Trace Elements in Street and Household Dusts in Amman,Jordan

This research aims at quantifying the concentrations of heavy metals within the home environment in Amman, the capital city of Jordan, and to compare the total concentrations of indoor dusts to that of exterior dusts and soils. Housedust samples were collected from different zones of Amman. Street dust samples and garden soil samples were collected in the immediate vicinity within 10–50 m of each residence. The geometric mean concentrations of metals in the household dust were Pb, 169 mg/kg; Cd, 2.92 mg/kg; Zn, 1985 mg/kg; Cu, 133 mg/kg; Cr, 66 mg/kg; Co, 21 mg/kg; Ni, 31 mg/kg; Mn, 284 mg/kg; Be, 3.0 mg/kg; Ba, 43 mg/kg; B, 697 mg/kg and Al, 1441 mg/kg. Comparisons of household dust, garden soil and street dust were based on the same particle size fraction. Results showed housedust samples to contain higher concentrations for Pb, Zn, Cr, Ni, Cd, Cu and B, than either street dust or garden soil samples. However, the differences between Pb and Cr levels in the three different sample categories were insignificant. Enrichment factor calculations and the enrichment factor ratios indicated that patterns of enrichment of indoor dust differ from that of exterior dusts.     

Chemical Extraction of Arsenic from Contaminated Soils in the Vicinity of Abandoned Mines and a Smelting Plant Under Subcritical Conditions

Under subcritical conditions, we studied the chemical extraction of arsenic (As) from contaminated soils that were sampled from the vicinity of abandoned mines and a smelting plant in South Korea. The total initial concentrations of As in the soil samples from the Myungbong and Cheongyang mines and the Janghang smelting plant were 298.6, 145.6, and 103.7 mg/kg, respectively. X-ray photoelectron spectroscopy analysis showed that the species of As identified in the soil was As(+V), including As₂O₅ and AsO₄ ^3? _. At 20°C, only 27.4, 26.5, and 40.1% of the total As was extracted from the Myungbong, Cheongyang, and Janghang soil samples, respectively, with 100 mM of NaOH. As the temperature was increased to 300°C, the extraction efficiencies remarkably increased. However, to achieve the complete extraction of As from the soils, 100 mM of citric acid, EDTA, or NaOH was needed at 200, 250, or 300°C. Extraction with subcritical water at 300°C resulted in incomplete extraction of As from the soils. The results of these experiments indicate that extraction mechanisms other than oxidative dissolution of As(+III) species may be responsible for the enhancement of As extraction. Our results suggest that subcritical water extraction combined with extracting reagents can effectively remediate As-contaminated soil regardless of the As species.     

Effects of incubation temperature on the organic amendment‐mediated control of Fusarium wilt of tomato

Organic soil amendments play important roles in the reduction of plant diseases caused by soil‐borne plant pathogens. This study examined the combined effects of concentrations of organic amendments, temperature and period of incubation in soil on the management of Fusarium wilt of tomato caused by Fusarium oxysporum f. sp. lycopersici (Fol). In an experiment with substrate mixture, Fol reduction was higher when the soils were incubated at 35°C than at 30°C. Disease severity was proportionally reduced as the volume of amendment added increased. Furthermore, disease was significantly lower in substrates incubated for 30 days at both temperatures, as compared to substrates incubated for only 15 days. The most effective control was achieved with pelletised poultry manure (PPM). In experiments with natural sandy soil, the effects of amendments on Fol populations, measured by real‐time quantitative PCR with TaqMan probes, were significant. The highest decreases in Fol DNA resulted when the soil was amended with 2% PPM and incubated at 35°C. The reductions in DNA concentrations was most likely related to the accumulations of high concentrations of NH₃ (27.3 mM) in soils treated with 2% PPM and incubated at room temperature (RT; 23 ± 2°C), or at 35°C. Severity of plants grown in soils incubated at RT decreased by over 40%, and more than 73% when incubated at 35°C, regardless of the rate of PPM. The results indicate that the management with PPM, when combined with heating or solarisation, is an effective control measure against Fusarium wilt of tomato.     

