Atrazine degradation by anodic Fenton treatment

Anodic Fenton treatment (AFT), an hydroxyl radical oxidation process recently developed for the degradation of aqueous pesticide waste, was applied to the degradation of atrazine, seven degradation products, and a formulated atrazine product. Using AFT, degradation of the parent compound occurred in 3 min. The concentration profiles of seven degradation products formed during treatment were measured, and degradation pathways are proposed for the treatment. The primary termination product after 10 min was dechlorinated ammeline. Three different ¹⁴C labeled atrazine compounds (ethyl, isopropyl and U-triazine ring labeled atrazine) were also treated in an air-tight AFT apparatus and the mass balance was calculated. The triazine ring was not cleaved during this treatment process. Formulated atrazine was 70% degraded in 3 min. AFT holds promise as an effective pesticide-laden water treatment technology.     

Atrazine removal using adsorption and electrochemical regeneration

This paper demonstrates the removal of atrazine using a novel carbon-based adsorbent to below 1.0 microg l(-1) and its subsequent electrochemical regeneration in a simple electrochemical cell. Effective electrochemical regeneration can be achieved with a treatment time as low as 20 min over a number of adsorption/regeneration cycles using laboratory-prepared solutions. The results suggest that electrochemical modification of the particulate surface on electrochemical regeneration can result in adsorptive capacities three times greater than originally achieved.     

Atrazine degradation in anaerobic environment by a mixed microbial consortium

Atrazine degradation by anaerobic mixed culture microorganism in co-metabolic process and in absence of external carbon and nitrogen source was studied at influent atrazine concentration range of 0.5-15 mg/l. Wastewater of desired characteristic was prepared by the addition of various constituents in distilled water spiked with atrazine. In co-metabolic process, dextrose of various concentrations (150-2000 mg/l) was supplied as external carbon source. The reactors were operated in sequential batch mode in which 20% of treated effluent was replaced by the same amount of fresh wastewater everyday, thus maintaining a hydraulic retention time (HRT) equal to 5 days. In co-metabolic process, 40-50% of influent atrazine degradation was observed. First-order atrazine degradation rate (expressed in day(-1)) was better in co-metabolic process (5.5 x 10(-4)) than in absence of external carbon source (2.5 x 10(-5)) or carbon and nitrogen source (1.67 x 10(-5)). In presence of 2000 mg/l of dextrose, atrazine degradation was between 8% and 15% only. Maximum atrazine degradation was observed from wastewater containing 300 mg/l of dextrose and 5mg/l of atrazine. Influent atrazine concentration did not have much effect on the methanogenic bacteria which was clear from methane gas production and specific methanogenic activity (SMA).     

The progressive salination of groundwater in Beirut,Lebanon

The degradation in groundwater quality in Greater Beirut, the subject of several investigations in the past two decades, is attributable to seawater infiltration into the coastal aquifer induced by the excessive and uncontrolled groundwater utilization. The present study elucidates the increasing trend in seawater infiltration from 1971 to 1985. The brackish groundwater, generally used domestically for washing and flushing, is now creating extensive corrosion and scale‐formation problems that have to be faced by the users. At this critical stage, effective measures must be instituted that include the provision of adequate public water supplies to facilitate the control of groundwater utilization.     

The Degradation of Atrazine and Other Pesticides by Photolysis

Groundwaters from chalk aquifers which are used as a supply for drinking water are often contaminated with pesticides - in particular, atrazine. This paper discusses the use of an industrial-scale ultraviolet chamber to reduce the concentration of atrazine in a chalk-derived water which is used for drinking water supply. The concentration of atrazine varied between 0.1 μg/l and 0.5 μg/l, and the raw water was spiked when necessary. Results for other pesticides contaminants are also presented.
The efficiency of atrazine removal is dependent only on the energy input and is constant, regardless of the initial concentration. Hydrogen peroxide improves the efficiency of ultraviolet irradiation but requires high doses.     

