Browsing by Subject "BOREAL REGION"

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  • Liu, Xinxin; Hui, Nan; Kontro, Merja H. (2020)
    The triazine herbicide atrazine easily leaches with water through soil layers into groundwater, where it is persistent. Its behavior during short-term transport is poorly understood, and there is no in situ remediation method for it. The aim of this study was to investigate whether water circulation, or circulation combined with bioaugmentation (Pseudomonassp. ADP, or four isolates from atrazine-contaminated sediments) alone or with biostimulation (Na-citrate), could enhance atrazine dissipation in subsurface sediment-water systems. Atrazine concentrations (100 mg L-1) in the liquid phase of sediment slurries and in the circulating water of sediment columns were followed for 10 days. Atrazine was rapidly degraded to 53-64 mg L(-1)in the slurries, and further to 10-18 mg L(-1)in the circulating water, by the inherent microbes of sediments collected from 13.6 m in an atrazine-contaminated aquifer. Bioaugmentation without or with biostimulation had minor effects on atrazine degradation. The microbial number simultaneously increased in the slurries from 1.0 x 10(3)to 0.8-1.0 x 10(8)cfu mL(-1), and in the circulating water from 0.1-1.0 x 10(2)to 0.24-8.8 x 10(4)cfu mL(-1). In sediments without added atrazine, the cultivable microbial numbers remained low at 0.82-8.0 x 10(4)cfu mL(-1)in the slurries, and at 0.1-2.8 x 10(3)cfu mL(-1)in the circulating water. The cultivated microorganisms belonged to the nine generaAcinetobacter,Burkholderia,Methylobacterium,Pseudomonas,Rhodococcus,Sphingomonas,Streptomyces,VariovoraxandWilliamsia; i.e., biodiversity was low. Water flow through the sediments released adsorbed and complex-bound atrazine for microbial degradation, though the residual concentration of 10-64 mg L(-1)was high and could contaminate large groundwater volumes from a point source, e.g., during heavy rain or flooding.
  • Kerminen, Kaisa Aino Maria; Moël, Romain Le; Harju, Anu Vilhelmiina; Kontro, Merja Hannele (2018)
    Pesticides leaching from soil to surface and groundwater are a global threat for drinking water safety, as no cleaning methods occur for groundwater environment. We examined whether peat, compost-peat-sand (CPS) mixture, NH4NO3, NH4NO3 with sodium citrate (Na-citrate), and the surfactant methyl-beta-cyclodextrin additions enhance atrazine, simazine, hexazinone, dichlobenil, and the degradate 2,6-dichlorobenzamide (BAM) dissipations in sediment slurries under aerobic and anaerobic conditions, with sterilized controls. The vadose zone sediment cores were drilled from a depth of 11.3-14.6m in an herbicide-contaminated groundwater area. The peat and CPS enhanced chemical atrazine and simazine dissipation, and the peat enhanced chemical hexazinone dissipation, all oxygen-independently. Dichlobenil dissipated under all conditions, while BAM dissipation was fairly slow and half-lives could not be calculated. The chemical dissipation rates could be associated with the chemical structures and properties of the herbicides, and additive compositions, not with pH. Microbial atrazine degradation was only observed in the Pseudomonas sp. ADP amended slurries, although the sediment slurries were known to contain atrazine-degrading microorganisms. The bioavailability of atrazine in the water phase seemed to be limited, which could be due to complex formation with organic and inorganic colloids. Atrazine degradation by indigenous microbes could not be stimulated by the surfactant methyl-beta-cyclodextrin, or by the additives NH4NO3 and NH4NO3 with Na-citrate, although the nitrogen additives increased microbial growth. (C) 2017 Elsevier B.V. All rights reserved.
  • Harju, A. Vilhelmiina; Narhi, Ilkka; Mattsson, Marja; Kerminen, Kaisa; Kontro, Merja H. (2021)
    Views on the entry of organic pollutants into the organic matter (OM) decaying process are divergent, and in part poorly understood. To clarify these interactions, pesticide dissipation was monitored in organic and mineral soils not adapted to contaminants for 241 days; in groundwater sediment slurries adapted to pesticides for 399 days; and in their sterilized counterparts with and without peat (5%) or compost-peat-sand (CPS, 15%) mixture addition. The results showed that simazine, atrazine and terbuthylazine (not sediment slurries) were chemically dissipated in the organic soil, and peat or CPS-amended soils and sediment slurries, but not in the mineral soil or sediment slurries. Hexazinone was chemically dissipated best in the peat amended mineral soil and sediment slurries. In contrast, dichlobenil chemically dissipated in the mineral soil and sediment slurries. The dissipation product 2,6-dichlorobenzamide (BAM) concentrations were lowest in the mineral soil, while dissipation was generally poor regardless of plant-derived OM, only algal agar enhanced its chemical dissipation. Based on sterilized counterparts, only terbutryn appeared to be microbially degraded in the organic soil, i.e., chemical dissipation of pesticides would appear to be utmost important, and could be the first response in the natural cleansing capacity of the environment, during which microbial degradation evolves. Consistent with compound-specific dissipation in the mineral or organic environments, long-term concentrations of pentachloroaniline and hexachlorobenzene were lowest in the mineral-rich soils, while concentrations of dichlorodiphenyltrichloroethane (DTT) and metabolites were lowest in the organic soils of old market gardens. OM amendments changed pesticide dissipation in the mineral soil towards that observed in the organic soil; that is OM accelerated, slowed down or stopped dissipation.