Wastewater irrigation is an environmentally sound wastewater disposal practice, but sewage is more saline than the supplied fresh water and the salts are recycled together with the water. Salts have negative environmental effects on crops, soils, and groundwater. There are no inexpensive ways to remove the salts once they enter sewage, and the prevention of sewage salt enrichment is the most immediately available solution. The body of initiatives presently structured by the Ministry of the Environment of Israel are herein described, with the aim to contribute to the search for a long-term solution of salinity problems in arid countries. The new initiatives are based on: (1) search for new technologies to reduce salt consumption and discharge into sewage; (2) different technologies to cope with different situations; (3) raising the awareness of the public and industry on the environmental implications of salinity pollution; and (4) an elastic legal approach expressed through new state-of-the-art regulations. The main contributor to the salinity of sewage in Israel is the watersoftening process followed by the meat koshering process. Some of the adopted technical solutions are: the discharge of the brine into the sea, the substitution of sodium by potassium salts in the ion-exchangers, the construction of centralized systems for the supply of soft water in industrial areas, the precipitation of Ca and Mg in the effluents from ion-exchangers and recycling of the NaCI solution, a reduction of the discharge of salts by the meat koshering process, and new membrane technology for salt recovery. 相似文献
Management of hazardous waste is an increasing problem for both the companies that generate the waste and for the communities that eventually experience the consequences of the management decisions. Thus, both social and political aspects must be considered when solving these problems. It is thus important that waste management technologies are evaluated by a panel of experts with various backgrounds. The methodology for developing an expert system for waste treatment technology evaluation was discussed. An expert system was developed to select the “best” waste treatment alternatives. This expert system includes two different knowledge bases: one for the economic and technical parts of the problem and another for the social and political aspects. This expert system was developed on an IBM personal computer using Turbo Prolog™. The pulp and paper industry was selected as an example problem for developing this expert system, which system was tested using two example waste streams from the pulp and paper industry. The results agree with the current treatment facilities the companies are using. 相似文献
Objective: We compared the differences in the braking response to vehicle collision between an active human emergency braking (control condition) and cruise control (CC) or adaptive cruise control (ACC).
Methods: In 11 male subjects, age 22 to 67 years, we measured the active emergency braking response during manual driving using the accelerator pedal (control condition) or in condition mimicking CC or ACC. In both conditions, we measured the brake reaction time (BRT), delay to produce the peak braking force (PBD), total emergency braking response (BRT + PBD), and peak braking force (PBF). Electromyograms of leg and thigh muscles were recorded during braking. The tonic vibratory response (TVR), Hoffman reflex (HR), and M-waves were recorded in leg muscles to explore the change in sensorimotor control.
Results: No difference in PBF, TVR amplitude, HR latency, and Hmax/Mmax ratio were found between the control and CC/ACC conditions. On the other hand, BRT and PBD were significantly lengthened in the CC/ACC condition (240 ± 13 ms and 704 ± 70 ms, respectively) compared to control (183 ± 7 ms and 568 ± 36 ms, respectively). BRT increased with the age of participants and the driving experience shortened PBD and increased PBF.
Conclusions: In male subjects, driving in a CC/ACC condition significantly delays the active emergency braking response to vehicle collision. This could result from higher amplitude of leg motion in the CC/ACC condition and/or by the age-related changes in motor control. Car and truck drivers must take account of the significant increase in the braking distance in a CC/ACC condition. 相似文献
The accumulation of arsenic (As) by vegetables is a potential human exposure pathway. The speciation of As in vegetables is
an important consideration due to the varying toxicity of different As species. In this study, common Australian garden vegetables
were hydroponically grown with As-contaminated irrigation water to determine the uptake and species of As present in vegetable
tissue. The highest concentrations of total As were observed in the roots of all vegetables and declined in the aerial portions
of the plants. Total As accumulation in the edible portions of the vegetables decreased in the order radish ≫ mung bean > lettuce = chard.
