农田土壤环境监测渗漏池系统的构建技术及应用

粗放的农田管理措施导致耕地质量连年下降,过量的投入品从农田流失至河流湖泊,特别是农田养分、重金属和农残等的淋溶加剧了农业面源污染的风险。渗漏池作为农业环境监测的重要装置,可分析土壤渗滤液的各成分及其淋洗特征,建立运移模型,评估不同农业措施对农田生态系统的影响,进而为完善农田管理措施提供技术支持。该文针对农业环境研究中的主要渗漏池类型,归纳总结了各类渗漏池的构建与布设方法,对渗漏池中的土壤装填、土壤表层隔离和渗漏液取样的方法等进行了系统描述,分析了不同渗漏池类型的优缺点,讨论了影响渗漏池监测结果的主要因素,并结合渗漏池在农田环境监测中的发展现状,提出了建议与展望。总体而言,各类渗漏池各有优缺点,渗漏池的构建应以具体研究需求为导向,结合地质地形条件、作物种植环境及自身建设水平等情况,在试验可接受的偏差范围和建设预算内,有针对性地构建适宜自身条件平台的渗漏池,从而实现低成本和高精确度的研究体系。

Construction technology and application of lysimeter in agricultural soil environment monitoring

In recent years, intensive and extensive farm managements have resulted in a decline in the quality of cultivated land. Excessive inputs have been leached from farmland to rivers and lakes, especially the leaching of nutrients, heavy metals and pesticide residues, which has aggravated the risk of pollution to agricultural environment. As a critical methodology of agricultural environment monitoring, the lysimeter has been applied to monitor the characteristics of soil leaching components, to simulate the migration of soil water and nutrients, and to assess the effects of farm managements on agricultural ecosystems, eventually to provide technical assistance for scientists to make a better management decision in the farmland ecosystem. In this paper, the methods of construction, layout, soil filling, soil surface isolation and sampling in the main types of lysimeters monitoring system were summarized. Based on that, the merits and shortcomings of different types of lysimeters were analyzed, and the main factors affecting the monitoring results of lysimeter were discussed. In the end, suggestions and prospects were put forward based on the current situation of lysimeter in agricultural environment monitoring. Overall, for the rectangular concrete lysimeter, the biggest advantage is that cost of construction and operation and requirements for technology is relatively low, however, large quantities of soil excavation, concrete construction and soil back filling are always time-consuming and usually cause high soil disturbance and significant artificial effect and need to undergo a transition period. Besides that, the problem of infiltration from inside to outside at the bottom and side of concrete lysimeter also needs to be overcome. Conversely, for barrel or vessel lysimeter, the monolith soil usually undergoes minimal disturbance by extracting and filling the cylindrical blocks, the process is much more simple, which can be achieved just by mechanical equipment including cutting system, crane, trucks and so on. It takes shorter time compared to concrete lysimeter, the whole procedure of obtaining monolith soil just takes one day or more and can be put into use immediately without transition period. Consequently the soil conditions are more comparable to natural field conditions and data could be accurately detected and collected. However, the technological and equipment requirements of monolith soil extraction, filling and transportation are relative high, as well as the cost of construction and operation. Besides that, boundary effect is much more significant compared to the concrete lysimeter due to the minimal soil base area. The artificial effect and boundary effect cannot be eliminated completely at the same time in the semi-closed lysimeter system, the selection and construction of lysimeter system should be depended on specific research needs, local geological and topographic conditions and their own technology level. Therefore, a more practical strategy need to be taken into consideration, that is to build a more suitable lysimeter within the acceptable deviation range and the given budget, being able to implement higher data accuracy with lower costs. Finally, building and running a long-term lysimeter station with continuously improved technologies, joining a platform, sharing methods, data and models, and constructing a network of lysimeter system are also recommended.