Mineralogical and chemical characterization of suspended atmospheric particles over the east Mediterranean based on synoptic-scale circulation patterns

Suspended atmospheric particles were collected in Israel in order to identify their nature and relationships with the major synoptic-scale circulation patterns. The particles were analyzed for their major and trace element concentrations and mineralogical composition. Samples were collected during three synoptic systems associated with desert dust storms: Red Sea trough, Sharav cyclone and cold depression, and during deep and shallow modes of Persian Gulf trough, which prevails in the summer months and is not associated with dust storms.All samples mostly contain particles smaller than 2 μm. The suspended desert dust is composed primarily of illite–smectite and calcite. Some indicative secondary minerals were found for each of the dust transporting synoptic systems (e.g., palygorskite for Red Sea trough). The bulk chemistry data support the mineralogical observations and reveal additional chemical signatures of each dust transporting system. For instance, Red Sea trough samples have significantly higher Ca/Al and Ca/Mg in the carbonate and Mg/Al in Al-silicate fraction than cold depression samples. Nevertheless, Sharav cyclone samples have intermediate values in spite of the fact that the source of the dust during these conditions is similar to cold depression (i.e., North Africa). Even though differences in the chemical and the mineralogical composition of desert dust do exist, this study reveals their overall chemical and mineralogical similarities.In contrast to the synoptic systems that carry desert dust, the inorganic fraction of the Persian Gulf trough samples contains significant amount (up to 50%) of non-mineral material that has a pronounced chemical signature in terms of major element concentrations (e.g., Al, Ca, Mg, Na, S) implying their anthropogenic nature, probably from countries around the Black Sea. This striking finding is indicative for atmospheric pollution in the Eastern Mediterranean region during the summer.     

Sorption and detoxification of toxic compounds by a bifunctional organoclay

Organoclays are excellent sorbents for nonionic contaminants and therefore may have many environmental applications. A major limitation on the use of organoclays is that the contaminant merely changes its location from one environmental compartment to another while still remaining intact. In this study, a new type of organoclay, termed a bifunctional organoclay, has been prepared. It is able not only to sorb organophosphate pesticides, but also to catalyze their hydrolysis, and thereby detoxify them. The bifunctional organoclay prepared in this study is based on sodium montmorillonite, in which the inorganic counter ions are replaced by N-decyl-N,N-dimethyl-N-(2-aminoethyl) ammonium (DDMAEA). The detoxifying capacity of this organoclay for two organophosphate pesticides, methyl parathion [O,O-dimethyl O-(p-nitrophenyl) thionophosphate] and tetrachlorvinphos [2-chloro-1-(2,4,5-trichlorophenyl)ethenyl dimethyl phosphate], was demonstrated. It was shown that although the sorption of these pesticides on the bifunctional organoclay is very similar to that on N-decyl-N,N,N-trimethyl ammonium (DTMA) organoclay (the corresponding nonbifunctional organoclay), the hydrolysis of these pesticides is substantially enhanced only by the bifunctional organoclay. The half-life for the hydrolysis of the investigated pesticides in the presence of the bifunctional organoclay is about 12 times less than for their spontaneous hydrolysis, and the enhancement is even more pronounced relative to the hydrolysis of these pesticides in the presence of the DTMA organoclay (which actually inhibits their hydrolysis). Based on kinetic measurements, the pK(a) of the ethylamino group of the bifunctional organoclay was estimated to be around 9.0. It is postulated that the catalytic effect of the bifunctional organoclay can be attributed to a nucleophilic attack of the unprotonated ethylamino group of the organoclay on the organophosphate ester.     

Gaseous nitrogen emissions and mineral nitrogen transformations as affected by reclaimed effluent application

Irrigation with reclaimed effluent (RE) is essential in arid and semiarid regions. Reclaimed effluent has the potential to stimulate gaseous N losses and affect other soil N processes. No direct measurements of the N2 and N2O emissions from Mediterranean soils have been conducted so far. We used the 15N gas flux method in a field and a laboratory experiment to study the effect of RE irrigation on gaseous N losses and other N transformations in a Grumosol (Chromoxerert) soil. The fluxes of N2, N2O, and NH3 were measured from six Grumosol lysimeters following application of either fresh water or RE. The N fertilizer was applied either as 15NH4 or 15NO3. Only up to 0.3% from the applied N fertilizer was lost as N2O + NH3. Reclaimed effluent enhanced the losses of NH3, but did not affect those of N2O. Nitrification and denitrification were equally important to N2O production. Laboratory incubations were performed to both confirm the influence of the irrigation water type and to test the effect of moisture content. Significant quantities of N2 and N2O (up to 3.1% of the applied fertilizer) were emitted from saturated soils. Reclaimed effluent application did not induce higher N2O emissions, yet significantly more (approximately 33%) N2 was emitted from RE-irrigated soils. Denitrification contributed up to 75% of the N2O amounts emitted from saturated soils. Reclaimed effluent application inhibited nitrification in the Grumosol by 15 to 25% and induced NO2 accumulation in soils incubated at a field-capacity moisture content.     

On the optimal allocation of pesticides with increasing resistance: The case of alfalfa weevil

The problem of pesticide application under increasing pesticide resistance is explored. A theoretical model is developed to determine optimal pesticide use. This allocation is compared to the laissez-faire solution and to the centralized solution with incomplete information about pesticide resistance. The methodology is then applied in a case study on the Egyptian alfalfa weevil in California.     

Estimating undiscovered oil resources: An engineering approach

This paper is an evaluation of the earlier work of M.K. Hubbert with the aim of more objectively estimating total recoverable (i.e. producible) oil in the United States and Nigeria. The results, based upon an engineering model, indicate that 198 billion barrels are ultimately recoverable in the United States of which 113.8 billion barrels have been produced through 1977. For Nigeria, 19.4 billion barrels are ultimately recoverable of which 6.1 billion barrels have been produced at the end of 1977.