The use of nitrogen fertilizers leads to substantial nitrogen losses and subsequent environmental pollution. Biochar (BC) demonstrates considerable potential for enhancing N fixation and reducing emissions, but it frequently induces a liming effect that increases ammonia (NH₃) volatilization. Nano-biochar (NBC) is attracting considerable attention due to its higher surface energy. However, little information is available whether it could enhance nitrogen adsorption and reduce NH₃ volatilization. Therefore, this study utilized a one-step ball milling method to produce NBC, characterized its physicochemical properties, and investigated its effects and mechanisms on NH₄⁺–N adsorption and NH₃ volatilization. Our results showed that the specific surface area, pore volume and acidic functional groups (carboxyl, lactone group and phenolic hydroxyl groups) of NBC were higher than those of bulk BC, while the pore diameter, zeta potential and pH were the opposite, which was more conducive to promoting adsorption. The maximum adsorption amount of NBC for NH₄⁺–N was 6.880 mg g⁻¹, approximately 1.9 times that of bulk BC. The adsorption process conformed to the Langmuir adsorption isotherm model and the pseudo-second-order kinetic equation, indicating that the adsorption was monolayer and chemical. The primary adsorption mechanisms included physical adsorption, ion exchange, electrostatic and π–π interactions. The addition of 0.30–30% of bulk BC and NBC reduced NH₃ volatilization by 6.40–31.50% and 5.00–42.20%, relative to no BC addition, respectively. The main reason for lower NH₃ volatilization observed with NBC was its ability to improve soil mineral nitrogen content, mineralization and nitrification rates, and decrease urease activity and pH. Therefore, NBC is a green and efficient adsorbent for reducing nitrogen emissions.

中文翻译：

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球磨法制备稻草纳米生物炭高效吸附铵态氮和减少氨挥发的效果与机理


氮肥的使用会导致大量的氮损失和随之而来的环境污染。生物炭 （BC） 在增强固氮和减少排放方面表现出相当大的潜力，但它经常诱导石灰效应，从而增加氨 （NH₃） 的挥发。纳米生物炭 （NBC） 因其较高的表面能而引起了相当大的关注。然而，关于它是否可以增强氮吸附和减少 NH₃ 挥发的信息很少。因此，本研究采用一步法球磨法生产 NBC，表征其理化性质，并研究其对 NH₄⁺–N 吸附和 NH₃ 挥发的影响和机制。结果表明，NBC 的比表面积、孔体积和酸性官能团（羧基、内酯基和酚羟基）高于块体 BC，而孔径、zeta 电位和 pH 值相反，更有利于促进吸附。NBC 对 NH₄⁺–N 的最大吸附量为 6.880 mg ^g-1，约为散装 BC 的 1.9 倍。吸附过程符合 Langmuir 吸附等温线模型和准二级动力学方程，表明吸附为单层化学吸附。主要吸附机制包括物理吸附、离子交换、静电和 π-π 相互作用。与未添加 BC 相比，添加 0.30-30% 的散装 BC 和 NBC 分别使 NH₃ 挥发降低了 6.40-31.50% 和 5.00-42.20%。 用 NBC 观察到的 NH₃ 挥发较低的主要原因是它能够提高土壤矿物氮含量、矿化和硝化速率，并降低脲酶活性和 pH 值。因此，NBC 是一种绿色高效的吸附剂，用于减少氮气排放。