| 摘要: | 近年來國內環保署所大力推動的畜牧糞尿資源化政策，此舉雖有效改善承受水體的污染狀況以及實現農廢農用的訴求，但從抗生素抗藥性的角度來看，沼渣沼液作為農地肥分對於環境依舊有公共衛生的風險。基於當前政策的限制下，採取適當的管末處理以降低經沼液沼渣施肥後農地抗生素抗藥性的傳播，或許為一可行方案。本研究提出以生物炭應用於經沼液沼渣施肥後土壤中，可能影響重金屬生物有效性及土壤微生物的群落變化導致ARGs在土壤生態系統中的傳播有所減緩的假說，進一步以多種統計分析判斷不同生物炭對於經沼液沼渣澆灌後土壤中的抗生素抗藥性影響程度及影響機制。生物炭特性分析結果顯示以高錳酸鉀改質後生物炭會存在錳官能基並被確實固定在材料上，證實了錳改質生物炭 (M300、M600)的製備。而以不同生物炭吸附水相中Cu(II)、Zn(II)的實驗結果則表明錳改質生物炭 (M300、M600)對兩種重金屬的吸附能力遠高於常規生物炭 (B300、B600)，且低溫煅燒而成生物炭吸附能力更強，M300對Cu(II)及Zn(II)的最高吸附容量達到136.986 μmol/g 及133.333 μmol/g，同時發現所有生物炭對於Cu(II)、Zn(II)的吸附模式皆屬於化學吸附。本研究也以不同生物炭進行為期一個月的縮模試驗後，在土壤環境參數分析結果中發現經生物炭處理後的土壤樣品中的TOC及TN顯著上升，但生物可利用性銅含量則顯著下降，與控制組C2相比，加入M300生物炭後可從23%下降至13%，其次在各目標基因檢測中，檢測了1種管家基因 (16S rRNA gene)，3種不同的抗生素抗性基因(ermB、sul1、tetM)，還有1種流動性基因元素 (intI1)，結果發現高溫煅燒之生物炭 (B600、M600)使土壤樣品中的16S rRNA基因豐度隨著培養時間的增加顯著減少 (p < .05)，顯示B600、M600生物炭對於降低經沼液沼渣澆灌後土壤中的抗生素抗藥性機制，應屬於減少縮模試驗土壤系統中的菌數進而減少其ARGs/MGE豐度；而在相對豐度的統計結果中，M300生物炭對於土壤中抗生素抗藥性的減輕更為顯著 (p < .05)，發現其減輕機制可能為M300生物炭固定了土壤中的Cu(II)，使土壤系統中的可被微生物利用的Cu(II)轉換為更不易被利用的相態。相關性分析與冗餘分析中則證實生物可利用性銅含量與ARGs/MGE的強烈正相關 (p < .05)，進一步表明沼液沼渣中的重金屬Cu(II)對土壤中的ARGs/MGE豐度具有一定程度上的貢獻。可惜的是並未在次世代定序分析中發現生物炭對於縮模試驗土壤中在以門 (Phylum) 為層級的細菌群落組成所造成的變化，但細究對於可能帶有ARGs的Genus菌屬 (Clostridium、Nocardioides) 的豐度下降趨勢，則可以看到B300及B600組別受到細菌群落的影響可能更多。但根據上述結果而言，生物炭，尤其是改質生物炭應可透過不同機制減輕以沼液沼渣施肥後土壤中的抗生素抗藥性。;In recent years, the domestic Environmental Protection Agency has vigorously promoted the policy of resource utilization of livestock manure. Although this measure has effectively improved its pollution of water bodies and fulfilled the demands of agricultural waste utilization, the commonly used mesophilic and thermophilic anaerobic digestion processes adopted by domestic livestock farmers are not sufficient to effectively reduce the total amount of antibiotic resistance genes (ARGs) in livestock manure. Therefore, the application of biogas slurries and residues as fertilizer in agricultural land may pose risks of promoting the development and dissemination of antibiotic resistance in the environment. Given the limitations of current policies, implementing appropriate post-treatment measures to reduce the spread of antibiotic resistance after the application of biogas slurries and residues as fertilizer on farmland may be a feasible solution. This study proposes a hypothesis that the application of biochar in the soil after the application of biogas slurries and residues as fertilizer may affect the bioavailability of heavy metals and the community changes of soil microorganisms, resulting in a reduction in the spread of ARGs in the soil ecosystem. Furthermore, multiple statistical analyses are conducted to determine the degree and mechanisms of the impact of different biochars on antibiotic resistance in the soil after the application of biogas slurries and residues as irrigation. The experimental results of biochar characterization analysis show that biochar modified with potassium permanganate possesses manganese functional groups that are effectively fixed on the material, confirming the preparation of manganese-modified biochar (M300, M600). The experimental results of different biochar adsorbing Cu(II) and Zn(II) from the aqueous phase indicate that manganese-modified biochar (M300, M600) has a much higher adsorption capacity for both heavy metals compared to conventional biochar (B300, B600), and biochar produced by low-temperature calcination exhibits even stronger adsorption capacity. The maximum adsorption capacities for Cu(II) and Zn(II) reached 136.986 and 133.333 μmol/g, respectively. It is also found that all biochars exhibit chemical adsorption modes for Cu(II) and Zn(II). Subsequently, after conducting a one-month simulated test using different biochars, the analysis of soil environmental parameters reveals a significant increase in total organic carbon (TOC) and total nitrogen (TN) in soil samples treated with biochar. The bioavailable copper (bioCu) content significantly decreased, dropping from 23% to 13% when M300 biochar was added compared to the control group C2. One stewardship gene (16S rRNA gene), three different antibiotic resistance genes (ermB, sul1, tetM), and one mobile genetic element (intI1) were tested, and the results indicated that high-temperature biochars (B600, M600) significantly reduced the abundance of 16S rRNA gene in soil samples with increasing incubation time (p < .05). The results indicate that B600 and M600 biochars likely reduce antibiotic resistance mechanisms in soil after biogas slurry irrigation by decreasing bacterial counts and subsequently reducing ARGs/MGE abundance in the shrinkage test soil
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system. In terms of relative abundance, the statistical results indicate that M300 biochar has a more significant effect on reducing antibiotic resistance in the soil (p < .05), and its mechanism may be related to the fixation of Cu(II) in the soil by M300 biochar, transforming the bioavailable Cu(II) in the soil system into a less accessible form for microorganisms. The correlation analysis and redundancy analysis confirm a strong positive correlation (p < .05) between bioavailable copper content and ARGs/MGEs, further suggesting that the heavy metal Cu(II) in biogas slurries and residues contributes to the abundance of ARGs/MGEs in the soil to some extent. Unfortunately, significant changes in bacterial community composition in the simulated soil due to the application of biochar were not observed in the next-generation sequencing analysis. However, based on the above results, it can be concluded that biochar, specially modified biochar, may reduce antibiotic resistance in the soil after the application of biogas slurries and residues as fertilizer through different mechanisms. |
