II.B. Trace Metals, Nutrients, Chloride, and Sulfate: Concentrations and Deposition
II.B1. Summary of Inorganic Concentrations and Fluxes
The following sections summarize the main features of the atmospheric concentrations and deposition fluxes of inorganic analytes in New Jersey precipitation and fine aerosols and highlight some important features of these results. More detailed evaluations of trace metals, mercury and nutrients are found in separate sections below and the complete results are tabulated in the appendices.
The primary focus of the inorganic section of NJADN is the quantification of atmospheric concentrations and fluxes of mercury and other trace metals. However, the precipitation concentrations and wet deposition of nitrate and phosphorus are also an important component of the Network and these plus a partial data set of chloride and sulfate results are discussed below.
Precipitation Concentrations and Wet Deposition of Inorganic Analytes
Volume-weighted mean concentrations (VWM) of the inorganic chemical measured in rain collected in New Brunswick, Jersey City, the Pinelands, and Camden are shown in Table 16. The concentrations of most elements were greatest in Jersey City and Camden, lowest in the Pinelands, and intermediate in New Brunswick (see Al, As, Cl, Co, Cr, Fe, Pb, S, and V). Notable exceptions are Cd, Cu, and Zn for which New Brunswick concentrations were among the highest and Ag, Mn, P, and Sb for which the highest concentrations were measured in the Pinelands. Since rain depths were similar at all four sites (83-98 cm y-1), spatial differences may indicate the presence of local sources. By contrast, the uniform VWM concentrations of Hg, nitrate, and phosphate at all four sites, indicates that regional processes control the atmospheric concentrations and deposition of these substances.
Table 16. Volume-weighted mean concentrations (all in mg L-1 except Hg, ng L-1) of inorganic chemicals in New Jersey precipitation.
Element / New Brunswick / Jersey City / Pinelands / CamdenAg / 0.039 / 0.020 / 0.096 / 0.059
Al / 19 / 26 / 16 / 32
As / 0.046 / 0.15 / 0.059 / 0.15
Cd / 0.078 / 0.072 / 0.023 / 0.077
Cl / 380 / 730 / 320 / 540
Co / 0.044 / 0.12 / 0.017 / 0.10
Cr / 0.13 / 0.17 / 0.048 / 0.20
Cu / 1.7 / 2.1 / 0.45 / 1.6
Fe / 22 / 45 / 13 / 48
Hg (ng/L) / 13 / 14 / 12 / 15
Mg / 61 / 90 / 56 / 74
Mn / 2.0 / 1.8 / 3.1 / 2.7
Ni / 0.77 / 1.1 / 0.26 / 0.59
NO3-N / 370 / 390 / 360 / 450
PO4-P / 7.4 / 5.9 / 7.7 / 7.5
Pb / 1.6 / 2.4 / 0.55 / 2.8
Pd / 0.017 / 0.019 / 0.012 / 0.022
Sb / 0.083 / 0.16 / 0.16 / 0.14
SO4-S / 720 / 840 / 630 / 910
V / 0.52 / 0.83 / 0.38 / 0.91
Zn / 8.6 / 8.2 / 5.4 / 11
The annual wet deposition fluxes of inorganic contaminants are shown in Table 17. These fluxes reflect the spatial patterns of the VWM concentrations. Because the annual rain fall in New Jersey is about 100 cm and the conversion factor between cm, mg L-1, and mg m-2 is 10, wet deposition is approximately (and fortuitously) equal to 103 x VWM rainwater concentrations.
Table 17. Annual deposition fluxes (mg m-2 y-1) of inorganic chemicals in New Jersey precipitation.
Element / New Brunswick / Jersey City / Pinelands / CamdenAg / 39 / 21 / 110 / 66
Al / 19,772 / 27,962 / 18,696 / 35,689
As / 49 / 161 / 71 / 163
Cd / 79 / 78 / 27 / 87
Cl / 338,694 / 748,158 / 215,121 / 559,944
Co / 44 / 131 / 20 / 116
Cr / 138 / 180 / 56 / 220
Cu / 1,764 / 2,269 / 519 / 1,831
Fe / 22,454 / 47,937 / 15,535 / 54,580
Hg / 14 / 13 / 13 / 18
Mg / 63,953 / 95,419 / 63,921 / 83,241
Mn / 2,040 / 1,950 / 3,612 / 2,984
Ni / 791 / 1,199 / 296 / 660
NO3-N / 380,865 / 377,911 / 419,608 / 494,806
PO4-P / 7,420 / 6,290 / 8,922 / 8,474
Pb / 1,599 / 2,527 / 631 / 3,109
Pd / 17 / 21 / 13 / 25
Sb / 84 / 172 / 181 / 155
SO4-S / 644,750 / 884,516 / 417,942 / 945,896
V / 528 / 889 / 438 / 1,020
Zn / 8,820 / 8,862 / 6,176 / 12,597
Fine Aerosol (PM2.5) Concentrations and Dry Particle Deposition of Trace Metals
The arithmetic mean concentrations and annual dry particle deposition fluxes of trace metals in fine aerosols are presented in Tables 18 and 19. Element concentrations in atmospheric particles often show log-normal distributions in which the geometric mean may more accurately represent the frequency of a given concentration (Polissar et al., 2001). Thus it is important to recognize that unusually high average concentrations and annual fluxes of PM-bound metals may result from individual high concentration events. For example, the very high average PM2.5 concentrations and annual dry deposition fluxes of Ag and Pb in Jersey City are partly due to very high values measured on a single day (August 4, 2000; see Appendix A3). However, the arithmetic mean does provide a conservative estimate of metal concentrations in atmospheric PM and dry deposition fluxes and is useful for comparing fluxes from NJADN sites with those from other atmospheric monitoring experiments.
