Human Influences on Water Quality in Great Lakes Coastal Wetlands

A better understanding of relationships between human activities and water chemistry is needed to identify and manage sources of anthropogenic stress in Great Lakes coastal wetlands. The objective of the study described in this article was to characterize relationships between water chemistry and multiple classes of human activity (agriculture, population and development, point source pollution, and atmospheric deposition). We also evaluated the influence of geomorphology and biogeographic factors on stressor-water quality relationships. We collected water chemistry data from 98 coastal wetlands distributed along the United States shoreline of the Laurentian Great Lakes and GIS-based stressor data from the associated drainage basin to examine stressor-water quality relationships. The sampling captured broad ranges (1.5–2 orders of magnitude) in total phosphorus (TP), total nitrogen (TN), dissolved inorganic nitrogen (DIN), total suspended solids (TSS), chlorophyll a (Chl a), and chloride; concentrations were strongly correlated with stressor metrics. Hierarchical partitioning and all-subsets regression analyses were used to evaluate the independent influence of different stressor classes on water quality and to identify best predictive models. Results showed that all categories of stress influenced water quality and that the relative influence of different classes of disturbance varied among water quality parameters. Chloride exhibited the strongest relationships with stressors followed in order by TN, Chl a, TP, TSS, and DIN. In general, coarse scale classification of wetlands by morphology (three wetland classes: riverine, protected, open coastal) and biogeography (two ecoprovinces: Eastern Broadleaf Forest [EBF] and Laurentian Mixed Forest [LMF]) did not improve predictive models. This study provides strong evidence of the link between water chemistry and human stress in Great Lakes coastal wetlands and can be used to inform management efforts to improve water quality in Great Lakes coastal ecosystems.     

Distribution of copper, zinc, and phosphorus in coastal plain soils receiving repeated liquid biosolids applications

Continuous N-based application of biosolids contributes to a gradual increase of trace elements and P in soils. The objectives of this study were to assess the accumulation and vertical transport of Cu, Zn, C, N, and P within the profile of two coastal plain soils. Liquid (6-8% total solids) biosolids were applied to an Acredale silt loam (fine silty, mixed, thermic typic Ochraqualfs) and Bojac loamy sand (coarse loamy, mixed, thermic typic Hapludult) annually from 1984 to 1998. The repeated applications supplied 70, 204, and 3823 kg ha(-1) of Cu, Zn, and P, respectively, to the Acredale and 81, 225, and 4265 kg ha(-1) of Cu, Zn, and P, respectively, to the Bojac. The total C and N contents were not different than background levels in the Bojac soil and were slightly higher in the Acredale soil 7 years after cessation of biosolids application. Phosphorus, Cu and Zn are still concentrated in the top 0.25 m of the Acredale soil. Enrichment of P, Cu, and Zn were detected to the deepest soil increment in the coarse-textured Bojac soil. Approximately 20 to 40% of the Cu and Zn applied in the biosolids could not be accounted, which was likely due to a combination of leaching and incomplete extraction. Excessive Mehlich 1-P concentrations and a high degree of P saturation were found in amended soil, raising the potential for P release to runoff or leaching water.     

WATER RESOURCE MANAGEMENT AND DROUGHT FORECASTS IN SOUTH CAROLINA1

ABSTRACT: Despite potential benefits for resource planning, community water systems managers have not used seasonal climate forecasts extensively. Obstacles to forecast use include a lack of awareness of their existence, distrust of their accuracy, perceived irrelevance to management decisions, and competition from other technological innovations. In this paper, ways in which seasonal forecasts might be extended to address more directly some concerns of South Carolina community water systems managers are explored. From May 1998 through August 2002, this group experienced drought conditions that threatened water quality and supply and required restrictions on water consumption. Methods for incorporating long lead forecasts with joint probabilities of monthly temperature and precipitation to produce drought forecasts are demonstrated. When tailored to specific places, such forecasts show the likelihood of exceeding drought thresholds that would trigger water use restrictions. The methods illustrate how long lead forecasts can be extended and customized into secondary products that address issues of greater relevance to water resource managers.     

Spectrophotometric analyses of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) in water

A simple and accurate spectrophotometric method for on-site analysis of royal demolition explosive(RDX) in water samples was developed based on the Berthelot reaction. The sensitivity and accuracy of an existing spectrophotometric method was improved by:replacing toxic chemicals with more stable and safer reagents; optimizing the reagent dose and reaction time; improving color stability; and eliminating the interference from inorganic nitrogen compounds in water samples. Cation and anion exchange resin cartridges were developed and used for sample pretreatment to eliminate the effect of ammonia and nitrate on RDX analyses. The detection limit of the method was determined to be 100 μg/L. The method was used successfully for analysis of RDX in untreated industrial wastewater samples. It can be used for on-site monitoring of RDX in wastewater for early detection of chemical spills and failure of wastewater treatment systems.     

The effects of salt exclusion during ice formation on circulation in lakes

Laboratory experiments have been performed to investigate the effects of salt exclusion on the behaviour of lakes with salinities up to 8 g L^?1. At these salinities the freezing temperature is less than the temperature of maximum density and, unlike sea-ice, a reverse temperature stratification forms beneath the ice that can support at least some of the excluded salt. Temperature time series at four depths showed that salt exclusion drives cascades of localised overturning, while the persistence of reverse temperature stratification indicated that mixing was not complete. While our array of temperature sensors had insufficient spatial resolution to provide full details of the flow, we hypothesize that: at salinities of 1 and 2 g L^?1  salt is released relatively uniformly and forms a layer of elevated salinity immediately below the ice, which supports double-diffusive salt-fingering; and at salinities of 4 and 8 g L^?1, salt plumes penetrate the reverse stratification. After the ice melted, a relatively fresh surface layer formed above a more saline layer, sufficient to suppress spring turnover. Our measurements compare favourably with field observations from lakes, and highlight the importance of salt exclusion on biogeochemical processes in lakes.     