Temperature dependence of the photosynthetic activities in the thylakoid membranes from the blue-green alga Anacystis nidulans

The photosynthetic electron transport and phosphorylation reactions were measured in the room temperature region in the thylakoid membranes prepared from the blue-green alga, Anacystis nidulans. The Arrhenius plot of the Hill reaction with 2,6-dichlorophenolindophenol showed a distinct break of straight lines at 21°C in the membranes from cells grown at 38°C, and at 12°C in those from cells grown at 28°C. The Arrhenius plot of the Hill reaction with ferricyanide showed a break at 13°C in the membranes from cells grown at 38°C, and at 7°C in those from cells grown at 28°C. On the other hand, the Arrhenius plot of the System I reaction with methylviologen as an electron acceptor and 2,6-dichlorophenolindophenol and ascorbate as an electron donor system was composed of a straight line in the membranes from cells grown at 28°C as well as at 38°C. The Arrhenius plot of the System II reaction measured by the ferricyanide reduction mediated by silicotungstate in the presence of 3-(3′,4′-dichlorophenyl)-1,1-dimethylurea also showed a break at 11°C in the membranes from cells grown at 38°C.The Arrhenius plot of the phosphorylation mediated by N-methylphenazonium methylsulfate showed a break at 21°C in the membranes from cells grown at 38°C and at 12°C in those from cells grown at 28°C. The Arrhenius plot of the phosphorylation mediated by the System I reaction showed a break at 24°C in the membranes from cells grown at 38°C.The characteristic features in the Arrhenius plots of the photosynthetic electron transport and phosphorylation reactions are discussed in terms of the transition of physical phase of the thylakoid membrane lipids.     

Assessment of heavy metal contamination of rice grains (Oryza sativa) and soil from Ada field,Enugu, Nigeria: Estimating the human healtrisk

The concentrations of heavy metals in rice grains and soils from Ada cultivated fields were investigated. Rice and soil samples were digested and the heavy metal concentrations determined using atomic absorption spectrophotometer. The results showed the following concentrations of metals (mg/kg): soil—Pb (4.64 ± 2.18), Cd (0.83 ± 0.83), Zn (20.26 ± 18.60), Mn (68.90 ± 19.91), Ni (3.46 ± 2.42), and Cr (21.41 ± 14.6); rice—Pb (3.99 ± 1.43), Cd (1.10 ± 0.53), Zn (65.37 ± 58.09), Mn (37.81 ± 5.82), Ni (3.12 ± 1.49), and Cr (10.87 ± 6.47). The Canadian, Nigerian and Chinese maximum allowable concentration for cadmium in soil were exceeded by 15%, 30%, and 85% of the soil samples, respectively. Heavy metals in all the rice samples evaluated were found to be above the World Health Organization (WHO) maximum permissible limit for lead, cadmium, and chromium. Strong positive and significant correlations were observed between some metal pairs in soil and rice indicating the similarity in origin. The estimated daily intakes of Pb and Cd from rice grown on the fields were higher than the safety levels established by WHO and the Joint FAO/WHO Expert Committee Food Additive, respectively. Hazard quotients and total hazard index for Pb and Cd were greater than 1. This indicates that consumption of rice from these fields will likely induce adverse health effects arising largely from Pb and Cd exposure.     

Effects of suboptimal root zone temperatures and shoot demand on net translocation of micronutrients from the roots to the shoot of maize

