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Accumulation of heavy metals

Discussion in 'Water Chemistry' started by Soilwork, 14 Feb 2017.

  1. Soilwork

    Soilwork Member

    Messages:
    265
    Does anyone else worry about heavy metals becoming too excessive? If dosing from dry salts etc. My water is really soft and Walstad's book goes in to great detail about this. I'm worried this could damage my plants and livestock. I've had pretty severe stunting, Chlorosis, necrosis, curling, browning and it also seems to be associate with my chelated trace mix targeting EI levels or iron. It takes a couple of weeks but this is the third time this has happened now.
     
  2. alto

    alto Member

    Messages:
    2,137
    Yes it's very possible
    In "hard" water significant amounts of the added chemicals may be precipitated or sequestered by existing compounds in the water, this does not happen in soft water systems - eg, my tap has KH <1 & GH < 2 or <1 depending on rainfail
    I'm very conservative with regards dosing ... I mostly just add Tropica fertilizers now combined with their aquarium soil line - it's simple

    If you spend the time researching you can find toxity data for plants (mostly land, some aquatic) re amounts of various compounds including nitrogens & especially elements that are considered "trace"

    I'm not a proponent of the EI method - out of concern for the very soft water fish I keep but also just not convinced of the merits of overdosing
     
    Soilwork and dw1305 like this.
  3. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    I'm like <"@alto"> as well, I think micro-element toxicity is a potential danger in soft water, particularly if you don't have any tannins. There is scientific work on the protective effects of DOC by <"Dr Christian Steinberg">.
    I'm not an EI user either, and I think one of the problems is that levels of Fe addition that would still be sub-optimal in hard water are potentially toxic in very soft-water.

    This is partially why I like using floating plants as a bio-indicator. I think this offers advantages over either "recipe" methods or water testing, in that the plant response is a sensitive indicator of nutrient conditions.

    cheers Darrel
     
    zozo, Soilwork and Tim Harrison like this.
  4. Soilwork

    Soilwork Member

    Messages:
    265
    Thanks. It's good to know Im not alone. Darrel I think you know how soft my water is.

    When I set up my Walstad's tank things were pretty rough. Plants would die and I would get algae still not sure why but the soil was John innes no3 unmineralised and very newly laid. I increased my light and turned to co2 and EI because of this but things actually got worse. I developed every algae going including cyano and I was losing fish regularly. Almost subconsciously I correlated 'bad things' and micros and I stopped dosing them. It took a little bit of time cleaning up the algae but the tank exploded. If I knew how to upload pics via iPhone that were not too big a size I would show you.

    Of course I didn't need micros when I had soil. Despite my very low tap water mg i never saw any deficiencies but I now realise the soil can provide mg.

    Fast forwards to my new tank with eco complete. Started dosing EI again with new scape (I only just made the connection from the micros in the soil tank so wasn't expecting things to go wrong) and its bad.

    I lost a cardinal tetra (swollen gills, laboured breathing) and an Amano shrimp which just turned white and died. Algae again has crept in. BBA all over substrate and hardscape. I read about toxicity threads on the planted tank forum and decided to stop dosing the dry powders did lots of water changes and purchased easylife profito and ferro. I dosed small amounts of both but things got worse again and the BBA has just turned a nice green.

    I'm absolutely convinced my micros have caused this.

    I have done lots of water changes recently including 90% ones and most all of my plants are stuck in terms of growth. The top part of my Pogostemon stellatus has just snapped off on it's own this evening.

    Could the eco complete have taken in heavy metals?

    if I do large water changes and using a heavy metal chelate conditioner then dose easylife ferro, could the iron bind more tightly to the EDTA and cause the metals in my tap water to become harmful? My tap has small amounts of copper, boron, manganese etc.
     
  5. Soilwork

    Soilwork Member

    Messages:
    265
    Alto, I know this is a 'how long is a piece of string question' but how long is that substrate suppose to last? I'm going to restart the tank keeping nutrients in the substrate away from algae whilst letting the plants take up wherever nutrients they require from their roots. This has to be a more synergistic approach.

    Also what Is the exact name of this brand?
     
  6. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    You could have a number of issues with JI No.3.

    The "loam" component is actually the soil riddled from potatoes and sugar beet during processing, and it could be both nutrient rich and contaminated with pesticide residues. Have a look at <"Low tech, no CO2....">.

