鉛的危害
鉛是一種銀灰(hui)色質軟(ruan)的重(zhong)金屬, 比重(zhong)大,熔(rong)點(dian)低(327.40C),沸點(dian)高(16200C),密度11.34g/cm3。鉛煙鉛塵無色、無臭,以氣溶膠(jiao)狀態存在于大氣之中, 用(yong)顯微鏡觀察(cha):鉛煙顆粒直徑大部分在0.l μ m 左右,屬于呼(hu)吸性(xing)粉塵, 對人體危害極大。
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有(you)資(zi)料表明: 當空(kong)氣中鉛(qian)(qian)(qian)(qian)的濃度(du)(du)達(da)到千萬分之一、地面(mian)水中鉛(qian)(qian)(qian)(qian)含(han)(han)量超過(guo)0.1mg/L,人(ren)體血(xue)(xue)液中含(han)(han)鉛(qian)(qian)(qian)(qian)量超過(guo)0.1～0.15mg/l 時(shi),就會(hui)對人(ren)體產生(sheng)危害, 引(yin)起(qi)鉛(qian)(qian)(qian)(qian)中毒。鉛(qian)(qian)(qian)(qian)是(shi)通過(guo)呼吸道、消(xiao)化(hua)(hua)道進(jin)入機(ji)體, 在人(ren)體半衰期可長達(da)20 年(nian),其含(han)(han)量隨年(nian)齡增(zeng)(zeng)長而增(zeng)(zeng)加。鉛(qian)(qian)(qian)(qian)進(jin)入人(ren)體后(hou)先(xian)蓄積于(yu)骨骼以(yi)及肝(gan)、腎、脾(pi)和(he)(he)大腦(nao)等處, 以(yi)不溶解(jie)和(he)(he)磷酸鹽形式沉積在骨骼中,有(you)25% 與(yu)血(xue)(xue)液進(jin)行交換,血(xue)(xue)鉛(qian)(qian)(qian)(qian)濃度(du)(du)達(da)到(0.6～0.8)× 10-9 時(shi),將損害神(shen)經系統(tong)(tong)、造血(xue)(xue)系統(tong)(tong)、泌尿系統(tong)(tong)、消(xiao)化(hua)(hua)系統(tong)(tong)和(he)(he)生(sheng)殖器官,引(yin)起(qi)貧血(xue)(xue)、肌肉關(guan)節(jie)疼痛、消(xiao)化(hua)(hua)系統(tong)(tong)異(yi)常、末端神(shen)經麻痹(bi)等癥狀, 特別是(shi)使兒童(tong)的身(shen)體發育和(he)(he)智力受損。
所以(yi)保護(hu)環境、減(jian)少鉛污染, 一直(zhi)是人(ren)們(men)重視的研究(jiu)課題(ti)。
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