The effects of suboptimal root zone temperatures (RZTs) on net translocation rates from the roots to the shoots and the concentrations of Fe, Mn, Zn, and Cu were examined in maize grown in nutrient solution or soil. Plants were grown at 12 °C, 18 °C and 24 °C RZT. At each RZT, the growth-related shoot demand for nutrients was varied by independently modifying the temperature of the shoot base (SBT) including the apical shoot meristem. The net translocation rates of Mn and Zn from the roots to the shoots were reduced at low RZTs, irrespective of the SBT and of the substrate (soil or nutrient solution). Obviously, the net translocation rates of Mn and Zn at low RZT were mainly regulated by temperature effects on the roots and not by the chemical nutrient availability in the rhizosphere or by shoot growth rate as controlled by SBTs. When both RZT and SBT were reduced, the decrease in net translocation rates of Mn and Zn was similar to the decline in the shoot growth rate and concentrations of Mn and Zn in the shoot fresh matter were not greatly affected or were even increased by low RZT. However, at high SBT and low RZT in nutrient solution, the depressed net translocation rates of Mn and Zn combined with the increased shoot growth resulted in significantly decreased concentrations of Mn and Zn in the shoot, indicating that Mn and Zn may become deficient even at high chemical availability. By contrast to Mn and Zn, the net translocation rates of Fe and Cu at all RZTs were markedly enhanced by increased SBTs. Accordingly, the concentrations of Fe and Cu in the shoot fresh matter were not greatly affected by RZTs, irrespective of the SBTs. These results indicate that the ability of roots to supply Fe and Cu to the shoot was internally regulated by the growth related shoot demand per unit of roots. Deceased 21 September 1996 Deceased 21 September 1996     

Bioremediation of a petroleum‐contaminated cryic soil: Effects of phosphorus,nitrogen, and temperature

Bioremediation has been shown to be an effective means of treating petroleum‐contaminated soils in cold areas, although the conditions required to maximize bioremediation in cold region (cryic) soils are not well documented. A laboratory study was conducted to investigate the effects of nitrogen and phosphorus levels and temperature on petroleum bioremediation. A cryic entisol contaminated with diesel fuel was treated with nitrogen (0, 400, 800, or 1200 mg/kg of soil) and phosphorus (0, 60, 120, or 180 mg/kg of soil) and incubated at two temperatures (10 and 20°C). At 10°C, bioremediation rates were not affected by fertility treatments. At 20°C, reaction rates were increased by the addition of P, but unaffected by N. Regardless of fertility regime, the rate of diesel loss was much greater in soil incubated at 20°C than in soil incubated at 10°C.     

Manganese application alleviates the water deficit-induced decline of N2 fixation

Water deficit is a very serious constraint on N₂ fixation rates and grain yield of soybean (Glycine max Merr.). Ureides are transported from the nodules and they accumulate in the leaves during soil drying. This accumulation appears responsible for a feedback mechanism on nitrogen fixation, and it is hypothesized to result from a decreased ureide degradation in the leaf. One enzyme involved in the ureide degradation, allantoate amidohydrolase, is manganese (Mn) dependent. As Mn deficiency can occur in soils where soybean is grown, this deficiency may aggravate soybean sensitivity to water deficit. In situ ureide breakdown was measured by incubating soybean leaves in a 5 mol m ^{? 3} allantoic acid solution for 9 h before sampling leaf discs in which remnant ureide was measured over time. In situ ureide breakdown was dramatically decreased in leaves from plants grown without Mn. At the plant level, allantoic acid application in the nutrient solution of hydroponically grown soybean resulted in a higher accumulation of ureide in leaves and lower acetylene reduction activity (ARA) by plants grown with 0 mol m ^{? 3} Mn than those grown with 6·6 mol m ^{? 3} Mn. Those plants grown with 6·6 mol m ^{? 3} Mn in comparison with those grown with 52·8 mol m ^{? 3} Mn had, in turn, higher accumulated ureide and lower ARA. To determine if Mn level also influenced N₂ fixation sensitivity to water deficit, a dry‐down experiment was carried out by slowly dehydrating plants that were grown in soil under four different Mn nutritions. Plants receiving no Mn had the lowest leaf Mn concentration, 11·9 mg kg ^{? 1}, and had N₂ fixation more sensitive to water deficit than plants treated with Mn in which leaf Mn concentration was in the range of 21–33 mg kg ^{? 1}. The highest Mn treatments increased leaf Mn concentration to 37·5 mg kg ^{? 1} and above but did not delay the decline of ARA with soil drying, although these plants showed a significant increase in ARA under well‐watered conditions.     

