Effect of an attendant anion on the balance of cations in the soil-solution system with an ordinary chernozem as an example

The effect of different anions on the balance of heavy metal cations in the soil-solution system has been assessed under model laboratory conditions. It has been found that the uptake of the Cu, Zn, and Pb cations by an ordinary chernozem from solutions of different salts is accompanied by the displacement of the exchangeable cations to the solution in the following order: Ca²⁺ > Mg²⁺ > Na⁺ > K⁺. The sum of the displaced exchangeable cations in most cases exceeds the amount of the adsorbed heavy metal cations. According to the effect of the anions on the displacing capacity of the metal cations, the following series are formed: for copper, SO ₄ ^2? ? Cl^? > OAc^? > NO ₃ ^? ; for lead, Cl^? ? NO ₃ ^? > OAc^?; and, for zinc, SO ₄ ^2? ? Cl^? ? OAc^? > NO ₃ ^? .     

Bioavailability of an organophosphorus pesticide,fenamiphos, sorbed on an organo clay

Hydrolysis of an insecticide/nematicide, fenamiphos [ethyl-3-methyl-4-(methylthio)phenyl-(1-methylethyl)phosphoramidate], immobilized through sorption by cetyltrimethylammonium-exchanged montmorillonite (CTMA-clay) by a soil bacterium, Brevibacterium sp., was examined. X-ray diffraction analysis, infrared spectra, and a negative electrophoretic mobility strongly indicated that fenamiphos was intercalated within the bacterially inaccessible interlayer spaces of CTMA-clay. The bacterium hydrolyzed, within 24 h, 82% of the fenamiphos sorbed by the CTMA-clay complex. There was a concomitant accumulation of hydrolysis product, fenamiphos phenol, in nearly stoichiometric amounts. During the same period, in abiotic (uninoculated) controls, 4.6% of the sorbed insecticide was released into the aqueous phase as compared to 6.0% of the sorbed fenamiphos in another abiotic control where activated carbon, a sink for desorbed fenamiphos, was present. Thus, within 24 h, the bacterium hydrolyzed 77% more fenamiphos sorbed by organo clay than the amounts desorbed in abiotic controls. Such rapid degradation of an intercalated pesticide by a bacterium has not been reported before. Evidence indicated that extracellular enzymes produced by the bacterium rapidly hydrolyzed the nondesorbable fenamiphos, even when the enzyme itself was sorbed. Fenamiphos strongly sorbed to an organo clay appears to be readily available for exceptionally rapid degradation by the bacterium.     

Validation of an extended critical state model using the mechanical behaviour of an agricultural soil

A validation of an extended critical state model was conducted using a heavy agricultural clay soil from Quebec Province, eastern Canada. The numerical model used for this purpose simulated the behaviour of Sainte-Rosalie clay under triaxial compression and one-dimensional compression loading paths. Under triaxial compression, simulations were done for three soil suctions: 0, 300, and 500 kPa. Under one-dimensional compression, simulations were done for suctions 0 and 300 kPa. The model used five parameters while simulating soil mechanical behaviour under saturated condition. Three additional parameters were required for simulating soil mechanical behaviour under unsaturated condition. Results of simulations were then compared to those of laboratory tests. Experimental data compared well with simulation results. It was found that the model reasonably predicted soil behaviour under both saturated and unsaturated conditions. However, some discrepancies arose in both soil conditions: the model predicted an earlier rupture in each case of triaxial compression and it failed to reach the smallest void ratio obtained during one-dimensional compression. These small divergences were attributed to the fact that numerical development of the tested model was based on densified sand behaviour.     

Effects of an acid precipitation event on the near-surface water chemistry of an oligotrophic lake

Reported here are the first data that examine direct chemical interactions between acid precipitation and near-surface lake waters. Temporal snapshots of the dissolved phase chemical dynamics at several depths in the surface 0.5 m water column of an oligotrophic low-alkalinity lake are presented for a storm event which occurred on August 17, 1983. During precipitating periods pH decreases of up to 0.35 pH units were observed in surface waters. The good agreement between the time-depth profiles of temperature, excess H⁺, and excess SO₄ ^2? strongly suggested that the major acidity component of the rain water (H₂SO₄) was primarily responsible for the decreased surface water pH. As a result of intrusion of cooler rain water into warmer surface waters, suspended particulate matter apparently became trapped within layers of cooler water and was subsequently removed from near-surface waters by the sinking of these layers. Significant solubilization of Zn occurred within these layers, presumably representing release from particulate matter subjected to lowered solution pH. In contrast to Zn, significant decreases occurred in the concentrations of dissolved Al and Fe that may have resulted principally from formation of solid phases.     

