为什么大多数天然淡水(如湖泊水)的 pH 能长期稳定在 6–9 之间,而不会因持续吸收大气 CO2 或接受酸性沉降而无限酸化?
Why does the pH of most natural freshwaters, such as lake water, stay stable between 6 and 9 over long periods instead of becoming ever more acidic through continued CO2 uptake and acid deposition?
天然水体依靠碳酸盐缓冲体系(HCO3-/CO32-)工作:外加的 H+ 或 OH- 被碳酸的两级平衡反应消耗,pH 被钳制在 pKa 约 6.3 与 10.3 之间。缓冲容量来自流域内方解石、白云石等碳酸盐矿物风化溶解所积累的碱度。因此在同等酸负荷下,天然水的 pH 漂移远小于纯水,只有碱度耗尽后才会发生明显酸化。
Natural waters rely on the bicarbonate/carbonate buffer system: added H+ or OH- is consumed by the coupled carbonic acid equilibria, holding pH between the two pKa values of H2CO3, about 6.3 and 10.3. The buffering capacity comes from alkalinity accumulated through weathering dissolution of carbonate minerals such as calcite and dolomite in the catchment. Under the same acid load, pH therefore shifts far less than in pure water, and marked acidification occurs only once alkalinity is exhausted.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 来源待核验 · Source pending review
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出处备注：此条未指向带版次的可引用著作（通识性内容、机构文件或未展开的英文书名），本库不提供独立书目出处；如需精确引用，需由编辑补全具体篇目与版次。
Stumm W., Morgan J. J., Aquatic Chemistry, 3rd ed., Wiley, 1996, 第 8 章(碳酸盐平衡)
Stumm W., Morgan J. J., Aquatic Chemistry, 3rd ed., Wiley, 1996, Ch. 8 (carbonate equilibria)
#碳酸盐缓冲 #水体碱度
自来水厂为什么先加明矾再过滤？
Why do water plants add alum before filtering?
明矾水解产生带正电的氢氧化铝絮团，能吸附悬浮颗粒并沉到一起，方便后续过滤去掉浊物。
Alum hydrolyzes to positively charged aluminum hydroxide flocs that grab suspended particles and clump, letting filtration remove the turbidity.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#明矾 #絮凝 #净水
自来水为什么要加氯消毒？
Why is chlorine added to tap water?
氯在水中生成次氯酸，能氧化并杀灭细菌、病毒等病原微生物，成本低且余氯还能持续保护管网。
Chlorine forms hypochlorous acid that oxidizes and kills pathogens; it is cheap and residual chlorine keeps pipes safe.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#自来水 #氯 #消毒
天然水体的碱度由哪些组分构成?为什么说它比pH更能反映水体抵抗酸化的能力?
What species make up the alkalinity of natural waters, and why does alkalinity reflect resistance to acidification better than pH does?
碱度是水中接受质子的总容量,天然淡水以碳酸氢根为主,再计入碳酸根、氢氧根以及少量硼酸盐和有机酸盐。pH只给出当前的氢离子活度,碱度则代表缓冲储备,决定外来酸进入时pH下坠的幅度。灰岩流域湖水的碱度可达每升一百毫克碳酸钙当量,而花岗岩流域水体碱度趋近于零,对酸沉降敏感得多。
Alkalinity is the total proton-accepting capacity of a water; in natural freshwaters bicarbonate dominates, joined by carbonate, hydroxide, minor borate, and organic anions. pH reports only the instantaneous hydrogen-ion activity, whereas alkalinity measures the buffer reserve that sets how far pH will plunge when acid arrives. Lakes on limestone bedrock can carry alkalinities near one hundred milligrams per liter as calcium carbonate, while waters on granite approach zero alkalinity and prove far more sensitive to acid deposition.
难度 进阶 · 适合 初中(12-15)
CC BY 4.0 · 已核验 · Verified 2026-10-04
来源 · Source
Kramer J, Tessier A. Acidification of aquatic systems: a critique of chemical approaches. Environ. Sci. Technol., 1982, 16: 606A-615A
Kramer J, Tessier A. Acidification of aquatic systems: a critique of chemical approaches. Environmental Science & Technology, 1982, 16: 606A-615A
独立核验依据 · Independent verification: 核验依据 1 DOI 10.1021/es00105a719
#天然水化学 #碳酸盐缓冲体系
为什么有些温泉有臭鸡蛋味还治病？
Why do some hot springs smell of rotten eggs yet are 'healing'?
含硫化氢（H2S）及多种矿物质的温泉能促进血液循环、舒缓关节，但高浓度硫化氢有毒，不可吸入过多；中日温泉文化悠久。
Sulfur (H2S) and mineral hot springs boost circulation and ease joints, but high H2S is toxic—don't over-inhale. Japan and China have long spa cultures.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#温泉 #硫化氢 #矿物质
为什么温泉有硫磺味？
Why do hot springs smell of sulfur?
地热把地下硫化物带出，释放刺鼻的硫化氢气体。
Geothermal activity brings sulfides up, releasing pungent hydrogen sulfide.
难度 入门 · 适合 小学低段(6-8)
CC BY 4.0 · 已核验 · Verified 2026-08-23
来源 · Source
Brown, LeMay 等,《Chemistry: The Central Science》第14版,Pearson,2017
T. L. Brown et al., Chemistry: The Central Science, 14th ed., Pearson, 2017
#硫磺 #硫化氢 #地热