Determination of total petroleum hydrocarbons in soil from different locations using infrared spectrophotometry and gas chromatography

Total petroleum hydrocarbons (TPH) are important environmental contaminants which are toxic to human and environmental receptors. Several analytical methods have been used to quantify TPH levels in contaminated soils, specifically through infrared spectrometry (IR) and gas chromatography (GC). Despite being two of the most used techniques, some issues remain that have been inadequately studied: a) applicability of both techniques to soils contaminated with two distinct types of fuel (petrol and diesel), b) influence of the soil natural organic matter content on the results achieved by various analytical methods, and c) evaluation of the performance of both techniques in analyses of soils with different levels of contamination (presumably non-contaminated and potentially contaminated). The main objectives of this work were to answer these questions and to provide more complete information about the potentials and limitations of GC and IR techniques. The results led us to the following conclusions: a) IR analysis of soils contaminated with petrol is not suitable due to volatilisation losses, b) there is a significant influence of organic matter in IR analysis, and c) both techniques demonstrated the capacity to accurately quantify TPH in soils, irrespective of their contamination levels.

Nanoparticles based Permeable Reactive Barriers as an Eco-efficient Technology for nitrate remediation in soil and groundwater

The need to increase agricultural yield led, among others, to an increase in the consumption of nitrogen based fertilizers. As a consequence, there are excessive concentrations of nitrates, the most abundant of the reactive nitrogen (Nr) species, in several areas of the world. The demographic changes and projected population growth for the next decades, and the economic shifts which are already shaping the near future are powerful drivers for a further intensification in the use of fertilizers, with a predicted increase of the nitrogen loads in soils. Nitrate easily diffuses in the subsurface environments, portraying high mobility in soils. Moreover, the presence of high nitrate loads in water has the potential to cause an array of health dysfunctions, such as methemoglobinemia and several cancers. Permeable Reactive Barriers (PRB) placed strategically relatively to the nitrate source constitute an effective technology to tackle nitrate pollution. Ergo, PRB avoid various adverse impacts resulting from the displacement of reactive nitrogen downstream along water bodies. A four stages literature review was carried out in 34 databases. Initially, a set of pertinent key words were identified to perform the initial databases searches. Then, the synonyms of those initial key words were used to carry out a second set of databases searches. The third stage comprised the identification of other additional relevant terms from the research papers identified in the previous two stages. Again, databases searches were performed with this third set of key words. The final step consisted of the identification of relevant papers from the bibliography of the relevant papers identified in the previous three stages of the literature review process. The set of papers identified as relevant for in-depth analysis were assessed considering a set of relevant characterization variables.

The frequency rate of Toxocara species contamination in soil samples from public yards in a urban area "Payathai", Bangkok, Thailand

Toxocara species are most common roundworms of Canidae and Felidae. Human toxocariasis develops by ingesting of embryonated eggs in contaminated soil. There is no previous report of Toxocara contamination in the soil samples from the public areas in Bangkok. For this reason our study have been carried out to examine the frequency of Toxocara eggs in public yards in Bangkok, Thailand. A total of 175 sand and clay samples were collected and examined for parasite eggs. According to this study, Toxocara eggs were detected from 10 (5.71%) of 175 soil samples. The high rate of contamination in this study implies the importance of the control of this possible zoonotic disease: control of abandon of dogs and cats, is still necessary.

The use of nanoparticles in soil and water remediation processes

Environmental nanoremediation of various contaminants has been reported in several recent studies. In this paper, the state of the art on the use of nanoparticles in soil and groundwater remediation processes is presented. There is a substantive body of evidence on the growing and successful application of nanoremediation for a diversity of soil and groundwater contamination contexts, particularly, for heavy metals, other inorganic contaminants, organic contaminants and emerging contaminants, as pharmaceutical and personal care products. This review confirms the competence of the use of nanoparticles in the remediation of contaminated media and the prevalent use of iron based nanoparticles.

