Analysis of Lead and Cadmium in Sediment and Soil Samples

From that we have:

Standard Deviation (S): 0.1532 Mean: 0.45 Degrees of Freedom (n-1): 6

The t value is checked in the table with 99% confidence: 3.143 GHPH= t X S = 3.143 X 0.153 = 0.48(  g/l).

3.9 Analysis of lead and cadmium in sediment and soil samples

3.9.1. Analysis of lead and cadmium in soil and sediment samples

We conducted analysis to determine the content of cadmium and lead forms in soil and sediment samples according to the procedure (as shown in Figure 1.2):

Weigh accurately 1 g of the dried sample into a 50 ml centrifuge tube, add 10 ml of 1M CH 3 COONH 4 , shake well for 1 hour with a shaker at room temperature, then centrifuge at 3000 rpm for 15 minutes to collect the exchange fraction (F1) in the extract.

The remaining residue was continued to add 20 ml of CH 3 COONH 4 1M acidified to pH = 5 with CH 3 COOH, shaken well for 5 hours with a shaker at room temperature, then centrifuged at 3000 rpm for 15 minutes to collect the carbonate-bound fraction (F2) in the extract.

The remaining residue was added with 20 ml of NH 2 OH.HCl 0.04M in (v/v) 25% HOAc, shaken well for 5 hours at 95 0 C with a shaker, then centrifuged at 3000 rpm for 15 minutes to collect the fraction bound to iron - manganese oxide (F3) in the extract.

Add 10 ml of CH 3 COONH 4 3.2M in 20% HNO 3 to the residue, shake well at room temperature for 0.5 hour, then centrifuge at 3000 rpm for 15 minutes to collect the fraction associated with organic compounds (F4) in the extract.

The remaining residue was transferred to a 50 ml glass beaker, 21 ml of hydrochloric acid was added, then 7 ml of nitric acid (aqua regia mixture) was slowly added, and soaked.

for 16 hours at room temperature then reflux at 80 0 C for 2 hours until almost dry. Cool, make up to 25 ml with distilled water and filter to get the solution containing lead and cadmium in the form of excess residue (F5).

3.9.2. Analysis to determine total lead and cadmium content in sediments and soils

Soil and sediment samples were also digested with aqua regia: Weigh 1 g of dry sample into a 50 ml glass beaker and proceed as with the residue.

Determination of content by HTNT method with flame and flameless techniques.

The test was carried out 3 times, each time at each sampling location, 2 parallel samples were taken under the same conditions, rough errors were eliminated and the results were processed. The results are presented in tables 3.21 and 3.22:

Table 3.21 Concentrations of lead and cadmium forms and total metals in sediments

Sampling location

Forms	Pb(mg/kg)	Cd(mg/kg)
Cau Dien	F1	0.09 ± 0.01	0.254  0.013
	F2	23.81 ± 0.29	0.609  0.030
	F3	20.00  0.23	0.406 ± 0.020
	F4	3.81 ± 0.19	0.036  0.002
	F5	43.95 ± 1.20	0.158 ± 0.008
	Total 5 forms	91.67 ± 1.28	1.463  0.073
	Total water destruction	86.5 ± 0.31	1.193±0.006
Thanh Liet	F1	0.03 ± 0.01	0.990  0.049
	F2	7.62 ± 0.38	4.569  0.228
	F3	15.24  0.76	2.183  0.109
	F4	1.87 ± 0.09	0.508 ± 0.025
	F5	52.15 ± 1.61	0.825  0.041

