Yasser El-nahhal - Academia.edu (original) (raw)

Papers by Yasser El-nahhal

This study investigated acute toxicity of Diuron, Diquat and Terbutryn to cyanobacterial mats col... more This study investigated acute toxicity of Diuron, Diquat and Terbutryn to cyanobacterial mats collected from Wadi Gaza, Palestine. Toxicity was measured by the reduction of population growth of cyanobacterial mats exposed to various herbicide concentrations in the range of 0-15.44 µmole L-1. Optical density of cyanobacterial suspension was recorded using a spectrophotometer at 680 nm from time zero up to 8 days and taken as an indicator of growth. EC 50 and ET 50 values were estimated using linear regression equations. Results showed that cyanobacterial mats adapted and grew fast under laboratory conditions. The toxicity of Diuron, Terbutryn and Diquat reached 89.35, 76.02 and 71.24%, respectively. Toxicity of binary mixtures (Diuron and Diquat) decreased from 77.35% to 65.33% due to the reduction of Diuron concentration in the mixture. EC 50 values for Diuron, Terbutryn and Diquat were 0.009, 0.031and 0.381 µmole L-1 whereas ET 50 values were 32.32, 35.89 and 23.45 h, respectively. EC 50 values of binary mixtures (B1-B3) were 0.004, 0.01 and 0.012 toxicity units. Tertiary mixtures (T1-T7) had a wide range of EC 50 (0.043-2.9E-07) TUs. The mixture toxicity index (MTI) had positive and negative value in mixtures, indicating synergetic and antagonistic effects. Application of the above-mentioned herbicides may severely damage the ecosystem. Our results are the first of its kind in the region and may be considered as a guideline for future studies.

Phytoparasitica, 1999

The growing season of carrot is all year long, whereas Orobanche crenata and Orobanche aegyptiaca... more The growing season of carrot is all year long, whereas Orobanche crenata and Orobanche aegyptiaca parasitize this crop only in specific seasons. The aim of this study was to examine the effect of sowing dates on the parasitism level of those two Orobanche species. Experimental plots were sterilized with methyl bromide and then artificially infested with the mentioned Orobanche seeds; non-infested plots were used as a control. Carrots were sown at the beginning of each month from September 1995 to March 1997. Those sown at the winter sowing dates were parasitized by the two Orobanche species, which caused severe damage reaching 50% yield reduction in the cold winter months. However, carrots sown at the spring-summer sowing dates were free of Orobanche parasitism. These results exhibit a requirement for low temperatures for O. crenata and O. aegyptiaca parasitism on carrot, in spite of parasitism of the latter on other summer crops. Presumably, carrot resistance to O. crenata and O. aegyptiaca is expressed only in the summer growing season. Furthermore, the parasitism process is significantly slower at the autumn sowing dates than in the winter because of the requirement of cold temperatures for parasitism. In laboratory studies, Orobanche seeds exhibited a high germination rate when preconditioned at high temperatures and germinated by GR24, proving that this resistance is non-dependent on parasite germination ability. In spite of the fact that carrot yields in summer are lower than in winter, carrot growers could evade Orobanche damage by advancing or delaying the carrot growth season. In conclusion, it was demonstrated clearly that carrot has seasonal resistance to 19. aegyptiaca and O. crenata which is expressed at summer cropping and disappears at low temperatures. The precise conditions for resistance of carrot to O. aegyptiaca and O. crenata are presently under study in phytotron experiments.

Bulletin of Environmental Contamination and Toxicology, 2003

... REFERENCES Abed MR, Safi N, Köster J, De Beer D, El-Nahhal Y, Rullkötter J, Garcia-Pichel F (... more ... REFERENCES Abed MR, Safi N, Köster J, De Beer D, El-Nahhal Y, Rullkötter J, Garcia-Pichel F (2002). Microbial Diversity of a Heavily Polluted Microbial Mat and Its Community Changes Following Degradation of Petroleum Compounds. ...