    I don't think mineralising the soil would make a huge amount of difference, as it will have a low organic matter content (%OM) anyway.
    Yes it could, the multivalent cations are more strongly bound. You can get the sequence from the <"lyotropic series">, with the proviso that it also depends upon the ratio of ions. Al+++ and Fe+++ are the most strongly bound ions, and Na+, K+ and NH4+ the least strongly. Copper, Zinc etc are divalent and will be bound less strongly than iron, but more strongly bound that K+ or Ca++ & Mg++.
    Yes it can, it is cation exchange, so if a Fe+++ ion replaces another ion it will become available.

    In harder water that cation will nearly always be a Ca++, but in very soft water it could potentially be a Zn++ etc. ion.

    cheers Darrel
     
  7. Soilwork

    Soilwork Member

    Messages:
    265
    Cheers Darrel. So i could still potentially have heavy metals leeching back in to the water column from the eco complete? I think it may be a good idea to cut my losses with the Eco and go for a superior substrate. I had no idea Innes no3 could cause issues. What should i use in future? I started a new substrate thread in the substrate section if you would care to pop over there.

    Cheers,

    Craig
     
  8. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    You could, but my suspicion would be that you don't, and that it would be an unlikely scenario.
    I always PYO my soil.

    Our garden soil (in NW Wiltshire) is a limestone & clay brash, but to the south and east of us there are bands of greensand and gault clay, where I can collect soil from mole hills on road verges, commons etc.

    cache_10259966.jpg

    When I set up a new tank I just mix a small amount (5 - 10% by volume) of the PYO soil, with a similar proportion of Beech (Fagus sylvatica) leaf mold and ~90% silica sand.

    cheers Darrel
     
  9. Soilwork

    Soilwork Member

    Messages:
    265
    But if the Eco has taken the metals in this could still cause issues with toxicity taking all other factors in to consideration?
     
  10. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    I don't think you can say categorically that it couldn't, but I think the levels of trace metals added are so low that it is extremely unlikely.

    The problem with things like cation exchange is that they aren't exact sciences.

    If you add sodium bicarbonate (NaHCO3) to alkaline tank water with a high dKH and dGH you know that the water is fully saturated with HCO3- ions and CaCO3 will precipitate out via the common ion effect and the known solubilities of carbonate compounds. But when you add an ion to a tank with an active substrate and some humic compounds (both with a high CEC) then there are a lot of potential interactions that can effect ions exchange.

    cheers Darrel
     
  11. Soilwork

    Soilwork Member

    Messages:
    265
    Are they really that small though targeting 0.2ppm Fe at 3 x a week?

    http://www.aquariumplantfood.co.uk/fertilisers/dry-chemicals/chelated-trace.html.

    Even when replacing 50% water every week i am adding 13 micro grams per litre back in from the tap (average) with an average water change being about 40 litres. dosing from this powder according to rotalabutterfly will yield

    Fe 0.6
    Mn 0.129
    Zn 0.084
    B 0.075
    Mo 0.012
    Cu 0.015

    at week end.
     
    Last edited: 15 Feb 2017
  12. xim

    xim Member

    Messages:
    375
    Yes. But I would regard the 0.6 PPM a week as medium though, not small.
    To give you some perspective:

    The EI article here ( https://www.ukaps.org/index.php?page=dosing-with-dry-salts ) calls for 0.5 PPM of Fe a week.

    ADA Green Brighty Step 3 will give 0.017 PPM of Fe daily (or 0.119 weekly) per normal dose. But ADA also recommends overdosing it 2-3x if the plant mass is large. Which makes it 0.357 PPM a week for 3x.

    From EI daily methods or PMDD + PO4 thread posted by Tom Barr ( https://www.ukaps.org/forum/threads/ei-daily-methods-or-pmdd-po4.915/ )
    Adding 2.5 ml of Tropica TMG (now it's called Premium Fertiliser) to a 20 US gallon (75L) tank daily is 0.024 PPM of Fe a day, or 0.168 PPM a week.

    Target of Fe in Aquaponics (which is a system where people keep fish to eat and use the water to grow vegetables) is...... 3 PPM (yep, three PPM)!!!. They don't dose other metals though, just iron. They test the water and try to keep Fe level at that level. Fe-DTPA and Fe-EDDHA are popular in this area.

    Me? I used to dose 0.162 PPM of Fe daily because the DTPA chelator I used was of low quality. The iron precipitated easily. Now since I've changed to a better DTPA (Dissolvine D-Fe-11), I now dose 0.07 PPM daily, or 0.49 PPM a week and still get better results than before. I do 66% water change weekly.
     