Influence of Sugarcane Cropping on the Quality of an Oxisol and an Inceptisol in Mauritius

Productive capacity of Mauritius soils could be declining with sugarcane monoculture. Effects of short- and long-term sugarcane cropping on quality of an Oxisol and an Inceptisol were assessed to a depth of 50 cm. In the short term (<25 years), cropping led to less organic matter and topsoil microbial biomass (0 to 15 cm), probably through increased microbial breakdown of organic matter (OM) and downward movement by tillage. The pH of both soils and the cation exchange capacity (CEC) of the Oxisol increased following application of lime, fertilizers, and organic amendments. Physical properties were also affected. Aggregate stability decreased and topsoil was compacted, whereas plant-available water and permeability improved. In the long-term (>50 years), OM and microbial biomass increased with inputs of crop residues, whereas exchangeable base levels improved in the Inceptisol with organic amendments. Physical properties did not change much in the long term, even if some improvement was noted in structural and hydraulic properties.     

Selenitadsorption an Waldhumusformen

Adsorption of selenite on different types of forest humus In the present investigation the adsorption of selenite selenium on L-, O-, and A-horizons of the humus forms mull, moder, and mor was studied. Selenite adsorption decreased in the order mull > moder > mor. The organic layers adsorbed nearly the same amount of selenium as the underlying A-horizons. Among the L- and O-layers selenadsorption increased with increasing pH. Amounts of organic carbon, “free” oxides did not influence the adsorption capacity. The Freundlich equation was valid to describe selenite adsorption of all layers under investigation. Additionally the Langmuir equation fitted the adsorption curves of the mull soil and the moder L-horizon. Adsorption experiments using perfusion apparatuses showed microorganismus to incorporate high amounts of selenite under natural conditions.     

Interaction between an acidic mine water and an agricultural soil material

A column filtering experiment was conducted to investigate interaction between an acidic mine water and an agricultural soil material during percolation of the mine water through the soil column. The results show that the mine water-borne mineral acid, Cu, Pb, Zn and Cd was markedly held by the soil during the earlier stage of the experiment. Approximately 1/3 of the retained acid was only physically held by the soil while the remaining 2/3 of the retained acid was either physiochemically or chemically bound to soil colloids. There was a tendency that the retained acid decreased with increasing depth of the soil column. Except for Cd, the capacity of soil to remove these heavy metals from the mine water persisted longer, compared to mineral acid. In contrast with mineral acid, the concentration of retained heavy metals increased with increasing depth, suggesting that these metal ions are less competitive than major acidic cations such as Al³⁺, H⁺ and Fe³⁺ for available adsorption sites in the upper soil layers. Mine water-borne Cu, Cd and Pb were immobilized predominantly in exchangeable and oxide-bound forms while mine water-borne Zn was immobilized mainly in carbonate- and organic-bound forms. During mine water infiltration, some soil-borne metals were mobilized and leached out of the soil under acidic conditions during the latter stage of filtration operations. Unlike Cu, Pb, Zn and Cd, mine water-borne Fe was transformed into colloidal Fe oxides/hydroxides which were carried by the downflowing water. A large proportion of mine water-borne Mn was only physically held, probably not necessarily in soluble forms but in colloidal forms.     

Development of an agricultural weather policy

Climate is one of the most important factors determining the sustainability of agricultural production systems. More emphasis must be placed on understanding the influence of changing climate conditions on sustainable agricultural systems, given the increasing limitations of the natural resource base. Agrometeorologists can play a leading role in bridging the gaps between the diverse multi-disciplinary fields of science, by reaching out to farmers, extension service personnel, and the agricultural business community. The farming community must cope with issues of climate variability and climate change, and, the challenge for agricultural meteorologists is to develop a coordinated national agricultural weather policy to assist agriculture as it deals with these issues. Agricultural weather policy must be formulated so that proactive long-term preparedness activities are strengthened to ensure agricultural sustainability and to preserve natural resources. Preparedness must be the essential foundation of an agricultural weather policy that builds upon mitigation measures and adaptation strategies to cope with climate variability and climate change as it affects agriculture, forestry, rangelands, and fisheries.     

