UFZ-Helmholtz Centre for Environmental Research, Leipzig, Germany.
Lyles School of Civil Engineering, Purdue University, West Lafayette, IN, USA.
Nat Commun. 2020 Dec 9;11(1):6302. doi: 10.1038/s41467-020-19955-8.
Subsurface contamination due to excessive nutrient surpluses is a persistent and widespread problem in agricultural areas across Europe. The vulnerability of a particular location to pollution from reactive solutes, such as nitrate, is determined by the interplay between hydrologic transport and biogeochemical transformations. Current studies on the controls of subsurface vulnerability do not consider the transient behaviour of transport dynamics in the root zone. Here, using state-of-the-art hydrologic simulations driven by observed hydroclimatic forcing, we demonstrate the strong spatiotemporal heterogeneity of hydrologic transport dynamics and reveal that these dynamics are primarily controlled by the hydroclimatic gradient of the aridity index across Europe. Contrasting the space-time dynamics of transport times with reactive timescales of denitrification in soil indicate that ~75% of the cultivated areas across Europe are potentially vulnerable to nitrate leaching for at least one-third of the year. We find that neglecting the transient nature of transport and reaction timescale results in a great underestimation of the extent of vulnerable regions by almost 50%. Therefore, future vulnerability and risk assessment studies must account for the transient behaviour of transport and biogeochemical transformation processes.
由于养分过剩导致的地下水污染是欧洲农业区长期存在且广泛存在的问题。特定地点对反应性溶质（如硝酸盐）污染的脆弱性取决于水文传输和生物地球化学转化之间的相互作用。目前关于地下水脆弱性控制的研究并未考虑根区传输动力学的瞬态行为。在这里，我们利用先进的水文模拟，由观测到的水文气候强迫驱动，展示了水文传输动力学的强烈时空异质性，并揭示了这些动力学主要由欧洲干旱指数的水文气候梯度控制。将运输时间的时空动态与土壤中反硝化的反应时间尺度进行对比表明，欧洲约 75%的耕地至少有三分之一的时间可能容易受到硝酸盐淋失的影响。我们发现，忽略传输和反应时间尺度的瞬态性质会导致对脆弱区域范围的极大低估，约为 50%。因此，未来的脆弱性和风险评估研究必须考虑传输和生物地球化学转化过程的瞬态行为。
