农作物秸秆COD负荷测定及我国弃置秸秆可能形成的面源COD总量极大值估算

Determining COD Load of Crop Straws and Estimating Possible Maximal Total Amount of COD from Discarded Crop Straws in China

为估算我国弃置秸秆可能形成的面源COD总量极大值,首先对用于测定废水样品COD的传统重铬酸钾回流法进行了改进,即农作物秸秆样品先在75%浓硫酸条件下进行预溶解、然后再按传统酸性重铬酸钾回流法条件进行氧化分解,经过实验证明改进后的农作物秸秆COD测定方法确实可行;然后采用改进后的75%浓硫酸下预溶解+传统重铬酸钾回流法分别测定了麦秸、稻草、玉米秆和高粱秆的COD负荷值。结果表明,实测得到单位绝干秸秆物质所对应的COD负荷值分别为1.301kg·kg-1绝干麦秸、1.247kg·kg-1绝干稻草、1.311kg·kg-1绝干玉米秆、1.415kg·kg-1绝干高粱秆,最后估算得到我国农作物秸秆随意弃置可能形成的面源COD总量极大值约为488万t·a-1,相当于2004年我国工业生产和生活排放的COD总量的36.4%。因此,需要各有关方面对农作物秸秆随意弃置可能形成的面源COD总量及其所伴随的水环境问题的预防与管理给予足够的重视。

To estimate possible maximal COD （Chemical Oxygen Demand） amount from discarded crop straw in China, several experiments were carried out. Some modifications were made with traditional method of COD determination with acidic potassium dichromate circumfluence which is used to determine COD of wastewater samples. Crop straw samples were dissolved in advance with the solution of 75% sulphuric acid, and then were decomposed with acidic potassium dichromate circumfluence. It was proved that the modified method is practical and reliable in determining COD load of crop straw samples. Using the improved method, COD loads of wheat straw, rice straw, corn straw and grain sorghum straw were determined. The averaged COD load were respectively 1.301, 1.247, 1.311and 1.415 kg·kg^-1 oven dry straws for wheat straw, rice straw, corn straw and grain sorghum straw. Finally, It was estimated that possible maximal COD amount form discarded crop straws in China was about 4,880,000 t, which accounted for 36.4% of total COD amount discharged from all industries and urban population in 2004, China. Therefore, it was obvious that more attention should be paid to prevent and manage water environmental issues which were related with possible COD amount resulted from discarded crop straws.