Validation of an estimated food record

OBJECTIVE: To validate an estimated food record (EFR), using a weighed food record (WFR) as the reference method, for the determination of food consumption and nutrient intakes in a group of Costa Rican adults. DESIGN: For the WFR, all foods consumed by subjects during seven consecutive days were weighed and recorded by nutrition students. Two EFRs (a 4-day and a 3-day record) were recorded by subjects with the use of home measures and photographs to estimate amounts. SETTING: Costa Rica. SUBJECTS: Sixty adults: 30 men and 30 women; 30 living in urban and 30 in rural areas. RESULTS: The EFR gave statistically significant lower average intake estimates for energy and 12 of the 22 nutrients examined. The correlation coefficients ranged from 0.68 (polyunsaturated fats) to 0.87 (calcium). The percentage of subjects classified into the same quartile ranged from 45.0% (polyunsaturated fats) to 68.3% (vitamin B12). For all nutrients except vitamin C, 0 or 1.7% were misclassified into extreme quartiles. For food group consumption, the EFR gave statistically significant lower estimates for six of the 17 groups and correlation coefficients ranged from 0.22 (fish) to 0.93 (beverages). Greater differences in estimates of mean energy and nutrient intakes were detected among subjects from rural areas, caused in part by a tendency to underestimate the amounts of rice and beans consumed. CONCLUSION: Validation of the EFR using a WFR as the reference method gave results that compare favourably with those reported by other authors, and support the use of the EFR for dietary surveys among Costa Rican adults.     

基于MCR模型的江西省抚州市生态安全格局构建

[目的]开展城市生态安全格局构建和主要生态廊道识别研究,为城市国土空间规划中生态格局的优化提供科学参考。[方法]以江西省抚州市为研究区,选取土地利用因子,水土保持功能重要性以及生态敏感性等多种因子构建最小累积阻力模型,依据生物多样性维护功能重要性评价、全域水文分析、生态保护红线以及自然保护地识别生态源地,依托MCR模型和ArcGIS中的空间分析工具开展研究。[结果](1)抚州市整体生态环境良好,水土保持功能极重要性区所占比例为49.97%,主要集中在抚州市中部地区,以黎川县、乐安县、宜黄县和南丰县为主;抚州市生态敏感性极重要区所占比例为1.39%;(2)生态源地面积3302.34 km~2,所占比例为17.57%,以抚州市东部和西南部为主;(3)以全域的生态要素和地形地貌等为基底,抚州市呈现出“一轴、两屏、多廊、多节点”的生态安全格局。[结论]结合生态源地、生态廊道和生态节点,形成完整、系统的生态保护格局和开敞空间网络体系,维护抚州市生态安全和生物多样性。     

Mental workload associated with operating an agricultural sprayer: an empirical approach

Agricultural spraying involves two major tasks: guiding a sprayer in response to a GPS navigation device, and simultaneous monitoring of rear-attached booms under various illumination and terrain difficulty levels. The aim of the present study was to investigate the effect of illumination, task difficulty, and task level on the mental workload of an individual operating an agricultural sprayer in response to a commercial GPS lightbar, and to explore the sensitivity of the NASA-TLX and SSWAT subjective rating scales in discriminating the subjective experienced workload under various task, illumination, and difficulty levels. Mental workload was measured using performance measures (lateral root mean square error and reaction time), physiological measures (0.1 Hz power of HRV, latency of the P300 component of event-related potential, and eye-glance behavior), and two subjective rating scales (NASA-TLX and SSWAT). Sixteen male university students participated in this experiment, and a fixed-base high-fidelity agricultural tractor simulator was used to create a simulated spraying task. All performance measures, the P300 latency, and subjective rating scales showed a common trend that mental workload increased with the change in illumination from day to night, with task difficulty from low to high, and with task type from single to dual. The 0.1 Hz power of HRV contradicted the performance measures. Eye-glance data showed that under night illumination, participants spent more time looking at the lightbar for guidance information. A similar trend was observed with the change in task type from single to dual. Both subjective rating scales showed a common trend of increasing mental workload with the change in illumination, difficulty, and task levels. However, the SSWAT scale was more sensitive than the NASA-TLX scale. With the change in illumination, difficulty, and task levels, participants spent more mental resources to meet the increased task demand; hence, the illumination, task difficulty, and task level affected the mental workload of an agricultural sprayer operator operating a sprayer in response to a GPS lightbar.     