Contamination of horticultural crop samples by organic chemicals has become a pressing problem in... more Contamination of horticultural crop samples by organic chemicals has become a pressing problem in many countries in WANA Region. This paper reviews the current safety status of plant food in terms of pesticide contamination and correlate it with the associated health risk. Safety status was assessed by comparing the determined contamination level of pesticide with that of world health organization (WHO) maximum residue limits (MRL). A range of low contamination levels were detected in cucumber and tomato in Palestine, Jordan and Egypt.

This study characterized the chemical contamination of drinking water in Gaza Strip. Twenty one f... more This study characterized the chemical contamination of drinking water in Gaza Strip. Twenty one fresh samples from different supply sites were analyzed for metals and anions concentration. Results showed that samples contained higher level of nitrates than the EPA standards. Concentrations of sodium, potassium, calcium, magnesium salts are high in several water supply sites but they are in the acceptable levels or in the boarder line of rejection. Concentration of lead, cadmium, iron, and chromium are above EPA standards in some wells. This situation may have health risks to the local population. Improvement of water quality may be possible by implementing pollution control measures and clean water act.

Contamination of water resources with pesticides residues becomes a pressing problem in Gaza due ... more Contamination of water resources with pesticides residues becomes a pressing problem in Gaza due to the frequent application of pesticides in the intensive agricultural system. This study tests the potential of using organo-bentonite as a porous material to remove bromoxynil residues from contaminated water. Bentonite surfaces were activated for removal of bromoxynil residues from water by simple ion exchange reaction using Hexadecyl tributyl phosphonium (HDTBP + ) or N-cetylperidinium (NCP) salts. HPLC results showed that raw bentonite is a poor material for removing bromoxynil residues, whereas NCP + -/HDTBP + -bentonite are powerful materials for removing bromoxynil residues due to changing bentonite surfaces from hydrophilic to hydrophobic. Reducing the temperature or the pH of the solution further enhanced the removal process. These results suggest that NCP + -/HDTBP + -Bentonite are promising porous material for removing bromoxynil residues from water. The application of these materials in water filter may be a promising and economically feasible technology for water purification.

This study aims to characterize the adsorption pattern of benzene and naphthalene on montmorillon... more This study aims to characterize the adsorption pattern of benzene and naphthalene on montmorillonite modified with hexadecyltrimethylammonium (HDTMA), tetramethylammonium (TMA), tetraethylammonium (TEA), tetrabutylammonium (TBA) or benzyltrimethylammonium (BTMA). Adsorption isotherms of benzene and naphthalene from water followed Langmuir and Freundlich models respectively. The Langmuir form of the isotherms suggests that benzene and naphthalene adsorbed to the surfaces as a monolayer. Binding coefficient of naphthalene increased as the molecular weight of the pre-adsorbed surfactant increased. Adsorption of benzene and naphthalene follows the sequence: montmorillonite-benzyltrimethylammonium > montmorillonite-hexadecyltrimethylammonium > montmorillonite-tetrabutylammonium > montmorillonite-tetraethylammonium > montmorillonite-tetramethylammonium. The results indicate that using those complexes can be useful in removing pollutants from water.

This article reviews the application of pesticides in Gaza Strip, Palestine and discusses its ass... more This article reviews the application of pesticides in Gaza Strip, Palestine and discusses its associated health risks. This study is based on data collection and analysis. Data showed that large quantities of pesticides are used in Gaza Strip and the quantities are increased annually. Analyzing the data indicates that large numbers of pesticides are used for controlling different types of pests. Some pesticides are restricted by law but are available in the local market. Classification of pesticides according to its biological activity indicates that insecticides are the largest uses among other pesticides. Reviewing the acute poisonous cases in health records indicates that the reported acute toxic cases were among local farmers in Gaza and the number of acute toxic cases increased annually indicating direct health risks associated with pesticide use. In addition, the increased number of congenital malformation among the newborns indicates indirect health risks. Moreover, the number of cancer cases in Khan Younis governorate indicates a positive association with pesticide use. Classification of pesticides according to WHO standards identified extreme toxic pesticides (e.g parathion), highly toxic (dichlorvos), moderately toxic (malathion) and less toxic ones. These Pesticides have a wide range of octanol-water partitioning coefficient (K ow , log P) values (-0.8 -6.6), which results in a variety of storage and transport patterns in human bodies. They may move from the storage sites (e.g fat bodies) via partitioning to other parts of the human body. A pesticide with high K ow log P value (hydrophobic) such as Fenvalerate can be stored in fat containing particles and be released in milk secretion exposing fetus, mother, and infants to health risks. A satisfactory solution to these problems is the implementation of restriction measures and the performance of frequent pesticide residue analysis of food samples.

