Environmental toxicology and biogeochemistry of ecosystems

Environmental Science and Pollution Research -     

The effect of biochar on severity of soil water repellency of crude oil-contaminated soil

Environmental Science and Pollution Research - Crude oil contamination adversely affects soil water repellency. In this study the effect of biochar on this soil characteristic has been investigated...     

Treatment of dynamic mixture of hexane and benzene vapors in a Trickle Bed Air Biofilter integrated with cyclic adsorption/desorption beds

One of the main challenges that face successful biofiltration is the erratic loading pattern and long starvation periods. However, such patterns are common in practical applications. In order to provide long-term stable operation of a biofilter under these conditions, a cyclic adsorption/desorption beds system with flow switching was installed prior to a biofilter. Different square waves of a mixture containing n-hexane and benzene at a 2:1 ratio were applied to the cyclic adsorption/desorption beds and then fed to a biofilter. The performance of this integrated system was compared to a biofilter unit receiving the same feed of both VOCs. The cyclic adsorption/desorption beds unit successfully achieved its goal of stabilizing erratic loading even with very sharp peaks at the influent concentration equalizing influent concentrations ranging from 10-470 ppmv for n-hexane to 30-1410 ppmv for benzene. The study included different peak concentrations with durations ranging from 6 to 20 min. The cyclic beds buffered the fluctuating influent load and the followed biofilter had all the time a continuous stable flow. Another advantage achieved by the cyclic adsorption/desorption beds was the uninterrupted feed to the biofilter even during the starvation where there was no influent in the feed. The results of the integrated system with regard to removal efficiency and kinetics are comparable to published results with continuous feed studies at the same loading rates. The removal efficiency for benzene had a minimum of 85% while for n-hexane ranged from 50% to 77% according to the loading rate. The control unit showed very erratic performance highlighting the benefit of the utilization of the cyclic adsorption/desorption beds. The biofilter was more adaptable to concentration changes in benzene than n-hexane.     

Effect of chromium on growth attributes in sunflower (Helianthus annuus L.)

Heavy metal soil pollution takes place when the metal concentration of soil exceeds natural background level and causes ecological destruction and deterioration of the environment.In the present study,a pot experiment was conducted to evaluate the effect of chromium-contaminated soil in sunflower(Helianthus annuus L.)growth attributes.Three different levels of chromium(Cr)i.e.,20, 40,and 60 mg/kg were applied to three varieties of sunflower(G-3,G-9,and G-59).The results of morphological,chemical,and yield p...     

Radiological aspects of some Egyptian thermo-mineral springs

In Egypt, nineteen water springs with temperatures exceeding 35 degrees C, which can be considered thermal waters, were reported. The radiological aspects of thermal water in three northern regions of Egypt (Gulf of Suez, Cairo, and Bahariya Oasis) were investigated. The activity concentrations of natural radionuclides of 226Ra, 40K, total uranium and 210Pb (210Po) in water samples were determined using gamma spectrometry, laser fluorimetry and alpha spectrometry after chemical separation, respectively. The highest concentrations are detected in two locations, namely Sudr and Hammam Faroun springs, which are the hottest waters in Egypt (89 and 72 degrees C respectively). It seems that the presence of 226Ra is correlated to the water mineralization and the depth and the temperature of the reservoir's base. Also, these results seem evidence of uranium accumulation at depth in the mother bedrock and/or uranium immobilization due to uranium reduction to the immobile 4+-oxidation state in the reservoir base. The average activity concentrations of 40K are dependent on the water's origin, i.e. meteoric water mixed with sea water (Gulf of Suez springs) and meteoric water (Bahariya Oasis wells). There is no prescribed dose limit for short term and temporary exposure to thermal water. Workers at the thermal springs should be regularly monitored because of their continuous exposure to enhanced radiation levels over a long period of time. The hydrochemical characteristics, environmental isotopes aspects and water origin are briefly discussed based on published data.     

Phosphate-arsenate relations to affect arsenic concentration in plant tissues,growth, and antioxidant efficiency of sunflower (Helianthus annuus L.) under arsenic stress

Environmental Science and Pollution Research - Relations between phosphate and arsenate are important but inconsistent to influence arsenic (As) phytotoxicity depending on many plant and soil...     

Evaluation of recycling waste materials and by-products in highway construction

SUMMARY

The generation, handling, and safe disposal of waste materials has become a major concern in North America. Approval of facilities for waste processing and proper disposal is becoming more difficult to obtain. Furthermore, there is a growing public awareness of the importance of conserving and preserving our valuable natural resources. This expanding awareness has given rise to the trend towards recycling or reuse of awide variety of solid wastes. Experiences with using waste materials in highway construction can vary considerably, depending on material characteristics, construction processes, and climatic differences. A number of waste materials may be suitable for use in highway construction, but others may not. The objective of this paper is introduced in two tasks. The first is to include a survey of the waste materials and by-products that have been used successfully, or may be used, as materials for highway construction or maintenance work. This also includes determination of the state of practice concerning economic and technical factors for these wastes. The second is to rank these materials based on three criteria: number of uses by State agencies, economic uses and performance aspects.