Introduction

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Introduction Understanding the P Chemistry In the Everglades Agricultural Area(EAA) Canals. Jaya Das 1 , Samira Daroub 2 , Manohardeep S. Josan 2 and Timothy Lang 2 1 North Florida Research and Education Center, University of Florida, Quincy, FL 2 Everglades Research and Education Center, University of Florida, Belle Glade, FL The Everglades Agricultural Area (EAA) is 280,000 ha of rich organic soils. The EAA lies between lake Okeechobee in the north and the Everglades Protection Area to the south. Once a part of the original Everglades, the EAA was channelized and drained for agricultural, residential and commercial purposes in the early 1900s. The EAA is cropped to sugarcane, vegetables, rice and sod. Flat topography in the EAA necessitates drainage which is accomplished through a network of pumps and farm canals and SFWMD (South Florida Water Management District) main canals. Drainage waters from the EAA contributes phosphorus (P) ecosystems including the Water Conservation Areas and Everglades National Park. Three main canals chosen for our study Miami, West Palm Beach (WPB) and Ocean canal. Main canals in EAA originate from the lake and end downstream into the Ocean. Sediments in the canals can act as a source or a sink of P, affecting the P concentration in canal waters. Sediments can be resuspended due to flow or wind effects giving rise to turbidity and/or release of nutrients. Dissolved and Particulate P from all different sources end up in main canals. Understanding the main canals can help improve management practices in Storm Treatment Areas(STAs). To formulate possible management practices for canals. Dissolved and Particulate P from Lake Okeechobee Average P conc. 149 ppb Range: 46-884 ppb Total P load 478 metric tons (2010). Dissolved and Particulate P from EAA farms. Farm Best Management Practices (BMPs), soil properties important. P load169 metric tons P concentration127 ppb Dissolved and Particulate P from EAA farm canals. BMPs for farm canals pump velocity, canal depth and canal maintenance important factors for P load. The canals were constructed by digging till the bedrock, which consists of carbonate deposits. But the soils are mostly organic Histosols reclaimed from draining Everglades wetlands So the question lies what are what are the resulting sediment properties? What is the P content of the canal sediments? Are the total P values low or high that would be a concern? What is the mineralogical composition of the sediments? Are there any stable P containing minerals? How are the different P fractions distributed within the total P? Knowledge of sediment properties can help us compare /contrast canal sediments and understand sediment properties Current load to Storm Water Treatment areas (STAs) range from 96 -264 ppb. Figure 3. Lake Okeechobee Figure 4. EAA farms Figure 5. EAA farm canals Figure 6. Storm Water Treatment Areas The problem Unknowns and Research Objectives Sediments were analyzed for bulk density, loss on ignition (LOI), Total P and pH. LOI is a rough estimate of organic C content. Materials and Methods Sediments were extracted with: • 1.0 M KCl, • 0.1 M NaOH, and • 0.5 M HCl at 298 o K using a 1:100 soil : solution ratio. Residual fractions were determined after 6M HCl digestion. The silt and clay size portions (<50 μ) were separated as leachate. Leachate was filtered using 0.45 μ filter paper using vacuum suction. The contents on filter paper were collected and rinsed with distilled water followed by magnesium chloride for magnesium saturation. The thin layer of silt and clay was mounted onto a labeled glass slide and scanned on a X-ray diffractometer. X-ray analyses of the samples were done at a scan rate of 2 o 2θ per minute using Cu anode and Kα radiation. Physicochemical Properties: P fractions: Mineralogical Assessment: Results and Discussions T1 T2 T3 T4 T1 T2 T3 T4 T1 T2 T3 T4 Miami Canal West Palm Beach Canal Ocean Canal 0 200 400 600 800 1000 1200 1400 1600 1800 KCl - P NaOH - Pi NaOH - Po HCl - P P Concentration (mg kg -1) 0 200 400 600 800 1000 1200 1400 0 10 20 30 40 50 60 Intensity (counts) 2θ T1 T2 T3 T4 CA AR QZ AR CA QZ SP AR CA AR CA CA AR CA AR SP Figure 1. Everglades Agricultural Area and the main canals C anal TotalP BD % LO I pH m g kg -1 g cm -3 M iami W PB Ocean 1430 a 0.26 b 26.1 ns 7.4 b 1130 a 0.22 b 26.7 7.4 b 590 b 0.35 a 24.5 7.9 a Table 1. Selected physicochemical properties of the EAA main canals Total