American Journal of Analytical Chemistry, 2014

International Journal of Geosciences, 2014

This study characterized the physicochemical properties of sewage sludge collected from Gaza wast... more This study characterized the physicochemical properties of sewage sludge collected from Gaza wastewater treatment plant. Sludge samples were collected from the drying beds, air-dried, sieved through 2 mm and stored in plastic bags at room temperature. Sludge density, particle size distribution, water holding capacity, void volume, pH, EC, total organic carbon and hydrophobicity were determined. Results showed the bulk density is about 1.18 g/cm 3 whereas the real density is 2.12 g/cm 3 and void volume is 50%; Particle size distribution showed that the major size of sludge is sand-like size (630 -200 µm) and the minor size is silt-like size (200 -20 µm) and clay-like size are less than 20 µm. Sludge has an acidic pH reaction (6.78 ± 0.02) with an electric conductivity equal to (2.49 ± 0.04) mS•cm −1 . The hydrophobicity of sludge is very high, water drop penetration time (WDPT) is 114.77 ± 18.78 sec with a radius of 0.44 ± 0.08 cm. In the way around, oil drop penetration time (ODPT) of sludge is 5.05 ± 1.28 sec with a radius of 1.25 ± 0.14 cm. The WDPT/ODPM ration is very high value 22.73 indicating extreme hydrophobicity. High value of hydrophobicity may reduce water filtration in soil when sludge applied for agriculture. These results suggest that sludge application to soil may change the physicochemical properties of soil.

American Journal of Plant Sciences, 2013

Nahrung/Food, 2002

Three techniques of gas chromatography (GC) either with flame photometric-detector (FPD), electro... more Three techniques of gas chromatography (GC) either with flame photometric-detector (FPD), electron capture detector (ECD), or with mass-spectrometry (MS) were applied for identification and quantification of pesticide residues on 45 samples of cucumber, tomatoes, and strawberries in fifteen locations in Gaza Governorates. GC-FPD analysis showed the presence of four different organo-phosphorus (OP) pesticides, their levels were very low and below maximum residue limits (MRL's). GC-ECD detected ten different pesticides at levels below the MRL's. Using the GC-MS technique, alpha and beta-endosulfan, chlorpyrifos, carbofuran, chlorfluazuron, triadimenol I and II, penconazole, coptafolmetabolite, pyrimethanil and iprodione were detected and confirmed on some samples of cucumber, tomatoes and strawberries. All GC-MS pesticide residues detected on tomato were below the MRL's except chlorfluazuron while on strawberry were below the MRL's except penconazole, chlorfluazuron and pyrimethanil, but on cucumber were slightly higher than the MRL's except alpha and beta-endosulfan. Also, statistical analysis of pesticide residues in all samples showed that most of the detected residues mean were significantly lower than the MRL's (p < 0.05). Generally, tomatoes showed the least number and level of pesticide residues by all the GC-techniques. On the other hand, strawberries showed greater number and levels of pesticide residues, particularly by the GC-MS technique. These results indicate that the protective period to elapse before harvesting should be increased especially on strawberry. The results also can help in risk assessment of consumers exposure to the expected pesticide residues.

Journal of Pesticide Science, 2010

ABSTRACT