基于氮流失控制的种植结构调整与配套生态补偿措施——以竺山湾小流域为例

通过实地和查阅文献的方式调研了竺山湾小流域稻麦、蔬菜和果树的常规生产、清洁生产模式下的经济效益和氮(N)素流失等数据,采用线性优化模型,统筹考虑经济收益最大和污染排放总量控制,根据N流失总量高低对竺山湾小流域种植业结构设置了五种情景(Ⅰ、Ⅱ、Ⅲ、Ⅳ和Ⅴ)进行调整。情景Ⅰ以经济收益最高为目标,情景Ⅱ、Ⅲ分别在削减情景Ⅰ设定的N流失量20%和30%的约束下,各自实现其经济收益最高的两个情景。对于情景Ⅱ和情景Ⅲ,其N投入量、N流失量分别为6 267 t、511 t和5 567 t、447 t。与常规种植结构相比,这两种情景均达到了N肥投入减少20%、N流失量减少30%的项目预期目标,相对净收益分别达到8.456亿元、7.966亿元,高于未调整前常规种植结构的7.873亿元,属于五种结构调整情景中的最优和次优情景。估算了与种植结构调整相配套的生态补偿资金,包括机会成本补贴和生态效益奖励两部分。除去交易成本后,最优情景和次优情景相应的生态补偿总金额分别为961万元和3 507万元,补偿标准分别为739 Yuan hm~(-2)和2 696 Yuan hm~(-2)。提出了本区域内种植业结构调整的政策建议,以促进竺山湾小流域农田面源污染治理,加快本区域种植业由传统生产方式向清洁生产方式的转型升级。

N-Loss-Control-Oriented Readjustment of Planting Structure and Its Matching Ecological Compensation Measures-A Case Study of Zhushanwan Catchment

Through consultation of literature and field survey,data were collected of the conventional rice,wheat,vegetable and fruit production,the economic benefit of the production under the model of cleaner production and the nitrogen loss in the Zhushanwan catchment,a subwatershed in the northwest of the Taihu Lake Region,and other relevant social-economic data. An attempt was made to readjust the planting structure of the catchment in line with five simulated scenarios(Ⅰ,Ⅱ,Ⅲ,ⅣandⅤ),separately, high to low in total nitrogen loss,using the linear optimization model(Software Lingo 11)and taking into full account maximal economic benefit and total volume control of pollution discharge. In Scenario Ⅱand Ⅲ, the total N input was found to be 6 267 t and 5 567 t,respectively,and the total N loss 511 t and 447 t, respectively,which indicates that both scenarios meet their respective intended targets of reducing total N input by 20% and total N loss by 30% as compared with that in the conventional planting structure. Besides, the two scenarios may generate a relative net economic profit of 845.6 million yuan and 796.6 million yuan, respectively,both higher than that(787.3million yuan)the conventional planting structure does. So among the five scenarios,Scenario Ⅱ is the optimal one and Scenario Ⅲ the second to follow for readjustment of the planting structure of the region. The quota of eco-compensation was calculated according to opportunity cost and ecological benefit reward,and the compensation policy and mechanisms were suggested to facilitate implementation of cleaner production. The ecological compensation funds,excluding transaction cost,about 15% of the total compensation for Scenario Ⅱ andⅢ is estimated to be 9.61 and 35.07 million yuan(RMB), respectively,according to the standard for compensation,739 and 2 696 Yuan hm-2,respectively. Implementation of the policy and its matching eco-compensation measures may effectively help control non-point source agricultural pollution and expedite the process of transformation or escalation of the farming industry in the region from the traditional one to the one of cleaner production.