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Sampling location

Forms	Pb(mg/kg)	Cd(mg/kg)
	Total 5 forms	76.90 ± 1.85	9.074  0.454
	Total water destruction	64.77±0.23	7.898±0.055
Khe Tang	F1	0.06 ± 0.01	0.482  0.024
	F2	7.62 ± 0.38	1.878  0.094
	F3	14.29 ± 0.71	1.066  0.053
	F4	3.33 ± 0.17	0.228 ± 0.011
	F5	40.42 ± 1.02	0.571  0.029
	Total 5 forms	65.71 ± 1.31	4.226  0.211
	Total water destruction	61.36±0.25	3.409±0.014
Ba Da	F1	0.05 ± 0.01	0.203 ± 0.010
	F2	10.48 ± 0.52	0.060  0.003
	F3	12.38 ± 0.23	0.457  0.023
	F4	2.38 ± 0.12	0.126 ± 0.006
	F5	40.43 ± 2.02	0.071  0.004
	Total 5 forms	65.71 ± 2.10	0.917 ± 0.012
	Total water destruction	56.82±0.20	0.682±0.002
Cinnamon	F1	0.02 ± 0.01	0.006 ± 0.001
	F2	2.56 ± 0.13	0.114  0.006
	F3	7.62 ± 0.18	0.457  0.023
	F4	2.86 ± 0.14	0.190 ± 0.010
	F5	22.42 ± 1.12	0.007 ± 0.001
	Total 5 forms	35.48 ± 1.15	0.773  0.026
	Total water destruction	32.95±0.16	0.739±0.003
Te Tieu	F1	0.03 ± 0.01	0.015 ± 0.001
	F2	2.65 ± 0.13	0.058 ± 0.003
	F3	6.67  0.33	0.129 ± 0.005

Sampling location

Forms	Pb(mg/kg)	Cd(mg/kg)
	F4	2.86 ± 0.14	0.122 ± 0.007
	F5	16.37  0.52	0.136  0.008
	Total 5 forms	25.70  0.64	0.461 ± 0.012
	Total water destruction	26.14±0.09	0.398±0.001
Mai Linh	F1	0.09±0.00	0.001±0.000
	F2	22,381±0.85	0.008±0.000
	F3	28,571±0.83	0.457±0.016
	F4	9.52±0.48	0.221±0.011
	F5	45,714±1.37	0.147±0.004
	Total 5 forms	106.19±1.88	0.834±0.020
	Total water destruction	89.77±0.54	0.455±0.002
Phung Dam	F1	0.03±0.00	0.014±0.000
	F2	2.38±0.09	0.001±0.000
	F3	15.24±0.76	0.457±0.014
	F4	10.48±0.30	0.166±0.003
	F5	38.10±1.45	0.003±0.000
	Total 5 forms	66.19±1.67	0.640±0.014
	Total water destruction	55.68±0.19	0.739±0.003
Do Bridge	F1	0.18±0.00	0.015±0.001
	F2	6.23±0.12	0.268±0.013
	F3	8.74±0.12	0.383±0.015
	F4	7.63±0.38	0.266±0.011
	F5	14.85±0.53	0.788±0.019
	Total 5 forms	37.62±0.68	1.719±0.030
	Total water destruction	33.38±0.20	1.788±0.012

Dien Bridge Sediment

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Element

F5 F4 F3 F2

Thanh Liet Sediment

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F5 F4 F3 F2

Pb Element Cd

Khe Tang Sediment

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F5 F4 F3 F2 F1

Ba Da sediments

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F5 F4 F3 F2

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Phung Dam Sediment

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Pb Element Cd

F5 F4 F3 F2 F1

Mai Linh Sediment

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F5 F4 F3 F2

Te Tieu Sediment

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F5 F4 F3 F2 F1

Cinnamon Sediment

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F5 F4 F3 F2

Pb Element Cd

The distribution of lead and cadmium species in the sediments of each site is presented in the form of graph 3.6 below.

Do Bridge Sediment

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Pb Element Cd

F5 F4 F3 F2

Figure 3.6: Distribution of metal species in sediments

Total lead content at points on Nhue River

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The Legend of Khe Tang

Ba Da

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Total lead content at points on the Day River

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Phung Mai Linh, the Imperial Cinnamon and Pepper Factory

Compare

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Sampling location

mg/kg content

An overview of the total lead and cadmium concentrations of the survey sites on the Nhue and Day rivers from upstream to downstream is presented in the graph in Figure 3.7.

