DRAFT
II.B4. Nutrients
Non-point source inputs, such as atmospheric deposition, are increasing recognized as important factors with regard to surface water quality. This is especially true for macronutrients like nitrogen and phosphorus, which are linked to excess primary production in New Jersey’s fresh and coastal waters. Atmospheric deposition of nitrogen and phosphorus has been shown to be a significant contributor to the total loading of nutrients to aquatic ecosystems (Eisenreich et al., 1977; Lindberg et al., 1986; Morales et al, 2001; Manny and Owens, 1983; Delumyea, R.G. and Petel, R.L., 1977). Due to its nature as a limiting nutrient in biological systems, excess phosphorus can lead to enhanced biological activity resulting in premature eutrophication that can damage aquatic systems for in-stream uses such as power generation, navigation, and recreation. Prior to the 1960s, most detergents contained phosphates that, when discharged to surface waters, acted as fertilizers perpetuating the growth of undesirable species, such as algae and excess amounts of aquatic plant life. Some detergents underwent tertiary wastewater treatment processing prior to discharge into streams and other water bodies that allowed for some degree of control of phosphate content. However, the same was not true for primary and secondary-treated wastewater streams, agricultural run-off of phosphates, phosphorus from bird droppings and insects (Ahn, 1999), and the contribution from atmospheric deposition.
Introduction of nitrogen and phosphorus into water bodies can lead to the enhanced growth of primary producer species, like algae, which play an important role in the aquatic food chain. Algae convert carbon dioxide into biomass that is used by small aquatic organisms (i.e. phytoplankton) as a food source. Hydrophobic organic compounds (HOCs), like PCBs, can enter the aquatic food chain by sorption to the algae, which can then be taken up by organisms progressively higher up the food chain. HOCs can also enter the food chain by direct passive sorption to phytoplankton, due to the organic-carbon rich nature of phytoplankton cells. The bioconcentrated HOCs can become incorporated into higher-level fish that can be consumed by humans. Therefore, the bioconcentration of HOCs in aquatic ecosystems is enhanced when phosphorus additions drive excessive algae production and subsequently, excessive growth in higher-level organisms (Kramer, et al., 1996).
Macronutrient wet deposition into the ocean and other major bodies of water can cause excessive growth of phytoplankton leading to dangerous blooms that affect the hierarchy of organisms in the ocean (Migon, 1999). These blooms can also pose a danger to humans, as the algae can poison filter-feeding organisms, and, when consumed by humans, lead to illness and death. Considerable effort has gone into the abatement of point sources of nitrogen and phosphorus; however controlling non-point source additions (i.e. via agricultural runoff, weathering/soil erosion, atmospheric deposition, incineration and biomass burning (Migon, 1999)) of these nutrients is significantly more difficult. Here we present results regarding the atmospheric deposition of nitrate and phosphorus in NJADN, which together with a comprehensive analysis of streamflow, surface water concentrations, and other nutrient sources, will be useful in modeling nutrient cycling in New Jersey’s surface waters and estimating nutrient loads to impacted waterbodies.
Nitrate in New Jersey Precipitation
Nitrate concentrations in precipitation collected in New Brunswick, Jersey City, the Pinelands, and Camden ranged from 1.3 to 130 mM, but volume-weighted mean (VWM) concentrations at all four sites ranged from 26 to 32 µM (Table 16). The lowest VWM NO3- concentrations (19 – 20 mM) were measured in the winter samples at the Pinelands and New Brunswick and the highest (38 mM) in Camden in the summer. All four sites showed higher NO3- concentrations in the spring and summer than fall and winter. The average seasonal NO3- concentrations in rain collected at the NJADN sites are similar to those measured at Washington’s Crossing (12 to 34 µM), but generally higher than those measured at the Forsythe Reserve in southern coastal NJ (10 to 17 µM) in 1999 as part of the NADP measurements (NADP, 2001). This spatial trend in nitrate concentrations in precipitation likely reflects greater NOx emissions in the areas surrounding the primarily urban/suburban NJADN sites than at the relatively pristine, coastal Forsythe Reserve location.
The annual wet depositional flux of NO3- in the NJADN ranged from 27 to 35 mmol m-2 y-1 (Table 17) compared with 20 and 15 mmol m-2 y-1 at Washington’s Crossing and the Forsythe Reserve, respectively. Since NO3- represents roughly half of the total dissolved nitrogen in rain, the remainder being NH4+ and dissolved organic nitrogen, total N fluxes are approximately twice these values. Precipitation NO3- fluxes at the NJADN sites are comparable to those (22 to 26 mmol m-2 y-1) measured in other Mid-Atlantic states (Pennsylvannia, Maryland, New York; NADN).
