Toxicity of sodium nitrilotriacetate (NTA) to the fathead minnow and an amphipod in soft water

Amphipods, Gammarus pseudolimnaeus Bousfield and fathead minnows, Pimephales promelas Rafinesque, were submitted to acute (96-h) and chronic (generation-cycle) bioassays with sodium nitrilotriacetic acid (NTA). All measurements are reported as Na₃NTA. The average 96-h TL50 values under flow-through conditions were 98 mg 1⁻¹NTA for the amphipod and 114 mg 1⁻¹ for the fathead minnow. The acute toxicity of NTA was caused in part by the high pH resulting from the addition of large amounts of NTA (> 100 mg 1⁻¹) to soft water. Controlling pH reduced the lethality of NTA by at least one-half to fathead minnow larvae. The chronic no-effect level of NTA to the amphipods was 19 mg 1⁻¹; in fathead minnows, it exceeded the highest exposure level (> 54 mg 1⁻¹).     

Activity and adaptation of nitrilotriacetate (NTA)-degrading bacteria: field and laboratory studies

Adaptation of bacterial activity for the degradation of nitrilotriacetate (NTA) was studied using natural sediment samples and an NTA-degrading bacterium (strain ATCC 29600). Sediment samples from a river with persistent levels of NTA had much higher NTA-degradative activity than comparable samples from a less contaminated control site. When sediment from the control site was exposed to high levels of NTA a 5 day lag preceded an abrupt increase in NTA degradation while strain 29600 colonized on sand and grown in the absence of NTA became induced within eight hours. The induction of strain 29600 was compared between bacteria in suspension and cells attached to sand. The sand-associated bacteria became induced 4 to 5 h before the planktonic suspension and displayed over threefold greater specific activity. Suspensions of strain 29600 became adapted within 8 h when placed in membrane diffusion chambers that were immersed within a municipal wastewater reactor containing NTA. These findings support the concept that induction is a part of the process of bacterial adaptation to degrade NTA and sand-associated bacteria can adapt more quickly to and have a greater degradative activity for NTA than planktonic cells.     

Use of the electrolytic respirometer to measure biodegradation in natural waters

The electrolytic respirometer was used to study the biodegradation of anionic, cationic and nonionic surfactants at ppm levels in Ohio River water. Below saturation or toxic concentrations, rates of oxygen consumption for all surfactants tested were directly proportional to surfactant concentration. Respiration data were fit by iterative techniques to a non-linear mathematical model to generate estimates of the rate constants for and extent of biodegradation. Estimates of biodegradability obtained from respiratory studies agreed well with estimates obtained in carbon dioxide evolution screening studies where surfactant was used as the sole carbon source by a sewage inoculum. The data indicate that the electrolytic respirometer can be used to measure biodegradation of complex organics in natural waters when specific analytical methods or radiolabelled materials are unavailable.     

Complexation of trace metals by ethylenediaminetetraacetic acid (EDTA) in natural waters

EDTA was determined in detergents, in primary and secondary sewage and in river water. A method for calculating the extent of complexation of trace metals by EDTA in the presence of calcium and other complexing agents is presented. Possible effects on the behaviour of trace metals in the context of sewage treatment, mobility in watercourses, and toxicity to aquatic organisms and in chemical analysis are discussed.     

Biodegradation of nitrilotriacetate (NTA) by bacteria—I. Isolation of bacteria able to grow anaerobically with NTA as a sole carbon source

Bacterial strains with the ability to utilize nitrilotriacetate (NTA) under aerobic and anaerobic conditions have been isolated from natural waters exposed to NTA. One of these strains (NTA-A2) is a facultative anaerobe which grows under anaerobic conditions on NTA if nitrate is available in the medium. (Under aerobic conditions this strain can utilize acetate, glucose and some other sugars as well as NTA but not EDTA (ethylenediaminotetraacetate) or lactose as the sole carbon source.) The properties and characteristics of the strain NTA-A2 are described.     

