Enzymatic treatment of sanitary landfill leachate

The objective of this investigation was to study the effectiveness of applying enzymes (bioaugmentation) for enhancement of biological treatability of leachates generated in a typical municipal solid waste sanitary landfill. The basic purpose of enzyme use is to enforce the biodecomposition of organic constituents, as well as to reduce nitrogen content. A laboratory-scale sequencing batch (bio)reactor (SBR) was used for the examination of enzymatic application. The effect of different operation strategies on the efficiency of this biological treatment process was studied to optimize performance, especially for the removal of nitrogen compounds and of biodegradable organic matter. It was found that the enzymatic process was able to remove organic matter effectively (expressed as BOD5 and COD) and nitrogen content, color and turbidity.     

Enhanced transport of pesticides in a field trial with treated sewage sludge

This study was designed to provide high-density data on spatial distribution of three herbicides with different physiochemical characteristics in a sludge-amended and non-amended control field over the course of an irrigation season. The field experiment was carried out on a sandy loam Hamra Red Mediterranean soil (Rhodoxeralf) at Bet Dagan, Israel. After a single 50 mm irrigation event, the mean centers of mass (COM) in the control field were at 15.6, 14.9, and 17 cm for bromacil, atrazine and terbuthylazine, respectively; in the sludge-amended field, mean COMs were at 28.8, 31.2, and 34.1 cm, respectively. After 500 mm of irrigation in the control field, the COM depth distribution of the three pesticides was inversely correlated with octanol-water (Kow) distribution coefficients and soil sorption coefficients (Koc), and positively correlated with aqueous solubilities. After 500 mm irrigation in the sludge-amended field, the mean terbuthylazine COM was at 19.8 cm versus 13.8 cm for the control field, demonstrating a sustained enhanced effect on terbuthylazine transport. Downward transport of atrazine was also enhanced by sludge amendment, albeit less than terbuthylazine. Bromacil was preferentially accumulated in the upper soil layers of the sludge-amended field as compared with the control field after 500 mm irrigation. The enhanced transport of all three pesticides in the sludge-amended field after a single irrigation event is attributed to development of preferential flow pathways around hydrophobic clods of sludge. Enhanced transport of terbuthylazine, and to a lesser extent, atrazine, throughout the irrigation season, is attributed to their transport as complexes with dissolved, colloidal and suspended organic matter derived from sludge degradation.     

Critical remarks on the use of terrestrial moss (Hylocomium splendens and Pleurozium schreberi) for monitoring of airborne pollution

Duplicate samples of the two terrestrial moss species Hylocomium splendens and Pleurozium schreberi, which are widely used to monitor airborne heavy metal pollution, have been collected from eight catchments spread over a 1,500,000 km2 area in northern Europe. These were analysed for a total of 38 elements by inductively coupled plasma-mass spectrometry, inductively coupled plasma-atomic emission spectrometry and cold vapour-atomic absorption spectometry techniques. Results show that the moss species can be combined without interspecies calibration for regional mapping purposes. For the majority of elements the observed within-catchment variation is large--big composite samples over a large area should thus be collected when moss is to be used for monitoring purposes. For the majority of elements the input of dust governs moss chemistry. For a reliable 'contamination' signal over a sizeable area a major source is needed. Some elements show a dependence on climate/vegetation zone. In coastal areas the input of marine aerosols will alter the chemical signal obtained from moss samples.     

Contribution of dissolved sulfates and sulfites in hydrogen sulfide emission from stagnant water bodies in Sri Lanka

Accumulation of sulfur-containing compounds and their bacterial mediated reductions have led to the emission of pungent odors from stagnant water bodies. This study is focused on the contribution of inorganic sulfur compounds in the emission of hydrogen sulfide. The measured dissolved oxygen levels have demonstrated good negative correlations with the dissolved sulfide levels implying the oxygen deficiency is the key for the reduction of sulfate ion and sulfite ion to sulfide ion. Particularly, the dissolved molar fractions of sulfide from the total dissolved sulfur compounds (sulfates, sulfites and sulfides) have a very good correlation with the dissolved oxygen for the stagnant water bodies except the artificially aerated prawn farms. For the stagnant water bodies with significant correlations, linear regressions are reported for them to be utilized in estimating one component of the regression from the measurement of the other. The measured data were further utilized to estimate the levels of hydrogen sulfide gas. The pH of the water bodies has confined much of the dissolved sulfides in the form of bisulfide ion and they can be easily escaped to the atmosphere upon acidification due to industrial discharges and/or acidic precipitations. The estimated levels of hydrogen sulfide just above the water surface were plotted for the most polluted stagnant water body in Sri Lanka for the pH range of 5-10 and temperature range of 25-35 degrees C.     