Arsenic was present in the roots of radish, chard, and lettuce as arsenate (AsV) and comprised between 77 and 92% of the total As present, whereas in mung beans, arsenite (AsIII) comprised 90% of the total As present. In aerial portions of the vegetables, As was distributed equally between both AsV and AsIII in radish and chard but was present mainly as AsV in lettuce. The presence of elevated As in vegetable roots suggests that As species may be complexed by phytochelatins, which
limits As translocation to aerial portions of the plant. 相似文献
Here we investigate the photodegradation of structurally similar organophosphorus pesticides; methyl-parathion and fenitrothion in water (20 °C) and ice (−15 °C) under environmentally-relevant conditions with the aim of comparing these laboratory findings to limited field observations. Both compounds were found to be photolyzed more efficiently in ice than in aqueous solutions, with quantum yields of degradation being higher in ice than in water (fenitrothion > methyl-parathion). This rather surprising observation was attributed to the concentration effect caused by freezing the aqueous solutions. The major phototransformation products included the corresponding oxons (methyl-paraoxon and fenitroxon) and the nitrophenols (3-methyl-nitrophenol and nitrophenol) in both irradiated water and ice samples. The presence of oxons in ice following irradiation, demonstrates an additional formation mechanism of these toxicologically relevant compounds in cold environments, although further photodegradation of oxons in ice indicates that photochemistry of OPs might be an environmentally important sink in cold environments. 相似文献
Time-minimizing migrants should leave a stopover site if the instantaneous speed of migration drops to the average speed
of migration in the environment. This argument has been used in two different ways: either there is local variation in the
fuel deposition rate and a fixed expected speed or there is global variation in the fuel deposition rate, i.e. locally experienced
variation represents global variation along the route. The first case leads to a far steeper relationship between departure
load and fuel deposition rate than the second case. So far, data on departure loads have mainly been analysed within the concept
of local variation of the fuel deposition rate and the result that the observed slopes are much lower than predicted has been
explained by changes in the expected speed along the route or by individual differences in the expected speed. We show here
that the observed relationships generally fall close to the predictions for global variation. We propose that migrants use
a behavioural rule which projects the current experience into the future and therefore interprets local variation as global
variation.
Received: 3 April 1999 / Received in revised form: 22 April 1999 / Accepted: 26 April 1999 相似文献
Mobile measurements of ambient noise and particle number concentrations were carried out within an urban residential area in Essen, Germany, during summer 2008. A busy major road with a traffic intensity of about 44,000 vehicles per day was situated within the study area. The spatio-temporal distribution of noise and particles was closely coupled to road traffic on the major road. Total particle number concentrations in proximity to the main road were on average between 25,000 cm?3 and 35,000 cm?3 while sound levels reached 70–78 dB(A). These estimates were more than double-fold (factor 2.4) in comparison to the urban residential background. At a 50 m distance off the road particle number concentrations were decaying to about 50% of the initial value. The measurements were characterised by close spatial correlation between total particle number concentration and ambient noise with correlation coefficients of up to r = 0.74. However, during one measurement day coupling between both quantities was weak due to higher turbulent mixing within the canopy layer and a change in ambient wind directions. Enhanced dilution of particle emission from road traffic by turbulent mixing and ‘decoupling’ from the influence of road traffic are believed to be responsible. 相似文献
The construction of high resolution chronologies of sediment profiles corresponding to the last 50-100 years usually entails the measurement of fallout radionuclides 210Pb and 137Cs. The anthropogenic radionuclide, 137Cs, originating from atmospheric nuclear weapons testing can provide an important “first appearance” horizon of known age (1954-1955), providing much-needed validation for the sometimes uncertain interpretations associated with 210Pb geochronology. However, while 137Cs usually provides a strong signal in sediment in the northern hemisphere, total fallout of 137Cs in the southern hemisphere was only 25% that of the north and the low activities of 137Cs seen in Australian and New Zealand sediments can make its horizon of first appearance somewhat arguable. Low 137Cs fallout also limited the size of the 1963-1964 fallout peak, a peak that is usually seen in northern hemisphere sediment profiles but is often difficult to discern south of the equator.This paper shows examples of the use of nuclear weapons fallout Pu as a chronomarker in sediment cores from Australia (3 sites) and New Zealand (1 site). The Pu profiles of five cores are examined and compared with the corresponding 137Cs profiles and 210Pb geochronologies. We find that Pu has significant advantages over 137Cs, including greater measurement sensitivity using alpha spectrometry and mass spectrometric techniques compared to 137Cs measurements by gamma spectrometry. Moreover, Pu provides additional chronomarkers associated with changes in the Pu isotopic composition of fallout during the 1950s and 1960s. In particular, the 238Pu/239+240Pu activity ratio shows distinct shifts in the early 1950s and the mid to late 1960s, providing important known-age horizons in southern hemisphere sediments. For estuarine and near-shore sediments Pu sometimes has another significant advantage over 137Cs due to its enrichment in bottom sediment relative to 137Cs resulting from the more efficient scavenging of dissolved Pu in seawater by sediment particles. 相似文献