NTA biodegradation and removal in subsurface sandy soil

This lab-scale study examined the biodegradation and removal of nitrilotriacetic acid (NTA) in the subsurface environment, mainly sandy soils. Batch tests indicated that NTA adsorption on the sandy soils played a minor role in its removal in these soils. Removal of NTA was investigated in 50.5 mm i.d. by 1.17 m long soil columns under unsaturated conditions at 15°C. Septic tank effluent containing 20 mg NTA l⁻¹ was dosed to soil columns four times a day at an overall loading rate of 1 gpd ft⁻² for a 43-day period. This feed NTA concentration was routinely reduced to a steady-state concentration of 0.1 mg l⁻¹ by passage through the 1.17 m of soil, after an indigenous soil microflora became sufficiently established over a 25 day period. In addition, the results of samples taken on day 21 demonstrated that greater than 75% removal of NTA can be expected in a soil depth of less than one-third meter.     

Microbial degradation of nitrilotriacetate (NTA) during river water/groundwater infiltration: Laboratory column studies

In laboratory column experiments with aquifer material collected from a natural river water/groundwater infiltration site, the effects of changes in NTA concentration (0.06–3.40 μM), temperature (5–20°C), and redox conditions on the microbial degradation of NTA during infiltration have been investigated. Under both aerobic and denitrifying conditions, NTA was rapidly mineralized and supported microbial growth as a sole carbon and energy source. The presence of other degradable organic compounds and of trace metals had no significant effect on the total rate of NTA elimination after a 21.8 cm flow distance. At concentrations between 0.02 and 0.05 μM, NTA degradation was still rapid (apparent pseudo first-order rate constants of up to 15 d⁻¹). From the results of the column experiments it may be concluded that under environmental conditions typical for Switzerland, very low residual NTA concentrations (< 0.01 μM) should be present at all times of the year in the groundwater after only a few meters of infiltration, even when concentrations of NTA in river water reach 3–4 μM. This conclusion is corroborated by results of field measurements.     

The chelation of cadmium with NTA in sea water as a model for the typical behaviour of trace heavy metal chelates in natural waters

As a typical example for chelates of heavy metal traces in sea water, the chelation of the toxic metal cadmium with the potential pollutant nitrilotriacetic acid (NTA) as ligand at the low Cd(II) concentration of 10^?7 M and less, realistic for polluted waters, has been studied by differential pulse polarography. Detailed investigations with model solutions of singular macro-salt-components of sea water, with artificial and with natural sea water from the Adriatic have revealed the specific influences of the significant relevant macro-components of sea water on the stability of heavy metal chelates in the sea in principle, and on the chelation of Cd(II) with NTA in particular. From the methodological aspect the approach described in generally applicable to the study of other chelates with heavy metal traces in sea water and inland waters. The distribution of Cd(II) over various chemical species to be expected in sea water in the presence of given amounts of NTA has been evaluated.     

Biodegradation of nitrilotriacetate (NTA) by bacteria—II. Cultivation of an NTA-degrading bacterium in anaerobic medium

Bacterial strains with the ability to utilize nitrilotriacetate (NTA) under aerobic and anaerobic conditions have been isolated from natural waters exposed to NTA. One of these strains (NTA-A2) is a facultative anaerobe which grows under anaerobic conditions on NTA if nitrate is available in the medium. (Under aerobic conditions this strain can utilize acetate, glucose and some other sugars as well as NTA but not EDTA (ethylenediaminotetraacetate) or lactose as the sole carbon source.) The properties and characteristics of the strain NTA-A2 are described.     

Influence of salinity and mineralization on trace metal sorption to cyanobacteria in natural waters

The equilibrium distribution of Cd, Cu and Pb between the cyanobacterium Anabaena spp. and natural lake water as a function of salinity and degree of algal decomposition, was studied using batch experiments. Adsorption isotherms could be described with the Freundlich equation. Distribution coefficients (K_d) for Anabaena spp. were largest for Pb, followed by Cd and Cu. The variation in K_d values for Cd was explained by a model accounting for metal complexation to the algal surface and complexation by dissolved ligands of variable concentration. The phytoplankton/water distribution of Cd in waters of different salinity appears to be regulated by the free Cd²⁺ activity in solution. Mineralization of Anabaena spp. for 42 d resulted in a decrease of the solid to water ratio by a factor of 12, and an increase in K_d for Cd (factor four), Cu (factor eight) and Pb (factor 10–20). The increase in K_d is attributed to a higher affinity of the metals for the adsorbent. The use of constant K_d values for mineralizing phytoplankton and detritus in trace metal fate models, may result in underestimations of bound fractions. The extent to which this fraction is underestimated, depends on the time course of the distribution coefficient and the solid to water ratio during the mineralization process.     