Spatial variation of boron in groundwater in South Iraq

The research investigated boron variability in space and time, using 450 groundwater samples from 75 representative wells in the Safwan–Zubair area of Basra district, South Iraq, collected monthly from January to June 2000, with also 75 soil samples from selected farms in the same area. Minimum and maximum values of boron concentrations range from 1.49 to 9.49 ppm respectively. Boron concentration in groundwater spatially occurs in 90% in frequency between 2 and 4 ppm, while 5% below 2 ppm and 5% is more than 4.0 ppm to more than 9.0 ppm, where the soluble boron concentrations of soil samples range from 0.60 to 7.02 ppm. Soil boron concentration spatially occurs 95% below 6.0 ppm and 5% more than 6.0 ppm. The results show that the variability of boron concentration in groundwater and in soil mostly depends upon irrigation water, cyclic differences of the sediment facies horizontally and vertically, and also the period of precipitation (rainfall); i.e. wetting and drying processes. The results indicate that there will always be available boron in the soil at the end of the irrigation period (May–June) ready to be leached again by the first percolated rainfall (effective rainfall) to join the groundwater at higher concentration. The results show that the variability of boron concentration in groundwater and in soil mostly depends upon irrigation water, cyclic differences of the sediment facies horizontally and vertically, and also the period of precipitation (rainfall); i.e. wetting and drying processes. The results indicate that there will always be available boron in the soil at the end of the irrigation period (May–June) ready to be leached again by the first percolated rainfall (effective rainfall) to join the groundwater at higher concentration.     

Manganese concentrations in Scottish groundwater

Groundwater is increasingly being used for public and private water supplies in Scotland, but there is growing evidence that manganese (Mn) concentrations in many groundwater supplies exceed the national drinking water limit of 0.05 mg l^− 1. This study examines the extent and magnitude of high Mn concentrations in groundwater in Scotland and investigates the factors controlling Mn concentrations. A dataset containing 475 high quality groundwater samples was compiled using new data from Baseline Scotland supplemented with additional high quality data where available. Concentrations ranged up to 1.9 mg l^− 1; median Mn concentration was 0.013 mg l^− 1 with 25th and 75th percentiles 0.0014 and 0.072 mg l^− 1 respectively. The Scottish drinking water limit (0.05 mg l^− 1) was exceeded for 30% of samples and the WHO health guideline (0.4 mg l^− 1) by 9%; concentrations were highest in the Carboniferous sedimentary aquifer in central Scotland, the Devonian sedimentary aquifer of Morayshire, and superficial aquifers. Further analysis using 137 samples from the Devonian aquifers indicated strong redox and pH controls (pH, Eh and dissolved oxygen accounted for 58% of variance in Mn concentrations). In addition, an independent relationship between Fe and Mn was observed, suggesting that Fe behaviour in groundwater may affect Mn solubility. Given the redox status and pH of Scottish groundwaters the most likely explanation is sorption of Mn to Fe oxides, which are released into solution when Fe is reduced.Since the occurrence of elevated Mn concentrations is widespread in groundwaters from all aquifer types, consideration should be given to monitoring Mn more widely in both public and private groundwater supplies in Scotland and by implication elsewhere.     

Geochemistry of some rare earth elements in groundwater,Vierlingsbeek, The Netherlands

