Quality of water in the subsidence area related to coal mining is important for water usage in the coal mining areas. In this study, forty-two samples from the subsidence pools in the Luling coal mine, northern Anhui Province, China have been collected and measured for their major ion concentrations, and the data have been applied for quality evaluating of drinking and irrigation purposes. The results suggest that the water samples from different pools have different concentrations of major ions and all of them can be classified to be Na-HCO3 type. According to the results of water quality index, all of them are suitable for drinking (considering only about the major ion concentrations). However, sodium absorption ratio (SAR) and residual sodium carbonate (RSC) give different answers about irrigation purpose, the water can be used for irrigation according to SAR whereas cannot be used according to RSC, and can be attributed to the high concentrations of CO32− and HCO3. Gibbs diagrams and relationships between Na+ normalized Ca2+, Mg2+ and HCO3 suggest that different extents of contributions from weathering of silicate, dissolution of carbonates and evaporates are the main mechanism controlling the major ion concentrations of water from the subsidence areas in this study, which is related to the natural conditions of the pools.

INTRODUCTION

Coal mining has greatly contributed to the development of the economy and society in China with the social-economic development, because more than 50% of the primary energy was contributed by coal during the recent years. However, more than 90% of the coal production comes from underground (Yao et al. 2010), and a series of geological and environmental problems have been induced (e.g. contamination of water, soil and air, ground subsidence and other engineering geological hazard) (Li et al. 2007), which have severely affected the life of human, ecological environment and the development of regional economy in mining areas (Yang & Liu 2012).

Among those problems, subsidence related to coal mining is a common environmental geologic hazard, which can not only destroy the construction and vegetation, but also have an influence on the surface water and groundwater systems that may seriously deteriorate the ecological environment of mining areas (Yin 1997). And now, it has been considered to be the most serious one among the environmental problems related to coal mining: the increasing of the area of the subsidence is up to 130 km2 per year and the subsidence land area has raised up to 700,000 km2 by the end of 2006 (Meng et al. 2009).

Water shortage in China is serious, especially in coal mining areas. Previous studies revealed that more than 71% of the coal mining areas in China were lacking of water and 40% of them were serious (Gui et al. 2011). And therefore, the large amount of water in the subsidence area might be a good choice for solving the issue except for the water from underground (Gui et al. 2009). And therefore, the restoration of the subsidence area is becoming more and more important and attracted large number of studies. These studies suggested that the main techniques related to restoration include improvement of soil, vegetation, and applications of soil animals and micro-organisms (Liu & Lu 2009).

However, the subsidence area is a system can be affected by multi factors, including natural and anthropogenic (e.g. water rock interaction, precipitation, evaporation and waste dispose). Therefore, before the application of the water in the subsidence area, the quality evaluation, as well as the source of the chemical constitutes in the water should be firstly understood, because these studies will determine whether the water can be used or, how to use.

In this study, a total of forty-two water samples have been collected from the subsidence water area in the Luling coal mine, a representative coal mine in northern Anhui Province, China, and their major ion concentrations have been measured for evaluating the quality of the water (drinking and irrigation) and identifying the main mechanisms controlling the chemical variations of the water. The study can provide information for the usage of the water and the management of the subsidence area.

MATERIALS AND METHODS

Study area

There are five coal mines located in the region of Suzhou City: the Zhu Xianzhuang and Luling coal mines in the southeast, and the Taoyuan-Qinan-Qidong coal mines in the south. The Luling coal mine is located 20 km southeast to the Suzhou City (GPS: E117°06′30″, N33°35′59″) (Figure 1). The annual production of coal is 1.5 million tons and the designed service life is 66 years.
Figure 1

Location of the study area (I, II, III and IV are sample locations in subsidence water areas around the Luling coal mine).

Figure 1

Location of the study area (I, II, III and IV are sample locations in subsidence water areas around the Luling coal mine).

The main coal seams in the coal mine are 8th and 10th. After coal mining, eight subsidence areas have been formed before 2002, including 81, 82, 83, 84, 86, 88, 101 and 102 (Wang et al. 2002). And the area has been increased up to 1,000 acres today. Most of the subsidence depth is higher than 7 m, and the water depth is near 3 m (Figure 1).

