N达勒姆.H. — Every year excess fertilizer runs off agricultural farms along the Mississippi River and flows into the Gulf of Mexico creating a dead zone that reduces oxygen levels and kills marine organisms. Restoring wetlands along field-margins has long been proposed as a way to stop some of this overflow, but research from the 永利app新版本官网地址 finds that current restoration programs fall short. Instead of the intended reduction of 45%-60% of the damaging nitrates from the fertilizer ending up in the river, 他们发现硝酸盐的出口量反而减少了, 最多, by 30%.

“Restoring the wetlands is a good first step but the range in the amount of nitrogen potentially reduced by the restoration efforts can vary widely depending on other factors like the flow of groundwater, 工程约束, 湿地的季节差异和位置,单祖德马说, UNH地球系统研究中心的研究科学家和主要作者.

在他们的 研究, 发表在PNAS Nexus杂志上, researchers used process-based physical modeling to evaluate two hypothetical wetland restoration strategies intended to reduce nutrient export to the Gulf of Mexico, 这反映了美国的两个联邦项目. 的y found that existing programs that focused on the construction of field-margin wetlands, 在庄稼和河流之间有条状的土地, 失败有三个原因.

第一个, 水被肥料污染后流入地下水, 这使得湿地更难拦截化肥径流. 这降低了湿地减少氮输出的机会. 研究人员指出，与之前的研究不同, their models first constrained riverine fluxes to match observed fluxes throughout the basin. 的 second reason the policies are limited is the locations of many wetlands that could be restored. 的y are geographically disconnected from heavily fertilized croplands which limits their ability to help intercept the harmful runoff. 和第三, the model simulations took into account seasonal factors—like storms and rain—and how they can inhibit the wetland nutrient removal because peak time wetlands are able to mitigate the nitrate does not coincide with when the fertilizer is leaving the field.

“为了改善墨西哥湾的健康, efforts to eliminate excess nutrient loading should be implemented beyond the field-margin wetland strategies investigated here,祖德玛说.

Researchers agree that field-margin wetlands are an important step towards mitigating the hypoxia, 或者死区, in the Gulf of Mexico because they have the capacity to reduce a meaningful fraction of nitrate and have existing conservation mechanisms in place to facilitate adoption. But they say other factors to consider are interventions to restoring fluvial wetlands, whose position in the watershed can mitigate more of the nitrogen actually reaching the coast.  Future changes in both climate and cropping practices need to be considered to ensure feasibility of these approaches.

合著者包括威尔弗雷德·沃尔海姆和理查德·拉默斯, 都在UNH, 以及克里斯托弗·库查里克, 在威斯康辛大学麦迪逊分校.

 Funding for this research was provided by the National Science Foundation Innovations at the Nexus of Food, 能源和水系统项目. Partial funding was provided by the New Hampshire Agricultural Experiment Station through the USDA National Institute of Food and 农业.

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