Ecological tax reforms and environmental benefits in Italy and Sweden

The paper calculates the implications of including monetary measurements of environmental emission changes for the welfare impacts of ecological tax reforms in Italy and Sweden. Taxes on emissions of SO₂, NO_x and CO₂ are investigated. Country-specific computable equilibrium models are used for estimating net welfare changes of the introduction of these taxes, the incomes of which are used for reducing distorting labour taxes. The results indicate that the inclusion of environmental benefits reduces the costs of ecological tax reforms considerably for both countries, and may even turn into net welfare gains.     

Uranium transport around the reactor zone at Bangombé and Okélobondo (Oklo): examples of hydrogeological and geochemical model integration and data evaluation

The sites at Bangombé and Okélobondo (Oklo) in Gabon provide a unique opportunity to study the behaviour of products from natural nuclear reactions in the vicinity of reactor zones which were active around two billion years ago. The Commission of the European Communities initiated the Oklo Natural Analogue Programme. One of the principal aims was to study indications of present time migration of elements from the reactor zones under ambient conditions. The hydrogeological and hydrochemical data from the Oklo sites were modelled in order to better understand the geochemical behaviour of radionuclides in the natural system, by using independent models and by comparing the modelling outcome. Two modelling approaches were used: M3 code (hydrochemical mixing and mass balance model), developed by the Swedish Nuclear Fuel and Waste Management Company (SKB) and HYTEC (reactive transport model) developed by Ecole des Mines de Paris. Two different reactor zones were studied: Bangombé, a shallow site, the reactor being at 11 m depth, and OK84 at Okélobondo, situated at about 450 m depth, more comparable with a real repository location. This allowed the validation of modelling tools in two different sedimentary environments: one shallow, with a more homogeneous layering situated in an area of meteoric alteration, and the other offering the opportunity to study radionuclide migration from the reaction zone over a distance of 450 m through very heterogeneous sedimentary layers. The modeling results indicate that the chemical reactions retarding radionuclide transport are very different at the two sites. At Bangombé, the decomposition of organic material consumes oxygen and at Okélobondo the oxygen is consumed by inorganic reactions resulting, in both cases, in uranium retardation. Both modelling approaches (statistic with M3 code and deterministic with HYTEC code) could describe this situation. The goal of this exercise is to test codes which can help to describe and understand the processes taking place at the sites, validate the models with in situ data, and thus build confidence in the tools used for future site characterization. Ultimately, this allows identifying and selecting processes and parameters that can be used as input into repository performance assessment calculations and modelling exercises.     

Radon levels in Cyprus

Radon levels in atmospheric and aquatic systems in Cyprus have recently been measured using the radon monitor Alpha Guard. Indoor and outdoor radon levels were obtained in situ, whereas analysis of radon concentrations in water was performed using tap and ground water samples collected from several areas of the island. The average value for outdoor and indoor radon concentration is 11+/-10 and 7+/-6 Bq m(-3), respectively, and for tap and ground water 0.4 Bq l(-1) and 1.4 Bq l(-1), respectively. From these data the annual dose equivalent of airborne radon to the Cypriot population is about 0.19 mSv y(-1), which is quite low compared to the total dose equivalent of natural and man-made ionising radiation in Cyprus. Radon levels in aquatic systems are relatively low due to an exhaustive utilisation of ground water resources and also to the increased input of desalinated sea water in the water distribution network and eventually into the ground water reservoirs.     