    Last edited: 15 Feb 2017
    dw1305 likes this.
  13. Soilwork

    Soilwork Member

    Messages:
    265
    Thanks for the reply. This calculator http://rotalabutterfly.com/ The one I have been using targets 0.2ppm iron each dose for EI using any diy powder.

    It used to be 0.5ppm but it has been changed recently to 0.2ppm.

    GLA has also altered there mix instructions for PPS-Pro too which targets lower amounts of overall trace using CSM+B.

    http://blog.greenleafaquariums.com/2013/02/28/our-new-pps-pro-fertilizer-pack-just-mix-dose/

    I can't help but thinking that the alterations have been made due to discussions such as

    http://www.barrreport.com/forum/barr-report/estimative-index/14637-how-easily-csm-b-can-become-toxic

    http://www.plantedtank.net/forums/1...ameters/853001-csm-b-toxicity-experiment.html

    http://www.plantedtank.net/forums/11-fertilizers-water-parameters/503585-toxicity-csm-b.html

    My trace mix is more potent in some of the heavy metals than CSM+B and like nearly all cases in those threads my source water is similarly as soft.

    I bought liquid ferts now which are far less concentrated but I think the damage has already been done. After a brief improvement from some plants after removing lots of water several times most plants didn't grow over the course of about 3 weeks. I'm taking them out now.
     
  14. AverageWhiteBloke

    AverageWhiteBloke Member

    Messages:
    1,327
  15. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    It is all smokes and mirrors.

    In situations where iron becomes toxic it will be the ferrous (Fe++) ion, because iron toxicity is associated with low levels of oxygen and low pH. In the aquarium water the ions will always be ferric (Fe+++), rather than ferrous (Fe++), you can actually tell on colour iron II compounds are green in colour and iron III (rust) red. In the presence of oxygen Fe++ ions will become Fe+++. I don't have the exact figures to hand, but you need quite a large negative REDOX potential to retain ferrous (Fe++) iron ions.

    In most substrates you will have zones of low REDOX potential where ferric iron (Fe+++) will become reduced to ferrous iron (Fe) and become plant available.

    cheers Darrel
     
    xim likes this.
  16. Soilwork

    Soilwork Member

    Messages:
    265
    Hi Darrel

    If iron is toxic in fe2 form in low o2 environments and low pH. How is the condition of anaerobic areas in low pH soils beneficial to plant uptake and not detrimental?

    Cheers
     
  17. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    The problem is that a lot of the trace elements are essential for plant growth in trace amounts, but the range from deficiency ~ optimal ~ toxic is really small.

    trace2.jpg
    The very specialised plants that grow in peat bogs have methods for reducing the toxicity of iron under conditions of low oxygen and high acidity, and this will also apply to a lot of aquatic plants. If you don't have access to <"Iron toxicity for fen plant species"> I can send you a copy.

    cheers Darrel
     
  18. AverageWhiteBloke

    AverageWhiteBloke Member

    Messages:
    1,327
    Am I right in thinking if the centre of that graph is 0.5ppm Iron then toxic levels in soft water would be 1ppm? I take it "Death" on the deficient side would mean death of flora and death on the toxicity side would be fauna or do plants also suffer at high concentrations?
     
  19. dw1305

    dw1305 Expert

    Messages:
    5,813
    Hi all,
    It would depend on the plant, but I would expect the toxic values for nearly all plants would be much higher, and would be in the hundreds for plants from wet acid soils.

    In the linked paper earlier in the thread (<"iron toxicity to fen plant species">) it has figures for Cotton grass (Eriophorum angustifolium), which show that it could grow in a solution containing 5000 ppm Fe++.

    A major factor in ameliorating the toxic effects of ferrous iron is the oxygen diffusing from the roots of Reeds (Phragmites australis), Water lilies (Nymphaea alba) etc which oxidises the Fe++ to Fe+++ in a zone surrounding the root. The technical term is "oxidative precipitation".

    A lot of the work on iron toxicity is either in Rice (Oryza sativa), or looks at the effects of flooding on terrestrial plants. In both cases the plant could go from a situation where the soil is oxygenated and maybe alkaline (where the iron will be unavailable) to one where it is anaerobic and acidic and all the iron becomes available.
    I don't know about animals, but plants will definitely die.

    cheers Darrel
     

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