Trace metal contamination of soils and sediments in the Port Kembla area, New South Wales, Australia

Transcription

1 University of Wollongong Thesis Collections University of Wollongong Thesis Collection University of Wollongong Year 9 Trace metal contamination of soils and sediments in the Port Kembla area, New South Wales, Australia Yasaman Jafari University of Wollongong Jafari, Yasaman, Trace metal contamination of soils and sediments in the Port Kembla area, New South Wales, Australia, Master of Environmental Science - Research thesis, School of Earth & Environmental Sciences - Faculty of Science, University of Wollongong, 9. This paper is posted at Research Online.

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3 Chapter 4 Results of the Study This chapter presents the results of grain size and total metal concentration analysis of ninety one grab and three core sampling sites, and also the extraction analysis of soil samples from the study area (Figure 3.1). Trace metal values were gained via XRF analysis and were recorded as metal concentrations in mg/kg (ppm). All results of this study are complied in a Microsoft Excel format database. All data presented are in Appendices Quality Control Quality Controls for XRF: All XRF runs were checked against internal certified standard references with results always being within 5% of the expected standard values. All soil and sediment samples were analysed in duplicate to ensure consistent results for the XRF data Quality Controls in the Extraction Experiments: Blanks: Blank solutions were used as a check to see if there is any contamination of the samples due to use of different reagents or airborne pollutants. As could be observed from the results in Appendix 5, the reagents contributed such a minute amount of metals to the results as to be negligible. Replicates: Replicates were analysed on some samples randomly to see whether there is any inconsistency in the procedures which the analyst is using, i.e., they are used to check how good the analyst s experimental methods are. The rationale behind this is that replicates of the same sample should yield similar final concentrations of the metals being tested. If a notable variation in the values is seen then the techniques employed by the experimenter may be very poor and the results of the study should be questioned. As can be seen from the percentage variation data in the Appendix 5, most of the replicate values are within 3% of each other, therefore, the results of this study could be considered reliable. 38

4 Certified Reference Material for Extraction Experiments: In addition to blanks and replicates, sample YH 118 was used to check the quality of the results of this study which would be expected to show 1±5 ppm values for trace metals namely Cu, Zn and Pb however ICPMS results of current study show considerable differences in the amounts of Zn in this sample (Table 4.1). Table 4.1: XRF results for YH 118. Test Av. Cu (ppm) Av. Zn (ppm) Av. Pb (ppm) XRF ICPMS Soil samples: Grain size analysis for soil samples: Full grain size analyses have been completed for all samples using a Mastersizer particle size analyser to establish the percentage of sand (63 µm- µm), silt (3.9 µm- 63µm) and clay (< 3.9 µm). Also the graphical standard deviation (StdD), skewness (G Skew) and kurtosis (Kurt) factors have been measured to detect the sorting and skewness of each sample. The full results for this are contained in Appendix. From the results, it has been observed that the average percentage of sand is about 54.6, silt is about 37.9 and clay is 7.5. Also according to the results of StdD and GSKew the soil samples seemed to be poorly sorted and near symmetrical. Figure 4.1 (a) presents the relative proportions of sand and clay contents in soil samples in the study area and shows a strong negative correlation between the variables. Figure 4.1 (b) shows the distribution of sand, silt and clay in a triangular diagram and indicates that most of the samples consist of silty sand or sandy silt based on the classification of Folk (1974). Figure 4. (A-I) shows the grain size analysis results and descriptions of typical selected representative soil samples. 39

5 a Clay (%) Soils y = -.673x +.78 R = Sand (%) b sand clay silt Figure 4.1 (a-b): Sand, silt and clay content distributions in soil samples 4

6 A-Laser Size Analysis for S4 3 Frequency percentage by volume Particle diameter (micrones) Figure 4. (A): Polymodal, very poorly sorted, fine skewed and leptokurtic. 5 B-Laser Size Analysis for S3 Frequency percentage by volume Particle diameter (microns) Figure 4. (B): Bimodal, poorly sorted, near symmetrical and mesokurtic. 5 C-Laser Size Analysis for S35 Frequency percentage by volume Particle diameter (microns) Figure 4. (C): Unimodal, poorly sorted, fine skewed and leptokurtic. 41

7 D-Laser Size Analysis for S39 3 Frequency percentage by volume Particle diameter (microns) Figure 4. (D): Polymodal, very poorly sorted, fine skewed and platykurtic. 5 E-Laser Size Analysis for S45 Frequency percentage by volume Particle diameter (microns) Figure 4. (E): Bimodal, poorly sorted, fine skewed and mesokurtic. 1 F-Laser Size Analysis for S46 Frequency percentage by volume Particle diameter (microns) Figure 4. (F): Bimodal, poorly sorted, strongly fine skewed and very leptokurtic. 4