Analytical methods

A total of forty two water samples have been collected from the 81, 82, 83, 84 subsidence water areas (12, 13, 10 and 7 samples from pools I, II, III and IV in the Figure 1, respectively). Concentrations of eight kinds of major ions (Na+, K+, Ca2+, Mg2+, Cl, SO42–, and CO32−) and total dissolved solids (TDS) have been analyzed. The analytical methods are as follows: Na+, K+, Ca2+, Mg2+, Cl and were analyzed by ion chromatography, whereas and CO32− were analyzed by acid–base titration in the Engineering and Technological Research Center of Coal Exploration, Anhui Province, China.

RESULTS AND DISCUSSIONS

Ion concentrations

The analytical results of the major ion concentrations are listed in Table 1 and shown in Figure 2. As can be seen from the table, samples from same subsidence pool have similar major ion concentrations, whereas the major ion concentrations of samples from different subsidence pools vary significantly: Na+, K+, Ca2+, Mg2+, Cl, , and concentrations for samples from these four pools are 115–151, 2.81–6.60, 13.6–25.0, 12.9–20.8, 41.6–55.0, 69.4–114, 347–604 and 0–111 mg/l, respectively. The decreasing order of mean concentrations of major ions are (433 mg/l) >Na+ (136 mg/l) > (93.0 mg/l) >Cl (50.4 mg/l) >CO32− (33.7 mg/l) >Ca2+ (17.7 mg/l) >Mg2+ (16.0 mg/l) >K+ (4.04 mg/l). The Total dissolved solids (TDS) varied from 475 to 680 mg/l (mean = 568 mg/l), which is similar to fresh water (<1,000 mg/l).
Table 1

Mean major ion concentrations of water from the subsidence areas (mg/l)

ID Na+ K+ Ca2+ Mg2+ Cl SO42− HCO3 CO32− TDS 
I (n = 12) 141 3.03 14.2 13.1 51.8 113 372 34.6 556 
II (n = 13) 116 3.82 15.6 15.1 44.7 74.9 365 43.4 496 
III (n = 10) 149 4.30 24.8 20.6 54.2 86.1 571 17.8 642 
IV (n = 7) 149 5.84 17.7 15.8 53.3 103 466 37.1 614 
ID Na+ K+ Ca2+ Mg2+ Cl SO42− HCO3 CO32− TDS 
I (n = 12) 141 3.03 14.2 13.1 51.8 113 372 34.6 556 
II (n = 13) 116 3.82 15.6 15.1 44.7 74.9 365 43.4 496 
III (n = 10) 149 4.30 24.8 20.6 54.2 86.1 571 17.8 642 
IV (n = 7) 149 5.84 17.7 15.8 53.3 103 466 37.1 614 

Note: I, II, III and IV are symbols of different pools.

Figure 2

Piper diagram.

Figure 2

Piper diagram.

Comparatively, samples from the pool I have the lowest mean concentrations of K+ (3.03 mg/l), Ca2+ (14.2 mg/l) and Mg2+ (13.1 mg/l) but highest mean concentration of (113 mg/l), samples from the pool II have the lowest mean concentrations of Na+ (116 mg/l), Cl (44.7 mg/l), (74.9 mg/l) and (365 mg/l). However, samples from the pool III have the highest mean concentrations of Na+ (149 mg/l), Ca2+ (24.8 mg/l), Mg2+ (20.6 mg/l), Cl (54.2 mg/l) and (571 mg/l), whereas samples from the pool IV have the highest mean concentrations of K+ (5.84 mg/l).

Hydrochemical facies

Classification of hydro-chemical types for groundwater is important because of the dominant anion species of water change systematically from , to Cl as groundwater flows from the recharge zone to the discharge zone (e.g. Toth 1999). However, it is also important for surface water because it can provide information for determine the main mechanism controlling the water chemistry as evaporation controlling tends to obtain higher concentrations of and Cl relative to .

Classification of water in this study is based on the concentration of cations and anions by using Aquachem and Piper diagram, and the result is shown in Figure 2. The result indicates that all of the water samples are classified to be Na–HCO3 types, suggesting that evaporation is not important for the chemistry of these water samples. Moreover, slight differences can be found in Figure 2 that samples from pool I have relative higher concentrations of relative to other samples, which might be an indication of higher contribution of evaporation in pool I relative to other pools.