Groundwater samples were taken from seven bore holes at depths ranging from 2 to 41m nearby drinking water pumping station Vierlingsbeek, The Netherlands and analysed for Y, La, Ce, Pr, Nd, Sm and Eu. Shale-normalized patterns were generally flat and showed that the observed rare earth elements (REE) were probably of natural origin. In the shallow groundwaters the REEs were light REE (LREE) enriched, probably caused by binding of LREEs to colloids. To improve understanding of the behaviour of the REE, two approaches were used: calculations of the speciation and a statistical approach.For the speciation calculations, complexation and precipitation reactions including inorganic and dissolved organic carbon (DOC) compounds, were taken into account. The REE speciation showed REE(3+), REE(SO(4))(+), REE(CO(3))(+) and REE(DOC) being the major species. Dissolution of pure REE precipitates and REE-enriched solid phases did not account for the observed REEs in groundwater. Regulation of REE concentrations by adsorption-desorption processes to Fe(III)(OH)(3) and Al(OH)(3) minerals, which were calculated to be present in nearly all groundwaters, is a probable explanation.The statistical approach (multiple linear regression) showed that pH is by far the most significant groundwater characteristic which contributes to the variation in REE concentrations. Also DOC, SO(4), Fe and Al contributed significantly, although to a much lesser extent, to the variation in REE concentrations. This is in line with the calculated REE-species in solution and REE-adsorption to iron and aluminium (hydr)oxides. Regression equations including only pH, were derived to predict REE concentrations in groundwater. External validation showed that these regression equations were reasonably successful to predict REE concentrations of groundwater of another drinking water pumping station in quite different region of The Netherlands.     

Human impacts on groundwater flow and contamination deduced by multiple isotopes in Seoul City, South Korea

The influence of human activities on the flow system and contamination of groundwater were investigated in Seoul City, South Korea, one of the largest Asian cities, using a combination of isotopes (δD, T, δ¹⁵N, δ¹⁸O, δ³⁴S, and ⁸⁷Sr/⁸⁶Sr). Eighteen representative groundwater and river water samples, which were collected over a wide area of the city, were compared with previously reported data. The distribution of stable isotopes (δD and δ¹⁸O) with groundwater potential data shows that recharged groundwater from either the surrounding mountainous area as well as the Han River and other surface streams discharged towards the northern-central part of the city, where a subway tunnel pumping station is located. It is suggested from T values (3.3 to 5.8 T.U.) that groundwater was recharged in the last 30 to 40 years. The δ³⁴S and δ¹⁵N of SO₄²⁻ and NO₃⁻ data were efficiently used as indicators of contamination by human activities. These isotopes clarified that the contribution of anthropogenic contaminants i.e., industrial and household effluents, waste landfills, and fertilizers, are responsible for the enrichment by SO₄²⁻ (> 30 ppm as SO₄²⁻) and NO₃⁻ (> 20 ppm as NO₃⁻) of groundwater. The ⁸⁷Sr/⁸⁶Sr values of groundwater vary (0.71326 to 0.75058) in accordance with the host rocks of different origins. Mineral elements such as Ca are also suggested to be derived naturally from rocks. The groundwater under Seoul City is greatly affected by transportation of pollutants along the groundwater flow controlled by subway tunnel pumping, contributing to the degradation of water quality in urbanized areas.     

Quantitative assessment of intrinsic groundwater vulnerability to contamination using numerical simulations

Intrinsic vulnerability assessment to groundwater contamination is part of groundwater management in many areas of the world. However, popular assessment methods estimate vulnerability only qualitatively. To enhance vulnerability assessment, an approach for quantitative vulnerability assessment using numerical simulation of water flow and solute transport with transient boundary conditions and new vulnerability indicators are presented in this work. Based on a conceptual model of the unsaturated underground with distinct hydrogeological layers and site specific hydrological characteristics the numerical simulations of water flow and solute transport are applied on each hydrogeological layer with standardized conditions separately. Analysis of the simulation results reveals functional relationships between layer thickness, groundwater recharge and transit time. Based on the first, second and third quartiles of solute mass breakthrough at the lower boundary of the unsaturated zone, and the solute dilution, four vulnerability indicators are extracted. The indicator transit time t₅₀ is the time were 50% of solute mass breakthrough passes the groundwater table. Dilution is referred as maximum solute concentration C_max in the percolation water when entering the groundwater table in relation to the injected mass or solute concentration C₀ at the ground surface. Duration of solute breakthrough is defined as the time period between 25% and 75% (t_25%-t_75%) of total solute mass breakthrough at the groundwater table. The temporal shape of the breakthrough curve is expressed with the quotient (t_25%-t_50%) / (t_25%-t_75%). Results from an application of this new quantitative vulnerability assessment approach, its advantages and disadvantages, and potential benefits for future groundwater management strategies are discussed.     

