Degradation of 13C-labeled pyrene in soil-compost mixtures and fertilized soil

Abstract

Polycyclic aromatic hydrocarbons (PAH) are toxic pollutants widely distributed in the environment due to natural and anthropogenic processes. In order to mitigate tar oil contaminations with PAH, research on improving bioremediation approaches, which are sometimes inefficient, is needed. However, the knowledge on the fate of PAH-derived carbon and the microbial degraders in particular in compost-supplemented soils is still limited. Here we show the PAH carbon turnover mass balance in microcosms with soil-compost mixtures or in farmyard fertilized soil using [(13)C6]-pyrene as a model PAH. Complete pyrene degradation of 100 mg/kg of soil was observed in all supplemented microcosms within 3 to 5 months, and the residual (13)C was mainly found as carbon converted to microbial biomass. Long-term fertilization of soil with farmyard manure resulted in pyrene removal efficiency similar to compost addition, although with a much longer lag phase, higher mineralization, and lower carbon incorporation into the biomass. Organic amendments either as long-term manure fertilization or as compost amendment thus play a key role in increasing the PAH-degrading potential of the soil microbial community. Phospholipid fatty acid stable isotope probing (PLFA-SIP) was used to trace the carbon within the microbial population and the amount of biomass formed from pyrene degradation. The results demonstrate that complex microbial degrader consortia rather than the expected single key players are responsible for PAH degradation in organic-amended soil.

Microbial communities in pyrene amended soil–compost mixture and fertilized soil

“…These analyses complement results from microcosm experiments for which the degradation kinetics and the pyrene turnover mass balances were published recently (Adam et al 2015). Complete pyrene degradation was observed in the soil-compost mixture and fertilized soil as shown in Table 1, and the incorporation of 13 C-pyrene-derived labelled carbon into microbial biomass has been evidenced by phospholipid fatty acid stable isotope probing (PLFA-SIP), albeit on a low level (Adam et al 2015). …”

“…In the experiments described previously (Adam et al 2015), soil and soil-compost mixtures were tested for pyrene degradation activity in a microcosm study simulating bioremediation. [ 13 C 6 ]-pyrene was used for tracing the turnover.…”

“…The compost was fully rotten and consisted of a mixture of vegetable and animal organic waste and green waste. Briefly, unfertilized soil was mixed with compost at a ratio of 3:1 (fw/fw) and replicates of soil-compost mixture and fertilized soil were spiked with [ 13 C 6 ]-pyrene to a final concentration of about 100 mg kg −1 following the procedure described previously (for details see Adam et al 2015; Kästner and Mahro 1996). The material was thoroughly mixed for homogenization and the water content was adjusted and controlled to 60% of the maximum water holding capacity of the mixtures.…”

“…addition of mature compost to soil (Adam et al 2015; Haderlein et al 2001; Kästner and Mahro 1996; Kästner et al 1995; Loick et al 2009; Semple et al 2001; Wu et al 2013) or incubation with fresh organic waste [composting] (Peng et al 2013; Zhang et al 2011). Also long-term organic fertilization of soil with farmyard manure (FYM) (Adam et al 2015) was proven to facilitate PAH degradation. This kind of biostimulation was reviewed recently (Kästner and Miltner 2016) and is comprehensively affecting the soil, since compost amendment provides living microorganisms, organic matter and nutrients, but also improves aeration as well as water and pH buffer capacities of the soil matrix (Kästner and Mahro 1996).…”

“…Complete pyrene degradation was observed in the soil-compost mixture and fertilized soil as shown in Table 1, and the incorporation of 13 C-pyrene-derived labelled carbon into microbial biomass has been evidenced by phospholipid fatty acid stable isotope probing (PLFA-SIP), albeit on a low level (Adam et al 2015). …”