CAJ | 학술논문

铀（U）矿冶过程中产生了大量铀废石。通常认为其放射性核素含量低，大多沿山谷露天自然堆放，一般不对堆场做防渗漏处置，对铀废石可能产生的潜在环境影响尚未引起重视。以广东某花岗岩型铀矿山的一个废石堆周边土壤为研究对象，在废石堆上、下游方向分别采集了2条（即BP1和BP2，视作背景土壤，距离废石堆的距离分别为10和20 m）和3条土壤剖面（即WP1、WP2和WP3，视作潜在U污染土壤，距离废石堆的距离分别为50、100和180 m）。通过对剖面间U分布特征的对比，定量估算了受污染土壤中外源U的输入通量；结合逐级化学提取技术，分析了U在土壤剖面的赋存形态及其环境有效性。结果表明：1）铀废石堆对周边土壤产生了显著的放射性污染，废石堆下游方向由近及远的3条U污染剖面（WP1、WP2和WP3）中U平均质量分数比背景剖面分别富集了634.6、10和3.7倍，其外源U的平均输入通量分别为4840.36、86.72和20.46μg·g-1。距污染源（废石堆）愈近，土壤中外源U的输入通量愈大；2）在近源区，大量的外源U优先在土壤表层聚集，随着远离污染源，逐渐转变为优先在剖面的深部淀积；3）与U 污染剖面相比，背景剖面（BP2）的惰性态 U（晶质铁锰氧化物/氢氧化物结合态+残渣态）所占比例最大，活性态 U（可交换态（包括水溶态）+碳酸盐结合态）所占比例最小，说明U污染土壤的外源U输入更倾向于对活性态U的贡献，这是对植物影响最直接的部分。另外，距污染源由近及远，U污染土壤中活性态U所占比例增大，潜在活性态U（有机质结合态+无定形铁锰氧化物/氢氧化物结合态）所占比例降低；4）3条U污染剖面中，平均90%以上的U（活性态和潜在活性态）对生态系统构成了威胁。因此，铀废石堆对周边环境产生的风险应得到充分重视。本研究为开展铀矿冶地域的放射性环境影响评价和土壤修复提供了有益的参考。鈾（U）礦冶過程中產生瞭大量鈾廢石。通常認為其放射性覈素含量低，大多沿山穀露天自然堆放，一般不對堆場做防滲漏處置，對鈾廢石可能產生的潛在環境影響尚未引起重視。以廣東某花崗巖型鈾礦山的一箇廢石堆週邊土壤為研究對象，在廢石堆上、下遊方嚮分彆採集瞭2條（即BP1和BP2，視作揹景土壤，距離廢石堆的距離分彆為10和20 m）和3條土壤剖麵（即WP1、WP2和WP3，視作潛在U汙染土壤，距離廢石堆的距離分彆為50、100和180 m）。通過對剖麵間U分佈特徵的對比，定量估算瞭受汙染土壤中外源U的輸入通量；結閤逐級化學提取技術，分析瞭U在土壤剖麵的賦存形態及其環境有效性。結果錶明：1）鈾廢石堆對週邊土壤產生瞭顯著的放射性汙染，廢石堆下遊方嚮由近及遠的3條U汙染剖麵（WP1、WP2和WP3）中U平均質量分數比揹景剖麵分彆富集瞭634.6、10和3.7倍，其外源U的平均輸入通量分彆為4840.36、86.72和20.46μg·g-1。距汙染源（廢石堆）愈近，土壤中外源U的輸入通量愈大；2）在近源區，大量的外源U優先在土壤錶層聚集，隨著遠離汙染源，逐漸轉變為優先在剖麵的深部澱積；3）與U 汙染剖麵相比，揹景剖麵（BP2）的惰性態 U（晶質鐵錳氧化物/氫氧化物結閤態+殘渣態）所佔比例最大，活性態 U（可交換態（包括水溶態）+碳痠鹽結閤態）所佔比例最小，說明U汙染土壤的外源U輸入更傾嚮于對活性態U的貢獻，這是對植物影響最直接的部分。另外，距汙染源由近及遠，U汙染土壤中活性態U所佔比例增大，潛在活性態U（有機質結閤態+無定形鐵錳氧化物/氫氧化物結閤態）所佔比例降低；4）3條U汙染剖麵中，平均90%以上的U（活性態和潛在活性態）對生態繫統構成瞭威脅。因此，鈾廢石堆對週邊環境產生的風險應得到充分重視。本研究為開展鈾礦冶地域的放射性環境影響評價和土壤脩複提供瞭有益的參攷。
유（U）광야과정중산생료대량유폐석。통상인위기방사성핵소함량저，대다연산곡로천자연퇴방，일반불대퇴장주방삼루처치，대유폐석가능산생적잠재배경영향상미인기중시。이엄동모화강암형유광산적일개폐석퇴주변토양위연구대상，재폐석퇴상、하유방향분별채집료2조（즉BP1화BP2，시작배경토양，거리폐석퇴적거리분별위10화20 m）화3조토양부면（즉WP1、WP2화WP3，시작잠재U오염토양，거리폐석퇴적거리분별위50、100화180 m）。통과대부면간U분포특정적대비，정량고산료수오염토양중외원U적수입통량；결합축급화학제취기술，분석료U재토양부면적부존형태급기배경유효성。결과표명：1）유폐석퇴대주변토양산생료현저적방사성오염，폐석퇴하유방향유근급원적3조U오염부면（WP1、WP2화WP3）중U평균질량분수비배경부면분별부집료634.6、10화3.7배，기외원U적평균수입통량분별위4840.36、86.72화20.46μg·g-1。거오염원（폐석퇴）유근，토양중외원U적수입통량유대；2）재근원구，대량적외원U우선재토양표층취집，수착원리오염원，축점전변위우선재부면적심부정적；3）여U 오염부면상비，배경부면（BP2）적타성태 U（정질철맹양화물/경양화물결합태+잔사태）소점비례최대，활성태 U（가교환태（포괄수용태）+탄산염결합태）소점비례최소，설명U오염토양적외원U수입경경향우대활성태U적공헌，저시대식물영향최직접적부분。령외，거오염원유근급원，U오염토양중활성태U소점비례증대，잠재활성태U（유궤질결합태+무정형철맹양화물/경양화물결합태）소점비례강저；4）3조U오염부면중，평균90%이상적U（활성태화잠재활성태）대생태계통구성료위협。인차，유폐석퇴대주변배경산생적풍험응득도충분중시。본연구위개전유광야지역적방사성배경영향평개화토양수복제공료유익적삼고。
