Dear all:
I am studying the effects of agricultural production and European agricultural reforms on surface water quality (nitrates and suspended solids). As my understanding, the effects of pollutants on surface water can be appreciated in much shorter time in surface water than in groundwater. However, I have not found a worth publication about that. Might you know something else about this issue?
The answer of Alper Elci is correct. The influence of nitrate and SPM will be direct in surface waters. For the groundwaters, solids will have no influence (except in case of leaching of adsorbed contaminants), and the time necessary for dissolved pollutants to reach the aquifer is due to the infiltration rate, the depth of the water table and the retardation factor (the capacity of the soil to retain pollutant). It could be days, weeks or even decades ! So this last time will be very different from place to place, and I don't think that you will find a kind of compilation or review for that.
Hi
Take a look to my paper entitled: Modelling nonpoint source pollution by nitrate of soil in the Mateur plain, northeast of Tunisia.
https://www.researchgate.net/publication/260434813_Modelling_nonpoint_source_pollution_by_nitrate_of_soil_in_the_Mateur_plain_northeast_of_Tunisia
Article Modelling nonpoint source pollution by nitrate of soil in th...
A case where the pollutant might appreciably appear similar to surface water is in karst (caves, conduits) groundwater systems.
For most agricultural land uses, nitrate is leached to groundwater by vertical drainage from within the soil profile whereas sediment is transported overland to surface waters by occasional surface runoff events. Nitrate in surface water is transported there by discharge from groundwater. The time delay is determined by the ratio of the associated groundwater volume to the flow of soil-water drainage. Time delay, typically, ranges from a few years to several decades.
Nitrate discharges from various parts of a catchment follow individual groundwater flow paths which are combined at the discharge zones into surface waters. This effectively mixes all the nitrate discharges, and therefore leads to the simple concept of a "mixing tank" for which the response time is determined by groundwater volume divided by discharge.
A description of the theory is given in : Appelo, C. A. J. and D. Postma, 1993. Geochemistry, groundwater and pollution, p. 315-318.
The issue of nitrate transport through groundwater is also important in studies of the effects of agricultural management practices on water quality in the Chesapeake Bay, the largest estuary in the United States. Over half of the flow into the Bay comes from groundwater, and thus is subject to lag times. Acknowledging that there are lag times leads to the question - how long are the lag times, and how do they vary in different hydrogeologic settings? We assessed lag times by using groundwater age-dating and groundwater flow modeling (first 2 report links). A more recent paper addresses this issue through modeling (3rd report link). The percent of flow that comes from groundwater also affects this (4th report link). Another factor that affects this is whether or not nitrate is transported conservatively.
1. Fact Sheet: http://pubs.er.usgs.gov/publication/fs09103
2. Full report: http://pubs.er.usgs.gov/publication/wri034035
3. Sanford, W.E., and Pope, J.P., 2013, Quantifying Groundwater’s Role in Delaying Improvements to Chesapeake Bay Water Quality: Environmental Science & Technology, Journal Article. http://pubs.acs.org/doi/abs/10.1021/es401334k
4. http://pubs.er.usgs.gov/publication/70045272
Hi Gloria,
I'm a bit of a novice in groundwater ecology, but as far as I know the time that the water needs to reach the discharge points (springs) from the recharge point(s) varies with the geology. In my limited experience with karstic aquifers, the water (ice/snowmelt from the recharge point) may take as little as 15 d to reach the discharge points (springs at the karst/bedrock boundary). You can find some info and plenty of bibliographic references in the attached article (PDF and URL for the open-access official journal site provided), which focused on groundwater biology but has a solid hydrogeological basis to it. I believe the main hydrogeologist and one of the attached paper coauthors (M. Petitta) has a long-standing record of publications on this large karstic aquifer, and Dr. Petitta is also on ResearchGate.
I hope that this helps you a bit.
Good luck with your research!
-Paola
http://www.nature.com/srep/2014/140903/srep06273/full/srep06273.html
Dear Gloria
As agriculture affects groundwater quality defining nitrate concentration of rivers and hence the nitrate load of lakes, finally the nitrate residence time in the soil will co-determine the response time of rivers and lakes to changing agricultural practice.
However, be aware that in many environments nitrate does not behave conservatively; i.e., it is not only subject to physical transport but may be biologically removed e.g. by plant uptake or denitrification. Due to such removal processes the response times in the mentioned compartments will be shorter than expected based on purely physical transport considerations.
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