Atrazine removal from water by polycation-clay composites: Effect of dissolved organic matter and comparison to activated carbon

Atrazine removal from water by two polycations pre-adsorbed on montmorillonite was studied. Batch experiments demonstrated that the most suitable composite poly (4-vinylpyridine-co-styrene)-montmorillonite (PVP-co-S90%-mont.) removed 90-99% of atrazine (0.5-28 ppm) within 20-40 min at 0.367% w/w. Calculations employing Langmuir's equation could simulate and predict the kinetics and final extents of atrazine adsorption. Column filter experiments (columns 20 × 1.6 cm) which included 2 g of the PVP-co-S90%-mont. composite mixed with excess sand removed 93-96% of atrazine (800 ppb) for the first 800 pore volumes, whereas the same amount of granular activated carbon (GAC) removed 83-75%. In the presence of dissolved organic matter (DOM; 3.7 ppm) the efficiency of the GAC filter to remove atrazine decreased significantly (68-52% removal), whereas the corresponding efficiency of the PVP-co-S90%-mont. filter was only slightly influenced by DOM. At lower atrazine concentration (7 ppb) the PVP-co-S90%-mont. filter reduced even after 3000 pore volumes the emerging atrazine concentration below 3 ppb (USEPA standard). In the case of the GAC filter the emerging atrazine concentration was between 2.4 and 5.3 μg/L even for the first 100 pore volumes. Thus, the PVP-co-S90%-mont. composite is a new efficient material for the removal of atrazine from water.     

Atrazine contamination of groundwater in the platte valley of Nebraska from non-point sources

Groundwater under large portions of the corn (Zea mays L.) producing areas of the state of Nebraska is contaminated with trace levels of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine]. Concentrations generally range between 200 and 800 nanograms/liter (ppt), which is well below the levels that would damage even the most sensitive crops. Downward leaching appears to be the predominate route by which atrazine is entering into the aquifers. Studies with soil extractors, established beneath a corn field irrigated with a center pivot system, indicate that 0.07% of the atrazine applied to the soil surface leached to 1.5 m below the surface by the end of the growing season. Groundwater atrazine in wells increased by 0.7 ppb from the up gradient to the down gradient side of the treated field. Dissipation of atrazine, once it has entered into the aquifer is due to dilution and dispersion, and to a small amount of chemical hydrolysis resulting in the production of hydroxy-atrazine. Mathematical models indicate that the trace amounts of atrazine seasonally entering the aquifer are not cumulative since degradation is effectively keeping the level of contamination well below the levels of phytotoxicity.     

洞庭湖浅层地下水环境背景值的研究

依据洞庭湖区浅层地下水1720个水质检测数据,运用格拉布斯(Grubbs)准则和拉依达准则剔除异常数据,再运用数理统计方法和SPSS软件确定概率分布类型和不同类型的地下水的环境背景值,为该地区地下水污染评价和治理修复提供了重要的地球化学依据。     

Indicators of coastal groundwater quality changes induced by seawater infiltration

The diminishing public water supply in Greater Beirut induced by various factors since the 1960's reaching its climax during the civil war (1975–1992), led to the drilling of a multitude of private wells in the Cenomanian coastal aquifer. The increasingly high extraction of the groundwater led to progressive changes in the quality of the ground‐water due to seawater infiltration. This problem stimulated some studies directed at detecting and assessing the status and magnitude of the seawater infiltration, but most of them failed to apply any reliable diagnostic indicators designed to detect and to trace any changes in the quality of the groundwater. In contrast, the present study demonstrates the application of certain diagnostic indicators (DI) devised specifically for the detection, progress and trends of seawater infiltration into an aquifer.     