8 G-Laser Size Analysis for S58 4 Frequency percentage by volume Particle diameter (microns) Figure 4. (G): Bimodal, very poorly sorted, near symmetrical and mesokurtic. 5 H-Laser Size Analysis for S63 Frequency percentage by volume Particle diameter (microns) Figure 4. (H): Bimodal, very poorly sorted, strongly fine skewed and mesokurtic. 4 I-Laser Size Analysis for S85 Frequency percentage by volume Particle diameter (microns) Figure 4. (I): Bimodal, very poorly sorted, fine skewed and leptokurtic. 43

9 4.. Background values for soil samples The aim of this part of the study is to obtain background values for soils developed on both basaltic and sedimentary rock substrates. Samples S47a, S87c, S88 and S89 were collected to provide the Permian basalt background; sample S8 provides a Tertiary basalt dyke background; while samples S47b, S79, S81, S9, S91 and S9 represent the Permian sediment background category. Average compositions of these rock types are presented in Table 4.. Table 4.: Average compositions of rock substrates in the Port Kembla area. Element Average Permian basalt (ppm) Average Tertiary basalt dyke (ppm) V Cr Co Ni Cu Zn As 1 9 Se.5 1 Rb Sr Y Zr Sn 8 5 Ba Pb Th U Average Permian sediment (ppm) 44

10 4..3 Port Kembla copper smelter slag: Two slags were analysed by B. E. Chenhall (pers. comm.., 9). One was in situ at the Port Kembla copper smelter whereas the other was a floater collected on Military Road. The average concentrations of trace metals in these slags are Ni > ppm, Cu > 4 ppm, Zn > ppm and Pb > 4 ppm Total Trace Elements in Soil Samples as Measured by XRF: Full results of the XRF analyses of all the soil samples are contained in Appendix 3. To determine elements that show significant effects of pollution within the Port Kembla area enrichment factors were calculated for each trace element in the study area. Enrichment factors represent the amount by which each element exceeds the appropriate background value for the underlying rock substrate. Enrichment factor = mean trace metal concentrations in soil samples (influenced by anthropogenic activities) / mean trace metal concentrations in background samples (underlying rock). Table 4.3: Enrichment factors of the trace metals Ni, Cd, Cu, Zn, Pb, As, Sn, Se, V and Cr in soils. Trace Metals Maximum enrichment factor Mean enrichment factor Ni 17 3 Cu 1 Zn 5 Pb 3 5 As 31 8 Sn 1 3 Se 16 4 V 1 1 Table 4.4 separates trace elements which have concentrations that consistently exceed the appropriate background values from those that show no significant change or enrichment. The elements listed in Group will not be discussed in this project since they show no sign of anthropogenic contamination. 45

11 Table 4.4: Analysed trace metals in soil samples. Group 1: Elements showing significant V, Ni, Cu, Zn, Pb, As, Se and Sn. enrichment above substrate values Group : Other elements S, Cl, Ti, Mn, Fe, Cr, Co, Ga, Ge, Br, Rb, Sr, Y, Zr, Nb, Cd, Mo, Sb, Ba, La, Ce, Hf, Ta, W, Hg, Tl, Bi, Th & U. Maximum and mean enrichment factors for the elements in Group 1 in Table 4.4 are given in Table 4.3 where elements with mean enrichment factors of more than double background have been printed in bold. As can be seen from this table, As concentrations are significantly elevated above background values with a mean enrichment factor of 8 while the enrichment factor for Cu is just times the background. Also it is clear from Table 4.3 that concentrations of some of trace metals like V remained nearly constant compared to the background values. According to previous studies (Beavington, 1973; Martley et al., 4; Kachenko & Singh, 6) Port Kembla copper smelter has been identified as an important source of pollution in the study area. In this study also all XRF results for trace elements in Group 1 in Table 4.4 show distribution maps with high values of each element in samples located close to the Port Kembla copper smelter stack (e.g. copper in Figure 4.3 and subsequent GIS maps for Zn, Pb, As, Sn and Se) confirming that it probably acts as the main point source for at least these elements. Hence their concentrations are compared to the distance from the copper smelter stack in subsequent figures Spatial distribution of XRF results from soil samples: Figures below show the value in ppm of the enriched trace metals in soil samples (Group 1 in Table 4.4) located within 45 m distance of the copper smelter stack. As can be observed from the GIS maps and concentration plots, samples located close to the Port Kembla copper smelter stack show higher amounts of many elements but sample S58 from a slag dump represents a big anomaly in all figures (Appendix 3). Figure 4.3 depicts the geographic distribution of Cu in soil samples. Based on this figure it could be observed that samples in close proximity (< 1.5 km) to the Port Kemble copper 46

