Microbial populations of crude oil spill polluted soils at the Jordan-Iraq desert (the Badia region) / População microbiana de solos contaminados pelo derramamento de petróleo no deserto Jordão-Iraque (região de Badia)

Microbial populations' inhabitants in crude petroleum contaminated soils were analyzed in relation with the soil characteristics. A noticeable greater decline of bacterial counts and diversity but a prevalence of the genus Pseudomonas over the other identified genera in the fresh contaminated soils as compared to the old ones was observed.

Analisou-se a população microbiana de solos contaminados pelo derramamento de petróleo em função das características do solo. Uma diminuição notável foi observada nas contagens e diversidade bacterianas, mas observou-se a prevalência de Pseudomonas em relação aos demais gêneros identificados em solos recentemente contaminados, quando comparado com solos com contaminação antiga.

Microbial populations of crude oil spill polluted soils at the Jordan-Iraq desert (the Badia region).

Microbial populations' inhabitants in crude petroleum contaminated soils were analyzed in relation with the soil characteristics. A noticeable greater decline of bacterial counts and diversity but a prevalence of the genus Pseudomonas over the other identified genera in the fresh contaminated soils as compared to the old ones was observed.

Chemical alteration of the rhizosphere of the mycorrhizal-colonized wheat root.

Plexiglass pot growth chamber experiments were conducted to evaluate the chemical alterations in the rhizosphere of mycorrhizal wheat roots after inoculation with Glomus intraradices [arbuscular mycorrhizal fungus (AMF)]. Exchange resins were used as sinks for nutrients to determine whether the inoculated plant can increase the solubility and the uptake of P and micronutrients. Treatments included: (1) soil (bulk soil); (2) AMF inoculation no P addition (I-P); (3) no inoculation with no P addition (NI-P); (4) AMF inoculation with addition of 50 mg P (kg soil)(-1) (I+P), and (5) no inoculation with addition of 50 mg P (kg soil)(-1) (NI+P). The AMF inoculum was added at a rate of four spores of G. intraradices (g soil)(-1). The exchange resin membranes were inserted vertically 5 cm apart in the middle of Plexiglass pots. Spring wheat (Triticum aestivum cv. Len) was planted in each Plexiglass pot and grown for 2 weeks in a growth chamber where water was maintained at field capacity. Rhizosphere pH and redox potential (Eh), nutrient bioavailability indices and mycorrhizal colonization were determined. Mycorrhizal inoculation increased the colonization more when P was not added, but did not increase the shoot dry weight at either P level. The rhizosphere pH was lower in the inoculated plants compared to the noninoculated plants in the absence of added P, while the Eh did not change. The decrease in pH in the rhizosphere of inoculated plants could be responsible for the increased P and Zn uptake observed with inoculation. In contrast, Mn uptake was decreased by inoculation. The resin-adsorbed P was increased by inoculation, which, along with the bioavailability index data, may indicate that mycorrhizal roots were able to increase the solubility of soil P.

Survival and accumulation of microorganisms in soils irrigated with secondary treated wastewater.

Secondary-treated wastewater was used to irrigate forage crops during two years (1994 and 1995). The bacteriological quality of the soil irrigated with both secondary treated wastewater (without chlorination) and with potable water was evaluated. The following three treatments were investigated in this study: i) irrigation with potable water in amount equivalent to 100% of the class A Pan evaporation reading (as taken from the nearest Meteorological Weather Station); ii) irrigation with treated wastewater in amount equivalent to 100% of the A Pan reading and iii) irrigation with treated wastewater in amount equivalent to 125% of the A Pan reading. At the end of the last growing season, soil samples were collected at two soil depths and subjected to microbiological analysis. The bacteriological analysis showed that the total aerobic bacterial counts of surface soil were similar in all irrigated plots, suggesting that the use of this wastewater did not stimulate or inhibit these microflora. Surface soil was found to have higher bacterial counts than deeper soil suggesting bacterial removal from irrigation water by the first few centimeters of soil due to natural infiltration of soil. The total coliforms ranged from 2.1 x 10(3) CFU/g to 4.2 x 10(3) CFU/g while fecal coliforms were less, ranging from 1.2 x 10(2) CFU/g to 4.2 x 10(2) CFU/g. No detectable helminth eggs were recorded in the treated wastewater used for irrigation. The results strongly suggest the necessity to treat wastewater effluents to an extent to which no or very few residual bacterial contaminants will be detected.