中国农业科学 ›› 2019, Vol. 52 ›› Issue (2): 293-311.doi: 10.3864/j.issn.0578-1752.2019.02.009

• 土壤肥料·节水灌溉·农业生态环境 • 上一篇    下一篇

磷石膏农用的环境安全风险

王小彬,闫湘(),李秀英,冀宏杰   

  1. 中国农业科学院农业资源与农业区划研究所,北京 100081
  • 收稿日期:2018-05-24 接受日期:2018-08-22 出版日期:2019-01-16 发布日期:2019-01-21
  • 通讯作者: 闫湘 E-mail:yanxiang@caas.cn
  • 作者简介:王小彬,E-mail: xbwang@caas.ac.cn
  • 基金资助:
    农业部肥料登记专项(2130112)

Environmental Risks for Application of Phosphogysum in Agricultural Soils in China

WANG XiaoBin,YAN Xiang(),LI XiuYing,JI HongJie   

  1. Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081
  • Received:2018-05-24 Accepted:2018-08-22 Online:2019-01-16 Published:2019-01-21
  • Contact: Xiang YAN E-mail:yanxiang@caas.cn

摘要:

磷石膏是湿法磷酸生产过程中产生的工业废渣,是化学工业中排放量最大的固体废物之一。中国从20世纪50年代末开始发展磷复肥产业,但生产中排放的磷石膏废渣堆积量不断增加。为解决大量磷石膏堆存造成的环境问题,目前,磷石膏被再次利用作建筑材料,如用于生产水泥缓凝剂和制作石膏建材,以及用于充填矿坑和筑路等。自20世纪90年代也有研究尝试利用磷石膏替代天然石膏改良盐碱化土壤。然而,磷矿石中多种有害元素在湿法磷酸生产过程中残留或富集在磷石膏中,导致磷石膏中重金属、氟化物(F)及放射性元素镭( 226Ra)等污染元素含量较高,且存在不同程度超出国家土壤环境质量标准和地下水质量标准。如磷石膏中重金属Cr、As、Cd和Hg超过《土壤环境质量-农用地土壤污染风险管控标准》(GB 15618—2018)的农用地土壤污染风险筛选值的比率为20%—67%;且检出Hg、Cd、Pb、Ni、Cr和Be浸出浓度超过《地下水质量标准》(GB/T 14848—2017)中IV—V类水质标准。磷石膏中氟含量已超出中国地氟病发生区土壤全氟和水溶氟临界值的比率分别为89%和100%;且检出其浸出浓度远超出地下水V类水质标准,部分已超过《危险废物鉴别标准-浸出毒性鉴别》(GB 5085.3—2007)浸出限量。按照农用地土壤污染风险筛选值(GB 15618—2018),估算了磷石膏在不同施用量条件下带入土壤的污染物元素累积量超出农用地土壤污染风险筛选值所需要的年限,表明短期内即可能导致土壤中污染元素累积量超标,如在年投入量为22.5 t·hm -2条件下(如污染元素淋溶量忽略不计),对污染元素Cd、Hg、F和 226Ra而言,无污染土壤变为污染土壤的年限分别约为1、5、4和25年。已有田间试验显示,磷石膏农用可导致部分农产品中有害元素(如F、As、Cd、Hg、Pb和Zn等)超标。2017年国家出台的《固体废物鉴别标准 通则》(GB 34330—2017)明确规定,生产过程中产生的副产物,包括在无机化工生产过程中产生的磷石膏等属于固体废物;且以土壤改良、地块改造、地块修复和其他土地利用方式直接施用于土地的固体废物,仍然作为固体废物管理。为保证土壤健康、食品安全和环境安全,建议未经无害化处理、有害元素超标的、存在环境安全风险的工业固废磷石膏不得以土地处置方式为由直接施用于农田土壤,以免污染物进入食物链而危害人类健康。

关键词: 工业固体废物, 环境安全风险, 土壤污染, 磷石膏, 重金属

Abstract:

Phosphogypsum (PG) is an industrial by-product gypsum obtained from wet process production of phosphoric acid, and it is one of the largest solid waste emissions in the chemical industry. With the development of phosphate and compound fertilizer industry at the late 1950s, the PG waste residue discharged from the production process had continuously increased in China. To solve the environmental problems caused by massive PG stockpiling, at present, PG was mainly used as for building materials, such as cement retarder, and gypsum-building materials, as well as for filling mine pits and road construction. Some researches have also tried to use PG instead of natural gypsum for saline-alkali land amendment in agriculture since 1990s. However, several harmful elements in phosphate rock were preserved or enriched in PG in the process of wet process phosphoric acid production, resulting in high concentration of hazardous pollutants, including heavy metals, fluoride (F), and radioactive element radium ( 226Ra) in PG, and to some extent, even far beyond the limits of national standards for soil environmental quality and for groundwater quality. For example, the concentrations of heavy metals Cr, As, Cd and Hg in PG exceed the limits (about 20%-67%) of Soil Environmental Quality Risk Control Standard for Soil Contamination of Agricultural Land (GB 15618-2018); and the leachable concentrations of Hg, Cd, Pb, Ni, Cr and Be in PG exceeded the limits (IV-V) of Standards for Groundwater Quality (GB/T 14848-2017). The concentrations of total F and water-soluble F in PG exceeded the critical values of total and soluble F (about 89% and 100%, respectively) in soils of endemic fluorosis-affected areas in China, and the leachable concentration of F in PG exceeded the limit (V) of Standards for Groundwater Quality, and some exceeded the limit of Identification Standards for Hazardous Wastes Identification for Extraction Toxicity (GB 5085.3-2007). According to the concentration of pollutants in PG, as compared with the limits of Soil Environmental Quality Risk Control Standard (GB 15618-2018), the long-term impacts of PG application (if PG input was at rate of 22.5 t·hm -2·a -1, and with no leaching) on the accumulations of pollutants in the soil could be estimated. For instance, the accumulation of Cd, Hg, F and 226Ra from un-contaminated to contaminated soils would need 1, 5, 4 and 25 years, respectively. Some field experiments have shown that PG could lead to the risk of excessive pollutants (such as F, As, Cd, Hg, Pb and Zn) enriched in some agricultural products. In 2017, the Identification Standards for Solid Wastes General Rules (GB 34330-2017) was issued in China, which stipulated clearly that those by-products produced in the production process, including PG produced in the inorganic chemical production process, were solid wastes; and those directly used for soil amendment, land reconstruction, land restoration and other land use methods by solid waste disposal were still managed as solid wastes. In order to ensure soil health, food safety, and environmental quality, it was suggested that those industrial waste like PG without any harmless treatment of pollutants, and with harmful elements far beyond the limit standard should not be allowed to directly use as for soil remediation or conditioning in the farmlands by solid waste disposal methods, to prevent hazardous pollutants from entering food chain and harming to human health.

Key words: industrial waste, environmental safety risk, soil pollution, phosphogysum, heavy metals