ARSENIC CHEMISTRY AND REMEDIATION IN HAWAIIAN SOILS

Past use of arsenical pesticides has resulted in elevated levels of arsenic (As) in some Hawaiian soils. Total As concentrations of 20–100 mg/kg are not uncommon, and can exceed 900 mg/kg in some lands formerly planted with sugarcane. With high contents of amorphous aluminosilicates and iron oxides in many Hawaii's volcanic ash-derived Andisols, a high proportion (25–30%) of soil As was associated with either these mineral phases or with organic matter. Less than 1% of the total As was water soluble or exchangeable. Furthermore, the soils can sorb As strongly: the addition of 1000 mg/kg as As (+5) resulted in only between 0.03 and 0.30 mg/L As in soil solution. In contrast, soils having more crystalline minerals (e.g., Oxisols) sorb less As and thus often contain less As. Phosphate fertilization increases As bioaccessibility, whereas the addition of Fe(OH)₃ decreases it. Brake fern (Pteris vittata L.) can be used to remove some soil As. Concentrations of As in fronds varied on average from 60 mg/kg when grown on a low-As Oxisol to 350 mg/kg when grown on a high-As Andisol. Ratios of leaf As to CaCl₂-extractable soil As were 12 and 222 for the Oxisol and Andisol, respectively.     

Effects of phosphorus and iron fertilizers on the growth of two soybean varieties at two soil temperatures

The influence of FeEDDHA (0, 0.2 and 2 μg Fe g⁻¹ soil) and NaH₂PO₄·H₂O (0 and 120 μg Pg⁻¹ soil) on the growth of two Fe-ineffective soybean (Glycine max L. Merr.) varieties (anoka and T203) on a calcareous soil at two soil temperatures (16 and 24°C) was compared under greenhouse conditions. The two soybean varieties differed in the following respects: (a) T203 accumulated smaller concentrations of Fe in washed tops than Anoka under comparable conditions; (b) T203 was more susceptible to Fe deficiency and its accentuation by high levels of fertilizer P than Anoka; (c) T203 accumulated lower quantities of Mn in tops than Anoka under comparable conditions; (d) T203, but not Anoka, developed Mn deficiency symptoms when treated with P and 2 μg Fe g⁻¹ at 16°C. Fe deficiency was more severe in both varieties at the higher soil temperature due apparently to: (a) greater plant concentration of P in tops at 24°C; and/or (b) an increased rate of plant growth and greater dilution of Fe in young tissue at 24°C. Foliar P concentration was increased much more than foliar Fe concentration by an increase in soil temperature. Severely Fe deficient T203 plants grown without FeEDDHA at 24°C accumulated less foliar Mn than their FeEDDHA counterparts. Comparisons of Fe effectiveness of various soybean cultivars based on relative responses to FeEDDHA can be influenced by differential effects on Mn nutrition.     

Degradation of p-nitrophenol and pentachlorophenol mixtures by Sphingomonas sp. UG30 in soil perfusion bioreactors

The degradation of mixtures of pentachlorophenol (PCP) and p-nitrophenol (PNP) were evaluated in pure cultures of Sphingomonas sp. UG30, statically incubated soils (60% water-holding capacity) and soil perfusion bioreactors where encapsulated cells of UG30 were used as a soil inoculant. In pure-culture studies, conditions were optimized for mineralization of PCP and PNP mixtures at concentrations of 30 mg l⁻¹ each. Optimum in vitro mineralization of PCP and PNP mixtures by UG30 was facilitated using ammonium phosphate as a nitrogen source, while inhibition was observed with ammonium nitrate. The bioreactor system used columns containing soil treated with mixtures of 100, 225 or 500 mg kg⁻¹ of PCP and PNP. Rapid dissipation of both substrates was observed at the 100 mg kg⁻¹ level. Inoculation with UG30 enhanced PCP degradation at the 100 mg kg⁻¹ level in bioreactors but not in static soil microcosms. At higher PCP and PNP concentrations (225 mg kg⁻¹), occasional complete degradation of PNP was observed, and PCP degradation was about 80% compared to about 25% in statically incubated soils after 20 days at 22°C. There was no additional degradation of the PCP and PNP mixtures attributable to inoculation with encapsulated cells of UG30 in either soil system at concentrations of 225 or 500 mg kg⁻¹. Journal of Industrial Microbiology & Biotechnology (2000) 25, 93–99. Received 25 February 2000/ Accepted in revised form 07 June 2000     

