Heavy metal contamination in agricultural land is an alarming issue in Vietnam. It is necessary to develop suitable remediation methods for environmental and farming purposes. The present study investigated the effectiveness of using peanut shell-derived biochar to remediate the two heavy metals Zn and Pb in laboratory soil assays following Tessier’s sequential extraction procedure. The concentration of heavy metals was analyzed using Inductively coupled plasma mass spectrometry (ICP-MS). This study also compared the effectiveness of the blend of biochar and apatite applied and the mere biochar amendment on the chemical fractions of Pb and Zn in the contaminated agricultural soil. Results have shown that the investigated soil was extremely polluted by Pb (3047.8 mg kg−1) and Zn (2034.3 mg kg−1). In addition, the pH, organic carbon, and electrical conductivity values of amended soil samples increased with the increase in the amendment’s ratios. The distribution of heavy metals in soil samples was in the descending order of carbonate fraction (F2) > residue fraction (F5) > exchangeable fraction (F1) > Fe/Mn oxide fraction (F3) > organic fraction (F4) for Pb and F5F2 > F1 > F3 > F4 for Zn. The peanut shell-derived biochar produced at 400oC and 600 °C amended at a 10% ratio (PB4:10 and PB6:10) could significantly reduce the exchangeable fraction Zn from 424.82 mg kg−1 to 277.69 mg kg−1 and 302.89 mg kg−1, respectively, and Pb from 495.77 mg kg−1 to 234.55 mg kg−1 and 275.15 mg kg−1, respectively, and immobilize them in soil. Amending the biochar and apatite combination increased the soil pH, then produced a highly negative charge on the soil surface and facilitated Pb and Zn adsorption. This study shows that the amendment of biochar and biochar blended with apatite could stabilize Pb and Zn fractions, indicating the potential of these amendments to remediate Pb and Zn in contaminated soil.
Soil heavy metal contamination is a severe issue. The detrimental impact of contaminated heavy metals on the ecosystem depends on the chemical form of heavy metals. Biochar produced at 400 °C (CB400) and 600 °C (CB600) from corn cob was applied to remediate Pb and Zn in contaminated soil. After a one month amendment with biochar (CB400 and CB600) and apatite (AP) with the ratio of 3%, 5%, 10%, and 3:3% and 5:5% of the weight of biochar and apatite, the untreated and treated soil were extracted using Tessier’s sequence extraction procedure. The five chemical fractions of the Tessier procedure were the exchangeable fraction (F1), carbonate fraction (F2), Fe/Mn oxide fraction (F3), organic matter (F4), and residual fraction (F5). The concentration of heavy metals in the five chemical fractions was analyzed using inductively coupled plasma mass spectroscopy (ICP-MS). The results showed that the total concentration of Pb and Zn in the soil was 3023.70 ± 98.60 mg kg−1 and 2034.33 ± 35.41 mg kg−1, respectively. These figures were 15.12 and 6.78 times higher than the limit standard set by the United States Environmental Protection Agency (U.S. EPA 2010), indicating the high level of contamination of Pb and Zn in the studied soil. The treated soil’s pH, OC, and EC increased significantly compared to the untreated soil (p > 0.05). The chemical fraction of Pb and Zn was in the descending sequence of F2 (67%) > F5 (13%) > F1 (10%) > F3 (9%) > F4 (1%) and F2~F3 (28%) > F5 (27%) > F1 (16%) > F4 (0.4%), respectively. The amendment of BC400, BC600, and apatite significantly reduced the exchangeable fraction of Pb and Zn and increased the other stable fractions including F3, F4, and F5, especially at the rate of 10% of biochar and a combination of 5:5% of biochar and apatite. The effects of CB400 and CB600 on the reduction in the exchangeable fraction of Pb and Zn were almost the same (p > 0.05). The results showed that CB400, CB600, and the mixture of these biochars with apatite applied at 5% or 10% (w/w) could immobilize lead and zinc in soil and reduce the threat to the surrounding environment. Therefore, biochar derived from corn cob and apatite could be promising materials for immobilizing heavy metals in multiple-contaminated soil.
