Sources of nutrients impacting surface waters in Florida: A review

The promulgation of numeric nutrient criteria for evaluating impairment of waterbodies in Florida is underway. Adherence to the water quality standards needed to meet these criteria will potentially require substantial allocations of public and private resources in order to better control nutrient (i.e., nitrogen and phosphorus) releases from contributing sources. Major sources of nutrients include atmospheric deposition (195–380 mg-N/m2/yr, 6 to 16 mg-P/m2/yr), reclaimed water irrigation (0.13–29 mg-N/L, 0.02 to 6 mg-P/L), septic systems (3.3 × 103–6.68 × 103 g-N/person/yr, 0.49 × 103–0.85 × 103 g-P/person/yr) and fertilizer applications (8 × 106–24 × 106 mg-N/m2/yr). Estimated nitrogen loadings to the Florida environment, as calculated from the above rates are as follows: 5.9 × 109–9.4 × 109 g-N/yr from atmospheric deposition, 1.2 × 108–2.6 × 1010 g-N/yr from reclaimed water, 2.4 × 1010–4.9 × 1010 g-N/year from septic systems, and 1.4 × 1011 g-N/yr from fertilizer application. Similarly, source specific phosphorus loading calculations are also presented in this paper. A fraction of those nutrient inputs may reach receiving waterbodies depending upon site specific regulation on nutrient control, nutrient management practices, and environmental attenuation. In Florida, the interconnectivity of hydrologic pathways due to the karst landscape and high volumes of rainfall add to the complexity of tracking nutrient loads back to their sources. In addition to source specific nutrient loadings, this review discusses the merits of source specific markers such as elemental isotopes (boron, nitrogen, oxygen, strontium, uranium and carbon) and trace organic compounds (sucralose, gadolinium anomaly, carbamazepine, and galaxolide) in relating nutrient loads back to sources of origin. Although this review is focused in Florida, the development of source specific markers as a tool for tracing nutrient loadings back to sources of origin is applicable and of value to all other geographical locations.

► Nutrient (nitrogen and phosphorus) loading to waterways from point and non-point sources is an ecological concern.
► The promulgation of numeric nutrient criteria for evaluating impairment of waterbodies in Florida is underway.
► This review critically summarizes the occurrence and transport of nutrients (nitrogen and phosphorus) in Florida.
► This review summarizes recent developments in source specific markers to track nutrient sources contributing to a waterbody.