For a many of the contaminant metals (Cd, Hg, Pb, Sb, V, and Zn), the lowest fine aerosol concentrations were recorded at the rural and coastal sites of Pinelands, Tuckerton, and the Delaware Bay, but low levels of these metals were also observed at Washington Crossing, Chester, and Sandy Hook. Similar to the precipitation concentrations and deposition fluxes of metals, the PM2.5 results generally show higher fine aerosol metal concentrations in the highly developed urban areas of Jersey City, Camden, and New Brunswick than in other more suburban or rural areas of the state. However, differences in the relative concentrations of metals in fine aerosols and precipitation are likely due to the fact that the precipitation samples are time integrated and include the washout of a wider range of particle sizes than is represented by PM2.5.
Table 18. Arithmetic mean trace metal concentrations in New Jersey fine aerosols (PM2.5).
Element / NB / JC / PL / CC / WC / TK / XQ / SH / DBAg / 0.093 / 0.838 / 0.070 / 0.046 / 0.036 / 0.029 / 0.044 / 0.037 / 0.032
Al / 59 / 82 / 89 / 59 / 61 / 43 / 35 / 95 / 52
As / 0.74 / 0.97 / 0.45 / 0.68 / 0.66 / 0.99 / 0.88 / 0.62 / 0.62
Cd / 0.24 / 0.65 / 0.092 / 0.18 / 0.19 / 0.10 / 0.19 / 0.15 / 0.13
Co / 0.25 / 0.53 / 0.14 / 0.26 / 0.18 / 0.13 / 0.18 / 0.22 / 0.18
Cr / 5.2 / 6.0 / 7.2 / 13 / 4.8 / 2.2 / 9.9 / 3.0 / 3.1
Cu / 13 / 17 / 6.8 / 5.5 / 29 / 7.2 / 1.5 / 4.1 / 2.0
Fe / 129 / 243 / 112 / 178 / 107 / 74 / 76 / 135 / 52
Hg / 7.1 / 12 / 5.0 / 17 / 6.3 / 5.5 / 14 / 7.4 / 7.6
Mg / 36 / 41 / 103 / 59 / 36 / 32 / 10 / 75 / 35
Mn / 3.9 / 4.5 / 1.7 / 3.9 / 2.4 / 1.5 / 2.0 / 3.6 / 1.3
Ni / 4.1 / 12 / 4.1 / 5.4 / 11 / 3.5 / 7.0 / 5.5 / 8.7
Pb / 8.4 / 27 / 3.0 / 5.9 / 7.2 / 3.3 / 2.7 / 5.2 / 2.1
Pd / 0.059 / 0.028 / 0.079 / 0.042 / 0.023 / 0.030 / 0.025 / 0.023 / 0.028
Sb / 1.1 / 5.3 / 0.37 / 1.1 / 0.61 / 0.40 / 0.34 / 0.73 / 0.29
V / 3.5 / 10 / 2.1 / 5.1 / 2.5 / 3.6 / 1.5 / 6.4 / 2.6
Zn / 22 / 34 / 19 / 38 / 20 / 21 / 27 / 32 / 22
Table 19. Dry particle deposition fluxes (mg m-2 y-1) of trace metals in New Jersey.