Quantification of Odours from Piggery Effluent Ponds using an Electronic Nose and an Artificial Neural Network

An Artificial Neural Network (ANN) and an electronic nose, AromaScan, were used to predict the piggery odour concentrations emanating from an effluent pond and to develop a confident, rapid, and cost-effective technique for odour measurement. Odour samples from five different piggery effluent ponds were analysed using the AromaScan and dynamic dilution olfactometry. The resulting sensor data were used to train the artificial neural network to correlate the responses to the odour concentrations measured by olfactometry. Effectiveness was evaluated through simulation with various pre-processing techniques and network architectures. The simulation results have shown that a two-layer back-propagation neural network, which has a tan-sigmoid transfer function in the hidden layer and a linear transfer function in the output layer, could be trained to predict piggery odour concentrations with high value of the correlation coefficient R of 0·984 under the best network performance. The results from the application of scaling and principal component analysis suggest that these techniques are necessary not only to avoid the failure of the network caused by saturation but also to enhance performance. An early stopping technique was shown to provide benefits to the network performance in terms of a decrease in computation time and overfitting. It was found that the optimal number of hidden neurons for the network was 20. Odour concentration of unknown samples were able to be predicted with significant accuracy.     

Anatomische Untersuchungen an Gerstenwurzeln

Ohne Zusammenfassung     

Application of an Air Ionization Device Using an Atmospheric Pressure Corona Discharge Process for Water Purification

Pesticides presently being discharged into the aquatic environment are not only toxic but also only partially biodegradable, they are not easily removed by conventional water treatment plants. Air ionization devices using an atmospheric pressure corona discharge process show great promise in improving degradation of chemical and biological contaminants in water purification plants. In order to assess the effectiveness of this air ionization apparatus, laboratory scale degradation experiments were carried out systematically in a bubble column reactor containing a variety of pesticides such as triazines, carbamates, phenyl urea derivates and chlorophenols relative to the addition of humic acid and inorganic chemicals as well as to pH variation. Chemical oxygen demand (COD) decreased with air ionization treatment and the rate of the biological oxygen demand related to this (BOD/COD) showed improved pesticide biodegradability. Changes in water toxicity were monitored by Daphnia- and Luminescence Bacteria tests. This novel water treatment process is shown to be a potent oxidation technique for persistent organic pollutants such as pesticides.     

A check on the efficiency of an air-bubble screen using acoustic measurements and an artificial tracer

Purpose

A working group, composed of the University of Genoa (Italy), responsible for monitoring the dredging of the Port of Genoa, and Royal Boskalis Westminster N.V. (The Netherlands), responsible for the dredging activities, carried out an experiment on closing a landfill area with a double air bubble-screen (ABS) to verify the efficiency both of this method of containing sediment and of the measurement method applied.

Materials and methods

Within the Port of Genoa dredging, which was started in 2009, the dredged material is used to fill two areas between existing quays. To contain the sediment to be placed into a third subbasin without interrupting the passage of the barges which discharge the sediment, the use of an ABS was proposed as a barrier to the spreading of the sediment. The experiment was carried out during a 4-day oceanographic campaign to verify, preliminarily, the results under different weather and sea conditions. An artificial tracer, rhodamine water tracing (RWT), was used in varying concentrations to simulate the spreading of the sediment, and an RWT sensor and an acoustic Doppler current profiler (ADCP) were used to measure the RWT distribution and verify the efficiency of the ABS.

Results and discussion

The high turbidity in the port and the high rate of RWT dilution made it relatively difficult to detect the RWT. The RWT sensor sometimes measured higher values than expected probably due to the following: the recirculation of the tracer in current eddies, other sensible suspended matter and adsorption of RWT on suspended matter. The internal ABS could not retain all the RWT, possibly because it was much weaker than the external one, and because mitigating measures, like silt screens or ABSs, are not totally closed and should not be used if complete impermeability is required. The ABS introduction accentuated the natural separation between the basin and the channel water bodies creating a barrier between the two basins.

Conclusions

An ABS installed at the entrance to a confined area with low dynamics results in a circular vertical flow with the potential to retain suspended sediments within an enclosed area. The meteorological variability during the tests showed that a weak ABS could malfunction in the presence of strong wind condition. The results showed that the ADCP is a suitable instrument to highlight the ABS position and its effect on the surrounding hydrodynamics. Further research, using a sediment tracer, is required to study with greater detail the effects of the ABS on the water column.