Simulating endosulfan transport in runoff from cotton fields in Australia with the GLEAMS model

Endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9methano-2,4,3-benzodioxathiepin 3-oxide), a pesticide that is highly toxic to aquatic organisms, is widely used in the cotton (Gossypium hirsutum L.) industry in Australia and is a risk to the downstream riverine environment. We used the GLEAMS model to evaluate the effectiveness of a range of management scenarios aimed at minimizing endosulfan transport in runoff at the field scale. The field management scenarios simulated were (i) Conventional, bare soil at the beginning of the cotton season and seven irrigations per season; (ii) Improved Irrigation, irrigation amounts reduced and frequency increased to reduce runoff from excess irrigation; (iii) Dryland, no irrigation; (iv) Stubble Retained, increased soil cover created by retaining residue from the previous crop or a specially planted winter cover crop; and (v) Reduced Sprays, a fewer number of sprays. Stubble Retained was the most effective scenario for minimizing endosulfan transport because infiltration was increased and erosion reduced, and the stubble intercepted and neutralized a proportion of the applied endosulfan. Reducing excess irrigation reduced annual export rates by 80 to 90%, but transport in larger storm events was still high. Reducing the number of pesticide applications only reduced transport when three or fewer sprays were applied. We conclude that endosulfan transport from cotton farms can be minimized with a combination of field management practices that reduce excess irrigation and concentration of pesticide on the soil at any point in time; however, discharges, probably with endosulfan concentrations exceeding guideline values, will still occur in storm events.     

Atrazine, isoproturon, mecoprop, 2,4-D, and bentazone adsorption onto iron oxides

Iron oxides are important components influencing the adsorption of various inorganic and organic compounds in soils and sediments. In this study the adsorption on iron oxides of nonionic and ionic pesticides was determined as a function of solution pH, ionic strength, and pesticide concentration. The investigated iron oxides included two-line ferrihydrite, goethite, and lepidocrocite. Selected pesticides comprised atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine), isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea)], mecoprop [(RS)-2-(4-chloro-2-methylphenoxy)propionic acid], 2,4-D (2,4-dichlorophenoxyacetic acid), and bentazone [3-isopropyl-1H-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide]. The adsorption of the nonionic pesticides (atrazine and isoproturon) was insignificant, whereas the adsorption of the acidic pesticides (mecoprop, 2,4-D, and bentazone) was significant on all investigated iron oxides. The adsorption capacity increased with decreasing pH, with maximum adsorption reached close to the pKa values. The addition of CaCl2 in concentrations from 0.0025 to 0.01 M caused the adsorption capacity to diminish. The adsorption of bentazone was significantly lower than the adsorption of mecoprop and 2,4-D, illustrating the importance of a carboxyl group in the pesticide structure. The adsorption capacity on the iron oxides increased in the order: lepidocrocite < goethite < two-line ferrihydrite. The maximum adsorption capacities of meco-prop and 2,4-D on goethite were found to be equivalent to the site density of singly coordinated hydroxyl groups on the faces of the dominant (110) form, suggesting that singly coordinated hydroxyl groups are responsible for adsorption. Differences in adsorption capacities between iron oxides can be explained by differences in the surface site density of singly coordinated hydroxyl groups. The maximum measured adsorption capacity of mecoprop on two-line ferrihydrite was equivalent to 0.2 mol/mol Fe.     

Tillage, intercrop, and controlled drainage-subirrigation influence atrazine, metribuzin, and metolachlor loss

Atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) and metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] have been found with increasing occurrence in rivers and streams. Their continued use will require changes in agricultural practices. We compared water quality from four crop-tillage treatments: (i) conventional moldboard plow (MB), (ii) MB with ryegrass (Lolium multiflorum Lam.) intercrop (IC), (iii) soil saver (SS), and (iv) SS + IC; and two drainage control treatments, drained (D) and controlled drainage-subirrigation (CDS). Atrazine (1.1 kg a.i. ha-1), metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazine-5(4H)-one] (0.5 kg a.i. ha-1), and metolachlor (1.68 kg a.i. ha-1) were applied preemergence in a band over seeded corn (Zea mays L.) rows. Herbicide concentration and losses were monitored from 1992 to spring 1995. Annual herbicide losses ranged from < 0.3 to 2.7% of application. Crop-tillage treatment influenced herbicide loss in 1992 but not in 1993 or 1994, whereas CDS affected partitioning of losses in most years. In 1992, SS + IC reduced herbicide loss in tile drains and surface runoff by 46 to 49% compared with MB. The intercrop reduced surface runoff, which reduced herbicide transport. Controlled drainage-subirrigation increased herbicide loss in surface runoff but decreased loss through tile drainage so that total herbicide loss did not differ between drainage treatments. Desethyl atrazine [6-chloro-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine] comprised 7 to 39% of the total triazine loss.