National Assessment of Long-Term Groundwater Response to Pesticide Regulation.

Quantitative assessments of long-term, national-scale responses of groundwater quality to pesticide applications are essential to evaluate the effectiveness of pesticide regulations. Retardation time in the unsaturated zone () was estimated for selected herbicides (atrazine, simazine, and bentazon) and degradation products (desethylatrazine (DEA), desisopropylatrazine (DIA), desethyldesisopropylatrazine (DEIA), and BAM) using a multidecadal time series of groundwater solute chemistry (∼30 years) and herbicide sales (∼60 years). The sampling year was converted to recharge year using groundwater age.

Leaching of 1,2,4-triazole from commercial barley seeds coated with tebuconazole and prothioconazole.

Seed dressing with fungicide or insecticide is a standard procedure for growing major crops, but very little is known about the leaching risk and the general fate of pesticides from coated seeds. Triazole fungicides are commonly used seed dressing fungicides and recently, there has been increasing concern that 1,2,4-triazole, a major degradation product of several triazole fungicides, may leach to groundwater in concentrations exceeding the 0.1 μg/L threshold limit of the European Union.

Super-complex mixtures of aliphatic- and aromatic acids may be common degradation products after marine oil spills: A lab-study of microbial oil degradation in a warm, pre-exposed marine environment.

When assessing oil spills in marine environments, focus has often been on describing degradation and removal of hydrocarbons. However, more and more attention is now given to the formation of mineral oil transformation products, and their potential toxicity and persistency in the environment. The aim of this study was to investigate the formation of dissolved acidic degradation products from crude oil in sea water from the Persian Gulf in a lab-experiment.

Full-scale bioremediation of diesel-polluted soil in an Arctic landfarm.

A full-scale, experimental landfarm was tested for the capacity to biodegrade oil-polluted soil under high-Arctic tundra conditions in northeast Greenland at the military outpost 9117 Station Mestersvig. Soil contaminated with Arctic diesel was transferred to the landfarm in August 2012 followed by yearly addition of fertilizer and plowing and irrigation to optimize microbial diesel biodegradation. Biodegradation was determined from changes in total petroleum hydrocarbons (TPH), enumeration of specific subpopulations of oil-degrading microorganisms (MPN), and changes in selected classes of alkylated isomers and isomer ratios.

Test of vegetation-based surface exploration for detection of Arctic mineralizations: The deep buried Kangerluarsuk Zn-Pb-Ag anomaly.

The aim of our study was to test whether surficial geochemical techniques are applicable under arctic conditions where pedogenesis is slow or absent, and where the vegetation is arctic dwarf shrub tundra. To this end, we sampled vegetation and topsoil at a known Zn-Pb-Ag anomaly at Kangerluarsuk, northwest Greenland. This Zn-Pb-Ag mineralization surfaces in part of the test area and is deeply buried in other parts.

Soil Domain and Liquid Manure Affect Pesticide Sorption in Macroporous Clay Till.

Pesticides frequently leach through clayey tills, even when they are expected to be strongly adsorbed. In this study, we observed that sorption of two strongly sorbing pesticides, tebuconazole and glyphosate, varied by more than an order of magnitude across soil domains in 5-m-deep clay till profiles with biopores and fractures. Eight soil domains were identified in each of the profiles: five matrix soils and three in the macropores.

Arctic and Subarctic Natural Soils Emit Chloroform and Brominated Analogues by Alkaline Hydrolysis of Trihaloacetyl Compounds.

There has been increasing recognition of the occurrence of natural, halogenated organic compounds in marine and terrestrial environments. Chloroform is an example of a halogenated organic compound with natural formation as its primary source. Chloroform emission from soil has been reported from diverse Arctic, temperate, and (sub)tropical ecosystems.

Biodegradation of crude oil in Arctic subsurface water from the Disko Bay (Greenland) is limited.

Biological degradation is the main process for oil degradation in a subsurface oil plume. There is, however, little information on the biodegradation potential of Arctic, marine subsurface environments. We therefore investigated oil biodegradation in microcosms at 2 °C containing Arctic subsurface seawater from the Disko Bay (Greenland) and crude oil at three concentrations of 2.

