气候变化领域集成服务门户(CCPortal): Regional scale evaluation of nitrate fluctuations in groundwater using cluster analysis and standardised hydrometeorological indices

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DOI	10.1016/j.jhydrol.2024.131052
	Regional scale evaluation of nitrate fluctuations in groundwater using cluster analysis and standardised hydrometeorological indices
	Ascott, M. J.; Gooddy, D. C.; Marchant, B.; Kieboom, N.; Bray, H.; Gomes, S.
发表日期	2024
ISSN	0022-1694
EISSN	1879-2707
起始页码	634
卷号	634
英文摘要	Temporal fluctuations in nitrate in groundwater can result in concentrations temporarily exceeding drinking water standards. This can bring about the need for costly water treatment or blending. Despite this, the extent and potential controls on these fluctuations are poorly understood, particularly at regional to national scales. Applied to Southeast England (UK), here we develop the first application of cluster analysis and standardised hydrometeorological indices to evaluate nitrate fluctuations in groundwater at the regional scale. Hierarchical and K -means cluster analysis of 96 groundwater nitrate time series for the period 1995-2022 showed that nitrate time series can be divided into 4 clusters: (1) long term increasing trends (n = 23, mean trend = 0.26 mg NO3/l/ a), (2) long term decreasing trends (n = 19, mean trend = - 0.65 mg NO3/l/a), (3) long term increasing trends with seasonal fluctuations (n = 24, mean trend = 0.29 mg NO3/l/a) and (4) long term increasing trends superimposed on near-decadal scale fluctuations (n = 30, mean trend = 0.22 mg NO3/l/a). Boreholes in cluster 1 appear to be deeper than boreholes in cluster 2. In comparison to shallower boreholes, deeper boreholes are likely to be intersecting longer groundwater flow systems where nitrate concentrations are affected by historic legacy nitrate leaching. There is weak spatial coherence in the clustering, with clusters 3 and 4 present in the South and North Downs respectively. Cross -correlation analysis between groundwater nitrate time series with precipitation and groundwater level indices showed that rapid seasonal fluctuations in nitrate concentrations in cluster 3 in the South Downs are associated with rapidly responding groundwater level fluctuation. This is likely due to the highly fractured and faulted nature of the Chalk aquifer in this area. This is in contrast with the slower near-decadal fluctuations in cluster 4 in the North Downs. The strongest correlations between groundwater levels and nitrate concentrations in cluster 3 occurred when cross -correlating at a lag of zero months, which would suggest that matrix diffusion is unlikely to be a significant control on nitrate seasonality. Seasonal fluctuations in nitrate concentrations are likely to be associated with a combination of piston displacement at the water table and changing groundwater flow paths to the borehole. Future climate change may change the magnitude and timing of seasonal fluctuations caused by these processes. The methodology developed here is generic and can be applied wherever there is a large body of groundwater nitrate time series data.
英文关键词	Nitrate; Groundwater; Standardised hydrometeorological indices; Time series analysis
语种	英语
WOS研究方向	Engineering ; Geology ; Water Resources
WOS类目	Engineering, Civil ; Geosciences, Multidisciplinary ; Water Resources
WOS记录号	WOS:001208283900001
来源期刊	JOURNAL OF HYDROLOGY
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/306250
作者单位	Met Office - UK; UK Research & Innovation (UKRI); Natural Environment Research Council (NERC); NERC British Geological Survey
推荐引用方式 GB/T 7714	Ascott, M. J.,Gooddy, D. C.,Marchant, B.,et al. Regional scale evaluation of nitrate fluctuations in groundwater using cluster analysis and standardised hydrometeorological indices[J],2024,634.
APA	Ascott, M. J.,Gooddy, D. C.,Marchant, B.,Kieboom, N.,Bray, H.,&Gomes, S..(2024).Regional scale evaluation of nitrate fluctuations in groundwater using cluster analysis and standardised hydrometeorological indices.JOURNAL OF HYDROLOGY,634.
MLA	Ascott, M. J.,et al."Regional scale evaluation of nitrate fluctuations in groundwater using cluster analysis and standardised hydrometeorological indices".JOURNAL OF HYDROLOGY 634(2024).