Removal of Nonvolatile Hydrophobic Compounds from Artificially and Naturally Contaminated Soils by Column Flotation

Removal of a nonvolatile paraffin oil from spiked soils using column flotation with countercurrent bubbles was explored at both ambient and elevated temperatures. Up to 80% of the contaminant was separated from the coarse fraction (250 to 800?µm) by flotation at 45°C using aqueous solutions of anionic and nonionic surfactants or alkali salt as collectors. With the 75 to 800?µm fraction, removal efficiencies of up to 65% was achieved. Sodium dodecyl-sulfate and Triton 100X at 50?ppm concentrations as well as sodium carbonate at pH 10 were found to yield similar removal efficiencies. Same surfactants were tested in soil washing experiments at similar and higher dosages. Removal efficiency by flotation was higher than those obtained by soil washing in all cases. In addition, as high surfactant dosage are not used in flotation, unlike in the case of soil washing, the problem of formation of stable emulsions was absent. Experiments with soil polluted by hydrocarbons from a contaminated site demonstrated the feasibility of the flotation process for decontamination of coarse (250 to 830?µm) fractions. A 70% reduction of petroleum hydrocarbon in soil was achieved as a result of flotation at 45°C using the above surfactants.     

The effects of soil sterilisation with steam-air mixtures on the development of some glasshouse crops

Summary The undesirable side effects in lettuce crops grown on soils sterilised at 100°C, do not occur on soils sterilised with steam-air mixtures at 70°C. Both in pot experiments and in field trials, significantly higher yields were obtained on soil sterilised at 70°C than on soil sterilised at 100°C. In the pot experiments the average head weight of lettuce obtained from eight soil types was about 20% greater on the soil heated to 70°C than on the soil heated to 100°C. A similar increase in yield was found in the field trials conducted over two years. Apart from increased weight, lettuce grown on soil sterilised at 70°C was of significantly better quality with improved shape of head and showing less susceptibility to tipburn and marginal leaf scorch.In the field experiments mentioned tomatoes followed the lettuce crops. The reaction of cucumbers to soil sterilisation at different temperatures was investigated in another field experiment. No significant differences in yield resulting from the treatments were found in tomatoes and cucumbers.The manganese content of the crops grown on soil sterilised at 100°C was usually considerably higher than on soil sterilised at 70°C. This was the case particularly with lettuce which showed some very great differences on some soil types.     

Influence of temperature on the expression of manganese toxicity by two soybean varieties

Summary Two soybean varieties (Glycine max) were grown in nutrient solution to investigate their response to manganese toxicity at two different temperature regimes. Dry matter yields of both varieties were markedly reduced by lower temperature (21°C day/18°C night). At these temperatures leaf crinkle symptoms of Mn toxicity were very severe on Bragg and moderate on Lee at high levels of Mn in solution (15 ppm). However increasing the temperature to 33°C day/28°C night completely eliminated symptoms on both varieties. High levels (15 ppm) of Mn in nutrient solution decreased yields of both varieties at low temperature with Bragg showing the greater reduction. At high temperature neither variety showed yield reductions at 15 ppm Mn. Higher concentrations of Mn in shoots and roots were obtained at higher temperature, indicating that increased tolerance was not associated with lower plant Mn levels. Lee consistantly contained higher levels of Mn in the shoots than Bragg in the 15 ppm Mn solution at both temperatures although appearing to be more tolerant at low temperatures. The implications of these results for environmental effects on the expression of Mn toxicity in the field are discussed. re]19751202     

Soil chemical limitations to growth and development of Veronica officinalis L. and Carex pilulifera L.