P content of these sediments are high which is a concern Estimated total volume of sediments of Miami, WPB and Ocean canal are: 634, 402 and 533 mt. Huge quantities of P rich sediments stored in canals. Bulk density is lower than mineral sediments Organic matter content is higher than mineral soils pH is around neutral for Miami and WPB canal For Ocean canal pH is higher than both Miami and WPB canal. Sediment properties depend upon the composition of organic and mineral portions Physichochemical properties hint about predominant mineral character of Ocean and organic nature of Miami and WPB canal. KCl-P smallest P fraction ranges from 1 – 2% of TP Largest P fraction is HCl-P or Ca and Mg P composed of 50 -70% of Total P Residue P second highest P fraction ranging from 20 -30% TP NaOH-Pi and NaOH-Po corresponding to Fe/Al-P and Organic P range from 5-6 % of Total P P fractionation of sediments show that mojority of P in canal sediments are slowly available P This means it is not possible to mobilize the P stored to get rid of it completely. Different P fractions can be mobilized over time depending on canal conditions including local pH, availability of organic acids through decomposition of detritus. Figure 9. P fractions EAA main canal sediments Figure 10. X-ray diffraction patterns of Miami canal Table 2. Minerals present in EAA main canals Apart form Quartz all canals consists of different forms of carbonates of mineral and biogenic origin. No detectable P containing minerals. Reinforces the idea that P in canal sediments not recalcitrant but can be subject to being slowly available. Fe 3+ -P KCl-P Ca/M g-P R esidue-P N aOH -P o Aerobic canal water Aerobic Sedim entlayer Anaerobic Sedim ent layer Lim estonebedrock •Reduction of Fe 3+ - P in anaerobiclayer •Releaseofsoluble Fe 2+ -P along with •Reprecipitation of Fe 3+ -P in theaerobic layer Pi Pi Pi and DOP •Possiblerelease ofCa/M g P by hydrolysisoforganic acidsor •bychelation and release ofP •M icrozonesoflow pH regions dueto respiration bym acrophytes •Mineralization oforganicP Calcium carbonaterock fragm ents KCl-P Ca/M g-P R esidue-P N aOH -P o Aerobic sedim entlayer Anaerobic sedim ent layer Lim estone bedrock Aerobiccanal water Layersofcarbonates- reducesP release Fe 3+ -P Pi Pi Pi and DOP Aerobiccanal water K Cl-P Ca/M g-P Residue-P N aO H-P o Aerobicsedim ent layer A naerobic sedimentlayer Lim estone bedrock Fe 3+ -P Pi Pi Pi and DOP Figure 11a. Cross section of Miami canal Figure 11b. Cross section of WPB canal Figure 11c. Cross section of Ocean canal Similar to other canals carbonate bedrock present. Depth of sediments higher than WPB or Ocean canal. Organic matter comparable to WPB but higher than Ocean canal. Sediment properties similar to Miami canal. Comparable total P values. Distribution of P fractions follow same pattern. Difference form Miami canal: Stratified carbonate layers present. Very different from Miami and WPB canal. Depth of sediment shallow. Most mineral of all the canals. Sediment surface and entire canal scattered limestone rocks and carbonate shells present. Conclusions: Though the EAA canals were dug till bedrock the sediments accumulated over the years are 633, 402 and 533 mt. These sediments have high P stored. Considering only 0-10 cm depth amount of P stored in three canals is 73 mt. The P fractions indicate that most of the P exists as slowly available fractions. These fractions can be mobilized with fluctuations in local conditions including pH, mineral organic acids from Decomposing biological matter. Mineralogical studies supported the P fraction data by not being able to detect any P containing minerals Minerals identified were carbonates of mineral and biogenic origin. Phosphorus can in association to these carbonate minerals. Almost the entire P load in the EAA canals can be slowly released over time and it depends on not only physicochemical properties and distribution of P fractions but also canal specific structure and composition. Figure 2. Water flow through the Everglades system. P enriched w ater STAs W C A sand D ow nstream P Lim ited Ecosystem s M ain C anals Farm s Farm C anals Lake O keechobee C anal MineralsIdentified Calcite Dolomite Aragonite Q uartz Sepiolite Smectite Kaolinite Palygorskite M iami √ √ √ √ √ - - - W PB √ √ - √ √ √ √ √ Ocean √ √ √ √ √ - - - Figure 7. Dania soil series in EAA which is just inches from bedrock Miami canal: West Palm Beach canal: Ocean canal: P fractions: Physicochemical properties: Mineralogy:

