Water Chemistry of Typical Forestry at Zhangjiakou Site for 2022 Winter Olympics

To improve the water ecology in the forest at Chongli (the Peace Forest) of Zhangjiakou, Hebei in preparation for the upcoming 2022 Winter Olympics, the water chemistry of four typical forest types in the area was studied. The Picea wilsonii, Betula platyphylla, Pobulus davidiana and Larix principis-rupprechtii forestry were compared regarding the distribution of precipitation and the chemistry of rainfall, throughfall, stemflow, and surface runoff. The chemical oxygen demand (COD), ammonia nitrogen (NH₃-N), total nitrogen (TN) and total phosphorus (TP) in rainwater were determined by the methods of digestion, salicylic acid, persulfate oxidation, and ascorbic acid digestion, respectively. The results showed that:(1) the rains that fell through the tree canopy layer (throughfall) contained increasing COD and TN, but decreasing NH₃-N and TP, as compared to those outside the four forestry; (2) in the stemflow, the COD, NH₃-N, TN, and TP were higher inside than outside the four forestry; (3) the COD, TN and TP of surface runoff in the four forestry increased, while NH₃-N declined, as compared to the rain water outside the forest; and (4) the comprehensive indices on water chemistry were 0.65 for the rain fell outside the forest, 0.95 for the P. davidiana forestry, 2.09 for the P. wilsonii forestry, 1.30 for the B. platyphylla forestry, and 2.32 for the L. principis-rupprechtii forestry. Rainfalls seemed to exert a considerable effect on the chemicals leached in forest. With rainfalls, the net leaching of NH₃-N, TN and TP in the throughfall, stemflow and surface runoff at the forestry became negative, indicating that the trees were capable of reducing ammonia nitrogen in rainwater resulting in some water purification effect benefiting the ecology of the environment surrounding the forestry.