An evaluation of septic tank effluent movement in soil and groundwater systems

Recent studies have shown that septic tank systems are a major source of groundwater pollution. Many public health workers feel that the most cri^cal aspect of the use of septic tanks as a means of sewage disposal is the contamination of private water wells with attendant human health hazards. In this study the movement and attenuation of septic tank effluents in a range of soil/overburden types and hydrogeological situations was investigated. The suitability of a number of chemical and biological tracer materials to monitor the movement of septic tank effluent constituents to groundwater sources was also examined. The investigation was divided into three separate but inteiTelated sections. In the first section of the study the movement of septic tank effluent from two soil treatment systems was investigated by direct measurements of soil nutrient concentrations and enteric bacterial numbers in the soil beneath and downgradient of the test systems. Two sites with different soil types and hydrogeological characteristics were used. The results indicated that the attenuation of the effluent in both of the treatment systems was incomplete. Migration of nitrate, ammonium, phosphate and fecal bacteria to a depth of 50 cm beneath the inverts of the distribution tiles was demonstrated on all sampling occasions. The lateral migration of the pollutants was less pronounced, although on occasions high nutrients levels and fecal bacterial numbers were detected at a lateral distance of 4.0 m downgradient of the test systems. There was evidence that the degree and extent of effluent migration was increased after periods of heavy or prolonged rainfall when the attenuating properties of the treatment systems were reduced as a result of saturation of the soil. The second part of the study examined the contamination of groundwaters downgradient of septic tank soil treatment systems. Three test sites were used in the investigation. The sites were chosen because of differences in the thicknesses and nature of the unsaturated zone available for effluent attenuation at each of the locations. A series of groundwater monitoring boreholes were installed downgradient of the test systems at each of the sites and these were sampled regularly to assess the efficiency of the overburden material in reducing the polluting potential of the wastewater. Effluent attenuation in the septic tank treatment systems was shown to be incomplete, resulting in chemical and microbiological contamination of the groundwaters downgradient of the systems. The nature and severity of groundwater contamination was dependent on the composition and thickness of the unsaturated zone and the extent of weathering in the underlying saturated bedrock. The movement of septic tank effluent through soil/overburdens to groundwater sources was investigated by adding a range of chemical and biological tracer materials to the three septic tank systems used in section two of the study. The results demonstrated that a single tracer type cannot be used to accurately monitor the movement of all effluent constituents through soils to groundwater. The combined use of lithium bromide and endospores of Bacillus globigii was found to give an accurate indication of the movement of both the chemical and biological effluent constituents.

Process of fixation, imobilization and mineralization of ammonium in soil using N-15

The organic and inorganic forms of soil nitrogen and how they participate in the process of fixation, immobilization and mineralization of ammonium in soils were evaluated, after different periods of incubaton, utilizing two soils, a Lithic Haplustoll and a Typic Eutrorthox. The results obtained permit to suggest that : 1) The method for determination of the ammonium fixing capacity based on the extraction with 2N KC1, is considered to be subject to interferences of other soil fractions capable of retaining ammonium. 2) The increase in exchangeable ammonium content is related to the decrease in amino acids and hydrolyzable ammonium. 3) The immobilization and mineralization processes are still held under mil microbial. The forms more affected by this condition are amino acids and hydrolyzable ammonium.

Oxygen-sensing reporter strain of Pseudomonas fluorescens for monitoring the distribution of low-oxygen habitats in soil.

The root-colonizing bacterium Pseudomonas fluorescens CHA0 was used to construct an oxygen-responsive biosensor. An anaerobically inducible promoter of Pseudomonas aeruginosa, which depends on the FNR (fumarate and nitrate reductase regulation)-like transcriptional regulator ANR (anaerobic regulation of arginine deiminase and nitrate reductase pathways), was fused to the structural lacZ gene of Escherichia coli. By inserting the reporter fusion into the chromosomal attTn7 site of P. fluorescens CHA0 by using a mini-Tn7 transposon, the reporter strain, CHA900, was obtained. Grown in glutamate-yeast extract medium in an oxystat at defined oxygen levels, the biosensor CHA900 responded to a decrease in oxygen concentration from 210 x 10(2) Pa to 2 x 10(2) Pa of O(2) by a nearly 100-fold increase in beta-galactosidase activity. Half-maximal induction of the reporter occurred at about 5 x 10(2) Pa. This dose response closely resembles that found for E. coli promoters which are activated by the FNR protein. In a carbon-free buffer or in bulk soil, the biosensor CHA900 still responded to a decrease in oxygen concentration, although here induction was about 10 times lower and the low oxygen response was gradually lost within 3 days. Introduced into a barley-soil microcosm, the biosensor could report decreasing oxygen concentrations in the rhizosphere for a 6-day period. When the water content in the microcosm was raised from 60% to 85% of field capacity, expression of the reporter gene was elevated about twofold above a basal level after 2 days of incubation, suggesting that a water content of 85% caused mild anoxia. Increased compaction of the soil was shown to have a faster and more dramatic effect on the expression of the oxygen reporter than soil water content alone, indicating that factors other than the water-filled pore space influenced the oxygen status of the soil. These experiments illustrate the utility of the biosensor for detecting low oxygen concentrations in the rhizosphere and other soil habitats.

