## 3 Results
### Concentrations of Heavy Metals in Farmland Soil Dominated by Husbandry
#### 3.2.2 Concentrations of Heavy Metals in Soil Planted with Hulless Oats  
The statistics of heavy metals in soil planted with hulless oats is shown in Table 1. The pH of the soil ranged from 6.83 to 8.70. Namely, 72% of the soil samples had a pH greater than 7.5. The soil is weakly alkaline.  
Mean concentrations of Cd, Cu, Pb, Zn, Cr, As, Hg, and Ni were 0.2, 34.4, 14.3, 79.0, 88.1, 8.4, 0.07, and 72.2, respectively. The average contents of Cd, Cu, Pb, Zn, Cr, As, Hg, and Ni were lower than the screening value, respectively, indicating that there was no pollution risk in soil planted with hulless oats. However, the Cd, Hg, and Ni at 8%, 4%, and 8% of samples exceeded the screening value, respectively, indicating that Cd, Hg, and Ni were enriched in some samples. Similarly, Cd surpassing the screening value was observed in the farmland of Anxin county of Hebei province [55].  
The coefficient of variation of Cu, Cd, Pb, Zn, As, Cr, and Ni fell into the category of medium variability, and CV was highest for Hg (716%), which belonged to the category of strong variability, suggesting that some specific samples have very high concentrations. Such high concentrations may be the result of anthropogenic contamination. About 80% of  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline \hline \multicolumn{1}{c}{**Element**} & \multirow{2}{*}{**Min 1**} & \multirow{2}{*}{**Max 2**} & \multirow{2}{*}{**Median**} & \multirow{2}{*}{**Mean**} & \multirow{2}{*}{**SD 3**} & \multicolumn{3}{c}{**CV 4**} & \multicolumn{3}{c}{**Higher than Risk**} \\  & & & & & & & & & & **(\%)** & & **Screening Value 5 (\%)** \\ \hline \multirow{3}{*}{Cd} & P 6 & O 7 & P & O & P & O & P & O & P & O & P & O & P & O \\  & 0.05 & 0.07 & 0.34 & 0.97 & 0.18 & 0.17 & 0.18 & 0.20 & 0.06 & 0.17 & 36 & 83 & 0 & 8 \\ Cu & 19.72 & 20.45 & 40.72 & 54.84 & 27.76 & 31.70 & 28.90 & 34.43 & 5.54 & 10.76 & 19 & 31 & 0 & 0 \\ Pb & 2.96 & 2.58 & 20.36 & 21.45 & 16.22 & 15.43 & 15.44 & 14.31 & 3.38 & 4.16 & 22 & 29 & 0 & 0 \\ Zn & 48.37 & 52.81 & 95.84 & 122.53 & 68.68 & 74.82 & 69.39 & 79.01 & 11.63 & 21.82 & 17 & 28 & 0 & 0 \\ Cr & 15.79 & 24.8 & 107.63 & 124.24 & 80.11 & 90.16 & 78.43 & 88.12 & 17.17 & 22.90 & 22 & 26 & 0 & 0 \\ As & \(-8.50\) & \(-8.48\) & 14.15 & 14.18 & 8.43 & 8.58 & 8.37 & 8.37 & 4.08 & 4.29 & 49 & 51 & 0 & 0 \\ Hg & \(-0.18\) & \(-0.24\) & 0.25 & 2.42 & 0.02 & 0.02 & 0.02 & 0.07 & 0.10 & 0.51 & 405 & 716 & 0 & 4 \\ Ni & 33.87 & 36.32 & 76.89 & 141.37 & 51.63 & 56.58 & 53.09 & 72.22 & 15.73 & 31.24 & 20 & 43 & 0 & 8 \\ pH & 6.86 & 6.83 & 8.92 & 8.7 & 8.10 & 8.09 & 8.06 & 7.95 & & & & & \\ \hline \hline \end{tabular}  
* Minimum value; 2 Maximum value; 3 The standard deviation; 4 The coefficient of variation; 5 Risk screening value is shown in Table S1; 6 Soil planted with potato; 7 Soil planted with hulless oats.  
\end{table}
Table 1: Concentrations of eight heavy metals in soils planted with potato and hulless oats.  
anthropogenic sources of Hg result from fuel combustion, waste incineration or exhaust emissions [54]. The sources of heavy metals are different because of different types of land use and surrounding human activities. Thus, the sources of heavy metals in this survey region need to be identified according to a specific manner [44].