Quality evaluation for drinking

The water quality index (WQI) was calculated for evaluating the quality for drinking based on several key parameters of water chemistry, which has long been used for groundwater and surface water (Ramakrishnaiah et al. 2009; Vasanthavigar et al. 2010). To calculate the WQI, the weight has been assigned for the physico-chemical parameters according to the parameters relative importance in the overall quality of water for drinking water purposes. The assigned weight ranges from 1 to 5. The maximum weight of 5 has been assigned for TDS, Cl and , 4 for Na+, 3 for Ca2+ and Mg2+ (Varol & Davraz 2015). The relative weight is computed from the following equation: 
formula
1
where Wi is the relative weight, wi is the weight of each parameter, n is the number of parameters. 
formula
2
where Qi is the quality rating, Ci is the concentration of each chemical parameter (mg/l), and Si is the World Health Organization standard (Na+ 200 mg/l, Ca2+ 300 mg/l, Mg2+ 30 mg/l, Cl 250 mg/l, 250 mg/l, TDS 1,500 mg/l) (WHO 2008). 
formula
3

Based on results, the quality of the water for drinking can be classified to be five classes (excellent <50, good 50–100, poor 100–200, very poor 200–300 and unsuitable >300). The WQI for the water from the subsidence area in this study have WQI range from 29.4 to 39.3 (mean = 35.2), suggesting that these water are excellent for drinking when considering about only their major ion concentrations. However, the water from the four pools have different water qualities, samples from pool II have the lowest WQI (mean = 30.5), whereas samples from the pool III have the highest WQI (mean = 38.9).

Quality evaluation for irrigation

There are several parameters have been applied for quality evaluation of irrigation, including sodium absorption ratio (SAR), percentage sodium (% Na) and permeability index (PI), residual sodium carbonate (RSC), Kelly's ratio and magnesium ratio. In this study, the most popular applied parameters (SAR and RSC) have been chosen for quality evaluation for irrigation.

The index used is the Sodium Adsorption Ratio (SAR) that expresses the relative activity of sodium ions in the exchange reactions with the soil. This ration measures the relative concentration of sodium to calcium and Magnesium. SAR is an important parameter for determining the suitability of groundwater for irrigation. Excess sodium concentration can reduce the soil permeability and soil structure (Todd 1995). Irrigation using water with high sodium adsorption ratio may require soil amendments to prevent long-term damage to the soil (Michael et al. 2008). SAR is a measure estimated by 2 × Na+/(Ca2+ + Mg2+) (in meq/l). The calculated values of SAR in this study ranges from 4.37 to 7.07 (mean = 5.54), and all of the samples were within permissible limit (<10).

RSC exists in irrigation water when the carbonate (CO3) plus bicarbonate (HCO3) content exceeds the calcium (Ca2+) plus magnesium (Mg2+) content of the water. An excess value of RSC in water leads to an increase in the adsorption of sodium in soil (Eaton 1950). The results of this include direct toxicity to crops, excess soil salinity (EC) and associated poor plant performance, and where appreciable clay or silt is present in the soil, loss of soil structure and associated decrease in soil permeability. RSC is a measure employed by calculating -(Ca2+ + Mg2+) (Ragunath 1987). RSC value <1.25 meq/l indicates good water quality. If the value of RSC is between 1.25 and 2.5 meq/l, the water is slightly suitable while a value >2.5 meq/l the water is considered as unsuitable for irrigation. RSC values in this study range from 4.66 to 8.99 meq/l (mean = 6.02 meq/l) and suggesting that all of the water samples cannot be used for irrigation purpose.

Such results indicate that the water in this study have suitable Na+ concentrations relative to Ca2+ and Mg2+, however, they have higher concentrations of and relative to Ca2+ and Mg2+. The former will not lead to the decreasing of infiltration and permeability of the soil, whereas the latter can drastically reduce its infiltration capacity. And therefore, Ca2+ and Mg2+ should be added before the application of the water for irrigation, because it can balance additional and in the water.

Mechanism controlling water chemistry

Gibbs (1970) proposed a diagram to understand the relationship of the chemical components of water from their respective aquifer lithology. Various factors controlling groundwater chemistry are analyzed by the diagram. Gibbs diagram consists of three distinct fields namely precipitation dominance, evaporation dominance and rock dominance. Further, the Gibbs ratios are calculated by: Gibbs ratio and Gibbs ratio II = (Na+ + K+)/(Na+ + K+ + Ca2+) (in meq/l). In the present study, Gibbs ratio I values varied from 0.13 to 0.20 and Gibbs ratio II values varied from 0.69 to 0.78. From Figure 3, it is clear that all of the samples fell under rock dominance area with Gibbs ratio I, whereas the samples plotted outside the evaporation-rock-precipitation area according to Gibbs ratio II. The former indicates that water-rock interaction plays an important role in controlling the water chemistry in this study, whereas the later might be affected by the lower concentrations of Ca2+ and Mg2+ relative to Na+.
Figure 3

Gibbs diagrams.