Erratum to “Effects of intensive urbanization on the intrusion of shallow groundwater into deep groundwater: Examples from Bangkok and Jakarta”

Asian megacities have severe pollution problems in both coastal and urban areas. In addition, the groundwater potential has decreased and land subsidence has occurred because of intensive groundwater pumping in urban areas. To prevent the adverse effects of urbanization on groundwater quality, it is necessary to confirm the changes in groundwater flow and contaminant transport caused by urbanization. We examined the effects of urbanization on contaminant transport in groundwater. The research areas were located around Bangkok, Thailand, and akarta, Indonesia, cities with populations of approximately 8 and 12 million, respectively. Each metropolitan city is located on a river delta and is adjacent to a bay. We measured the water level and collected water samples at boreholes at multiple depths (100 to 200 m) in 2004 and 2006 in Bangkok and Jakarta, respectively. The current hydraulic potential is below sea level in both cities because of prior excess abstraction of groundwater. As a result, the direction of groundwater flow is now downward in the coastal area. The Cl⁻ concentration and δ¹⁸O distributions in groundwater suggest that the decline in hydraulic potential has caused the intrusion of seawater and shallow groundwater into deep groundwater. Concentrations of Mn and NO3⁻-N in groundwater suggest the intrusion of these contaminants from shallow to deep aquifers with downward groundwater flow and implies an accumulation of contaminants in deep aquifers. Therefore, it is important to recognize the possibility of future contaminant transport with the discharge of deep groundwater into the sea after the recovery of groundwater potential in the coastal areas.     

Remediation of bromate-contaminated groundwater in an ex situ fixed-film bioreactor

Use of a pilot-scale fixed-film bioreactor was investigated for remediation of bromate contamination within groundwater. Bromate reduction with stoichiometric production of bromide was observed, providing supporting evidence for complete reduction of bromate with no production of stable intermediates. Reduction of 87-90% bromate from an influent concentration of 1.1 mg L(-1) was observed with retention times of 40-80 h. Lower retention times led to decreases in bromate reduction capability, with 11.5% removal at a 10 h retention time. Nitrate reduction of 76-99% from a 30.7 mg L(-1) as NO(3)(-) influent was observed at retention times of 10-80 h, although an increase in nitrite production to 2.7 mg L(-1) occurred with a 10 h retention time. Backwashing was not required, with the large plastic packing media able to accommodate biomass accumulation without decreases in operational efficiency. This study has provided proof of concept and demonstrated the potential of biological bromate reduction by fixed-film processes for remediation of a bromate contaminated groundwater source.     

Phosphorus limitation in nitrifying groundwater filters

Phosphorus limitation has been demonstrated for heterotrophic growth in groundwater, in drinking water production and distribution systems, and for nitrification of surface water treatment at low temperatures. In this study, phosphorus limitation was tested, in the Netherlands, for nitrification of anaerobic groundwater rich in iron, ammonium and orthophosphate. The bioassay method developed by Lehtola et al. (1999) was adapted to determine the microbially available phosphorus (MAP) for nitrification. In standardized batch experiments with an enriched mixed culture inoculum, the formation of nitrite and nitrate and ATP and the growth of ammonia-oxidizing bacteria (AOB; as indicated by qPCR targeting the amoA-coding gene) were determined for MAP concentrations between 0 and 100 μg PO₄-P L⁻¹. The nitrification and microbial growth rates were limited at under 100 μg PO₄-P L⁻¹ and virtually stopped at under 10 μg PO₄-P L⁻¹. In the range between 10 and 50 μg PO₄-P L⁻¹, a linear relationship was found between MAP and the maximum nitrification rate. AOB cell growth and ATP formation were proportional to the total ammonia oxidized. Contrary to Lehtola et al. (1999), biological growth was very slow for MAP concentrations less than 25 μg PO₄-P L⁻¹. No full conversion nor maximum cell numbers were reached within 19 days. In full-scale groundwater filters, most of the orthophosphate was removed alongside with iron. The remaining orthophosphate appeared to have only limited availability for microbial growth and activity. In some groundwater filters, nitrification was almost totally prevented by limitation of MAP. In batch experiments with filtrate water from these filters, the nitrification process could be effectively stimulated by adding phosphoric acid.     