Growth and damping of interfacial waves on a diffuse interface

The resonant interaction of surface and internal waves produces a nonlinear mechanism for energy transfer among wave components in oceans, lakes, and estuaries. In many field situations, the stratification may be well approximated by a two-layer fluid with a diffuse interface. The growth and damping rates of sub-harmonic interfacial waves generated by a surface wave through a three-wave resonant interaction are measured in the laboratory. These measurements are compared with theoretical predictions. A diffuse interface reduces the damping rate and increases the growth rate. The predicted growth rate provides excellent comparison with the laboratory measurements. The inclusion of the effects of a diffuse interface significantly improve the comparison.     

The mobility of thiobencarb and fipronil in two flooded rice-growing soils

The mobility of the rice pesticides thiobencarb (S-[(4-chlorophenyl) methyl] diethylcarbamothioate) and fipronil ([5-amino-3-cyano-1-[2,6-dichloro-4-(trifluoromethyl)phenyl]-4-[(trifluoromethyl)sulfinyl]pyrazole) were investigated in the glasshouse under flooded conditions using two Australian rice-growing soils. When using leakage rates of 10 mm day(-1), less than 20% of applied thiobencarb and fipronil remained in the water column after 10 days due to rapid transfer to the soil phase. Up to 70% and 65% of the applied thiobencarb and fipronil, respectively, were recovered from the 0-1 cm layer of soils. Only 5-7% of each pesticide was recovered from the 1-2 cm layer, and less than 2% was recovered from each 1 cm layer in the 2-10 cm region of the soils. Analysis of the water leaking from the base of the soil cores showed between 5-10% of the applied thiobencarb and between 10-20% of the applied fipronil leaching from the soil cores. The high levels of pesticide in the effluent was attributed to preferential flow of pesticide-laden water via soil macropores resulting from the wetting and drying process, worm holes and root channels.     

Ozonation effects on emerging micropollutants and effluent organic matter in wastewater: characterization using changes of three-dimensional HP-SEC and EEM fluorescence data

The degradation of effluent organic matter (EfOM) in a municipal wastewater treated by ozonation was characterized using the methods of high-performance size-exclusion chromatography (HP-SEC) and excitation/emission matrix (EEM) fluorescence combined with parallel factor analysis (PARAFAC). The removal of 40 diverse trace-level contaminants of emerging concern (CEC) present in the wastewater was determined as well. Ozonation caused a rapid decrease of the absorbance and fluorescence of the wastewater, which was associated primarily with the oxidation of high and low apparent molecular weight (AMW) EfOM fractions. PARAFAC analysis also showed that components C1 and C2 decreased prominently in these conditions. The EfOM fraction of intermediate molecular weight ascribable to a terrestrial humic-like component (C3) tended to be less reactive toward ozone. Relative changes of EEM fluorescence were quantified using F _max values of PARAFAC-identified components (∆F/F ⁰ _max). Unambiguous relationships between ∆F/F ⁰ _max values and the extent of the degradation of the examined CECs (∆C/C₀) were established. This allowed correlating main parameters of the ∆C/C₀ vs. ∆F/F ⁰ _max relationships with the rates of oxidation of these CECs. The results demonstrate the potential of online measurements of EEM fluorescence for quantitating effects of ozonation on EfOM and micropollutants in wastewater effluents.

     

Lessons from the 2006 Louisiana health and population survey

The 2005 hurricane season caused extensive damage and induced a mass migration of approximately 1.1 million people from southern Louisiana in the United States. Current and accurate estimates of population size and demographics and an assessment of the critical needs for public services were required to guide recovery efforts. Since forecasts using pre-hurricane data may produce inaccurate estimates of the post-hurricane population, a household survey in 18 hurricane-affected parishes was conducted to provide timely and credible information on the size of these populations, their demographics and their condition. This paper describes the methods used, the challenges encountered, and the key factors for successful implementation. This post-disaster survey was unique because it identified the needs of the people in the affected parishes and quantified the number of people with these needs. Consequently, this survey established new population and health indicator baselines that otherwise would have not been available to guide the relief and recovery efforts in southern Louisiana.     

Recent Changes in Soil Total Phosphorus in the Everglades: Water Conservation Area 3

We assessed recent changes in the distribution of soil total phosphorus (TP) in Water Conservation Area 3 (WCA-3) of the Everglades. Soil cores were collected in 1992 and 2003 at 176 sites. To reflect hydrologic boundaries within the system, WCA-3 was divided into three zones (3AN, 3AS, and 3B). Total P was mapped on both a mass (TPm) and a volumetric basis (TPv) to determine if spatial distributions varied depending on the choice of units. Interpolated maps for both years showed that the highest levels of TPm were located in 3AN and in boundary areas of all zones that received surface water inputs of P from canals. Increases in TPm were greatest in central 3AN in an area adjacent to the Miami Canal that received inputs from a water control structure. Interpolated maps for TPv illustrated that a hotspot present in 1992 had disappeared by 2003. The highest levels of TPv in 2003 were located in northwestern 3AN, a region of WCA-3 that has been chronically overdrained and burned in 1999. From 1992 to 2003, increases in TPm were observed for 53% of the area of WCA-3, while only 16% of WCA-3 exhibited increases in TPv. In 1992, approximately 21% of WCA-3 had TPm concentrations in the 0–10 cm layer >500 mg kg⁻¹, indicating P enrichment beyond historic levels. Eleven years later, 30% of the area of WCA-3 had TPm >500 mg kg⁻¹. This indicated that during this period, the area of WCA-3 with enriched TPm concentrations increased about one % year⁻¹.