Detection and attribution of global change effects on river nutrient dynamics in a large Mediterranean basin

[摘要] Attributing changes in river water quality to specific factors ischallenging because multiple factors act at different temporal and spatialscales, and it often requires examining long-term series of continuous data.Data consistency is sometimes hindered by the lack of observations ofrelevant water quality variables and the low and uneven sampling frequencythat characterizes many water quality monitoring schemes. Nitrate anddissolved phosphate concentration time series (1980–2011) from 50 samplingstations across a large Mediterranean river basin were analyzed todisentangle the role of hydrology, land-use practices, and global climaticphenomena on the observed nutrient patterns, with the final aim ofunderstanding how the different aspects of global change affected nutrientdynamics in the basin. Dynamic factor analysis (DFA) provided themethodological framework to extract underlying common patterns in nutrienttime series with missing observations. Using complementary methods such asfrequency and trend analyses, we sought to further characterize the commonpatterns and identify the drivers behind their variability across time andspace. Seasonal and other cyclic patterns were identified as well as trendsof increase or decrease of nutrient concentration in particular areas of thebasin. Overall, the impact of global change, which includes both climatechange and anthropogenic impacts, on the dynamics of nitrate concentrationacross the study basin was found to be a multifaceted process includingregional and global factors, such as climatic oscillations and agriculturalirrigation practices, whereas impacts on phosphate concentration seemed todepend more on local impacts, such as urban and industrial activities, andless on large-scale factors.

[学科分类] 地球化学与岩石