Veronica officinalis and Carex pilulifera, widespread plants of acid soils in Europe, were grown in 50 soils of natural and seminatural ecosystems representing a wide range of soil chemical properties. The experiment was performed in a greenhouse at a soil moisture content of 55–65% WHC, ca. 60% R.H. of the air, temperature 14–16°C at night and 19–21°C by day; additional light 70 W m^-2 12 h d^-1. Properties closely related to soil acidity precluded growth of V. officinalis and limited the growth rate of C. pilulifera at soil pH-KCl < ca. 3.4. In slightly-moderately alkaline (calcareous) soils, growth was primarily limited by insufficient phosphate uptake. A low growth rate of C. pilulifera. in such soils was related to low concentrations of exchangeable soil phosphate and low tissue concentrations of phosphorus. However, in high-pH soils, secondary effects due to suboptimum trace element (probably Fe) conditions, giving rise to symptoms of chlorosis, were also indicated. The highest growth rates of both species were invariably measured in soils of intermediate acidity having very high concentrations of exchangeable phosphate. Multiple regression tests on the entire material indicated that 65–75% of the variability in several growth functions could be accounted for, when two or more soil characters were included in the equation. Besides phosphate, exchangeable Zn (in C. pilulifera) and nitrate (in V. officinalis) were of considerable importance in accounting for growth rates.     

青葙对土壤锰的耐性和富集特征

通过盆栽试验,研究了青葙(Celosia argentea Linn.)对不同浓度(0、50、100、200、300、500 mg/kg)锰(Mn)污染土壤的吸收和积累特性。结果表明,青葙的锰含量、生物富集系数和生物量均随着土壤锰浓度的增加而增加。当土壤锰含量为300 mg/kg时,青葙生长良好。在锰浓度500 mg/kg时,青葙叶片边缘出现轻微褪绿现象,但是植株的生长未受到抑制,并且叶片生物量显著增加(P0.05)。此时,叶片中锰含量达到最大值42927 mg/kg,生物富集系数为69.20。青葙吸收的锰有95%—97%被转移到地上部分,表明该植物对锰具有很强转运能力。本研究的结果为利用青葙修复锰污染土壤提供了有力证据。     

Effect of heating on properties of some soils from Southern Nigeria and growth of rice

Summary The effect of heating on the properties of Apomu (Psammentic Usthorthent), Egbeda (Oxic Paleustalf) and Gambari (Typic Plinthustalf) surface soils were studied under laboratory conditions. Heating at low temperatures (100°C) have no detrimental effects on soil properties, on the contrary it increased the soil extractable P, Mg, Fe, Mn and Zn levels. Pronounced reductions in total N, Org. C, Org. P and extractable Ca and Mg levels and marked increases in extractable P, Zn, Mn and Fe were observed by heating to 200°C. Heating to 500° had an adverse effect on soil chemical and physical properties.Plant height and dry matter yeild of rice plants were higher when grown on Egbeda soil previously heated to 100°C. With addition of N, P and K there was no observed beneficial effect of the heating treatment. Rice plants grown on Egbeda soil previously heated to 200°C showed high uptake of Mn. Plants grew badly in soil previously heated to 500°C.     

Plant-Growth-Promoting Fungicide-Tolerant Rhizobium Improves Growth and Symbiotic Characteristics of Lentil (Lens esculentus) in Fungicide-Applied Soil

The goal of this study was to identify lentil-specific rhizobial strains with the ability to tolerate fungicide and synthesize plant growth regulators even in soils contaminated with fungicides. A fungicide-tolerant and plant-growth-promoting rhizobial strain was used to assess its impact on lentil grown in fungicide-treated soils. The tebuconazole-tolerant Rhizobium sp. strain MRL3 produced plant-growth-promoting substances when grown in the presence and the absence of tebuconazole. Tebuconazole at the recommended and two and three times the recommended doses decreased consistently the dry biomass, symbiotic properties, nutrient uptake, and seed yields of lentil plants. In contrast, the fungicide-tolerant strain MRL3 significantly increased the measured parameters when lentil was grown in soils treated with varying concentrations of tebuconazole compared to uninoculated plants. As an example, strain MRL3 with 100 μg tebuconazole/kg soil significantly increased the root nitrogen, shoot nitrogen, root phosphorus, shoot phosphorus, and seed yield by 31, 10, 41, 21, and 117%, respectively, compared to the uninoculated plants grown in soil treated solely with 100 μg tebuconazole/kg soil. In conclusion, the Rhizobium strain MRL3 may be applied as biofertilizer to enhance the performance of lentil plants in fungicide-applied soils.     