Marine biodegradation of crude oil in temperate and Arctic water samples.

Despite increased interest in marine oil exploration in the Arctic, little is known about the fate of Arctic offshore oil pollution. Therefore, in the present study, we examine the oil degradation potential for an Arctic site (Disko Bay, Greenland) and discuss this in relation to a temperate site (North Sea, Denmark). Biodegradation was assessed following exposure to Oseberg Blend crude oil (100 mg L(-1)) in microcosms.

Polar metabolites of polycyclic aromatic compounds from fungi are potential soil and groundwater contaminants.

This study investigated the sorption to soil of water-soluble metabolites from polycyclic aromatic compounds (PACs). The soil fungus Cunninghamella elegans was used to produce PAC metabolites from two un-substituted PACs (phenanthrene, pyrene), three alkyl-substituted PACs (2-methylnaphthalene, 1-methylphenanthrene, 1-methylpyrene), and one sulfur-containing heterocyclic PAC (dibenzothiophene). Fifty-eight metabolites were tentatively identified; metabolites from the un-substituted PACs were hydroxylated and sulfate conjugated, whereas metabolites from alkyl-substituted PACs were sulfate conjugated and either hydroxylated or oxidized to carboxylic acids at the methyl group.

The potential for bioaugmentation of sand filter materials from waterworks using bacterial cultures degrading 4-chloro-2-methylphenoxyacetic acid.

Background: The herbicide 4-chloro-2-methylphenoxyacetic acid (MCPA) is found frequently in Danish groundwater in concentrations exceeding the EU threshold limit of 0.1 µg L(-1) . Groundwater is used for drinking water, and one potential remediation strategy is bioaugmentation using inoculation of sand filters at affected waterworks with degrader bacteria.

Quantification of small-scale variation in the size and composition of phenanthrene-degrader populations and PAH contaminants in traffic-impacted topsoil.

Small-scale colocalisation of microbial polycyclic aromatic hydrocarbon (PAH) degraders and PAHs in contaminated soil is a prerequisite for efficient biodegradation of the PAHs. We therefore tested the hypothesis that phenanthrene-degrading bacteria are colocalised with PAHs at the millimetre-to-centimetre-scale. Microbial populations and PAH concentrations were determined for 40-mg samples from a 112-mm transect of a traffic-impacted topsoil.

Does microbial centimeter-scale heterogeneity impact MCPA degradation in and leaching from a loamy agricultural soil?

The potential for pesticide degradation varies greatly at the centimeter-scale in agricultural soil. Three dimensional numerical simulations were conducted to evaluate how such small-scale spatial heterogeneity may affect the leaching of the biodegradable pesticide 2-methyl-4-chlorophenoxyacetic acid (MCPA) in the upper meter of a variably-saturated, loamy soil profile. To incorporate realistic spatial variation in degradation potential, we used data from a site where 420 mineralization curves over 5 depths have been measured.

The gompertz function can coherently describe microbial mineralization of growth-sustaining pesticides.

Mineralization of (14)C-labeled tracers is a common way of studying the environmental fate of xenobiotics, but it can be difficult to extract relevant kinetic parameters from such experiments since complex kinetic functions or several kinetic functions may be needed to adequately describe large data sets. In this study, we suggest using a two-parameter, sigmoid Gompertz function for parametrizing mineralization curves. The function was applied to a data set of 252 normalized mineralization curves that represented the potential for degradation of the herbicide MCPA in three horizons of an agricultural soil.

Centimeter-scale spatial variability in 2-methyl-4-chlorophenoxyacetic Acid mineralization increases with depth in agricultural soil.

Mineralization of organic chemicals in soil is typically studied using large homogenized samples, but little is known about the small-scale spatial distribution of mineralization potential. We studied centimeter-scale spatial distribution of 2-methyl-4-chlorophenoxyacetic acid (MCPA) mineralization activity at different depths (8-115 cm) in a Danish agricultural soil profile using a 96-well microplate C-radiorespirometric method for small-volume samples. The heterotrophic microbial population and specific MCPA degraders decreased 10- to 100-fold from the plow layer to a depth of 115 cm.

Protozoan predation in soil slurries compromises determination of contaminant mineralization potential.

