Abstract Green and/or black soiling on building facades worldwide is caused by airborne algae, which has strong drought tolerance and grows in the atmosphere. Poikilohydric plants such as algae and lichens have high heat resistance under dry conditions and high thermo-sensitivity under wet conditions. However, there have been no studies of heat shock treatments against airborne algae adhering to surfaces. This study investigated the relationship between heat shock conditions (treatment temperature and duration and the water content of algae) and algal mortality. Algae collected from the exterior wall of a building were heat-treated in a laboratory, and their chlorophyll fluorescence intensity was measured. The following results were obtained: (a) higher treatment temperature and longer treatment time increased the rate of algal death, (b) the survival rate of heat-treated dry algae was higher than that of wet algae and recovered after the treatment, and (c) the effects of continuous and intermittent heat shock were similar, and algal mortality increased with the total treatment time. It was concluded that the airborne algae died after heat shock treatment at 35 °C for 24 h and at 40 °C after 6 h under wet conditions. Algae from an exterior concrete wall were heat-treated in a wet condition, and algal death was confirmed by the decrease in surface L* values and a color change from green to yellow.

中文翻译：

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热休克处理引起的空气传播藻类死亡率的测量

摘要 世界范围内建筑外墙的绿色和/或黑色污染是由空气传播的藻类引起的，藻类具有很强的耐旱性并在大气中生长。藻类和地衣等变水植物在干燥条件下具有较高的耐热性，在潮湿条件下具有较高的热敏性。然而，还没有针对粘附在表面的空气传播藻类进行热休克处理的研究。本研究调查了热休克条件（处理温度和持续时间以及藻类的含水量）与藻类死亡率之间的关系。从建筑物外墙收集的藻类在实验室中进行热处理，并测量其叶绿素荧光强度。获得了以下结果：(a) 较高的处理温度和较长的处理时间增加了藻类死亡的速度，(b) 热处理干藻的存活率高于湿藻并在处理后恢复；(c) 连续和间歇热休克的效果相似，藻死亡率随着总处理时间的增加而增加。得出的结论是，空气中的藻类在 35°C 下热激处理 24 小时后死亡，在潮湿条件下在 40°C 下热激处理 6 小时后死亡。来自混凝土外墙的藻类在潮湿条件下进行热处理，通过表面 L* 值的降低和颜色从绿色变为黄色来确认藻类死亡。得出的结论是，空气中的藻类在 35°C 下热激处理 24 小时后死亡，在潮湿条件下在 40°C 下热激处理 6 小时后死亡。来自混凝土外墙的藻类在潮湿条件下进行热处理，通过表面 L* 值的降低和颜色从绿色变为黄色来确认藻类死亡。得出的结论是，空气中的藻类在 35°C 下热激处理 24 小时后死亡，在潮湿条件下在 40°C 下热激处理 6 小时后死亡。来自混凝土外墙的藻类在潮湿条件下进行热处理，通过表面 L* 值的降低和颜色从绿色变为黄色来确认藻类死亡。