Chlorophyll as an indicator of the upper critical tissue concentration of cadmium in plants

The upper critical concentration for Cd in wheat plants (Triticum aestivum) grown in Hoagland's solution, was found by the method of Beckett and Davis (1977) to be 44 μg g^?1 dry weight, using shoot chlorophyll levels as an indicator of plant health. Chlorophyll compared favorably with other indices of growth and may, in conditions where metal toxicity is manifest as chlorosis, be more accurate and sensitive than shoot dry weights or longest root lengths. It was not possible with the limited number of experiments conducted here to determine, with any degree of confidence, differences in the levels at which chlorophylls a and b were affected.     

Periphyton Assemblages as Bioindicators of Mine-Drainage in Unglaciated Western Allegheny Plateau Lotic Systems

In order to determine the influence of geologic patterns and coal mining on benthic algal assemblages, 56 stream sites throughout the unglaciated Western Allegany Plateau were investigated. These sites were categorized based upon catchment mining/reclamation history. At each site, select environmental parameters such as pH, temperature, dissolved oxygen, specific conductance, metallic salts concentration, turbidity, maximum wetted width, and average thalweg depth were measured. Periphyton from riffle areas and macroscopic algal taxa from a 20 m segment were collected. Relative importance values were developed and calculated for both the periphyton and macroalgal communities. Canonical correspondence analyses of the periphyton and macroalgal data set each showed five major groups of stream reaches that were defined by specific algal taxa and environmental characteristics. Two of the groups were dominated by variables associated with acid mine drainage (AMD) and had taxa known from very acidic waters. One group was entirely composed of sites receiving treated waters from active coal mines. Another group was dominated by sites classified as alkaline mine drainage (AkMD) and the last group was primarily reference sites with a few reclaimed reaches. The AMD impacted groups had a significantly lower species richness and diversity than the other three groups. Species-based models for inferring the level of critical environmental parameters related to mining showed the periphyton-based inference model for pH was highly predictable and may be quite useful for evaluation of coal mine remediation. Other promising periphyton- and macroalgal-based models, yielded poor r ² and root mean square error (RMSE) after cross-validation. Comparison of the relative importance values with more traditional assessments of community structure showed similar results with the diatoms and chlorophytes dominating the periphyton and macroalgae, respectively.     

A simple approach to soil loss prediction: a revised Morgan–Morgan–Finney model

A revised version of the Morgan–Morgan–Finney model for prediction of annual soil loss by water is presented. Changes have been made to the way soil particle detachment by raindrop impact is simulated, which now takes account of plant canopy height and leaf drainage, and a component has been added for soil particle detachment by flow. When tested against the same data set used to validate the original version at the erosion plot scale, predictions made with the revised model gave slopes of a reduced major-axis regression line closer to 1.0 when compared with measured values. The coefficient of efficiency, for sites with measured runoff and soil loss, increased from 0.54 to 0.65. When applied to a new data set for erosion plots in Denmark, Spain, Greece and Nepal, very high coefficients of efficiency of 0.94 for runoff and 0.84 for soil loss were obtained. The revised version was applied to two small catchments by dividing them into land elements and routing annual runoff and sediment production over the land surface from one element to another. The results indicate that, when used in this way, the model provides useful information on the source areas of sediment, sediment delivery to streams and annual sediment yield.     

Influence of lipid extraction process on the rheological characteristics, swelling power, and granule size of rice starches in excess water

The influence of the lipid extraction process on both macroscopic and microscopic characteristics of nonwaxy rice starch gelatinization in excess water was examined. Surface lipids extraction did not change the thermodynamics of starch gelatinization but lead to a significant reduction (33%) in the enthalpy of starch-lipid complex melting at high temperature, resulting in less viscous dispersions. Internal lipid extraction using hot aqueous alcoholic solutions resulted in an irreversible increase in starch granule diameter (50% increase in D[4,3]) and a dramatic change in cooking characteristics of the starch. Instead of the bimodal swelling observed for native nonwaxy rice starch, only one broad transition in swelling, solubility, granule size, and viscosity was observed in the case of the totally defatted starch. While the total removal of lipids resulted in a slight increase in starch swelling at intermediate temperatures, the harshness of the process caused irreparable changes leading to notably lower swelling at high temperatures.     