Figure 3

Gibbs diagrams.

Moreover, it can be obtained from Figure 4 that the water samples in this study have Ca2+/Na+ and Mg2+/Na+ ratios range from 0.11 to 0.19 and 0.17 to 0.26, respectively and suggest that dissolution of evaporate minerals cannot be ruled out, whereas weathering of silicate minerals and/or dissolution of carbonate minerals might also occurred in the pools. It is also supported by the correlation between Ca2+/Na+ and /Na+ (0.96 – 1.53) (Figure 4).
Figure 4

Na+ normalized Ca2+-HCO3 and Ca2+-Mg2+ plots.

Figure 4

Na+ normalized Ca2+-HCO3 and Ca2+-Mg2+ plots.

For getting more information about the source of major ions in the water, statistical analysis, including factor analysis and EPA Unmix model have been applied, which have long been used for quantifying the source of major ions in the groundwater (Sun 2015). With eigenvalue higher than one after varimax rotation, two factors have been obtained (Table 2). As can be seen from the table, factor one has high positive loadings of Mg2+, Ca2+ and , which accounts for 62.0% of the total variance, whereas factor two has high loadings of Na+, Cl and , which accounts for 27.0% of the total variance. According to the discussions above, as well as the relationships between major ions during dissolution or weathering of minerals, factor one and two can be explained to be carbonate and evaporate factors, respectively.

Table 2

Results of factor analysis

  Na+ K+ Mg2+ Ca2+ Cl SO42− HCO3 TDS Eigenvalue % variance 
Factor 1 0.35 0.24 0.98 0.97 0.38 − 0.44 0.88 0.60 4.96 62.0 
Factor 2 0.91 0.09 0.01 0.17 0.91 0.89 0.35 0.70 2.16 27.0 
  Na+ K+ Mg2+ Ca2+ Cl SO42− HCO3 TDS Eigenvalue % variance 
Factor 1 0.35 0.24 0.98 0.97 0.38 − 0.44 0.88 0.60 4.96 62.0 
Factor 2 0.91 0.09 0.01 0.17 0.91 0.89 0.35 0.70 2.16 27.0 

As to the analysis of Unmix model, three sources have been identified (Table 3) with Min Rsq = 1.00 (>0.8) and Min Sig/Noise = 5.35 (>2), which suggest that 100% of the information can be modeled by Unmix and the results are reliable (Ai et al. 2014). As can be seen from Table 3, source 2 has the lowest ratios of Ca2+/Na+ (0.10), Mg2+/Na+ (0.16) and HCO3/Na+ (0.88), whereas source 3 has the highest ratios (0.21, 0.29 and 1.53, respectively), and these ratios of source 2 are in the medium. And therefore, source 1, 2 and 3 can be explained to be silicate, evaporate and carbonate sources. In consideration with their contributions (Figure 5), samples from the pool III have the highest contributions from the carbonate source, which is consistent with the truth that that pool is surrounded by coal gangue, whose main mineral compositions are carbonate rocks. Moreover, samples from the pool I has the highest loadings of the evaporate source, it is also consistent with the truth that that pool is independent from other pools.
Table 3

Source compositions (mg/l)

 Na+ K+ Mg2+ Ca2+ Cl SO42− HCO3 TDS 
Source 1 35.1 1.78 3.71 3.75 12.8 24 106 148 
Source 2 47.1 0.728 3.93 4.17 17.4 40.4 110 182 
Source 3 54.1 1.53 8.26 9.84 20 28.7 219 238 
 Na+ K+ Mg2+ Ca2+ Cl SO42− HCO3 TDS 
Source 1 35.1 1.78 3.71 3.75 12.8 24 106 148 
Source 2 47.1 0.728 3.93 4.17 17.4 40.4 110 182 
Source 3 54.1 1.53 8.26 9.84 20 28.7 219 238 
Figure 5

Source contributions (samples 1–12, 13–25, 26–35 and 36–42 are samples from pools I, II, III and IV, respectively).

