Microplastics (MPs) pollution has caused a threat to soil ecosystem diversity and functioning globally. Recently, an increasing number of studies have reported effects of MPs on soil ecosystems. However, these studies mainly focused on soil bacterial communities and a few limited functional genes, which is why MPs effects on soil ecosystems are still not fully understood. Fertilization treatment often coinsides with MPs exposure in practice. Here, we studied effects of an environmentally relevant concentration of polyethylene on soil properties, microbial communities, and functions under different soil types and fertilization history. Our results showed that 0.2% PE MPs exposure could affect soil pH, but this effect varied according to soil type and fertilization history. Long-term fertilization history could alter effects of MPs on soil bacterial and fungal communities in diverse farmland ecosystems (P < 0.05). Soil fungal communities are more sensitive to MPs than bacterial communities under 0.2% PE MPs exposure. MPs exposure has a greater impact on the soil ecosystem with a lower microbial diversity and functional genes abundance and increases the abundance of pathogenic microorganisms. These findings provided an integrated picture to aid our understanding of the impact of MPs on diverse farmland ecosystems with different fertilization histories.

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BACKGROUND Tribromoethylene (TrBE), dibromoethylenes (DBEs) and 1,2‐dibromoethane (DBA) are widespread, toxic and persistent contaminants found in anaerobic soil and groundwater. The abiotic debromination of TrBE, DBEs and DBA using a layered iron(II)–iron(III) hydroxide (green rust, GR) with biochars acting as electron mediators was studied. A screening of biochar substrates was conducted. Reactive biochars were chosen for debromination of TrBE, DBEs and DBA in deionized water and groundwater. Post‐pyrolysis activation with CO2 was tested for reactivity enhancement. RESULTS Bone meal (BM) and shrimp shell (SS) biochars resulted in 60% and 90% debromination of TrBE, respectively. The SS biochar catalyzed debromination by elimination reactions of TrBE and DBEs resulting in formation of acetylene, while DBA was reduced to ethylene. All debrominations in deionized water followed pseudo‐first‐order kinetics with half‐lives t1/2 of 5.1, 1.3, 2.6 and 9.5 h for TrBE, cDBE, tDBE and DBA, respectively. For similar experiments in moderately hard groundwater, removal t1/2 values were on average 2.6 times slower, but still considered fast. Compared to removal t1/2 in deionized water, post‐pyrolysis activation with CO2 of an acid‐treated SS biochar produced a t1/2 11 times shorter for removal of TrBE and two times shorter for DBA. CONCLUSIONS Biochars are efficient mediators of reductive debromination of TrBE, DBEs and DBA. TrBE, DBEs and DBA can be effectively debrominated in deionized water and groundwater samples using a GR–SS biochar composite. The mediating ability of the SS biochar can be further improved by post‐pyrolysis CO2 activation. © 2022 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).