Research progress of agricultural non-point source pollution migration process and model in basins
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摘要:
当前农业面源污染仍是我国水污染的主要来源,面源污染过程涉及农业、水利、环境、生态等多学科交叉,是国内外环境污染学术研究和流域污染控制与管理关注的焦点之一。不同学科通常在不同的时空尺度上采用不同的方法研究农业面源污染的产生与迁移过程,如农业学科注重农田—山坡—流域尺度下灌溉、不同作物在不同阶段施肥、营养盐转化吸收及其土壤库收支与微生物对营养盐的作用等过程,但忽略了不同尺度或系统之间的迁移过程内在联系,尤其是较少开展集成模拟研究。本文综述了典型空间尺度(从田块到山坡,再到流域尺度)农业面源污染迁移过程及影响因素,总结了流域农业面源污染建模方法,提出在模型系统中除需要深入考虑田块、山坡等尺度的局部水文及其污染物产生、累积、释放与迁移外,还迫切需要综合考虑农田—山坡—流域系统的水文和污染物迁移过程与集成面源模型的研发。同时,针对农业面源污染迁移过程的尺度转换、建模方法和模型不确定性,分析了其现有研究存在的不足,并对未来研究进行了展望。
Abstract:Agricultural non-point source pollution is still the main source of water pollution in China. It involves multi-disciplinary intersection of agriculture, water conservancy, environment and ecology, etc., and is one of the key issues of both national and international environmental pollution academic research and watershed pollution control and management. Different disciplines usually use different methods to study the generation and migration of agricultural non-point source pollution at different time and space scales. For example, agriculture focuses on processes such as water irrigation on fields-hillsides-watershed scale, fertilization for different crops at different life stages, nutrient transformation and absorption, soil pool budget, and the effect of microorganisms on nutrients. However, it is often overlooked the internal relationship between different scales or systems, and there are few studies on the integrated simulation of the transportation process. The agricultural non-point source pollution transportation process and its influencing factors from different typical spatial scales (from fields to hillsides, and then to watershed scales), as well as the agricultural non-point source pollution modeling methods in watershed, were summarized. It was proposed that in addition to deeply considering local hydrological processes and the yield, accumulation, release and transportation of pollutants at the typical scales of field and hillside in the model system, the hydrological and pollutant migration processes and the development of an integrated non-point source model, which covered fields-hillsides-watershed system, should be highlighted. Meantime, the existing research problems related to the scale transformation, modeling methods and model uncertainty research of agricultural non-point source pollution migration process were analyzed, and the future research directions were prospected.
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表 1 流域面源污染模型机理统计
Table 1. Statistics of watershed non-point source pollution model mechanism
模型类型 模型名称 关键方程式 优缺点 经验模型
EC模型[40]$L = \displaystyle\sum\limits_{i = 1}^n { {E_{{ {{i} } } } }\left[ { {A_{ {j} } }\left( { {l_{{ {{k} } } } } } \right)} \right] + P}$