12 smelter stack contain appreciably higher amounts of Cu. Figures 4.4 (a-b) present the total concentrations of Cu in soil samples. Cu (ppm) a 9 y = -.155x R = Distance (m) Cu (ppm) b y = -.155x R = Distance (m) Figure 4.4: (a) total Cu concentrations with three outliers, and (b) total Cu concentrations without the outliers in soils, plotted as a function of distance from the Port Kembla copper smelter stack. As can be seen in Figure 4.4 (a) there are three notable outliers corresponding to samples S58, S34 and S33; due to their locations in slag dumps (Appendix 1) they have been omitted from other figures in order to allow a more representative assessment of the distribution of environmentally significant elements. Generally the trace metal concentrations show obvious decreases with increase in distance from the copper smelter stack. Figure 4.5 (a-c) shows the geographic distributions of Zn, Pb and As, respectively, in the soils of the study area. With the exception of sample S58, high values of each element are located in samples close to the smelter stack and these values reduce notably moving away from this point source. Figure 4.6 (a-c) presents the total concentrations of Zn, Pb and As, respectively, in soil samples of the study area. 47

13 Figure 4.3: Total distribution of copper (ppm) in soil samples. 48

14 Figure 4.5 (a): Total distribution of zinc (ppm) in soil samples. 49

15 Figure 4.5 (b): Total distribution of lead (ppm) in soil samples. 5

16 Figure 4.5 (c): Total distribution of arsenic (ppm) in soil samples. 51

17 a (Zn) b (Pb) 14 1 y = -.67x R = y = -.79x R = Zn (ppm) Pb (ppm) Distance (m) Distance (m) c (As) 3 5 y = -.1x R =.1834 As (ppm) Distance (m) Figure 4.6: (a) Zn, (b) Pb and (c) As total concentrations in soils plotted as function of distance from the Port Kembla copper smelter stack. The highest values of Zn, Pb and As measured in the soil samples were 117 ppm, 56 ppm and 7 ppm, respectively (Appendix 3). The highest concentrations of each metal are again found around the smelter and the concentrations decline dramatically with increasing distance away. The concentrations of As are obviously lower than those of Zn and Pb. Samples S3 and S4 showed high concentrations of Zn (at about 836 ppm and 787 ppm, respectively) despite their distance (at about 3391 m and 3585 m, respectively) from the stack. The reason could be that their locations are close to roadways and they must reflect local sources of contamination (Appendix 1). 5

18 Figure 4.7 (a-b) shows the geographic distributions of Sn and Se within the study area. The concentrations of Sn in samples close to the stack are about 1 times greater than that of Se in that part of the study area indicating that smelter emissions contain high values of Sn. Figure 4.8 (a-b) presents the total concentrations of Sn and Se, respectively, in soils of the study area. a (Sn) b (Se) Sn (ppm) y = -.5x R = Distance (m) Se (ppm) 5 y = -.4x R = Distance (m) Figure 4.8: (a) Sn and (b) Se total concentrations in soils plotted as function of distance from the Port Kembla copper smelter stack. Figure 4.8 (a) demonstrates a maximum value of about 8 ppm and a minimum of about 4 ppm for Sn in soils of the study area, while from Figure 4.8 (b) the maximum value of Se is just above 4 ppm with the minimum of around 1 ppm. As with other trace metals studied, the concentrations of these two elements decrease with distance from the stack. Samples S33, S34, S35, S36, S37 and S38 were located just inside the fence of the Port Kembla Primary School on the corner of Electrolytic St and Military Road (Appendix 1); analysis gave average concentrations of 543, 789, 6, 38 and 8 ppm for Cu, Zn, Pb, Sn and Se, respectively. These high values for some trace metals at this site are due to the close proximity of the site to the Port Kembla copper smelter stack. Figure 4.9 (a-d) presents the geographic distributions of V, Cr, Ni and Cd, respectively, within the study area; in contrast to other trace elements studied these samples contain relatively low concentrations of these metals close to the copper smelter stack. Figure 4.1 present the total concentrations of V in soils of the study area. 53