Figure 5

Source contributions (samples 1–12, 13–25, 26–35 and 36–42 are samples from pools I, II, III and IV, respectively).

CONCLUSIONS

Based on the major ion concentrations of water samples from the subsidence area in the Luling coal mine, northern Anhui Province, China, the following conclusions have been obtained:

  1. Water samples from different subsidence pools have different concentrations of major ions, whereas all of them are classified to be Na-HCO3 type;

  2. All of the samples have WQI range from 29.4 to 39.3 (mean = 35.2), suggesting that they are excellent for drinking when considering about only their major ion concentrations;

  3. SAR and RSC values for the samples are 4.37 to 7.07 (mean = 5.54) and 4.66 to 8.99 (mean = 6.02), respectively, lower than the permissible limit of SAR (<10) but higher than the permissible limit of RSC (<2.5), respectively, which is due to the higher concentrations of and relative to Ca2+ and Mg2+;

  4. Gibbs diagrams and correlations between Na+ normalized Ca2+, Mg2+ and suggest, as well as statistical analysis indicate that different kinds and extents of water rock interactions are responsible for the chemical variations of water samples in this study.

ACKNOWLEDGEMENTS

This work was financially supported by National Natural Science Foundation of China (41302274), the Foundation of Scholarship Leaders in Suzhou University (2014XJXS05) and the Foundation of Scientific Platform in Suzhou University (2014YKF05).

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Appendix

Detailed analytical results of major ion concentrations (mg/l)