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Understanding the P Chemistry In the Everglades Agricultural Area(EAA) Canals. Jaya Das 1 , Samira Daroub 2 , Manohardeep S. Josan 2 and Timothy Lang 2 - PowerPoint PPT Presentation

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IntroductionUnderstanding the P Chemistry In the Everglades Agricultural Area(EAA) Canals.Jaya Das1, Samira Daroub2, Manohardeep S. Josan2 and Timothy Lang21North Florida Research and Education Center, University of Florida, Quincy, FL2Everglades Research and Education Center, University of Florida, Belle Glade, FL

The Everglades Agricultural Area (EAA) is 280,000 ha of rich organic soils. The EAA lies between lake Okeechobee in the north and the Everglades Protection Area to the south.Once a part of the original Everglades, the EAA was channelized and drained for agricultural, residential and commercial purposes in the early 1900s.The EAA is cropped to sugarcane, vegetables, rice and sod. Flat topography in the EAA necessitates drainage which is accomplished through a network of pumps and farm canals and SFWMD (South Florida Water Management District) main canals.Drainage waters from the EAA contributes phosphorus (P) to the downstream ecosystems including the Water Conservation Areas and Everglades National Park.Three main canals chosen for our study Miami, West Palm Beach (WPB) and Ocean canal. Main canals in EAA originate from the lake and end downstream into the Ocean.Sediments in the canals can act as a source or a sink of P, affecting the P concentration in canal waters.Sediments can be resuspended due to flow or wind effects giving rise to turbidity and/or release of nutrients.Dissolved and Particulate P from all different sources end up in main canals.Understanding the main canals can help improve management practices in Storm Treatment Areas(STAs).To formulate possible management practices for canals.

Dissolved and Particulate P from Lake OkeechobeeAverage P conc. 149 ppbRange: 46-884 ppbTotal P load 478 metric tons (2010).Dissolved and Particulate P from EAA farms.Farm Best Management Practices (BMPs), soil properties important.P load169 metric tonsP concentration127 ppbDissolved and Particulate P from EAA farm canals.BMPs for farm canalspump velocity, canal depth and canal maintenance important factors for P load.The canals were constructed by digging till the bedrock, which consists of carbonate deposits.But the soils are mostly organic Histosols reclaimed from draining Everglades wetlandsSo the question lies what are what are the resulting sediment properties?What is the P content of the canal sediments? Are the total P values low or high that would be a concern?What is the mineralogical composition of the sediments? Are there any stable P containing minerals?How are the different P fractions distributed within the total P?Knowledge of sediment properties can help us compare /contrast canal sediments and understand sediment propertiesCurrent load to Storm Water Treatment areas (STAs) range from 96 -264 ppb.

Figure 3. Lake OkeechobeeFigure 4. EAA farmsFigure 5. EAA farm canalsFigure 6. Storm Water Treatment AreasThe problemUnknowns and Research ObjectivesSediments were analyzed for bulk density, loss on ignition (LOI), Total P and pH. LOI is a rough estimate of organic C content. Materials and MethodsSediments were extracted with: 1.0 M KCl, 0.1 M NaOH, and 0.5 M HCl at 298oK using a 1:100 soil : solution ratio. Residual fractions were determined after 6M HCl digestion.The silt and clay size portions (


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