Variations in soil culturable bacteria communities and biochemical characteristics in the Dongkemadi glacier forefield along a chronosequence

The variations in the soil culturable bacterial communities and biochemical parameters of early successional soils from a receding glacier in the Tanggula Mountain were investigated. We examined low organic carbon (C) and nitrogen (N) contents and enzymatic activity, correlated with fewer bacterial groups and numbers in the glacier forefield soils. The soil pH values decreased, but the soil water content, organic C and total N significantly increased, along the chronosequence. The soil C/N ratio decreased in the early development soils and increased in the late development soils and it did not correlate with the soil age since deglaciation. The activities of soil urease, sucrase, protease, polyphenol oxidase, catalase, and dehydrogenase increased along the chronosequence. The numbers of culturable bacteria in the soils increased as cultured at 25°C while decreased at 4°C from younger soils to older soils. Total numbers of culturable bacteria in the soils cultured at 25°C were significantly positively correlated to the soil total N, organic C, and soil water content, as well as the activities of soil urease, sucrase, dehydrogenase, catalase, and polyphenol oxidase. We have obtained 224 isolates from the glacier forefield soils. The isolates were clustered into 28 groups by amplified ribosomal DNA restriction analysis (ARDRA). Among them, 27 groups and 25 groups were obtained from the soils at 25°C and at 4°C incubation temperatures, respectively. These groups are affiliated with 18 genera that belong to six taxa, viz, Actinobacteria, Gammaproteobacteria, Bacteroidetes, Firmicutes, Alphaproteobacteria, and Betaproteobacteria. The dominant taxa were Actinobacteria, Gammaproteobacteria, and Bacteroidetes in all the samples. The abundance and the diversity of the genera isolated at 25°C incubation temperature were greater than that at 4°C.     

DDX Profiles in Agricultural Fields Used for Cucurbit Production in Sakarya,Turkey

DDT (2,2-bis(chlorophenyl)-1,1,1- trichloroethane) and its metabolites DDD (2,2-bis(chlorophenyl)-1,1 -dichloroethane) and DDE (2,2-bis(chloraphenyl)-1,1 –dichloroethylene) have half-lives in soil measured in years or decades and are classified as Persistent Organic Pollutants (POPs). In this study, p,p′-DDT, p,p′-DDD, and p,p′-DDE residues were investigated in select agricultural fields of Sakarya Province, Turkey, where Cucurbitaceae have been grown for many years. Total squash and pumpkin production in Sakarya is approximately 3% of total cucurbit production of Turkey but little is known about the concentrations of DDT, DDD, and DDE in these agricultural soils. Thirty-three soil samples were collected from agricultural fields in different counties of Sakarya. p,p′-DDT was detected in all soil samples, with concentrations ranging from 0.23 ng/g to 123 ng/g soil (dry weight). The concentrations of p,p′-DDT metabolites ranged from nondetectable (<0.06 ng/g) to 120 ng/g for p,p′-DDD and from nondetectable (<0.03 ng/g) to 294 ng/g for p,p′-DDE. The highest total DDX (sum of p,p′-DDT, p,p′-DDD, and p,p′-DDE) concentrations among the soil samples was 428 ng/g in a sample collected from Karasu County. Further research in this field was conducted to measure p,p′-DDT, p,p′-DDE, and p,p′-DDD concentrations at multiple locations as a function of soil depth. p,p′-DDT concentrations were measured from 52 ng/g to 1935 ng/g at 0–60 cm depth. The highest DDX concentration was observed at a location where plants have been actively grown since 1987. The lowest DDX concentrations were observed where crops have not been grown since 1987. Our data proved that soil DDX levels at the field gradually increased as a function of how extensively the field has been used for cucurbits production. However, it is not certain whether the application of p,p′-DDT was terminated or if there may still be illegal usage in agricultural soils.