ID Na+ K+ Ca2+ Mg2+ Cl SO42− HCO3 CO32− TDS 
I-1 140 3.06 14.2 12.9 51.5 113 362 29.7 545 
I-2 140 3.13 14.3 12.9 52.1 113 362 44.5 561 
I-3 143 3.11 14.1 12.9 51.1 113 377 29.7 555 
I-4 140 3.06 14.1 13.0 51.5 111 392 29.7 558 
I-5 140 3.06 14.0 12.9 51.5 111 362 29.7 543 
I-6 140 3.08 14.3 13.0 51.7 113 362 29.7 546 
I-7 139 2.81 14.9 13.6 52.7 113 362 29.7 547 
I-8 142 2.91 13.6 13.2 51.9 114 362 44.5 563 
I-9 139 2.91 14.0 13.7 51.7 110 377 44.5 564 
I-10 141 3.03 14.8 13.2 52.0 114 392 44.5 579 
I-11 141 3.13 14.4 13.0 51.9 114 377 29.7 556 
I-12 142 3.02 14.2 12.9 51.9 111 377 29.7 553 
II-1 117 3.91 15.9 15.2 45.1 75.5 362 59.4 513 
II-2 116 3.83 15.8 15.1 44.5 75.3 362 44.5 496 
II-3 116 3.89 15.4 15.1 45.2 75.0 362 29.7 481 
II-4 116 3.83 15.7 15.1 45.1 74.8 377 44.5 504 
II-5 116 3.82 15.3 15.1 44.8 75.3 347 44.5 488 
II-6 115 3.80 15.3 15.0 44.9 74.8 377 44.5 502 
II-7 116 3.71 15.4 15.1 41.6 69.4 377 14.8 465 
II-8 116 3.77 15.6 15.1 44.9 75.7 347 59.4 504 
II-9 116 3.76 15.7 15.2 44.2 74.5 347 44.5 487 
II-10 116 3.80 15.7 15.1 45.1 75.6 362 59.4 512 
II-11 116 3.84 15.8 15.1 45.4 76.2 377 44.5 505 
II-12 115 3.75 15.5 15.0 44.8 75.8 377 44.5 503 
II-13 117 3.91 15.2 15.2 45.3 75.8 377 29.7 491 
III-1 148 4.27 24.3 20.6 54.1 86.8 589 44.5 677 
III-2 148 4.32 24.8 20.6 53.1 85.0 559 615 
III-3 149 4.32 25.0 20.8 54.2 87.2 604 643 
III-4 148 4.26 24.9 20.7 53.7 84.2 589 630 
III-5 148 4.31 24.5 20.6 53.9 86.6 498 74.2 661 
III-6 148 4.31 24.6 20.5 53.8 86.2 574 624 
III-7 149 4.27 24.8 20.6 54.3 85.8 574 626 
III-8 150 4.34 25.0 20.7 55.0 86.8 604 644 
III-9 149 4.33 24.8 20.6 54.8 86.1 574 627 
III-10 149 4.30 24.9 20.6 54.6 86.4 543 59.4 671 
IV-1 148 6.46 16.9 15.7 53.2 102 483 584 
IV-2 147 6.60 17.0 15.6 53.0 102 513 598 
IV-3 148 6.59 17.0 15.7 53.3 102 453 111 680 
IV-4 151 5.52 18.3 15.8 54.2 105 468 29.7 614 
IV-5 148 5.53 18.3 15.8 52.8 103 468 29.7 607 
IV-6 149 5.13 18.7 16.0 53.1 103 423 44.5 601 
IV-7 149 5.07 17.8 15.7 53.4 103 453 44.5 615 
ID Na+ K+ Ca2+ Mg2+ Cl SO42− HCO3 CO32− TDS 
I-1 140 3.06 14.2 12.9 51.5 113 362 29.7 545 
I-2 140 3.13 14.3 12.9 52.1 113 362 44.5 561 
I-3 143 3.11 14.1 12.9 51.1 113 377 29.7 555 
I-4 140 3.06 14.1 13.0 51.5 111 392 29.7 558 
I-5 140 3.06 14.0 12.9 51.5 111 362 29.7 543 
I-6 140 3.08 14.3 13.0 51.7 113 362 29.7 546 
I-7 139 2.81 14.9 13.6 52.7 113 362 29.7 547 
I-8 142 2.91 13.6 13.2 51.9 114 362 44.5 563 
I-9 139 2.91 14.0 13.7 51.7 110 377 44.5 564 
I-10 141 3.03 14.8 13.2 52.0 114 392 44.5 579 
I-11 141 3.13 14.4 13.0 51.9 114 377 29.7 556 
I-12 142 3.02 14.2 12.9 51.9 111 377 29.7 553 
II-1 117 3.91 15.9 15.2 45.1 75.5 362 59.4 513 
II-2 116 3.83 15.8 15.1 44.5 75.3 362 44.5 496 
II-3 116 3.89 15.4 15.1 45.2 75.0 362 29.7 481 
II-4 116 3.83 15.7 15.1 45.1 74.8 377 44.5 504 
II-5 116 3.82 15.3 15.1 44.8 75.3 347 44.5 488 
II-6 115 3.80 15.3 15.0 44.9 74.8 377 44.5 502 
II-7 116 3.71 15.4 15.1 41.6 69.4 377 14.8 465 
II-8 116 3.77 15.6 15.1 44.9 75.7 347 59.4 504 
II-9 116 3.76 15.7 15.2 44.2 74.5 347 44.5 487 
II-10 116 3.80 15.7 15.1 45.1 75.6 362 59.4 512 
II-11 116 3.84 15.8 15.1 45.4 76.2 377 44.5 505 
II-12 115 3.75 15.5 15.0 44.8 75.8 377 44.5 503 
II-13 117 3.91 15.2 15.2 45.3 75.8 377 29.7 491 
III-1 148 4.27 24.3 20.6 54.1 86.8 589 44.5 677 
III-2 148 4.32 24.8 20.6 53.1 85.0 559 615 
III-3 149 4.32 25.0 20.8 54.2 87.2 604 643 
III-4 148 4.26 24.9 20.7 53.7 84.2 589 630 
III-5 148 4.31 24.5 20.6 53.9 86.6 498 74.2 661 
III-6 148 4.31 24.6 20.5 53.8 86.2 574 624 
III-7 149 4.27 24.8 20.6 54.3 85.8 574 626 
III-8 150 4.34 25.0 20.7 55.0 86.8 604 644 
III-9 149 4.33 24.8 20.6 54.8 86.1 574 627 
III-10 149 4.30 24.9 20.6 54.6 86.4 543 59.4 671 
IV-1 148 6.46 16.9 15.7 53.2 102 483 584 
IV-2 147 6.60 17.0 15.6 53.0 102 513 598 
IV-3 148 6.59 17.0 15.7 53.3 102 453 111 680 
IV-4 151 5.52 18.3 15.8 54.2 105 468 29.7 614 
IV-5 148 5.53 18.3 15.8 52.8 103 468 29.7 607 
IV-6 149 5.13 18.7 16.0 53.1 103 423 44.5 601 
IV-7 149 5.07 17.8 15.7 53.4 103 453 44.5 615