Soil suspensions (slurries) are commonly used to estimate the potential of soil microbial communities to mineralize organic contaminants. The preparation of soil slurries disrupts soil structure, however, potentially affecting both the bacterial populations and their protozoan predators. We studied the importance of this "slurry effect" on mineralization of the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA, (14)C-labelled), focussing on the effects of protozoan predation.

Centimetre-scale vertical variability of phenoxy acid herbicide mineralization potential in aquifer sediment relates to the abundance of tfdA genes.

Centimetre-scale vertical distribution of mineralization potential was determined for 2,4-dichlorophenoxyacetic acid (2,4-D), 4-chloro-2-methylphenoxyacetic acid (MCPA) and 2-(4-chloro-2-methylphenoxy)propanoic acid (MCPP) by 96-well microplate radiorespirometric analysis in aquifer sediment sampled just below the groundwater table. Mineralization of 2,4-D and MCPA was fastest in sediment samples taken close to the groundwater table, whereas only minor mineralization of MCPP was seen. Considerable variability was exhibited at increasing aquifer depth, more so with 2,4-D than with MCPA.

Triclosan affects the microbial community in simulated sewage-drain-field soil and slows down xenobiotic degradation.

Effects of the common antibacterial agent triclosan on microbial communities and degradation of domestic xenobiotics were studied in simulated sewage-drain-field soil. Cultivable microbial populations decreased 22-fold in the presence of 4 mg kg⁻¹ of triclosan, and triclosan-resistant Pseudomonas strains were strongly enriched. Exposure to triclosan also changed the general metabolic profile (Ecoplate substrate profiling) and the general profile (T-RFLP) of the microbial community.

Quantification of centimeter-scale spatial variation in PAH, glucose and benzoic acid mineralization and soil organic matter in road-side soil.

The aim of the study was to determine centimeter-scale spatial variation in mineralization potential in diffusely polluted soil. To this end we employed a 96-well microplate method to measure the mineralization of 14C-labeled organic compounds in deep-well microplates and thereby compile mineralization curves for 348 soil samples of 0.2-cm3.

Presence of psychrotolerant phenanthrene-mineralizing bacterial populations in contaminated soils from the Greenland High Arctic.

Fuel-contaminated soils from Station Nord (St. Nord) in Greenland were sampled with the aim of assessing the intrinsic attenuation potential by quantifying the presence and activity of degradative microbial populations using phenanthrene as a model compound. Mineralization of [(14)C]phenanthrene to (14)CO(2) was measured in contaminated soils at temperatures down to 0 degrees C and sizable naphthalene-, undecane-, biphenyl- and phenanthrene-degrading populations were measured by microplate-based most-probable-number analysis.

Fungal PAH-metabolites resist mineralization by soil microorganisms.

This study investigated the mineralization of water-soluble polycyclic aromatic hydrocarbon (PAH) metabolites produced by the soil fungus Cunninghamella elegans. Eleven soil fungi were screened for their ability to metabolize (14)C-phenanthrene, (14)C-fluoranthene, and (14)C-pyrene into water-soluble compounds. Eight fungi produced water-soluble metabolites from all or some of the PAHs.

A radiorespirometric method for measuring mineralization of [14C]-compounds in a 96-well microplate format.

A radiorespirometric method was developed for quantifying mineralization of [14C]-labeled substrates in deep-well microplates. Ninety-six 14CO2-traps were placed on an adhesive microplate sealing tape which made it possible to trap 14CO2 simultaneously from all wells. Trapped radioactivity was quantified by digital autoradiography.

Microplate MPN-enumeration of monocyclic- and dicyclic-aromatic hydrocarbon degraders via substrate phase-partitioning.

The high aqueous solubility of monoaromatic and some diaromatic oil components may hinder classical growth-based MPN enumeration of bacterial mono- and di-aromatics degraders because these aromatics are toxic in high concentrations. We developed a microplate MPN method for the enumeration of toluene-, xylene-, naphthalene-, biphenyl- and benzothiophene-degraders on the basis of phase-partitioning of substrate between a biologically inert organic phase and an aqueous mineral salt medium. This way, it was possible to maintain non-toxic, aqueous concentrations in the microplate wells.