import matplotlib.pyplot as plt
ax=plt.subplot(111)
ax.text(0.1,0.8,r"$PM2.5 [ug/{m^3}]$",fontsize=30,color="red")
# ax.text(0.1,0.3,r"$\sum_{n=1}^\infty\frac{-e^{i\pi}}{2^n}!$",fontsize=30)
plt.show()