There are large amounts of waste rocks produced during uranium mining and hydrometallurgy in China. As their radionuclide contents are generally considered as low, most of these rocks are stacked along the valleys and exposed to open air without percolation-proofing for the sites that store them. Currently, the potential environmental radioactive risks posed by these rocks have not yet received extensive attention. In his study, five soil profiles were selected from the area around a uranium waste rock pile in a granite-type uranium mine in Guangdong Province, China. Among them, two (i.e., BP1 and BP2 in the upstream direction of the pile, with the distances of 10 and 20 meters from the pile, respectively) and other three (i.e., WP1, WP2 and WP3 in the downstream direction, with the distances of 50, 100 and 180 meters from the pile, respectively) were used as the background and potentially uranium-polluted, respectively. Through the comparison between the uranium distributions of these profiles, the influx of exogenous uranium in the uranium-polluted soils was quantitatively estimated. In addition, the chemical speciation and environmental availability of uranium in the soil profiles were analyzed by the sequential chemical extraction procedures. The results demonstrated the following points: 1) A significant radioactive pollution to ambient soils from the uranium waste rock pile was detected. The average contents of the uranium in the downstream profiles WP1, WP2 and WP3 are about 635, 10, and 4 times as much as that of the background, respectively. On the other hand, the influx of exogenous uranium in the profiles WP1, WP2 and WP3 are 4 840.36, 86.72 and 20.46μg·g-1, respectively, indicating that the closer the profile is to the pile, the greater the influx of uranium is;2) A large amount of exogenous uranium detected at the soil surface close to the pollution source (i.e., the uranium waste rock pile) was precipitated in the deeper soil when the soil was away from the pile; 3) Compared with the uranium-polluted profiles, the background profile BP2 had the most inert uranium (i.e., crystalline ferromanganese oxide/oxyhydroxide and residual phases), but the least active uranium (i.e., exchangeable, including water-soluble, and carbonate-bound phases), indicating that the influx of exogenous uranium tended to contribute active uranium to the uranium-polluted soils, thereby producing a direct threat to plants. In addition, the active uranium increased, but the potentially active uranium (i.e., amorphous ferromanganese oxide/oxyhydroxide and organic matter-bound phases) decreased when the soil is more distant from the pollution source;4) In the three uranium-polluted soil profiles studied, over 90%of uranium (including active and potentially active) produced a threat to the ecological system. Therefore, the radioactive risk posed by the uranium waste rock piles should not be ignored. In this sense, this study provided a useful scientific reference for the environmental radioactivity impact assessment and the soil remediation in the fields of uranium mining and hydrometallurgy.