Occurence of larval Culicidae (Diptera) in water retained in Aquascypha hydrophora (Fungus: Stereaceae) in Central Amazônia, Brazil

The community structure of insects, especially mosquito larvae, in water held in the fungus Aquascypha hydrophora (Berk.) Reid (Stereaceae) is reported. The study was done in the Adolpho Ducke Forest Reserve, 26 km east of Manaus, AM, Brazil, from September 1998 through November 1999. The most abundant entomofauna were immature Culicidae (n = 121) 91.7%, followed by adult Dytiscidae (n = 3) 2.3%, immature Chironomidae (n = 5) 3.8% and immature Tipulidae (n = 3) 2.3%. Culicidae associated with A. hydrophora comprised species of the subfamilies Anophelinae and Culicinae.

Binding of ²³⁹Pu and ⁹⁰Sr to organic colloids in soil solutions: evidence from a field experiment.

Colloidal transport has been shown to enhance the migration of plutonium in groundwater downstream from contaminated sites, but little is known about the adsorption of ⁹⁰Sr and plutonium onto colloids in the soil solution of natural soils. We sampled soil solutions using suction cups, and separated colloids using ultrafiltration to determine the distribution of ²³⁹Pu and ⁹⁰Sr between the truly dissolved fraction and the colloidal fraction of the solutions of three Alpine soils contaminated only by global fallout from the nuclear weapon tests. Plutonium was essentially found in the colloidal fraction (>80%) and probably associated with organic matter. A significant amount of colloidal ⁹⁰Sr was detected in organic-rich soil solutions. Our results suggest that binding to organic colloids in the soil solutions plays a key role with respect to the mobility of plutonium in natural alpine soils and, to a lesser extent, to the mobility of ⁹⁰Sr.

Use of the frc gene as a molecular marker to characterize oxalate-oxidizing bacterial abundance and diversity structure in soil.

Oxalate catabolism, which can have both medical and environmental implications, is performed by phylogenetically diverse bacteria. The formyl-CoA-transferase gene was chosen as a molecular marker of the oxalotrophic function. Degenerated primers were deduced from an alignment of frc gene sequences available in databases. The specificity of primers was tested on a variety of frc-containing and frc-lacking bacteria. The frc-primers were then used to develop PCR-DGGE and real-time SybrGreen PCR assays in soils containing various amounts of oxalate. Some PCR products from pure cultures and from soil samples were cloned and sequenced. Data were used to generate a phylogenetic tree showing that environmental PCR products belonged to the target physiological group. The extent of diversity visualised on DGGE pattern was higher for soil samples containing carbonate resulting from oxalate catabolism. Moreover, the amount of frc gene copies in the investigated soils was detected in the range of 1.64x10(7) to 1.75x10(8)/g of dry soil under oxalogenic tree (representing 0.5 to 1.2% of total 16S rRNA gene copies), whereas the number of frc gene copies in the reference soil was 6.4x10(6) (or 0.2% of 16S rRNA gene copies). This indicates that oxalotrophic bacteria are numerous and widespread in soils and that a relationship exists between the presence of the oxalogenic trees Milicia excelsa and Afzelia africana and the relative abundance of oxalotrophic guilds in the total bacterial communities. This is obviously related to the accomplishment of the oxalate-carbonate pathway, which explains the alkalinization and calcium carbonate accumulation occurring below these trees in an otherwise acidic soil. The molecular tools developed in this study will allow in-depth understanding of the functional implication of these bacteria on carbonate accumulation as a way of atmospheric CO(2) sequestration.

Persistence and cell culturability of biocontrol strain Pseudomonas fluorescens CHA0 under plough pan conditions in soil and influence of the anaerobic regulator gene anr.

Certain fluorescent pseudomonads can protect plants from soil-borne pathogens, and it is important to understand how these biocontrol agents survive in soil. The persistence of the biocontrol strain Pseudomonas fluorescens CHA0-Rif under plough pan conditions was assessed in non-sterile soil microcosms by counting total cells (immunofluorescence microscopy), intact cells (BacLight membrane permeability test), viable cells (Kogure's substrate-responsiveness test) and culturable cells (colony counts on selective plates) of the inoculant. Viable but non-culturable cells of CHA0-Rif (106 cells g-1 soil) were found in flooded microcosms amended with fermentable organic matter, in which the soil redox potential was low (plough pan conditions), in agreement with previous observations of plough pan samples from a field inoculated with CHA0-Rif. However, viable but non-culturable cells were not found in unamended flooded, amended unflooded or unamended unflooded (i.e. control) microcosms, suggesting that such cells resulted from exposure of CHA0-Rif to a combination of low redox potential and oxygen limitation in soil. CHA0-Rif is strictly aerobic. Its anaerobic regulator ANR is activated by low oxygen concentrations and it controls production of the biocontrol metabolite hydrogen cyanide under microaerophilic conditions. Under plough pan conditions, an anr-deficient mutant of CHA0-Rif and its complemented derivative displayed the same persistence pattern as CHA0-Rif, indicating that anr was not implicated in the formation of viable but non-culturable cells of this strain at the plough pan.

