University of Wuppertal, Institute of Foundation Engineering, Waste and Water Management, School of Architecture and Civil Engineering, Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany.
University of Wuppertal, Institute of Foundation Engineering, Waste and Water Management, School of Architecture and Civil Engineering, Soil and Groundwater Management, Pauluskirchstraße 7, 42285 Wuppertal, Germany; Korea Biochar Research Center, O-Jeong Eco-Resilience Institute (OJERI) & Division of Environmental Science and Ecological Engineering, Korea University, Seoul 02841, Republic of Korea; Faculty of Agriculture, Suez Canal University, Ismailia 41522, Egypt.
Environ Int. 2019 Jun;127:276-290. doi: 10.1016/j.envint.2019.03.040. Epub 2019 Apr 2.
Mercury (Hg) is a highly toxic element, which is frequently enriched in flooded soils due to its anthropogenic release. The mobilization of Hg and its species is of ultimate importance since it controls the transfer into the groundwater and plants and finally ends in the food chain, which has large implications on human health. Therefore, the remediation of those contaminated sites is an urgent need to protect humans and the environment. Often, the stabilization of Hg using amendments is a reliable option and biochar is considered a candidate to fulfill this purpose. We tested two different pine cone biochars pyrolyzed at 200 °C or 500 °C, respectively, with a view to decrease the mobilization of total Hg (Hg), methylmercury (MeHg), and ethylmercury (EtHg) and/or the formation of MeHg and EtHg in a contaminated floodplain soil (Hg: 41 mg/kg). We used a highly sophisticated automated biogeochemical microcosm setup to systematically alter the redox conditions from ~-150 to 300 mV. We continuously monitored the redox potential (E) along with pH and determined dissolved organic carbon (DOC), SUVA, chloride (Cl), sulfate (SO), iron (Fe), and manganese (Mn) to be able to explain the mobilization of Hg and its species. However, the impact of biochar addition on Hg mobilization was limited. We did not observe a significant decrease of Hg, MeHg, and EtHg concentrations after treating the soil with the different biochars, presumably because potential binding sites for Hg were occupied by other ions and/or blocked by biofilm. Solubilization of Hg bound to DOC upon flooding of the soils might have occurred which could be an indirect impact of E on Hg mobilization. Nevertheless, Hg, MeHg, and EtHg in the slurry fluctuated between 0.9 and 52.0 μg/l, 11.1 to 406.0 ng/l, and 2.3 to 20.8 ng/l, respectively, under dynamic redox conditions. Total Hg concentrations were inversely related to the E; however, ethylation of Hg was favored at an E around 0 mV while methylation was enhanced between -50 and 100 mV. Phospholipid fatty acid profiles suggest that sulfate-reducing bacteria may have been the principal methylators in our experiment. In future, various biochars should be tested to evaluate their potential in decreasing the mobilization of Hg and to impede the formation of MeHg and EtHg under dynamic redox conditions in frequently flooded soils.
汞（Hg）是一种剧毒元素，由于人为释放，常富集在水淹土壤中。Hg 及其形态的迁移至关重要，因为它控制着向地下水和植物的转移，最终进入食物链，这对人类健康有重大影响。因此，修复受污染的场地是保护人类和环境的当务之急。通常，使用改良剂稳定 Hg 是一种可靠的选择，生物炭被认为是实现这一目的的候选材料。我们分别用 200°C 和 500°C 热解的松果生物炭，测试了两种不同的松果生物炭，以减少总汞（Hg）、甲基汞（MeHg）和乙基汞（EtHg）的迁移，或减少在受污染的洪泛区土壤中形成 MeHg 和 EtHg（Hg：41mg/kg）。我们使用了一种高度复杂的自动化生物地球化学微宇宙装置，系统地改变了从~-150 到 300mV 的氧化还原条件。我们连续监测氧化还原电位（E）、pH 值，并测定溶解有机碳（DOC）、SUVA、氯离子（Cl）、硫酸根（SO）、铁（Fe）和锰（Mn），以解释 Hg 及其形态的迁移。然而，生物炭的添加对 Hg 迁移的影响是有限的。在用不同的生物炭处理土壤后，我们没有观察到 Hg、MeHg 和 EtHg 浓度的显著降低，这可能是因为 Hg 的潜在结合位点被其他离子占据或被生物膜堵塞。土壤被洪水淹没时，与 DOC 结合的 Hg 可能会被溶解，这可能是 E 对 Hg 迁移的间接影响。然而，在动态氧化还原条件下，泥浆中的 Hg、MeHg 和 EtHg 分别在 0.9 至 52.0μg/l、11.1 至 406.0ng/l 和 2.3 至 20.8ng/l 之间波动。总 Hg 浓度与 E 呈负相关；然而，在 E 约为 0mV 时，Hg 的乙基化占优势，而在-50 至 100mV 之间，甲基化增强。磷脂脂肪酸谱表明，硫酸盐还原菌可能是我们实验中的主要甲基化菌。未来，应测试各种生物炭，以评估其减少 Hg 迁移的潜力，并在经常被洪水淹没的土壤中动态氧化还原条件下，阻碍 MeHg 和 EtHg 的形成。
