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- Rijk, Ingrid, 1985-, et al.
(författare)
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Biochar and peat amendments affect nitrogen retention, microbial capacity and nitrogen cycling microbial communities in a metal and polycyclic aromatic hydrocarbon contaminated urban soil
- 2024
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 936
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Tidskriftsartikel (refereegranskat)abstract
- Soil contaminants may restrict soil functions. A promising soil remediation method is amendment with biochar, which has the potential to both adsorb contaminants and improve soil health. However, effects of biochar amendment on soil-plant nitrogen (N) dynamics and N cycling microbial guilds in contaminated soils are still poorly understood. Here, a metal- and polycyclic aromatic hydrocarbon (PAH) contaminated soil was amended with either biochar (0, 3, 6 % w/w) and/or peat (0, 1.5, 3 % w/w) in a full-factorial design and sown with perennial ryegrass in an outdoor field trial. After three months, N and the stable isotopic ratio δ15N was measured in soil, roots and leaves, along with microbial responses. Aboveground grass biomass decreased by 30 % and leaf N content by 20 % with biochar, while peat alone had no effect. Peat in particular, but also biochar, stimulated the abundance of microorganisms (measured as 16S rRNA gene copy number) and basal respiration. Microbial substrate utilization (MicroResp™) was altered differentially, as peat increased respiration of all carbon sources, while for biochar, respiration of carboxylic acids increased, sugars decreased, and was unaffected for amino acids. Biochar increased the abundance of ammonia oxidizing archaea, while peat stimulated ammonia oxidizing bacteria, Nitrobacter-type nitrite oxidizers and comB-type complete ammonia oxidizers. Biochar and peat also increased nitrous oxide reducing communities (nosZI and nosZII), while peat alone or combined with biochar also increased abundance of nirK-type denitrifiers. However, biochar and peat lowered leaf δ15N by 2-4 ‰, indicating that processes causing gaseous N losses, like denitrification and ammonia volatilization, were reduced compared to the untreated contaminated soil, probably an effect of biotic N immobilization. Overall, this study shows that in addition to contaminant stabilization, amendment with biochar and peat can increase N retention while improving microbial capacity to perform important soil functions.
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- Rijk, Ingrid, 1985-, et al.
(författare)
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Effects of copper contamination on N cycling microbial guilds and plant performance in two contrasting grassland soils
- 2023
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Ingår i: Soil Biology and Biochemistry. - : Elsevier. - 0038-0717 .- 1879-3428. ; 180
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Tidskriftsartikel (refereegranskat)abstract
- Heavy metal pollution has important effects on ecosystem nitrogen (N) cycling, but factors driving differences between the direction, onset and intensity of responses are poorly understood. We used two contrasting grassland soils to examine the effects of copper (Cu) on the abundance and activity of N cycling microbial guilds and plant responses, including plant delta 15N as an integrator of the N cycle. A low pH sandy soil and a high pH sandy loam soil were aged two years in outdoor mesocosms with copper (Cu) treatments of background, 200, 400 or 1000 mg kg-1 Cu. After two years, increased Cu treatments resulted in significantly lower abundances of ammonia oxidizing archaea, Nitrospira nitrite oxidizing bacteria (NOB), potential ammonia oxidation rates and plant biomass in both soils. Plants possessed significantly increased N content and enriched shoot delta 15N in with higher Cu in both soils. While abundances of ammonia oxidizing bacteria were unaffected by Cu, the response among Nitrobacter NOB and denitrifiers and plant delta 13C differed between the two soils. In contrast to plants, differences in the intensity and direction of microbial guild responses were not explained by increasing soluble Cu but rather shaped by soil type. This indicates that the two soils differed in metal bioavailability to plants, as well as harbored microbial communities with inherent differences in metal sensitivity. Furthermore, effects of increasing Cu on microbial N-cycling guilds became more apparent with longer incubation time, emphasizing the importance of long-term studies to assess important ecosystem effects of Cu contamination. Taken together, we conclude that a combination of plant and microbial responses can give better insights on how Cu is affecting the N cycle in polluted soils.
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- Rijk, Ingrid, 1985-
(författare)
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Effects of heavy metal contamination on carbon and nitrogen cycling : An ecological approach to assess risks to soil functions
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Soil contamination with heavy metals may disrupt soil microorganisms with important roles in carbon (C) and nitrogen (N) cycling. However, there is a lack of understanding on how microorganisms are affected in soil, which may lead to a mismatch when assessing risks of contaminants to field soils.The overall aim of this thesis was to assess effects on C and N cycling in heavy-metal contaminated soils under realistic conditions. Two historically contaminated sites and two outdoor field trials were studied. A variety of microbial responses, such as in situ microbial soil respiration, biomass, and N cycling microbial guilds was applied, which were linked to slower responding plant and soil variables and stable isotopic content δ13C and δ15N.Lower microbial activity, accumulation of soil C and a lower soil and plant δ15N showed that high lead (2000 mg kg-1) content was slowing down C and N cycles in a grassland area. In a former wood impregnation site, microbial biomass ceased below 5 cm depth while no effects in upper soil (2300 mg kg-1 copper) were observed. In a mesocosm study, responses of N cycling microbial guilds were mostly shaped by soil type. Neither total nor soluble copper, a proxy for bioavailability, could explain the effects on N cycling microbial communities. Finally, addition of biochar and peat to a moderately contaminated soil was shown to immobilize contaminants and N simultaneously, thereby being a promising remediation method to improve ecological soil quality in situ.In summary, this thesis provides an increased understanding and a reality-check on effects on C and N cycling in heavy-metal contaminated soils. The different intensities of the ecosystem effects in the two field soils, and soil specificity of microbial responses in the N cycle, stress the need for site-specific approaches.
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- Rijk, Ingrid. J. C., 1985-, et al.
(författare)
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Carbon and nitrogen cycling in a lead polluted grassland evaluated using stable isotopes (δ13C and δ15N) and microbial, plant and soil parameters
- 2020
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Ingår i: Plant and Soil. - : Kluwer Academic Publishers. - 0032-079X .- 1573-5036. ; 449:1-2, s. 249-266
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Carbon (C) and nitrogen (N) cycling are key ecosystem functions potentially altered by heavy metal pollution. We used an ecosystem approach to study the long-term effect of lead (Pb) on C and N cycles in a natural grassland in a former shooting range.Methods: Microbial activity was evaluated by substrate-induced respiration (SIR) in situ, adding isotopically labelled C4-sugar to the soil. C and N contents and natural abundance of isotopes were measured in grass leaves, soil and microbial biomass together with root biomass.Results: A reduced microbial activity and microbial biomass per area, together with a higher soil C stock and C:N ratio suggested a lower microbial decomposition in high Pb compared to low Pb areas. A more closed N cycle in the high Pb area was indicated by 2–3‰ lower δ15N in leaves and soil compared to low Pb areas. Higher δ13C in leaves and higher root biomass but similar leaf nutrient contents indicated plant responses and adaptions to the high Pb. Conclusions: The applied ecosystem approach revealed that Pb slowed down the C and N cycles, possibly by indirect effects rather than by direct toxicity. The ecosystem seems to have adapted to altered conditions.
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