Conference Agenda

The occurrence and persistence of antibiotics in treated wastewater and animal manure fertilizers used for agricultural irrigation has led to growing concerns about possible crop safety issues. Meanwhile, uptake and bioaccumulation of antibiotics by crops is a pathway for human exposure to high levels of antibiotics through the food chain, and ultimately raises the potential risk to human health. Therefore, understanding the mechanisms of antibiotic entry and accumulation is crucial to address the problem of antibiotic contamination in crops. In this study, a series of hydroponic experiments are conducted to study the bioaccumulation and translocation of three antibiotics in Lactuca sativa. Norfloxacin (NOR), levofloxacin (LEV) and sulfamethoxazole (SMX) are identified by modified ultrasonic solid-phase extraction liquid chromatography-tandem mass spectrometry (Sonicate-SPE-LCMS/MS), and their concentrations are determined by matrix-matched calibration method. Five concentrations (0.1, 0.5, 1, 3, and 5 mg L-1) of each antibiotic in the hydroponic system showed no significant inhibition of lettuce growth. Only sulfamethoxazole groups shows increasing solution pH value with higher dosed concentration. Within this concentration range, lettuce has higher SMX uptake rate as well as BCF (Bioconcentration factor) compared to the LEV and NOR experimental groups. Overall, the roots had higher antibiotic accumulation than the shoots in all experimental groups. Moreover, SMX shows a tendency to accumulate more in the roots due to hydrophilic and molecular structure, as well as a lower transfer factor (TF) from the roots to the shoots.

Row crop production in the agricultural Midwest pollutes waterways with nitrate and exacerbates climate change through increased emissions of nitrous oxide and methane. Oxygenic denitrification processes in agricultural soils address nitrate and nitrous oxide pollution by short-circuiting the canonical pathway and not producing nitrous oxide. Furthermore, many oxygenic denitrifiers employ a nitric oxide dismutase (nod) to create molecular oxygen that is used by methane monooxygenase to oxidize methane in otherwise anoxic soils. The direct investigation of nod genes that could facilitate oxygenic denitrification processes in agricultural sites is limited, with no prior studies investigating nod genes at tile drainage sites. Thus, we performed a reconnaissance of nod genes at variably saturated surface sites and a variably saturated to fully saturated soil core in Iowa to expand the known distribution of potential oxygenic denitrifiers. We identified new nod gene sequences from agricultural soil and freshwater sediments in addition to identifying nitric oxide reductase (qNor) related sequences. Surface and variably saturated core samples displayed a nod to 16S rRNA gene relative abundance of 0.004% to 0.1% and fully saturated core samples had relative nod gene abundance of 1.2%. The relative abundance of the phylum increased from 0.6% and 1% in the variably saturated core samples to 3.8% and 5.3% in the fully saturated core samples. The more than ten-fold increase in relative nod abundance and almost nine-fold increase in phylum relative abundance in fully saturated soils suggests that oxygenic denitrification potential might play a greater role nitrogen cycling in these conditions.

The southwestern United States is increasingly impacted by severe water scarcity, and one possible solution for water security is reuse of wastewater. Prior to wastewater reuse implementation, a possible regulatory framework involving advanced wastewater treatment must be developed and understood. We collaborate with an Arizona Tribal College (Diné College) and two Navajo Nation wastewater reclamation facilities to establish a sustainable treatment process in the Navajo Nation to supplement the historical usage of groundwater and surface water used for irrigation. Results show that it is possible to use tertiary water treatment systems involving microfiltration and nanofiltration membrane filtration. The goals of the project are to demonstrate adequate removal of i) pathogens, ii) inorganic solutes, and iii) organic solutes and contaminants of emerging concern (CECs). We apply analytical chemistry methods to analyze pre- and post-treatment water quality and surface characterization techniques to analyze membrane surface changes post-treatment. Treatment results show that NF90, NF245, and NF270 remove inorganic solutes, organic solutes, and CECs to levels that exceed guidelines for using reclaimed water for irrigation purposes. The successful outcomes will facilitate the sustainable use of reclaimed wastewater for food production while engaging Tribal community stakeholders in the decision-making on effluent reuse for agriculture.

Nanotechnology can be leveraged to promote resilience and sustainability of agriculture in a rapidly changing climate. However, application of nanomaterials and nanocarriers developed for this purpose require them to be delivered into plants or to specific plant organs, and to respond to selected environmental or biological ques like temperature or plant stress. The design space for nanotechnology is enormous and requires better understanding of the nanomaterial-plant interactions that determines how they travel through plants and their ultimate fate. This talk will present novel nanocarriers with temperature and ROS-responsive active agent release mechanisms, and ways to make these approaches scalable and sustainable. It will also present the current state of understanding of factors influencing their uptake into leaves, mesophyll cells, and phloem, and how this subsequently influences their distribution to other tissues, e.g. roots, stem, younger leaves. Overall, this body of work provides design rules for precision delivery of agrochemicals to plants, and highlights opportunities for nanotechnology to promote sustainable agriculture in a changing climate.

Polymeric agrochemical nanocarriers have the potential to promote sustainable and climate resilient agriculture by efficient uptake and precision delivery into plants or specific plant organs. However, understanding in how nanocarrier properties direct their uptake and translocation behaviors in different plant species is limited. This talk will discuss the effect of nanocarrier charge, aspect ratio and plant species in their uptake efficiency, translocation pathway and distribution in both monocot wheat (T. aestivum) and dicot tomato (Solanum lycopersicum) plants. Cationic and anionic polymer nanocarriers with 10 nm diameter and length vary from 10 to 300 nm were synthesized and their interactions with plants after foliar application was studied. In tomato, translocation of anionic nanocarriers (20.7%) was higher than cationic nanocarriers (13.3 %). Only anionic nanocarriers were transported in wheat, and translocation was lower (8.7%) than in dicot tomato. Both low and high aspect ratio polymers translocated in tomato plants, but the highest aspect ratio bottlebrush polymer (~300 nm in length) did not translocate in wheat plants, suggesting a size cutoff for long systemic transport in wheat. Cationic nanocarriers also moved into leaf mesophyll cells more readily than anionic ones, decreasing apoplastic transport and phloem loading. These new understandings in polymer nanocarrier-plant interactions can be leveraged for more efficient agrochemical delivery in plants, improve plant health and promote climate change adaptation of agriculture.