Effect of temperature and dissolved oxygen on biodegradation of nitrilotriacetate

The effect of temperature and dissolved oxygen on the rate of biodegradation of nitrilotriacetate (NTA) was examined in water samples collected from the Rur River. Biodegradation of NTA was first order with respect to NTA concentration over a concentration range of 50–1000 μg l⁻¹. First order rate constants showed a typical temperature dependency (temperature coefficient, Q₁₀ = 2) and biodegradation of NTA was observed over a temperature range of 2–24°C. The effect of temperature on the rate of NTA biodegradation was described by the Arrhenius equation, with calculated activation energies in the range reported for ordinary enzyme reactions. Biodegradation of NTA was also observed at low dissolved oxygen concentrations (0.3 mg l⁻¹), although at reduced rates compared to high oxygen concentrations (13 mg l⁻¹). Biodegradation of NTA was oxygen-dependent, suggesting an obligate oxygen requirement for the initial steps in NTA metabolism by natural microbial communities in surface waters. In general, our results indicate that NTA biodegradation will occur in natural waters under conditions of low temperature and low dissolved oxygen and also at low NTA concentrations.     

Sampling and storage of natural waters for trace metal analysis

Methods for the collection, preservation and storage of natural water samples for the analysis of trace levels of heavy metals have been critically reviewed, with particular reference to the analysis of zinc, copper, lead, cadmium and mercury. Recommended prodecures are given which minimise the problems of sample contamination and adsorption losses. Carefully cleaned high-density polythene or Teflon containers are recommended for both sampling and storage, with a storage temperature of 4°C. Acidification to 0.05 M H⁺ with nitric acid is desirable, except in speciation studies. For mercury analysis the addition of an oxidant or complexing agent is also necessary.     

Photochemical fate of atorvastatin (lipitor) in simulated natural waters

Cholesterol-lowering statin drugs are among the most frequently prescribed for reducing human blood cholesterol and they have been detected as contaminants in natural waters. In this study the photochemical behavior of atorvastatin (lipitor) was investigated at two different concentrations of 35.8 μM (20 mg L⁻¹) and 35.8 nM (20 μg L⁻¹) using a solar simulator and a UV reactor. Photochemical fate in natural waters can be described in most cases by the sum of the loss due to hydrolysis, direct photolysis, and, reaction with hydroxyl radical (OH), singlet oxygen (¹O₂) (or O₂ (¹D)), and excited state dissolved organic matter (DOM). The absolute bimolecular reaction rate constant with OH was measured, using pulsed radiolysis, (1.19 ± 0.04) × 10¹⁰ M⁻¹ s⁻¹. The reaction rate constant of ¹O₂ was determined to be (3.1 ± 0.2) × 10⁸ M⁻¹ s⁻¹. Under the experimental conditions used, at high atorvastatin concentration (35.8 μM) the contribution of singlet oxygen (¹O₂) to the photodegradation of atorvastatin in natural waters was higher than that of hydroxyl radical, and accounted for up to 23% of the loss in aqueous solutions. Whereas, at a concentration of 35.8 nM, ¹O₂ (and OH) both played a minor role in the removal of this compound. Lastly, it also appears that atorvastatin reacts with ³DOM* contributing to its loss in simulated natural waters.     

Uranium (VI) in natural waters: Study of occurrence forms

A comparative study of U(VI) occurrence forms in natural waters has been conducted on the basis of experimental determination of the faction of U(VI) soluble and colloidal forms and the calculation of the specified forms by using the known stability constants. It was shown that the forms of U(VI) radionuclide in aqueous media could considerably change depending on the concentration of U(VI), carbonate ions, and suspended particles of different nature. It has been found out that uranium U(VI) at the level of its typical concentrations (several micrograms and less) occurs in natural waters in soluble different-metal and carbonate forms.     

Migration forms of trace elements in natural fresh waters and the effect of the water storage

The concentration and physico-chemical state of 18 trace and major elements in river and lake waters were studied as a function of time (2h-35 days), for which the samples of water were stored in polyethylene bottles. The methods of investigation were dialysis, centrifugation, ion exchange filtration and electrophoresis, combined with instrumental neutron activation analysis. It was shown that considerable amounts of Mn, Co, Al, Sc, La, Ce, Fe, Cr and Th may be lost by the adsorption to the walls of polyethylene containers and that the ratio of forms of existence of Co, Mn, La, Ce, Sm, Fe, and Cr in the solution may be substantially changed during the storage for one week or more. Probable interpretations of these changes are given. Conclusions are also drawn about the state of individual trace and major elements in the waters studied.     

