The paper comprehensively analyzes and evaluates the urban grid soil and rural soil quality and pollution characteristics through methods of single factor index and Nemero comprehensive pollution index on the physical and chemical nature of soil, the element pollutants, organic pollutants and other pollutants. The contents of soil pollutants in rural and urban areas showed that the overall soil quality is good and advice on how to improve soil quality in the region is put forward.
With the rapid development of industry and agriculture, the unreasonable use of pesticides and fertilizers, long- term sewage irrigation, as well as urban and industrial pollution and other factors since 1930s, through different ways, a great number of pollutants entered into the soil environment, did damage to the soil structure, destroyed the soil function [
Soil pollutants can be roughly divided into two kinds: inorganic pollutants and organic pollutants [
Grid distribution is used in urban soil, which means that 1 km × 1 km size square grid is drawn in administrative map with corresponding proportion, 1 monitoring point lying in each grid. According to the landscape, distribution of land use types, soil types and other factors in Northern Yangtze River area, the number of points is obtained by the formula that land use area/grid size = number of sample points. After optimization, points number of urban soil survey is ultimately determined as 62. The rural scope of the soil investigation involves the 7 villages of Wubao town and each village has 1 monitoring point, 7 monitoring points in total.
The evaluation on soil quality is mainly based on Soil environmental quality standard (GB15618-1995) [
Pi reflects the extent of pollution. Its values less than 1 means no pollution while that greater than 1 means pollution. It can be expressed as follows.
where Pi is the single pollution index of pollutant i in the soil; Ci is the measured concentration of pollutant i in the soil of surveyed locations; Si is standard referential value for the evaluation of pollutant i.
Nemero comprehensive pollution index are often used for comprehensive evaluation on soil pollution and the formulation is as below:
where PN is the Nemero comprehensive pollution index; Pmean is the average single pollution index;
Nemero index reflects the effect of the pollutants on the soil [
Grade division | Single pollution index | Class of pollution |
---|---|---|
I | PN ≤ 0.7 | Clean (SAFE) |
II | 0.7 < PN ≤ 1 | Relatively clean (alert limit) |
III | 1 < PN ≤ 2 | mild concentration |
IV | 2 < PN ≤ 3 | middle level pollution |
V | PN > 3 | heavy pollution |
There are 7 sampling rural fields for the survey, and the monitoring projects include 20 items: pH, full Nitrogen, full Phosphorus and full Kalium and the organics; elements: Arsenic, Cadmium, Cobalt, Chromium, Copper, Fluoride, Mercury, Manganese, Nickel, Lead, Selenium, Vanadium, and Zinc. The monitoring results of physicochemical properties, elemental pollutants and organics are shown in Tables 2-4, respectively.
Basic situation of soil fertility: the material composition, structure status and the natural conditions determine the level of soil fertility, which affects growth of plant and is the material basis for the crop yields [
According to the dry soil fertility grading standard (see
The content and distribution of pollutants : The monitoring result of element pollutants in
Urban grid soil sampling points are distributed across the whole are, a total of 62 points, and the monitoring projects include 14 items: pH, Arsenic, Cadmium, Cobalt, Chromium, Copper, Fluoride, Mercury, Manganese, Nickel, Lead, Selenium, Vanadium, and Zinc. The detailed monitoring result is shown in Tables 5-7.
Statistics of pH monitoring: Among 62 urban grid soil point locations, pH monitoring result is in the range of 4.72 - 8.40, the lowest is in the entry into 412 Park, the highest point is 708. There are 9 points with value of pH less than 6.5 accounting for 14.5% of the total grid number. The number of pH value ranging from the 6.5 - 7.5 is 14 accounting for 22.6% of the total grid number. The number of pH value greater than 7.5 is 39 accounting for 62.9% of the total grid number. The result shows that the pH in this area of soil is alkalescent (
Pollution index evaluation [
Sampling point | Projects and results | ||||
---|---|---|---|---|---|
pH | Total nitrogen (%) | Total phosphorus (mg/Kg) | Total potassium (mg/Kg) | organic matter (g/Kg) | |
A | 7.62 | 0.004 | ND | 25764 | 13.4 |
B | 7.83 | 0.002 | ND | 27702 | 9.9 |
C | 7.68 | 0.006 | ND | 19854 | 14.2 |
D | 7.25 | 0.005 | ND | 29687 | 13.5 |
E | 7.84 | 0.009 | ND | 25103 | 12.9 |
F | 8.02 | ND | ND | 20530 | 9.2 |
G | 6.93 | 0.003 | ND | 30605 | 11.5 |
Remarks: ND: Not detected.