Organic sulfur oxidation to sulfate in soil samples for total sulfur determination by turbidimetry

Sulfur in the soil occurs in two basic forms, organic and inorganic S. The organic form accounts for 95 % of S in most soils. The effectiveness of organic S to oxidate to sulfate was evaluated for total S determination in soil samples by wet (acid) and dry-ash (alkaline) oxidation methods. To evaluate the wet method and the possible use as a reference when evaluating the dry method proposed here, a reference standard from the US National Institute of Standards and Technology (NIST) was used (Montana Soil - NIST 2710). The dry-ash oxidation process with alkaline oxidizing agents is one of the simplest oxidation methods of organic S to the sulfate form and was compared with the wet process. The objective of the study was to develop a dry method that would be easy to apply and allow the complete conversion of organic S to sulfate in soil samples and later detection by turbidimetry. The effectiveness of organic S oxidation to sulfate was evaluated by means of three alkaline oxidation mixtures: NaHCO3 + Ag2O, Eschka mixture (17 % Na2CO3, 66 % MgO, and 17 % K2CO3), and NaHCO3 + CuO. The procedure to quantify the sulfate concentration was based on the reaction with barium chloride and turbidimetric detection. Sulfur quantification in the standard sample by the wet method proved adequate, precise and accurate. It should also be pointed out that no significant differences were found (95 % reliability) between the wet and dry processes (NaHCO3 and Ag2O oxidation mixture) in six different Brazilian soils. The proposed dry method can therefore be used in the preparation of soil samples for total S determination.

Transport of a biocontrol Pseudomonas fluorescens through 2.5-m deep outdoor lysimeters and survival in the effluent water

Application of wild-type or genetically-modified bacteria to the soil environment entails the risk of dissemination of these organisms to the groundwater. To measure vertical transport of bacteria under natural climatic conditions, Pseudomonas fluorescens strain CHA0 was released together with bromide as a mobile tracer at the surface of large outdoor lysimeters. Two experiments, one starting in autumn 1993 and the other in spring 1994 were performed. Shortly after a heavy rainfall in late spring 1994, the released bacteria were detected for the first time in effluent water from the 2.5-m-deep lysimeters in both experiments, i.e. 210 d and 21 d, respectively, after inoculation. Only a 10−9 to 10−8 fraction of the inoculum was recovered as culturable cells in the effluent water, but a larger fraction of the CHA0 cells was in a non-culturable state as detected with immunofluorescence microscopy. As much as 50% of the mobile tracer percolated through the lysimeters, indicating that, compared with bromide, bacterial cells were retained in soil. In the second part of this study, persistence of CHA0 in groundwater microcosms consisting of lysimeter effluent water was studied for 380 d. Survival of the inoculant as culturable cells was better under anaerobic than under aerobic conditions. However, a large fraction of the cells became non-culturable in both cases. When the experiment was performed with filter-sterilized effluent water, the total count of introduced bacteria did not decline with time. In conclusion, the biocontrol strain was transported in low numbers to a potential groundwater level under natural climatic conditions, but could persist for an extended period in groundwater microcosms.

Microbial and enzymatic activity in soil after organic composting

Microbial activity and biochemical properties are important indicators of the impact of organic composting on soil. The objective of this study was to evaluate some indicators of soil microbial and biochemical processes after application of compost (household waste). A Typic Acrustox, sampled at a depth of 10 cm under Cerrado biome vegetation, was evaluated in three treatments: control (soil without organic compost amendment) and soil with two doses of domestic organic compost (10 and 20 g kg-1 soil). The following properties were evaluated: released C (C-CO2): microbial respiration 15 days after incubation; microbial biomass C (MBC); total glucose (TG); metabolic quotient (qCO2); and enzyme activity of β-glucosidase and acid and alkaline phosphatase. The application of household compost, at doses of 10 and 20 g kg-1 Typic Acrustox, resulted in significant gains in microbial activity, organic C and C stock, as evidenced by increased MBC and TG levels. On the other hand, qCO2 decreases indicated greater microbial diversity and more efficient energy use. The addition of compost, particularly the 20 g kg-1 dose, strongly influenced the enzyme β-glucosidase and phosphatase (acid and alkaline). The β-glucosidase activity was significantly increased and acid phosphatase activity increased more than the alkaline. The ratio of β-glucosidase to MBC was greater in the control than in the composted treatments which suggests that there were more enzymes in the control than in the substrate or that the addition of compost induced a great MBC increase.