Properties of polyclonal, monoclonal, and recombinant antibodies recognizing the organophosphorus pesticide chlorpyrifos-ethyl

A rabbit polyclonal antiserum and two murine monoclonal antibodies recognizing the organophosphorus pesticide chlorpyrifos-ethyl were produced. The two hybridoma cell lines were then used as sources of immunoglobulin genes for the generation of recombinant scFv antibodies in Escherichia coli. The two scFvs showed either similar or improved limits of detection in an ELISA when compared with the monoclonal antibodies. Cross-reactivity studies showed that all of the antibodies were specific toward the chlorinated aromatic ring. Furthermore, scFv gene sequences were linked directly to sequences coding for either a c-Myc tag, a His-tag, or alkaline phosphatase. The fusion products generated were functional, and their properties were determined. The problems associated with producing scFvs and scFv derivatives for detection of pesticide residues from hybridoma are addressed and discussed.     

Laboratory studies on the leaching of aldicarb through a tropical soil from Belize,Central America

Studies in temperate regions indicate that the carbamate insecticide aldicarb and its metabolites leach readily through agricultural soils into groundwater. However, little is known about the fate of this nematicide in tropical regions, where its leaching potential may be even greater because of high annual rainfall and the acidic nature and low organic content of many tropical soils. Examination of the leaching behaviour of aldicarb and its metabolites in columns containing soil from Belize, Central America, indicated that total carbamate residues (TCR) could rapidly reach concentrations > 15 mg L^?1 in porewater 1 m below the soil surface within 70 days of application. These values are well in excess of the US EPA Health Advisory level of 0.01 mg L^?1. TCR retention within a given depth interval in the soil columns relative to incoming TCR flux was greatest between 0 and 0.1 m, reflecting high organic matter contents in the upper soil. Retention below 0.1 m was relatively consistent with depth, while differences in relative retention between columns were due to a greater duration of leaching for the second column. Aldicarb was rapidly oxidized to aldicarb sulfoxide and aldicarb sulfone in these soils. The high concentration and mobility of TCR in this acidic soil is attributed to the transformation of the parent compound to the sulfoxide metabolite, which has a lower degradation rate and organic carbon partioning coefficient than aldicarb.     

Functional scFv antibody sequences against the organophosphorus pesticide chlorpyrifos

Two functional single-chain Fv (scFv) antibodies that recognize specifically the widely used organophosphorus pesticide chlorpyrifos-ethyl were derived from two murine hybridoma cell lines. It is shown that the functional scFvs could be isolated without any rounds of selection, with a success rate dependent on the efficiency of amplification of the functional light chain gene family by the specific primers. Besides four new functional immunoglobulin variable gene sequences, the isolation of a new pseudogene is reported.     

The influence of grass density on effectiveness of contour grass strips for control of soil erosion on low angle slopes

Abstract. The effectiveness of contour grass strips in erosion control was investigated in a field experiment involving two grass treatments ( Festuca ovina and Poa pratensis ) and a bare soil control on an erodible sandy loam soil on a 5° slope using simulated rainstorms of 40 mm h^–1 for 45 minutes duration. The grass strips resulted in significantly ( P < 0.05) lower runoff and soil loss than the bare soil but there was no significant difference in the performance of the two grasses, despite their differences in density, height and leaf size. The effect of the lower density of the Poa pratensis was offset by its larger stem diameter so that the surface area facing the flow was similar for both grasses. Instead of acting as a filter with sedimentation occurring within the barrier, the grass strips operated by ponding water upslope of the barriers. Deposition then occurred in the ponded area above the barrier.