Sampling point | Projects and results | |||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|
Fluoride | As | Cd | Co | Cr | Cu | Hg | Mn | Ni | Pb | Se | Zn | |
A | 452 | ND | ND | ND | 58 | 43 | ND | 572 | ND | 24 | ND | 83 |
B | 361 | ND | ND | ND | 84 | 29 | ND | 560 | 33 | 20 | ND | 99 |
C | 204 | ND | ND | ND | 74 | 15 | ND | 505 | ND | 20 | ND | 46 |
D | 344 | ND | ND | 195 | 88 | 33 | ND | 880 | ND | ND | ND | 69 |
E | 382 | ND | ND | 460 | 104 | 35 | ND | 1551 | ND | ND | ND | 56 |
F | 189 | ND | ND | 521 | 140 | 27 | ND | 2544 | ND | ND | ND | 24 |
G | 293 | ND | ND | 1195 | 198 | 42 | ND | 7306 | ND | ND | ND | 26 |
Remarks: ND: Not detected.
Sampling point | A list of results of the monitoring results of soil organic chlorine pesticides in rural areas (unit: mg/Kg).Projects and results | |||||||
---|---|---|---|---|---|---|---|---|
α-benzene hexachloride | β-benzene hexachloride | γ-benzene hexachloride | δ-benzene hexachloride | p,p’-DDD | p,p’-DDE | p,p’-DDT | o,p’-DDT | |
A | ND | ND | ND | ND | ND | ND | ND | ND |
B | ND | ND | ND | ND | ND | ND | ND | ND |
C | ND | ND | ND | ND | ND | ND | ND | ND |
D | ND | ND | ND | ND | ND | ND | ND | ND |
E | ND | ND | ND | ND | ND | ND | ND | ND |
F | ND | ND | ND | ND | ND | ND | ND | ND |
G | ND | ND | ND | ND | ND | ND | ND | ND |
Remarks: ND: Not detected.
Grid name | pH | V | Cr | Mn | Co | Ni | Cu | Zn | As | Se | Cd | Hg | Pb |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
005 | 5.27 | 227 | 199 | 32,229 | 1866 | ND | 95 | 22 | ND | ND | ND | ND | 165 |
509 | 6.07 | 98 | 76 | 257 | ND | ND | 27 | 55 | 17 | ND | ND | ND | 14 |
306 | 6.33 | 370 | 77 | 6580 | ND | 67 | 37 | 68 | 23 | ND | ND | ND | 36 |
004 | 5.98 | 102 | 81 | 682 | ND | 30 | 42 | 104 | 17 | ND | ND | ND | 21 |
511 | 5.18 | 81 | 64 | 383 | ND | ND | 28 | 52 | ND | ND | ND | ND | 26 |
003 | 5.82 | 77 | 72 | 430 | ND | 51 | 29 | 68 | 11 | ND | ND | ND | 18 |
105 | 6.32 | 91 | 108 | 601 | 198 | ND | 39 | 77 | ND | ND | ND | ND | 25 |
412 | 4.72 | 73 | 72 | 459 | 110 | ND | 18 | 38 | 9 | ND | ND | ND | 13 |
304 | 6.26 | 97 | 69 | 528 | ND | ND | 31 | 78 | ND | ND | ND | ND | 31 |
Standard limit (≤) | / | / | 150 | / | / | 40 | 50 | 200 | 40 | / | 0.30 | 0.30 | 250 |
Remarks: ND: Not detected.
