high concentrations of metals. This study screened three other species of wetland plants: Alisma plantago-aquatica, Carex rostrata and Phalaris arundinacea for innate tolerance to zinc. The degree of tolerance was compared to known zinc-tolerant E. angustifolium and Festuca rubra Merlin. It was found that A. plantago-aquatica and P. arundinacea did not posses innate tolerance to zinc, but that C. rostrata was able to tolerate elevated levels of zinc, at levels comparable to those tolerated by E. angustifolium and F. rubra Merlin. The findings support the theory that some wetland angiosperm species tend to be tolerant to exposure to high levels of metals, regardless of their origin.     

Mobilizing environmental sentiment through the media

ABSTRACT

Recent research into the best ways to mobilize people to act on climate change suggests that careful, and relatively positive, emotional framing is critical. However, environmental non-governmental organizations (ENGOs) need to not only mobilize publics, but also attract media coverage. If the media prefers negativity or is skeptical of ENGOs’ emotive appeals, are ENGOs’ emotional frames damaging their ability to gain media attention? Quantitative sentiment analysis is used to identify emotional framing in a targeted case study of 350.org’s public press releases and their subsequent media coverage. The results suggest that appropriate emotional frames for mobilization are not necessarily detrimental to gaining media attention, and that ENGO press releases influence media coverage, when they are used. Several concrete suggestions emerge for how ENGOs might use press releases more effectively, if they seek to influence the media’s emotional tone on climate change.     

园林绿化树种香樟叶片的含硫量动态分析

植物对一定浓度范围内的大气污染物,具有一定程度的抵抗及吸收净化作用。为了解南京市主要园林绿化树种香樟（Cinnamomum camphora）叶片吸收净化SO2的能力,选择在5个不同污染靶区,以3个不同胸径级的香樟叶片为研究对象,采用硫酸钡比浊法测定了不同季节香樟叶片的含硫量。结果表明：香樟叶片对SO2具有一定的吸收净化能力,其叶片含硫量平均为0.2160%,且其含量随分布区、生长季节及个体胸径不同差异显著;并与异域大气中SO2污染指数成一定的正相关;与个体胸径大小成显著负相关;季节间呈现出＂先降后升再降＂的动态趋势,于春秋季较高,而夏冬季较低。