The use of reverse phase liquid chromatography for studying trace metal-organic associations in natural waters

Reverse-phase liquid chromatography was employed for the separation of natural water organics into fractions of varying polarity. Concomitant metals were monitored by electrothermal atomization atomic absorption spectrophotometry.     

Sulfolane biodegradation potential in aquifer sediments at sour natural gas plant sites

Sulfolane is used in the treatment of sour natural gas. It is a highly water soluble compound that has been introduced into soils and groundwaters at a number of sour gas processing plant sites. Aquifer sediments from contaminated locations at three sites in western Canada were assessed for microbial activity and their ability to degrade sulfolane under aerobic and five anaerobic (nitrate-, Mn(IV)-, Fe(III)-, sulfate- and CO₂-reducing) conditions. The microcosms were supplemented with 200 mg/L sulfolane and adequate supplies of N, P, and the appropriate terminal electron acceptor. Microcosms containing contaminated aquifer sediments from each of the three sites were able to degrade sulfolane aerobically at 8°C and 28°C, and the biodegradation followed zero-order kinetics. The lag times before the onset of sulfolane biodegradation were shorter when sulfolane-contaminated sediments were used as inocula than when uncontaminated soils were used. No anaerobic sulfolane biodegradation was observed at 28°C, nor was sulfolane biodegradation observed at 8°C under Fe(III)-, sulfate- and CO₂-reducing conditions. At 8°C, anaerobic degradation of sulfolane coupled to Mn(IV) reduction was observed in microcosms from two sites, and degradation coupled to nitrate reduction was seen in a microcosm from one of the contaminated sites.     

Evaluation of natural and enhanced PCP biodegradation at a former pesticide manufacturing plant

Pentachlorophenol (PCP) has been used in the past as a pesticide, herbicide, antifungal agent, bactericide, and wood preservative. Thus, PCP is among the most ubiquitous chlorinated compounds found in groundwater contamination. A former pesticide manufacturing plant located in southern Taiwan has been identified as a PCP spill site. In this study, groundwater samples collected from the PCP site were analyzed to assess the occurrence of natural PCP biodegradation. Microcosm experiments were conducted to (1) evaluate the feasibility of biodegrading PCP by indigenous microbial consortia under aerobic and cometabolic conditions, and (2) determine the potential of enhancing PCP biodegradation using cane molasses and biological sludge cake as the substitute primary substrates under cometabolic conditions. The inocula used in this microcosm study were aquifer sediments collected from the PCP site and activated sludges collected from the municipal and industrial wastewater treatment plants. Results from this field investigation indicate that the natural biodegradation of PCP is occurring and causing the decrease in PCP concentration. Microcosm results show that the indigenous microorganisms can biodegrade PCP under both aerobic and aerobic cometabolism conditions. A PCP-degrading bacterium was isolated from the collected aquifer sediments and identified as Pseudomonas mendocina NSYSU via some biochemical tests and further conformation of DNA sequencing. In batch cultures, P. mendocina NSYSU used PCP as its sole source of carbon and energy. The isolated bacterium, P. mendocina NSYSU, was capable of completely degrading PCP as indicated by the increase in biomass formation with the decrease in PCP concentrations occurred in the carbon-free medium simultaneously. Results indicate that the in situ or on-site aerobic bioremediation using indigenous microorganisms or inoculated bacteria would be a feasible technology to clean up the studied PCP-contaminated site. Results from this study will be useful in designing a scale-up in situ or on-site PCP bioremediation system (e.g., on-site bioreactor) for field application.     

Determination and differentiation of ethylenediaminetetra-acetic acid (EDTA) and nitrilotriacetic acid (NTA) in freshwater

A fast and simple spectrophotometric method for the determination and differentiation of ethylenediaminetetra-acetic acid (EDTA) and nitrilotriacetic acid (NTA) is described. Principles, detection limits and interferences of other recent methods for the analysis of EDTA and NTA are briefly reviewed. The proposed method is based on the light absorption of cobalt(III) complexes of NTA and EDTA at 555 and 535 nm. After the determination of the sum of EDTA and NTA, the NTA complex is selectively oxidized. The absorbance then represents EDTA only. The sensitivity of the method is 10 μg; with preconcentration of the water sample by means of rotary evaporation a detection limit of 10 μg 1^-1 is observed.