Grid name | pH | V | Cr | Mn | Co | Ni | Cu | Zn | As | Se | Cd | Hg | Pb |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
708 | 8.40 | 114 | 77 | 673 | ND | 29 | 21 | 82 | ND | ND | ND | ND | 24 |
708 | 8.40 | 133 | 83 | 742 | ND | 29 | 45 | 107 | ND | ND | ND | ND | 35 |
601 | 7.72 | 98 | 53 | 551 | ND | 35 | 37 | 70 | 16 | ND | ND | ND | 18 |
707 | 8.01 | 76 | 77 | 569 | ND | ND | 41 | 86 | ND | ND | ND | ND | 24 |
801 | 8.12 | 99 | 87 | 539 | ND | 31 | 39 | 83 | 12 | ND | ND | ND | ND |
701 | 7.55 | 94 | 127 | 668 | ND | 32 | 54 | 169 | 15 | ND | ND | ND | 47 |
603 | 7.72 | 105 | 77 | 846 | ND | 43 | 32 | 110 | ND | ND | ND | ND | 23 |
706 | 7.85 | 87 | 72 | 613 | ND | 35 | 45 | 86 | 15 | ND | ND | ND | 26 |
805 | 7.68 | 108 | 74 | 555 | ND | ND | 33 | 93 | 10 | ND | ND | ND | 18 |
308 | 8.06 | 101 | 69 | 614 | ND | 32 | 29 | 79 | 12 | ND | ND | ND | 16 |
211 | 7.93 | 89 | 54 | 448 | ND | ND | 22 | 61 | 9 | ND | ND | ND | 13 |
107 | 7.82 | 113 | 104 | 758 | ND | ND | 42 | 98 | 16 | ND | ND | ND | 21 |
712 | 7.94 | 91 | 86 | 665 | ND | 36 | 67 | 88 | ND | ND | ND | ND | 26 |
413 | 8.04 | 106 | 76 | 740 | ND | 33 | 22 | 74 | 11 | ND | ND | ND | 23 |
605 | 7.77 | 99 | 43 | 578 | ND | 36 | ND | 73 | ND | ND | ND | ND | 22 |
803 | 8.33 | 102 | 77 | 589 | ND | 40 | 55 | 89 | ND | ND | ND | ND | 31 |
607 | 7.86 | 131 | 65 | 541 | ND | ND | 82 | 321 | 23 | ND | ND | ND | 40 |
709 | 7.88 | 113 | 58 | 570 | ND | 42 | 32 | 90 | 14 | 5.5 | ND | ND | 31 |
406 | 7.78 | 100 | 60 | 570 | ND | 52 | 37 | 84 | ND | ND | ND | ND | 19 |
508 | 7.82 | 74 | 51 | 87 | ND | ND | ND | 37 | 17 | ND | ND | ND | 16 |
309 | 8.12 | 91 | 64 | 581 | ND | 28 | 41 | 84 | ND | ND | ND | ND | 24 |
408 | 7.68 | 97 | 79 | 881 | ND | 42 | 98 | 182 | ND | ND | ND | ND | 83 |
606 | 7.60 | 104 | 73 | 557 | ND | 36 | 23 | 87 | 14 | ND | ND | ND | 22 |
502 | 7.63 | 86 | 85 | 547 | ND | 48 | 34 | 69 | ND | ND | ND | ND | 24 |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
612 | 7.56 | 108 | 41 | 395 | ND | 34 | 27 | 64 | ND | ND | ND | ND | 17 |
409 | 7.74 | 90 | 102 | 594 | ND | ND | 24 | 97 | 12 | ND | ND | ND | 20 |
705 | 7.78 | 88 | 67 | 478 | ND | ND | 24 | 82 | ND | ND | ND | ND | 30 |
802 | 7.67 | 87 | 70 | 722 | ND | 45 | 36 | 77 | ND | ND | ND | ND | 30 |
202 | 7.84 | 115 | 52 | 510 | ND | ND | 39 | 76 | ND | ND | ND | ND | 22 |
204 | 8.25 | 111 | 73 | 650 | ND | 32 | 31 | 81 | 10 | ND | ND | ND | 13 |
106 | 7.90 | 87 | 52 | 639 | ND | ND | 35 | 68 | 14 | ND | ND | ND | 18 |
804 | 8.08 | 108 | 81 | 677 | ND | 38 | 44 | 85 | ND | ND | ND | ND | 27 |
307 | 8.18 | 95 | 60 | 623 | ND | 31 | 17 | 65 | ND | ND | ND | ND | 15 |
510 | 7.83 | 110 | 98 | 1150 | 373 | ND | 32 | 67 | ND | ND | ND | ND | ND |
103 | 8.32 | 128 | 114 | 1549 | 571 | ND | 32 | 60 | ND | ND | ND | ND | ND |
104 | 7.79 | 193 | 216 | 2887 | 1050 | ND | 54 | 62 | ND | ND | ND | ND | ND |
109 | 7.70 | 154 | 243 | 5659 | 1201 | ND | 65 | 42 | ND | ND | ND | ND | ND |
108 | 7.81 | 128 | 217 | 5221 | 1182 | ND | 52 | 25 | ND | ND | ND | ND | ND |
506 | 7.84 | 229 | 309 | 7554 | 1638 | ND | 223 | 216 | 19 | ND | ND | ND | ND |
110 | 7.66 | 169 | 258 | 13,001 | 1558 | ND | 56 | 22 | ND | ND | ND | ND | ND |
Standard limit (≤) | / | / | 250 | / | / | 60 | 100 | 300 | 25 | / | 0.60 | 1.0 | 350 |
Remarks: ND: Not detected.