Total cadmium concentration at river points

Nhuệ

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The Thanh Liet Khe Tang Ba Da

Total cadmium concentration at river points

Bottom

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Phung

1.50

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Mai Linh Te Pepper Cinnamon

Compare

Sampling location

Content mg/kg

Figure 3.7 Total metal content in sediments along the Nhue and Day river basins

Table 3.12 and Figure 3.7 show that the total lead content at the study sites in the Nhue River basin along the river basin from upstream decreases in order.

from Cau Dien  Thanh Liet  Khe Tang = Ba Da. This result is similar to previous studies [35, 36] that the total lead content at Cau Dien is greater than that at Thanh Liet. On the other hand, the total lead content at Khe Tang is equal to the total lead content at Ba Da although Khe Tang is closer to Thanh Liet and Cau Dien. This is not only due to the fact that the water in Khe Tang area contains a lot of domestic wastewater with low metal content, but also due to the influence of the discharge source at Ba Da containing a higher amount of lead than the discharge source of Dong Van industrial park. This result is also consistent with the study of heavy metals in water [6], the lead content in suspended solids at Khe Tang is low, therefore, the deposition of lead from suspended solids to sediments and the spread of pollution along the water flow are also low.

Total cadmium content increased from Cau Dien to Thanh Liet, then decreased gradually in the order Thanh Liet  Khe Tang  Ba Da. Previous studies [35, 36, 37] also showed that the total cadmium content at Thanh Liet was greater than Cau Dien, cadmium in suspended sediment of To Lich River at Thanh Liet point before converging with Nhue River was very high, cadmium content from 1.1 to 25 mg/kg. Thus, there was a spread of pollution from To Lich River to Nhue River through adsorption on suspended sediment and sedimentation, causing the total cadmium content at Khe Tang to be greater than Cau Dien. However, from Khe Tang to Ba Da, the total cadmium content decreased, which can be explained by the fact that the water in Khe Tang area as mentioned above contains mainly domestic wastewater with low metal content [6]. At the same time, cadmium in the exchangeable form (F1) at Ba Da compared to the total content there is relatively large (22.1%), the largest among all research points, so cadmium easily escapes into the water column, leading to a decrease in the amount of cadmium in the sediment at Ba Da.

In the Day River basin, the total content of both lead and cadmium increased from Phung Dam to Mai Linh Bridge, then decreased at Te Tieu and gradually increased from Te Tieu  Que Bridge  Do Bridge (Figure 3.7). The high metal content found at Mai Linh Bridge can be explained by the fact that there are many facilities here that collect, process, and recycle metal barrels, and untreated wastewater is discharged directly into the river [6]. On the other hand, the river section flowing through Mai Linh Bridge flows with a very small flow, low water level, and bed.

The river is as small as a ditch and there are times of the year when the river flowing through here is almost still, even flowing upstream. This is a characteristic that makes the heavy metal content here very high and is less spread by the water flow, so the amount of heavy metals decreases from Cau Mai Linh to Te Tieu. From Te Tieu  Cau Que  Cau Do, it can be explained that the heavy metal content increases gradually because production facilities, factories, and industrial parks in Ha Nam discharge wastewater directly into the river without treatment. At the same time, Cau Do is also the intersection of the two rivers Nhue and Day, so it is affected by both of these rivers.

Figure 3.6 shows that the lead content in both Nhue and Day rivers is mainly concentrated in the form of residual residue (F5) with a content of  40%.

Next is the distribution in the form of iron-manganese oxide binding with a content of  20%, only found in Cau Dien, the second highest lead content is in the form of binding with carbonate, accounting for 26%. However, the lead content in Cau Dien in the form of binding with iron-manganese oxide also accounts for more than 20% (21.8%).

The lowest lead content was in the exchangeable form, all  0.5% compared to their total content. This shows that the biological response level of lead is not high compared to the total content in sediments at the research sites in the Nhue - Day river basin.

The cadmium content at the sampling locations on the Nhue River is mainly concentrated in the carbonate form (more than 40%), followed by the form associated with iron-manganese oxide (greater than 20%), only at Ba Da the largest content is in the form associated with iron-manganese oxide (50%) followed by the exchange form (22.1%). The total of the two forms of exchange and association with carbonate at Ba Da is 28.7%, the rest at the sampling locations are all greater than 55%. The exchange form at the sampling locations on the Nhue River is all greater than 0.2 mg/kg (greater than 10% of the corresponding total content), the form associated with carbonate all has a content greater than 0.06 mg/kg, especially at Thanh Liet the exchange form has a content of

 1mg/kg (accounting for 10%), the carbonate-bound form has a content of  4.6 mg/kg (accounting for 50%). This shows the risk of affecting the ecological environment of

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