Five commercial (working) nurseries with a recycled pond were used for this study. The recycled ponds in these nurseries receive any water leaving the property (nursery site) following a significant rainfall and/irrigation event. All nurseries were located in the Hillsborough County, which drains into the Tampa Bay Watershed in the west coast of Florida. Due to the confidentiality agreement signed with the nursery growers, we cannot disclose the names and specific locations of nurseries. The county has an area of 2714 km². Of that area more than 84% (2350 km²) is unincorporated. The Hillsborough County land use/land cover consists of about 46% urban and built up, 19% agriculture and 17% wetlands. The remaining 18% is designated as recreational, open land, rangelands, upland forests, water and other uses [12] .

Water samples were collected from five commercial nursery ponds in April 2010 from 8 a.m. to 12 p.m. Three of the ponds were located within one nursery and two ponds were located at two other nurseries. The climate in the area is subtropical, with an average annual air temperature of 22˚C and daily extremes ranging from 0.7˚C to 35˚C and total rainfall varies from 120 to 130 cm per year.

Water samples were collected using a long-handled polyethylene 500 mL capacity dipper (SCIENCEWARE®). Samples for organochlorine pesticide analysis were collected in 1-L amber glass bottles (Fisher Scientific, Fair Lawn, NJ). Samples for nutrients, trace metals, and bacteria were collected in separate 250 mL high-density polyethylene (HDPE) bottles (Fisher Scientific, Fair Lawn, NJ). All samples were stored at 4˚C until analysis. At each pond, samples were also analyzed in-situ for pH, electrical conductivity (EC), temperature, and dissolved oxygen (DO) using a Manta Water Quality Multiprobe (Eureka Environmental Engineering, Austin, TX).

The pH is an important characteristic of water when considering reuse of recycled water for irrigation. It is well documented that the ideal pH for most plant production is 5.0 - 6.5 as this provides a balance of availability of essential plant nutrients [19] . The pH of recycled water at four sites was alkaline (8.1 - 9.3) and one site had neutral pH (6.5) (Table 1). In general, the measured values of pH were within the EPA recommended range (6 - 9) of water reuse for irrigation [20] . The pH values from sites C and D were slightly higher than the upper limit of the recommended range.

Electrical conductivity (EC) is directly related to the concentration of dissolved ions in the water. The EC values at all sites were 0.311 - 0.362 dS/m, which was equivalent to 199 - 232 mg/L of total dissolved solids (TDS; Table 1). The EC and TDS levels were well below the EPA limits of <2.0 dS/m EC and 500 - 2000 mg/L TDS in the irrigation water for nursery crops [20] . The water temperature in the ponds fluctuated from 21.4˚C to 25.3˚C at the sampling time. Other chemical properties of the recycled water included 2 - 12 mg/L DO, 23% - 145% saturated DO, and 9.2 - 25.8 mg/L Cl⁻ (Table 1); these values are in fact better than the typical values found in most stream waters, suggesting that the recycled water is of good quality.

Total cations concentrations in the recycled water ranged from 62.7 to 84.3 mg/L; of which, Ca²⁺ was the dominant cation accounting for 52% - 73% (39.3 - 55.3 mg/L) (Table 2). The concentration of other cations, i.e., Mg²⁺, K⁺, and Na⁺ were 5 - 11.5, 4.4 - 16.7, and 6.2 - 18.5 mg/L, respectively.

Concentrations of Fe, Al, Zn, B, and Mn were less than 0.4 mg/L in all pond waters (Table 3). Copper (Cu) and

^aTotal dissolved salts (EC (dS/m) × 640).

^aValues in parentheses are percent of total cations.

^aNot detected.

Mo were not detected in any of the samples. Values of detected trace metals were below EPA’s recommended range of reclaimed water quality for irrigation (i.e., 5 mg/L of Al and Fe; 0.2 mg/L of Cu and Mn; 2 mg/L of Zn) [20] .

Total N concentrations in the recycled water were 1.56 - 2.30 mg/L; of which, 78% to 98% was organic N (1.42 - 1.88 mg/L) with the remainder (2% - 22%) being in inorganic N forms such as NO₃-N + NO₂-N (not detected, ND-0.35 mg/L), and NH₄-N (0.03 - 0.37 mg/L; Table 4). Total Kjeldahl N (TKN) ranged from 1.47 to 2.17 mg/L. The NH₄-N concentration at site E was 10 times greater than other sites likely due to the low DO level as compared to other sites (see Table 4). The less aerobic conditions (i.e., low DO) present at the site E may have reduced the oxidation of to, resulting in higher concentrations. Across all sites, concentrations of NH₄-N were inversely correlated (R = −0.86) with DO.

Total P concentrations were 0.59 - 1.00 mg/L in the recycled water, of which, 87% - 96% was present as soluble inorganic P (PO₄-P, 0.32 - 0.94 mg/L) with the remainder (4% - 13%) as organic P forms (Table 4).

Five legacy organochlorine pesticides were detected in the recycled water, with concentrations below 2 μg/L (Table 5). Among the analyzed pesticides, endrin aldehyde (0.044 - 1.619 μg/L) was detected at all sites. Methoxychlor (ND-0.193 μg/L) and endosulfan sulfate (ND-0.157 μg/L) were found at three and two sites, respectively. Alpha-chlordane (ND-0.046 μg/L) and DDE (ND-0.053 μg/L) were only found at one site. These organochlorine pesticides found in pond waters may have been due to the past usage as most of them were banned in the United States in the 1970s. The past usage of these pesticides likely resulted in presence of these in the pond waters with eroded soil particles.

Total coliform and E. coli concentrations in recycled water were 22 - 47 and 20 - 35 CFU/100 mL, respectively (Figure 1). These values of total coliform and E. coli were within the safe range recommended by EPA (<1000 CFU/100 mL) [20] . Low values of total coliforms in recycled water, which can be used as an indicator of total load of pathogens, suggests a negligible risk of spreading of plant diseases with reclaimed water irrigation.

^aValues in parentheses are percent of total N; ^bValues in parentheses are percent of total P; ^cNot detected.

^aNot detected.