Grid name | pH | V | Cr | Mn | Co | Ni | Cu | Zn | As | Se | Cd | Hg | Pb |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
609 | 7.02 | 285 | 492 | 31,354 | 2676 | ND | 81 | 27 | ND | ND | ND | ND | 86 |
410 | 7.44 | 161 | 224 | 6435 | 1977 | ND | 93 | 95 | ND | ND | ND | ND | ND |
703 | 7.41 | 78 | 152 | 579 | ND | 37 | 84 | 286 | ND | ND | ND | ND | 86 |
310 | 6.86 | 84 | 64 | 133 | ND | 41 | 18 | 33 | 11 | ND | ND | ND | 20 |
402 | 7.20 | 110 | 89 | 580 | ND | ND | 33 | 85 | ND | ND | ND | ND | 17 |
702 | 7.46 | 114 | 77 | 554 | ND | 50 | 45 | 85 | ND | ND | ND | ND | 21 |
711 | 7.32 | 100 | 88 | 682 | ND | ND | 50 | 76 | 12 | ND | ND | ND | 25 |
312 | 6.95 | 101 | 59 | 520 | ND | 31 | 40 | 74 | ND | ND | ND | ND | 22 |
203 | 7.20 | 75 | 46 | 519 | ND | ND | ND | 72 | ND | ND | ND | ND | 55 |
710 | 7.29 | 100 | 72 | 551 | ND | 39 | 44 | 93 | ND | ND | ND | ND | 24 |
206 | 7.12 | 117 | 82 | 574 | ND | 31 | 39 | 94 | ND | ND | ND | ND | 30 |
208 | 7.26 | 102 | 75 | 452 | ND | ND | 29 | 78 | 10 | ND | ND | ND | 26 |
313 | 7.15 | 89 | 50 | 400 | ND | ND | 30 | 55 | 16 | ND | ND | ND | 22 |
207 | 7.22 | 93 | 89 | 536 | ND | ND | 28 | 99 | 15 | ND | ND | ND | 21 |
Standard limit (≤) | / | / | 200 | / | / | 50 | 100 | 250 | 30 | / | 0.30 | 0.50 | 300 |
Remarks: ND: Not detected.
Area | Sample number | Pi | Comprehensive pollution index | |||||
---|---|---|---|---|---|---|---|---|
Cr | Zn | Ni | As | Pb | Cu | |||
City Proper | 62 | 0.50 | 0.34 | 0.38 | 0.20 | 0.09 | 0.21 | 0.41 |
Countryside | 7 | 0.43 | 0.19 | 0.08 | / | 0.03 | 0.32 | 0.24 |
From
From the above investigations, the followings are concluded:
1) The contains of heavy metals and organ chlorine pesticides in the soil of the Northern Yangtze River area are low, abundant in the organics, N, P, K are obviously insufficient but in some areas the organic content is low and organic fertilizers should be added.
2) The total content of heavy metals in urban soils of Northern Yangtze River area is not very high, and the soil environment quality is good. In terms of the average pollutant index level of heavy metals, there is no pollution, but the heavy metal content in some regions is high, which leads to relatively high potential hazard.
Min Tang,Jianping Hou, (2016) Statistical Analysis and Evaluation of Heavy Metal Ions in Soil Environment. Open Access Library Journal,03,1-8. doi: 10.4236/oalib.1102690