Biological oxidation of arsenite in synthetic groundwater using immobilised bacteria

Biological oxidation of arsenite (As(III)) in synthetic groundwater was examined by using arsenite oxidising bacteria (AOB) isolated from an activated sludge. The phylogenetic analysis indicated that the isolated AOB was closely related to Ensifer adhaerens. Batch experiments showed that for an As(III) oxidation with the isolated AOB the optimum ratio of nitrogen source (NH₄-N) concentration to As(III) concentration was 0.5 (52 mg/L-110 mg/L) and the isolated AOB preferred pH values ranging from 6 to 8, and water temperatures greater than 20 °C. Further continuous experiments were conducted using a bioreactor with immobilised AOB. With an initial As(III) concentration of 1 mg/L at a hydraulic retention time (HRT) of 1 h, an As(III) oxidation rate was around 1 × 10⁻⁹ μg/cell/min and an As(III) oxidation efficiency of 92% was achieved. Although the maximum oxidation rate measured at an HRT of 0.5 h was 2.1 × 10⁻⁹ μg/cell/min, the oxidation efficiency decreased to 87%.These results advocate that a biological process involving immobilised AOB may be useful as an economical and environmentally friendly pre-treatment step for As removal from groundwater.     

Risk assessment of exposure to volatile organic compounds in groundwater in Taiwan

The purpose of this study is to assess the risks from exposure to 14 volatile organic compounds (VOCs) in selected groundwater sites in Taiwan. The study employs the multimedia environment pollutant assessment system (MEPAS) model to calculate the specific non-cancer and cancer risks at an exposure level of 1 μg/L of each VOC for a variety of exposure pathways. The results show that the highest specific non-cancer risk is associated with water ingestion of vinyl chloride (VC) and that the highest specific cancer risk is associated with indoor breathing of VC. The three most important exposure pathways for risk assessment for both non-cancer and cancer risks are identified as water ingestion, dermal absorption when showering, and indoor breathing. Excess tetrachloroethylene (PCE), trichloroethylene (TCE), dichloroethylene (DCE), and VC are detected in the groundwater aquifers of one dump site and one factory. However, the study suggests that the pollutants in the contaminated groundwater aquifers do not travel extensively with groundwater flow and that the resulting VOC concentrations are below detectable levels for most of the sampled drinking-water treatment plants. Nevertheless, the non-cancer and cancer risks resulting from use of the contaminated groundwater are found to be hundred times higher than the general risk guidance values. To ensure safe groundwater utilisation, remediation initiatives for soil and groundwater are required. Finally, the study suggests that the current criteria for VOCs in drinking water might not be capable of ensuring public safety when groundwater is used as the primary water supply; more stringent quality criteria for drinking water are proposed for selected VOCs.     

Certified reference materials for the quality control of trace element determinations in groundwater

Groundwater is currently monitored by EU laboratories to control the level of contamination by major or trace elements in line with EC directives. Compliance with these directives implies that data should be accurate, which requires the availability of representative CRMs as a tool for quality control. This paper describes the preparation of groundwater reference materials, CRMs 609 and 610 (low and high trace element content) and CRMs 611 and 612 (low and high bromide content), the homogeneity and stability studies and the analytical work performed for the certification of Al, As, Cd, Cu and Pb using a range of different techniques, and bromide based on ion-chromatographic measurements.