Heavy metal pollution in soils caused by mining activities is a severe issue worldwide. It is necessary to find a suitable approach to mitigate heavy metal-contaminated soil. Yet little is known about how soil amendments affect the chemical forms of heavy metals. Biochar produced from peanut shells (PSB300) and corn cob (CCB300) at 300 °C, and apatite (AP) were applied at various ratios to investigate their ability to adsorb lead (Pb) and zinc (Zn) in contaminated soil. The Pb and Zn’s chemical fractions were analyzed utilizing Tessier’s sequential extraction procedure and quantified using inductively coupled plasma mass spectroscopy. The one-month amendment incubation of biochar and AP could significantly diminish Pb and Zn’s exchangeable fractions, and CCB300 showed a slightly better effect on declining the exchangeable fractions of Pb and Zn than PSB300, which might be attributed to the higher values of OC and EC of CCB300 than those of PSB300. Moreover, the amendments could also transform the exchangeable fractions of Pb and Zn into stable fractions, resulting in immobility in natural conditions. Thus, PSB300 and CCB300 and the mixture of biochar/apatite could be hopeful amendments for immobilizing heavy metals in heavy metal multi-metal-contaminated field soil.
Việc phân tích dạng hóa học của các kim loại chì là cần thiết để đánh giá chính xác mức độ ô nhiễm và nguy cơ gây ô nhiễm tới môi trường xung quanh của Pb trong đất bãi thải ở vực khai thác khoáng sản. Nghiên cứu này áp dụng quy trình chiết Tessier để xác định các dạng kim loại của chì (Pb) trong các mẫu đất bãi thải ở khu vực mỏ chì/kẽm làng Hích, huyện Đồng Hỷ, tỉnh Thái Nguyên bằng phương pháp ICP-MS. Kết quả cho thấy, Pb tồn tại chủ yếu ở dạng cacbonat (F2) và ít nhất ở dạng liên kết hữu cơ (F4), ngoài ra còn tìm thấy ở dạng liên kết với Fe-Mn oxihydroxide (F3); dạng trao đổi (F1) và dạng cặn dư (F5). Thông qua chỉ số tích luỹ địa chất (Igeo), chỉ số đánh giá rủi ro (RAC) và quy chuẩn kỹ thuật quốc gia về chất lượng đất (QCVN 03-MT: 2015/BTNMT) đã đánh giá được hàm lượng Pb trong các mẫu đất ở khu vực bãi thải của mỏ chì/kẽm ở mức độ ô nhiễm cao và mức độ rủi ro môi trường rất cao.
Nghiên cứu này phân tích hàm lượng tổng và các dạng hóa học của Cr trong các mẫu bụi đường từ các khu công nghiệp đã được phân tích để đánh giá mức độ ô nhiễm. Dạng hoá học của Cr trong các mẫu bụi đường được phân tích theo quy trình chiết tuần tự của Tesser và đo bằng phương pháp ICP-MS, với tổng độ thu hồi Cr dao động từ 96,5% đến 102%. Kết quả cho thấy Cr tồn tại chủ yếu ở dạng cặn dư (F5: 58,9 %) > dạng liên kết với hợp chất hữu cơ (F4: 18,3%) > dạng liên kết Fe/Mn oxít (F3: 13,0%) > dạng trao đổi (F1: 5,52%), và dạng liên kết với cácbonat (F2: 4,31%). Các chỉ số ô nhiễm như chỉ số tích lũy địa chất (Igeo), hệ số ô nhiễm riêng lẻ (ICF) và chỉ số đánh giá rủi ro (RAC) để đánh giá mức độ ô nhiễm của Cr. Giá trị Igeo của Cr trong các mẫu đều < 0, cho thấy không có nguy cơ rủi ro địa chất. Các giá trị của ICF trung bình 1,32 (0,64 - 1,74), RAC dao động từ 6,64% đến 22,0%, với giá trị trung bình là 15,7%. Theo các chỉ số ICF và RAC nồng độ Cr trong hầu hết các mẫu nghiên cứu ở các khu công nghiệp được xếp vào mức độ ô nhiễm và rủi ro thấp.
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