生物炭添加對泥岩地區非點源污染之改善

Using Rice Hull Biochar to Deal with Non-Point Source Pollution in a Mudstone Area

簡士濠(Shih-Hao Jien) ； 陳俊元(Jyun-Yuan Chen) ； 簡廷澍(Ting-Shu Chien)

《土壤及地下水污染整治》 2卷4期 (2015/10) Pp. 317-327

https://doi.org/10.6499/JSGR.2015.0204.006

摘要

生物炭(biochar) 目前已被視為可有效改善土壤品質之有機資材；然而，至今被利用在減緩土壤沖蝕以及逕流水質的相關研究著墨甚少。本研究因此以台灣南部之泥岩土壤為主要研究對象，分別添加2.5%、5%、10% (w/w) 之400°C 與700°C 厭氧熱裂解之稻殼炭，評估添加稻殼炭可否有效降低泥岩地區之高沖蝕潛勢及逕流水質對集水區下游污染之影響。實驗結果顯示，添加生物炭後可顯著減少泥岩土壤沖蝕量至少25 ~ 91%，其中以10% 之生物炭添加量效果最佳。此外，添加稻殼炭可降低逕流水中銨態氮(ammonium, NH_4^+-N)、硝酸態氮(nitrate, NO_3^--N) 及總磷(totalphosphorous, TP) 的濃度。相較於對照組，添加2.5%、5% 及10% 之稻殼炭可分別減少逕流水中1.7%、25 ~ 32% 及48 ~ 62% 之銨態氮濃度；減少25 ~ 58%、38 ~ 75% 及51 ~ 62% 之硝酸態氮1.17 mg/L；亦降低50%、38 ~ 63% 及50 ~ 63% 逕流水中之總磷濃度。本試驗結果亦顯示，添加10% 之稻殼炭已可使逕流水中之銨態氮濃度接近地面水體水質規範( 銨態氮≤ 0.30 mg/L)，而添加2.5% 之稻殼炭已可使逕流水中總磷濃度符合規範中之乙類水體(TP ≤ 0.05 mg/L)。

關鍵字

生物炭 ； 泥岩 ； 逕流水 ； 無機態氮 ； 總磷

並列摘要

1. Introduction/Background Non-point source pollution is considered a major factor in eutrophication and sediment deposition in reservoirs, which threaten public health and also impact water resource usage. Mudstone areas in southwestern Taiwan suffer from severe soil erosion and a high degree of non-point source pollution. Moreover, the high turbidity and high contents of ammonium, nitrate and phosphate in rivers due to the high level of soil erosion and intense agricultural activities nearby these areas have led to the overloading of reservoirs in southwestern Taiwan. Biochar can be added to soil to significantly improve its fertility and reduce the potential for erosion. Some nutrients can be incorporated into the micropores of biochar, and thus adsorbed on the surface in order to prevent their loss due to runoff or leaching. This study therefore aims to evaluate the effects of biochar made at different temperatures on the erosion potential and runoff quality in a mudstone area in southwestern Taiwan. 2. Material and Methods The soil sample for this study was collected from the surface (0 ~ 25 cm) of a mudstone site in the Teinliao area, Kaohsiung, Taiwan (E 120°22'58＂; N 22°53'02＂). Sedimentary rocks created during the late Miocene Epoch to the Pleistocene Epoch can be several thousand meters deep. The geological stratigraphy is rather monotonic, consisting mainly of massive mudstones or alternating between mudstone and sandstone. These mudstone soils were classified as Typic Eutrustept, according to the U.S. soil classification system (Soil Survey Staff, 2010). Mudstone landscapes are characterized by sparse vegetation, and can be especially vulnerable to erosion during the rainy season. The biochar used in this study was produced from rice hulls and supplied by the Industrial Technology Research Institute of Taiwan. Rice hulls are considered agricultural waste, and at least one million tons of this is produced each year in Taiwan. One way to recycle this waste is to use it as a soil additive. The rice hull biochar samples used in this study were produced at pyrolization temperatures of 400°C and 700°C, and denoted as RHB-400 and RHB-700, respectively. After pyrolysis, the biochar was ground to enable it to pass through a 2-mm sieve, ensuring that all the biochar used in the experiments exhibited similar particle sizes. The soil erosion experiment was conducted using simulated rainfall equipment with a height of 9.5 m, a drop diameter of 2.5 mm, and a terminal velocity of 8.5 m s^(-1). The rainfall intensity used in this study was 100 mm/hr. 3. Results and Discussion Samples of 2.5%, 5% and 10% (w/w) rice hull biochar were incorporated into the soil, which then underwent 21 weeks incubation before a simulated erosion experiment was performed under a given rainfall intensity of 100 mm/hr and a slope gradient of 10°. The results revealed that soil loss was reduced by 25 ~ 91% after the use of biochar, with the best results seen with 10% biochar. In addition, the use of biochar could significantly decrease the concentration of NH_4^+-N by 1.7%, 25 ~ 35% and 48 ~ 62% for the treatments with 2.5%, 5% and 10% biochar, respectively. The nitrate (NO_3^--N) concentration was also decreased by 25 ~ 58%, 38 ~ 75% and 51 ~ 62% in the treatments with 2.5%, 5% and 10% biochar, respectively. The use of biochar application could effectively reduce the TP concentration in the runoff by ~ 40% as compared with the control. The use of 10% biochar is recommended, because this could markedly improve the quality of runoff water, so that it almost matched the 2nd grade of water quality as regulated by the Environmental Protection Agency in Taiwan. 4. Conclusion This study examined the recycling of a form of agricultural waste, namely rice hull, into a useful resource to reduce soil erosion and increase the quality of runoff water in a rural soil derived from mudstone. The results revealed that the use of biochar could effectively reduce soil losses by 25 ~ 90%, and reduced the concentrations of NH_4^ +-N, NO_3^--N and TP by ＞ 50%, 21 ~ 98% and 38 ~ 63%, respectively, in the runoff water from the mudstone area. This innovative practice has potential with regard to reducing eutrophication and sediment deposition in reservoirs in Taiwan.

並列關鍵字

biochar ； mudstone ； runoff ； inorganic nitrogen ； phosphorus