Neonicotinoid Pesticide and Nutrient Removal in Floating Treatment Wetland Mesocosms

Julia Lindgren

University of Nebraska-Lincoln

Co-Authors:

Pesticide application is important to the growing agricultural sector as the demand for production increases. However, the use of these agrochemicals brings potential environmental contamination to water resources. Neonicotinoids are a class of insecticides that may be harmful to critical pollinators such as honey bees and monarch butterflies. Recently neonicotinoids have been detected in surface water in the Midwest. Therefore, the objective of this study was to examine the impact of neonicotinoid pesticides on nitrogen removal in floating treatment wetlands along with quantifying pesticide removal potential in these ecosystems. A mesocosm experiment evaluated three treatments (1. Pesticide enriched water without floating treatment wetlands, 2. Floating treatment wetland with pesticides, 3. Floating treatment wetland without pesticides) in replicates of three over a 21 day period. Grab water quality samples were collected and evaluated for pesticide concentrations using LC MS/MS analysis and nutrient concentrations on an AQ300. Samples were evaluated for neonicotinoid species clothianidin, imidacloprid, and thiamethoxam. Additionally, qPCR was performed on water samples to detect pesticide effects on microbial communities. Reduced neonicotinoid concentrations in mesocosms with floating treatment wetlands suggest a potential for pesticide removal. Preliminary results indicate that neonicotinoid pesticides may enhance nitrate removal in floating treatment wetland systems. This study has direct implications on how pesticides and nutrients are removed in complex water chemistry scenarios in agroecosystems. Results are being used to determine placement and kinetic removal rates of pesticides and nutrients for floating treatment wetlands.

Author E-mail
juliakay28@gmail.com

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6 thoughts on “Neonicotinoid Pesticide and Nutrient Removal in Floating Treatment Wetland Mesocosms

  1. Hi there! Thank you for taking the time to make this presentation! Floating wetlands are such a cool eco-tech. I was wondering what you think the implications for this study could be on a larger scale? How might floating wetlands be used by a community, for example? Thank you so much!

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    1. Thank you for taking the time to respond!
      On a larger scale, a community could use floating treatment wetlands on lakes or ponds that have high nutrient concentrations and algae problems. Here in Nebraska, that is common to see algae problems along with a presence of neonicotinoids.
      This study could be used to recommend FTWs as a practice for neonicotinoid removal. Additionally, we can determine if pesticides are going into the shoots of the plants in concentrations that would be concerning for insects. For example monarch larvae consume milkweed leaves, so determining if leaf concentrations will be high enough to possibly cause harm to larvae is of interest before implementing on a field scale.
      Thank you again for the question. If you would like to talk further don’t hesitate to email me!

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      1. Thank you for your thoughtful response, you’ve answered all of my questions! I appreciate you spending the time to write back!

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  2. Interesting work!

    I do have several questions with the microbial related experiments. In the method section, you mentioned 6 genes were analyzed, while only the nirS result was shown in the presentation. Was that because you are still working on the rest of the experiments? In addition, did you only test the microbes in the water column? Have you considered that the biofilms that might grow on the mats and on/in the plant roots (in the rhizosphere, maybe)? Oh, and one more question, since the denitrification is considered as an anaerobic process, how do you evaluate importance of microbial denitrification in the FTW systems in removing NO3?

    And, by the way, the statements in the Methods Section may not be quite correct. The AOA and AOB genes are associated with “nitrifying microorganisms” instead of “denitrification”, and the 16S gene reflects to the abundance of total microbes.

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  3. Thank you for the great questions.
    You’re correct, it would be more accurate to say that these genes are associated with the nitrogen cycle and 16S is carried out first to characterize the abundance of microbes. qPCR for nos-Z is still in process and I included only one nitrite reductase gene in the poster since results for both were similar. Thank you for the correction.
    In this data set, we only looked at the microbes in the water column. But in our repeat experiment, we will be taking root samples to test the biofilm on the rhizosphere.
    Dissolved oxygen and redox readings were taken everyday and mescocosms with FTWs had less than 2 mg/L DO and redox was less than 200 mV.
    Thanks for the questions/comments! Feel free to email me if you have other questions.

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    1. WOW! It’s really surprising that the DO and redox were low in the mesocosms.
      Thank you very much for the reply. I am looking forward to see the final results in a journal article in the future!

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