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because it's really salty. come on guys. |
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I wonder what becomes of dredged stuff from sea harbors etc. It can't all go to the dump. Is it so salty as to be useless? |
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What effect will this have on the marine ecosystems which previously relied on a steady influx of organic matter flowing from the river's mouth? |
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Can anybody address the salinity question? Does much of the sediment settle in the area of fresh water? |
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I'd recommend considering the reversal of the
process that involved "bovril boats". |
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Tide possibly notwithstanding, wouldn't the mouth of rivers tend towards non-salinity ? |
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For big rivers the mouth is tidal, and the water in them is brackish (a bit salty). |
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I don't think it would be technologically challenging to rinse salt out of the mud, but it would be quite intensive: Mix the mud with several volumes of fresh water (perhaps from further up the river). Allow to settle. Discard slightly salty water. Repeat if necessary. |
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The settling might well take a long time, which would limit the amount of mud which could be processed. Perhaps you could optimise the rate a little with less time for subsequent washes, but reusing that water for the initial wash of a new batch. Centrifuging might also be an option, but of course would need more energy. Another possibility is filtering, perhaps with straw - which is already a beneficial soil additive. |
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A little bit of salt probably won't do much harm for most purposes. Pollution (particularly heavy metals) might be more of an issue. |
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Where there is heavy annual rainfall (like the UK) there may be a safe amount to add per year, with the salt being washed away over time. |
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//For big rivers the mouth is tidal, and the water in them is
brackish (a bit salty)//
Aren't you assuming a river that flows into the sea? What
about e.g. the Cuyahoga or Chicago rivers that flow into Lake
Michigan or Lake Erie? |
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//Pollution (particularly heavy metals) might be more of an
issue//
Oh, wait. Forget I said anything. |
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I doubt the salt in the recovered soil would be a problem.
Even if you put an inch of dredged mud on the land (which
would be an enormous amount of dredging, if you covered a
significant area of land), the salt would rapidly wash down.
Even if that amount of salt were retained in only the top
yard of soil, that would be the equivalent of watering heavily
once with a 1/36th dilution of seawater - negligible. |
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That salty 1" of soil will prevent all plant growth. The next time it rains or the wind blows there will be nothing there to hold it in place (its 100% ready to erode). The solution has to involve a viable soil that can grow plants and sustain worms and soil biota on day 1. River dredge (although it has problems) is already used quite a lot. The part of this idea that makes it unbaked is the sea bit. The salty bits, so to speak. We can't just gloss over that. If sea salt makes the soil harder to use not to mention acquire then we need to face that and see if the idea has any merit. |
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hmm... but the dredge has to come from somewhere: presumably the feeder rivers; why not dredge them *before* they hit the mouth and become salted ? |
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because that would be "baked" as we say. |
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There are salt-loving plants though, such as
samphires. |
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Simple utilize those with pica to process the soil, absorbing the salt into their systems and passing it better digested than it previously was. |
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Early Irish farmers used material from the shore and other salty sea sources. It looks like pretty rough going. Also it must be considered that this sort of constructed soil lacks the ability to gradually release bound nutrient minerals over time, it is "mature" and fertility will decline over time. It will also wash and blow away very easily. Not exactly a long term solution to problems of erosion. See my link for an illuminating journal article. |
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