Objective To develop a remover of formaldehyde in indoor air. Methods Activated carbon was used as the raw materials, potassium hydroxide as the activator. The activated carbon was modified through activation and impregnation. The influence factors for the formaldehyde adsorption property of activated carbons were evaluated, such as the size, activation temperature, activation time and impregnation time. Results The optimum technics conditions for developing the formaldehyde remover and the optimum conditions to absorb formaldehyde were confirmed. The mass adsorption capacity of the adsorbent was 49.6%, the BET surface area was about 1 591 m2/g and the total pore volume was 1.01 cm3/g. Conclusion The mass adsorption capacity of formaldehyde and the BET surface area of the modified activated carbon in the present paper are better than those of unmodified activated carbon.

Background With urbanization and residential space expansion, ecological environment and human health issues have become hot social topics. Forest health, as a way of seeking health in nature, has begun to receive public attention in the context of the gradually increasing sub-healthy population and various psychological and physical diseases at a young age. Objective To systematically evaluate the effects of forest therapy on selected physical and mental health indicators. Methods Relevant research literature was retrieved from domestic and international databases (China National Knowledge Infrastructure, Wanfang Database, China Biomedical Literature Service System, Web of Science, ScienceDirect, PubMed, Embase, and Cochrane Library), with a time range from database establishment to January 31, 2023. Relevant data were extracted for meta-analysis to explore the relationship between forest therapy and selected psychological and physiological indicators. Results A total of 85 articles were included, and the meta-analysis results showed that better scores of Profile of Mood States, Positive and Negative Affect Scale, Beck Depression Inventory, and State Trait Anxiety Scale were found in the forest group than those in the urban group (P<0.05); the levels of systolic blood pressure, diastolic blood pressure, heart rate, sympathetic nerve indicator [ln (LF/HF)], salivary cortisol, and serum inflammatory factors were lower in the forest group than in the urban group, while parasympathetic nerve indicator [ln (HF)] level was higher in the forest group than in the urban group (P<0.05). The results of subgroup analysis showed that the changes in heart rate (SMD=−1.62, 95%CI: −2.41, −0.82), ln (HF) (SMD=1.29, 95%CI: 0.73, 1.85), ln (LF/HF) (SMD=−1.49, 95%CI: −2.13, −0.86), and salivary cortisol (SMD=−0.53, 95%CI: −0.81, −0.25) were more significant when the duration of forest therapy was ≤ 0.5 h, the recovery effect on emotional state was better in the >0.5~3 h group (such as tension SMD=−2.40, 95%CI: −3.21, 1.59), and the reduction effects on systolic blood pressure (SMD=−0.53, 95%CI: −1.03, −0.03) and diastolic blood pressure (SMD=−0.42, 95%CI: −0.88, 0.04) were better in the >3 h group. Seated meditation showed better recovery effects on multiple indicators of Profile of Mood States (such as fatigue SMD=−2.26, 95%CI: −3.07, −1.45), while walking showed better recovery effects on physiological indicators such as blood pressure (systolic blood pressure SMD=−0.57, 95%CI: −1.07, −0.06; diastolic blood pressure SMD=−0.72, 95%CI: −1.36, −0.07) and heart rate (SMD=−1.51, 95%CI: −2.38, -0.64). Except for blood pressure, the health benefits of forest therapy in the younger age group were generally better than those in the middle-aged and elderly group. Conclusion Relaxed and comfortable psychological feeling is reported when practicing forest therapy; it can lower blood pressure and heart rate, regulate the autonomic nervous system; it can also reduce the release of stress hormones and lower serum levels of inflammatory factors, exerting an auxiliary recovery effect on cardiovascular and immune system disorders. At the same time, the therapy duration, form, and age of the subjects have a certain impact on the effects of forest therapy practice.