Phosphate in New Jersey Precipitation
Precipitation volumes varied significantly among sampling periods at the four NJADN sites, as shown by Figure 30. The data display no inherent seasonality in the amount of precipitation deposited at each site with the total volume of precipitation varying by as little as a factor of three between seasons. On an annual basis, precipitation was similar for all four sites, on the order of 1.0 m y-1.
Concentrations of total phosphorus in New Jersey precipitation for each individual sample ranged from 2.0 to 92 mg L-1 with both the lowest (July 2000) and highest (December 2000) concentrations measured at the New Brunswick site (Figure 31). The lowest volume-weighted mean concentration (Table 16) taken across all samples occurred at Jersey City (5.9 mg L-1). The volume-weighted mean concentrations over the other three sites (NB, PL, and CC) were of a similar magnitude to each other (7.4 mg L-1, 7.7 mg L-1, and 7.5 mg L-1, respectively).
The Jersey City site displayed the least amount of variability in total phosphorus concentration with a relative standard deviation of 38%. The New Brunswick, Camden and Pinelands sites show a larger degree of variability with higher relative standard deviations: New Brunswick (168%), Camden (78%), and Pinelands (68%). The New Brunswick and Pinelands sites are both expected to be influenced by the localized application of phosphorus-containing fertilizers and the re-suspension of biogenic material (soil, plant debris) subject to previous fertilizer application. The Pinelands site may also be subject to phosphorus input from incineration of biomass due to controlled burns initiated in the area. The Camden site is situated in the middle of an urban center and is, therefore, not expected to be influenced by the localized use of fertilizers. This site is influenced more by industrially associated phosphorus loadings (i.e. incineration). Three of the samples taken at this site (May 2000, January 2000, and May 2001) had high total phosphorus concentration, but if their influence is removed, the relative standard deviation for Camden is 41%, and on the same order of magnitude as the Jersey City site. This may be an indication that urbanized areas such as Jersey City and Camden are experiencing ‘background’ signals of phosphorus relative to those measured in agricultural areas. This may suggest that agricultural use of phosphorus is more important to loading in New Jersey than industrial sources.
Taking an average of all of the four sites in a particular season, the highest VWM concentrations occurred in the fall and spring, although they differ from the summer and winter
Figure 30. Precipitation volumes for each sampling period (L sample-1). Note: width of
bar corresponds to dates over which sample was integrated.
Figure 31. Concentrations of total phosphorus in precipitation (mg L-1). Note: width of bar
corresponds to dates over which sample was integrated. Width of the bar corresponds to the dates over which the sample was integrated.
by 1.5 times (Figure 32). There is no consistent pattern for the highest and lowest seasonal VWM concentration for any of the sites. For example, at some sites, the phosphorus concentration is highest in fall (New Brunswick) and in other cases, it is lowest in fall (Camden). For the individual sites, the seasonal VWM concentration varies minimally, between 4.1 ± 0.80 mg L-1 and 15 ± 8.8 mg L-1. This small variability suggests that the total amount of phosphorus loading due to wet deposition in New Jersey does not change on a spatial-scale.
Figure 32. Seasonal volume-weighted mean concentrations of total phosphorus in New Jersey
precipitation (mg L-1).
There are no consistent seasonal or spatial trends in total phosphorus wet-deposition, as shown by Figure 33. The lowest wet-deposition flux occurred at the Jersey City site in fall (3.9 mg m-2 y-1). The highest occurred in the Pinelands site in the fall (14 mg m-2 y-1). There is no statistically significant difference between the annual wet phosphorus deposition fluxes at the four NJADN sites, as shown by Figure 34.
The data collected for New Jersey is compared to that of other studies in Table 2, which shows that phosphorus concentrations and wet deposition fluxes in New Jersey are comparable to those measured elsewhere. Eisenreich et al. (1977) proposed that the dominant sources affecting phosphorus deposition to Lake Michigan are derived from both urban/industrial activities and agricultural sources, such as wind-blown soil and re-entrained dusts. The findings of this study, when compared to the study of Lake Michigan, suggest that the industrial and agricultural influences on total phosphorus loading are much greater in Michigan than in New Jersey, by as much as a factor of four. The total phosphorus concentration in South Florida reported by Ahn, et al (2001) is less than a factor of two higher than phosphorus concentrations at Camden, New Brunswick, and Pinelands.
Figure 33. Seasonal total phosphorus deposition flux by site (mg m-2 year-1).
Annual phosphorus wet deposition fluxes on the same order of magnitude as this study, were reported in a recent paper by Herut et al (1999). This study sampled at two sites on the Mediterranean coast of Israel and reported fluxes close to those in this study. The wet depositional flux of phosphorus reported in South Florida is greater than that of Jersey City by almost as much as an order of magnitude. This is in contrast to the similar deposition reported from the study, suggesting many short precipitation events, rather than fewer, longer ones.
Figure 34. Annual total phosphorus precipitation deposition fluxes (mg m-2 year-1).
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