式中:L为营养盐的损失量,kg;Ei为第i种营养源的输出系数;Aj为第j种土地利用类型面积(或牲畜或人口数),km2;lk为第k种营养源输入量,kg;P为降水的营养盐输入量,kg优点:简化面源污染形成过程,降低监测数据的依赖性。缺点:出口系数固定造成误差较大且不能定量 DECM(动态输出系数模型)[46] $\begin{gathered} L = \displaystyle\sum\limits_{i = 1}^n {D({\rm{pc} }{ {\rm{p} }_i})\left[ { {B_{{p} } }({J_{{q} } })} \right]} \\ {B_{{p} } }({J_{{q} } }) = f({\rm{land use,soil,slope,pcp} }) \\ \end{gathered}$
式中:L为营养盐的损失量,kg;${D({\rm{pc} }{ {\rm{p} }_i}) }$为第i种营养源的动态输出系数,取决于降水量;pcp为流域的年降水量,mm;Bp为第p类面源污染响应单元的面积,km2,取决于土地利用、土壤类型、坡度、人口、牲畜和肥料以及农药利用;Jq为第q类营养源的营养输入量,kg,取决于模型计算的降水量、肥料和农药利用的营养输入量优点:减少计算量,提高大型无资料流域精度。缺点:不能量化小流域到大流域参数的不确定性 机理过程模型 SWAT模型[44,47] $\begin{gathered} {P_{ {\text{surf} } } } = \dfrac{ { {P_{ {\text{sol} } } } \times Q} }{ { {\rho _{\text{b} } } \times {H_0} \times {k_{\text{d} } } } } \\ {\rm{N} }{ {\rm{O} }_{3{\text{surf} } } } = {\beta _{ {\rm{N} }{ {\rm{O} }_3} } } \times {C_{ {\rm{N} }{ {\rm{O} }_3},{\text{mob} } } } \times {Q_{ {\text{surf} } } } \\ \end{gathered}$
式中:Psurf和NO3surf分别为迁移到径流中的可溶性磷和硝酸盐的量,kg/hm2;Psol和$C_{ {\rm{NO} }_3,{\rm{mod}}}$分别为10 mm表层土壤流动水中磷和硝酸盐的浓度,kg/mm;$\beta_{ {\rm{NO} }_3 }$和kd分别为硝酸盐渗透系数和磷在土壤中的分配系数,m3/mg;ρb为干土的容重,mg/m3;H0为表层土壤的深度,取10 mm优点:考虑汇流和沉积物的影响过程,易于使用。缺点:不能用于模拟单个洪水事件,参数必须本土化 HSPF模型[45] $X ={\rm{ KF} } \times {C^{{N} } } + {\rm{XFIX} }$
式中:X为吸附达到平衡时泥沙的吸附浓度,μg/g;KF和N为经验常数;C为溶液浓度,μg/L;XFIX为单位土壤吸附的化学物质质量,μg/g优点:模拟径流形成的详细过程,时间步长连续。缺点:不适用于数据缺乏导致模型参数不完整的研究区域 AGNPS模型[43] $\begin{gathered} {\rm{Nu}}{{\rm{t}}_{ {\text{sed} } } } = {\rm{Nu}}{{\rm{t}}_{\text{f} } }{Q_{\text{s} } }(x){E_{\text{r} } } \\ {\rm{Nu}}{{\rm{t}}_{ {\text{sol} } } } = {C_{ {\text{nut} } } }{\rm{Nu}}{{\rm{t}}_{ {\text{ext} } } }Q \\ \end{gathered}$
式中:Nutsed为氮、磷随泥沙迁移量,kg/hm2;Nutf为氮、磷在土壤中的含量,kg/hm2;Qs(x)为土壤流失量,kg;Er为富集率;Nutsol为径流可溶性氮、磷浓度,mg/L;Cnut为表层土壤氮或磷的平均浓度,mg/kg;Nutext为土壤氮、磷的提取系数;Q为径流量,m3优点:模拟流域内侵蚀空间分布以及水质效果较好。缺点:模拟需要大量的输入参数,在缺乏数据的流域应用受到限制 CREAMS模型[42] $\begin{array}{l}{\rm{RON} }={c}_{2}\times {e}_{2}\times Q\times 0.01\\ {\rm{SON} }={C}_{ {\rm{S} } }\times 富集比\times 产沙量\end{array}$
式中:RON、SON为径流、泥沙吸附中氮通量,kg;c2为降水中的氮浓度,mg/L;e2为地表径流迁移系数;Q为径流量,m3/s;0.01为单位换算系数;CS为泥沙浓度,mg/L优点:适用于田块尺度的水文、侵蚀、污染物迁移转化模块计算。缺点:不能用于大规模流域,缺乏仿真功能 SWMM(暴雨洪水管理模型)[48] $\begin{gathered} B = {C_1}(1 - {{\rm{e}}^{ - {C_2}t} }) \\ W = {C_{\text{3} } }{q^{ {C_4} } }B \\ \end{gathered}$
式中:B为污染物累积质量,g/m2;C1为污染物单位面积累积质量,g/m2;C2为累积率常数,d-1;W为每小时污染物冲刷质量,g/h;C3为冲刷系数;C4为冲刷指数;t为污染物累积时间,d优点:适用于小尺度、单次城市洪水事件。缺点:在短管较多、坡度较大、输出步长较短条件下,结果波动较大 MIKE-SHE(地表水和地下水综合模拟软件)[49] $\dfrac{{\partial c}}{{\partial t}} = - \dfrac{\partial }{{\partial x}}(c{\nu _x}){\text{ + }}\dfrac{\partial }{{\partial y}}(c{\nu _y}) \pm R$
式中:c为污染物浓度,mg/L;vx、vy为x、y方向水流流速,m/s;R为源汇入项优点:以网格为单位计算适合河网密集的平坦区水文过程。缺点:不公开源代码,无法进行二次开发 -
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