Water Quality of Inflows to the Everglades National Park over Three Decades (1985–2014) Analyzed by Multivariate Statistical Methods

Lei Wan,Xiaohui Fan

doi:10.3390/ijerph15091882

Abstract

The Everglades, a vast subtropical wetland, dominates the landscape of south Florida and is widely recognized as an ecosystem of great ecological importance. Data from seven inflow sites to the Everglades National Park (ENP) were analyzed over three decades (1985–2014) for temporal trends by the STL (integrated seasonal-trend decomposition using LOESS) method. A cluster analysis (CA) and principal component analysis (PCA) were applied for the evaluation of spatial variation. The results indicate that the water quality change trend is closely associated with rainfall. Increasing rainfall results in increasing flow and thus, decreasing concentrations of nitrogen and phosphorus. Based on 10 variables, the seven sampling stations were classified by CA into four distinct clusters: A, B, C, and D. The PCA analysis indicated that total nitrogen (TN) and total phosphorus (TP) are the main pollution factors, especially TN. The results suggest that non-point sources are the main pollution sources and best management practices (BMPs) effectively reduce organic nitrogen. However, TN and TP control is still the focus of future work in this area. Increasing the transfer water quantity can improve the water quality temporarily and planting submersed macrophytes can absorb nitrogen and phosphorus and increase the dissolved oxygen (DO) concentration in water, continuously improving the water quality.

Highlights

Surface water, especially from rivers and lakes, is closely related to human activities, so the water quality cannot be ignored
The magnitudes of the mean values at each station were in the following order: S12B > S18C > S12A > S12C >S12D > S333 > S332
The mean values of total nitrogen (TN) at S12C, S12D and S333 were 1.29, 1.37, and 1.44 mg L−1, respectively, which are higher than the standard value, and total phosphorus (TP) exceeded this criterion at all stations except S332 and S18C

Summary

Introduction

Especially from rivers and lakes, is closely related to human activities, so the water quality cannot be ignored. Congress created the Everglades National Park (ENP) in 1947 to protect and preserve portions of the south Florida ecosystem. Because the Everglades is located in the upstream region of the ENP, the area is subject to upstream water management practices. In order to protect and monitor the ENP waters, Water Conservation Areas (WCAs) and Stormwater Treatment Areas (STAs) were constructed to improve the water quality in the north of the ENP. Some researchers have focused on water quality improvement in WCAs and STAs. For example, Entry [1] studied the impact of STAs and best management practices (BMPs) on nutrient concentration in the Florida Everglades using Kendall tau or Tobit trend analyses for the entire year. The trend analyses suggested that agricultural BMPs have led to a large initial reduction in nutrient concentrations in the ENP. Chen et al [2] examined annual phosphorus (P) removal in the six Everglades STAs during

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