Nitrate Removal in a Restored Spring‐Fed Wetland,Pennsylvania, USA1

ABSTRACT:  In 2001, the 1.04‐ha Hornbaker wetland in south‐central Pennsylvania was restored by blocking an artificial drainage ditch to increase water storage and hydraulic retention time (HRT). A primary goal was to diminish downstream delivery of nitrate that enters the wetland from a limestone spring, its main source of inflow. Wetland inflow and outflow were monitored weekly for two years to assess nitrate flux, water temperature, pH, and specific conductivity. In Year 2, spring discharge was measured weekly to allow calculation of nitrate loads and hydraulic retention time. Surface runoff was confirmed to be a small fraction of wetland inflows via rainfall‐runoff modeling with TR‐55. The full dataset (n = 102) was screened to remove 13 weeks in which spring discharge constituted < 85% of total inflows because of high precipitation and surface runoff. Over two years (n = 89), mean nitrate‐nitrogen concentrations were 7.89 mg/l in inflow and 3.68 mg/l in outflow, with a mean nitrate removal of 4.19 mg/l. During Year 2 (n = 47), for which nitrate load data were available, the wetland removed an average of 2.32 kg N/day, 65% of the load. Nitrate removal was significantly correlated with HRT, water temperature, and the concentration of nitrate in inflow and was significantly greater during the growing season (5.36 mg/l, 64%) than during the non‐growing season (3.23 mg/l, 43%). This study indicates that hydrologic restoration of formerly drained wetlands can provide substantial water quality benefits and that the hydrologic characteristics of spring‐fed wetlands, in particular, support effective nitrogen removal.     

河南省农业生态环境分析与生态建设

河南省是一个农业大省,其农业的可持续发展与否,对我国的农业发展有着重要影响。在广泛、深入调查的基础上,分析了河南省农业生态环境存在的主要问题,结合农业生态建设的指导思想及目标,提出了河南省农业生态建设的４大对策。     

陡坡地集流聚肥梯田技术的应用

本文根据径流农业和水土保持综合治理的基本原理,以及对辽西部陡坡地资源的调查研究,介绍了陡坡地集流聚肥梯田的内涵,集流,集流效果及其优化设计参数的确定。     

我国高效节水型可持续农业发展模式选择

通过发展高效节水农业的背景和技术基础分析,根据我国区域光热、水土资源特点,以提高大气水、地表水、土壤水和地下水等水资源的利用效率为目的,以提高土地的生物学产量和经济效益为目标,研究提出了抗旱型、立体型、设施型、 复合型、免耕型和集水型等高效节水型农业发展模式,为今后建立我国不同特色的集约高效节水型农业提供可供借鉴的模式。     

集水型生态农业：西北半干旱区可持续农业发展的模式

西北地区是中国的主要农牧业区之一,中国农业、农村、农民问题,在很大程度上也是西北地区问题,西北地区的生态环境问题不是工业的污染,而农业生产活动的破坏,因此,在西部大开发过程中,必须将生态环境的重建与当地农民的脱贫、与农业和农村经济发展紧密结合起来,采适应地区特点的集水型生态农业发展模式,实现西北地区农业的可持续发展和生态环境的逐步恢复和重建。     

低碳农业对农产品安全的影响研究

针对我国现代农业、农产品生产及安全的现状,深入分析高碳农业对农产品安全的危害,阐述低碳农业与农产品安全的关系,探讨低碳农业对农产品安全的保障机理,探索发展低碳农业、保障农产品安全实现的途径。通过对英国、美国以及国内有机农业实践的研究,指出保障农产品安全的关键因素是将农业的生态系统和经济系统结合起来,减少以化石燃料为基础的要素投入,提高农业系统生产力。该研究成果对加快转变农业发展模式,实现农业可持续发展,降低农产品的安全隐患具有一定的理论指导和实践参考价值。     

Agricultural Lakes in Finland: Current Water Quality and Trends

Agriculture is the largest source of nutrients into surface waters in Finland, and yet relatively little is known about the actual impact of the agricultural load on the state of lakes. We analysed the water quality data of 20 Finnish agricultural lakes and found that they had higher levels of nutrients, chlorophyll a and turbidity than did the other types of lakes (e.g. those receiving point-source load) in the national monitoring network (the Finnish Eurowaternet). Currently, six of the agricultural lakes can be classified as eutrophic and 14 as hypertrophic. Trend analysis (based on Kendall's tau-b) indicated that during 1976–2002 the water quality of the lakes either remained constant or showed signs of increasing eutrophication and elevated turbidity. Decreasing nutrient concentrations were found only in one intensively restored lake. In none of the lakes had the chlorophyll a concentration decreased. The results of the trend analysis are compatible with the recent finding that, despite vigorous efforts, the nutrient load from agriculture has not declined in Finland. Recovery of the most eutrophied agricultural lakes would call for a drastic reduction in the external nutrient load, possibly supplemented with in-lake restoration.     

Is there a Kuznets curve for cropland use? The evidence from international panel data

The environmental Kuznets curve (EKC) hypothesis assumes the nonlinear relationship between production and its environmental effects, suggesting that the negative effect of production on the natural environment is reversed at higher levels of development. In contrast to the majority of the studies, this paper considers the possibility of non-linear effects of per capita output on agricultural land use (cropland), as one of the natural resource stocks, and additionally examines the influence of demographic and productivity variables on the agricultural land use. The study draws on panel data from 143 economies over the 1990–2019 period and employs a series of panel econometrics techniques (including panel unit root and cointegration tests, panel ordinary least squares, generalized method of moments, and panel quantile models). The results unequivocally indicate the inverted U-shaped relationship between the GDP per capita and cropland use, as per EKC hypothesis. The results are robust with respect to employing different techniques, the identified turning points correspond to low and low-middle-income levels, and the effects of agricultural productivity and population density on land use are respectively negative and positive.     

农业面源污染现状及其对策措施

目前,农业面源问题日益严重,对农业面源污染的现状、成因、危害进行了分析,并针对污染现状与面源污染的特点,提出了用各种技术手段和经济、法律手段来控制农业面源污染的对策,主要思路有：对农业面源污染这一复杂过程进行分析模拟．积极推广“末端”治理方法,削减农业面源污染,改善农业生态环境。     

浙江省生态环境现状及其保护对策

通过对浙江省生态环境建设现状及其存在问题的分析 ,提出了加强该省生态环境建设 ,改善生态环境状况的对策措施。