Element / NB / JC / PL / CC / WC / TK / XQ / SH / DBAg / 15 / 132 / 11 / 7.2 / 5.7 / 4.6 / 7.0 / 5.8 / 5.0
Al / 9,255 / 12,870 / 13,963 / 9,308 / 9,685 / 6,856 / 5,448 / 14,958 / 8,238
As / 117 / 153 / 70 / 108 / 104 / 156 / 139 / 98 / 98
Cd / 37 / 102 / 14 / 29 / 30 / 16 / 30 / 23 / 21
Co / 39 / 84 / 22 / 40 / 28 / 20 / 28 / 34 / 29
Cr / 818 / 949 / 1,139 / 1,978 / 756 / 349 / 1,566 / 474 / 493
Cu / 2,049 / 2,689 / 1,077 / 863 / 4647 / 1,138 / 230 / 642 / 308
Fe / 20,293 / 38,337 / 17,676 / 28,042 / 16,927 / 11,715 / 12,039 / 21,239 / 8,213
Hg / 1.1 / 1.8 / 0.79 / 2.6 / 1.0 / 0.87 / 2.2 / 1.2 / 1.2
Mg / 5,656 / 6,437 / 16,248 / 9,302 / 5,667 / 5,050 / 1,608 / 11,753 / 5,551
Mn / 615 / 704 / 269 / 609 / 385 / 242 / 314 / 560 / 211
Ni / 643 / 1,956 / 654 / 847 / 1,737 / 550 / 1,111 / 870 / 1,376
Pb / 1,331 / 4,235 / 466 / 937 / 1,140 / 516 / 431 / 826 / 339
Pd / 9.2 / 4.5 / 12.5 / 6.7 / 3.6 / 4.8 / 4.0 / 3.6 / 4.4
Sb / 172 / 837 / 59 / 181 / 96 / 64 / 53 / 114 / 45
V / 560 / 1,637 / 330 / 808 / 399 / 563 / 231 / 1,013 / 418
Zn / 3,533 / 5,425 / 3,005 / 6,031 / 3,115 / 3,314 / 4,275 / 5,074 / 3,541
II.B2. Trace Metals Results
The following section presents a detailed examination of the atmospheric concentrations and fluxes of trace metals in New Jersey including seasonal variations, comparisons with other states, and an evaluation of the relative importance of wet and dry deposition fluxes. The elements As, Cd, Cu, and Pb will be used to illustrate specific points and represent the behavior of the 16 elements analyzed. These elements are emitted from a variety of industrial and municipal sources and, with the exception of As, are strongly associated with particulate matter. As seen in Tables 16-19 above, the atmospheric concentrations and deposition of As, Cd, Cu, and Pb are generally lowest in the Pinelands and highest in Jersey City and Camden. However, the high intra- and inter-seasonal variability at a specific site such as New Brunswick (Figure 18), complicates spatial comparisons.
Seasonal variations in the concentrations of As, Cd, and Cu were not uniform across New Jersey (Figures 19-22), indicating the importance of local sources and/or atmospheric transport processes to the deposition of these trace elements in the state. In contrast, the seasonal variation
Figure 18. Precipitation concentrations of As, Cd, Cu, and Pb in New Brunswick versus time.
in the concentrations of Pb was similar at all sites and showed the highest levels in the spring and the lowest levels in the fall (Figure 22). The delivery of Pb thus appears to be controlled by regional emissions and transport factors. Precipitation concentrations of all four of these trace elements generally showed similar seasonal patterns at the two most urbanized sites, Jersey City and Camden, but these patterns differed among the elements.
Figure 19. Seasonal As concentrations in New Jersey precipitation.
Figure 20. Seasonal Cd concentrations in New Jersey precipitation.
Figure 21. Seasonal Cu concentrations in New Jersey precipitation.
Figure 22. Seasonal Pb concentrations in New Jersey precipitation.
Figure 23. Fine aerosol concentrations of As, Cd, Cu, and Pb in Camden versus time.
Table 20. Annual precipitation and dry particle deposition fluxes (mg m-2 y-1) of trace elements from other atmospheric deposition studies. Dry particle deposition fluxes were calculated from reported average PM concentrations (VT: geometric mean PM2.5; MD: arithmetic mean PM10) and a deposition velocity of 432 m d-1.
Wet deposition / Dry particle depositionElement / Maryland1 / Florida2 / Vermont3 / Maryland4
As / 45 / 86 / 36 / 99
Cd / 36 / 20 / - / 21
Cr / 48 / - / 55 / 104
Cu / 244 / 430 / 156 / 369
Fe / 6800 / 32,000 / 2696 / 22706
Mn / 860 / 2130 / 118 / 445
Ni / 240 / 1880 / 61 / 626
Pb / 560 / 496 / 424 / 711
Zn / 1100 / 5320 / 965 / 1892
1Scudlark et al., 1994
2Landing et al., 1995
3Polissar et al., 2001
4Wu et al., 1994
The atmospheric deposition fluxes of Cd, Cu, and Pb illustrate the presence of an urban signal above the regional background that may indicate local sources. The wet deposition fluxes of Cd, Cu, and Pb at the urban/suburban NJADN sites (New Brunswick, Jersey City, Camden; Table 17) are two to nine times higher than those measured in the early 1990's at rural sites (Table 20) in Maryland (Scudlark et al., 1994) and Florida (Landing et al., 1995). These differences do not appear to be the result of methodological difference since precipitation fluxes of Cd, Cu, and Pb in the New Jersey Pinelands (Table 17) are similar to those in rural Maryland and Florida. This trend is similar for the dry particle fluxes of Cd, Cu, and Pb, although the Pinelands appears to have elevated particulate Cu with respect to the regional background as recorded at the Chester and Delaware Bay sites.
Arsenic wet deposition in NJ is highest at the urban sites (Jersey City and Camden), but also fairly high in the Pinelands perhaps indicating a shadow effect of Camden (Table 17; Figure 19). The wet deposition of As in New Brunswick is similar to that measured in rural Maryland (Table 20). Dry particle deposition fluxes of As in New Jersey are slightly higher than those measured in Maryland. The lower particle flux of As calculated for Vermont reflects the use of a geometric mean PM concentration (Polissar et al., 2001).
Figure 24. Relative importance of precipitation (blue) and dry particle (shaded) deposition to the atmospheric fluxes of As, Cd, Cu, and Pb in New Brunswick.