水稻土中氮素对微生物固砷的扰动及效应机制

我国是世界上最大的水稻生产国,水稻生产在粮食安全方面起着重要的作用.现阶段,我国稻田土壤的砷污染问题表现突出.稻田长期处于淹水的缺氧环境下,微生物在厌氧条件下介导的砷形态转化速率和程度均强于化学过程.理解和认知微生物对稻田土壤中砷固定的关键过程及作用机制将为开展稻田砷污染的有效治理提供理论依据.在综合分析了砷在稻田土壤中的迁移及其影响因素的基础上,主要综述了涉及淹水稻田土壤中微生物参与As （Ⅲ）固定两条重要途径：Fe （Ⅱ）氧化成矿耦合As （Ⅲ）固定（间接过程）与As （Ⅲ）直接氧化固定（直接过程）.同时,就氮素在土壤的形态及分配对微生物参与砷固定的响应过程也展开系统性论述.其中,总结了参与微生物砷固定与氮素转化的关键基因表达及代谢机制;最后,归纳了砷污染稻田微生物修复技术的相关研究进展,并提出了初步展望.     

Accumulation and Chemical Fractionation of Heavy Metals in Andisols after a Different, 6-year Fertilization Management (8 pp)

Goal, Scope and Background Andisols are widespread in Japan and have some special properties such as high anion exchange capacity, low bulk density, and high organic matter content, which might influence the accumulation or chemical fractionation of heavy metals. However, few such data exist in Japanese andisols. The primary objective of this study was to investigate the distribution and chemical fractions of Cu, Zn, Ni, and Cr in the soil profiles and subsequently to assess their potential environmental hazard. Materials and Methods Soil samples were taken from a field experiment conducted on Japanese andisols, which had received either swine compost or chemical fertilizers for 6 years. Concentrations of Cu, Zn, Ni, and Cr were determined for all of the obtained extract solutions by ICP-AES. Results and Discussion Considerably higher total concentrations of Cu and Zn were observed in the top 20 cm layer of the compost-amended soil, relative to the unfertilized soil, while chemical fertilizers had little effect. Application of the swine compost increased the concentrations of Cu and Zn, but not Ni and Cr, in all fractions in the top 20 cm layer. The greatest increase in the organically bound fraction (OM) Cu and dilute acid-exchangeable fraction (DAEXCH) Zn was observed. This suggests that Cu and Zn are potentially bioavailable and mobile in the andisol profiles after 6-year consecutive applications of the swine compost. On the other hand, distribution of Cu, Zn, Ni and Cr among various soil fractions was generally unaffected by chemical fertilizers. Conclusions We observed that 6-year consecutive applications of the swine compost led to an increase in total metals of Cu and Zn, as well as their all-chemical fractions, in the top 20 cm soil layers. Potential hazard of heavy metals, especially of Cu and Zn, as a result of the use of swine compost on andisols, must be taken into account. Recommendations and Outlook The long-term effect of the accumulation of heavy metals, particularly Cu and Zn, in various plant tissues and soils, as well as their potential risk to surface water via runoff and groundwater via leaching, needs to be carefully considered. Further investigations in the long-term experiments are therefore necessary. - Abbreviations. EXCH, exchangeable fraction of metals; DAEXCH, dilute acid-exchangeable fraction of metals; FeMnOX, iron and manganese-oxide-bound fraction; OM, organically-bound fraction; RESD, residual fraction. COMPOST, SRNF, RANF, and CONTROL stand for compost (from swine wastes), slow-release nitrogen fertilizer (coated urea), readily available nitrogen fertilizer (including NH4-N, P, and K fertilizers), and no fertilizer application, respectively.     

Levels of Lead in Urban Soils from Selected Cities in a Central Region of the Philippines (7 pp)

Background Aims, and Scope. Lead (Pb) is a naturally occurring element that poses environmental hazards when present at elevated concentration. It is being released into the environment because of industrial uses and from the combustion of fossil fuels. Hence, Pb is ubiquitous throughout global ecosystems. The existence of potentially harmful concentrations of Pb in the environment must be given full attention. Emissions from vehicles are major source of environmental contamination by Pb. Thus, it becomes imperative that concentrations of Pb and other hazardous materials in the environment not only in the Philippines, but elsewhere in the world be adequately examined in order that development of regulations and standards to minimize risk associated with these materials in urban areas is continued. The objectives of this study were: (1) to determine the levels of Pb in soil from selected urbanized cities in central region of the Philippines; (2) to identify areas with soil Pb concentration values that exceed estimated natural concentrations and allowable limits; and (3) to determine the possible sources that contribute to elevated soil Pb concentration (if any) in the study area. Methods This study was limited to the determination of Pb levels in soils of selected urbanized cities located in central region in the Philippines, namely: Site 1 – Tarlac City in Tarlac; Site 2 – Cabanatuan City in Nueva Ecija; Site 3 – Malolos City in Bulacan; Site 4 – San Fernando City in Pampanga; Site 5 – Balanga City in Bataan; and Site 6 – Olongapo City in Zambales. Soil samples were collected from areas along major thoroughfares regularly traversed by tricycles, passenger jeepneys, cars, vans, trucks, buses, and other motor vehicles. Soil samples were collected from five sampling sites in each of the study areas. Samples from the selected sampling sites were obtained approximately 2 to 3 meters from the road. Analysis of the soil samples for Pb content was conducted using an atomic absorption spectrophotometer. This study was conducted from 2003 to 2004. Since this study assumed that vehicular emission is the major source of Pb contamination in urban soil, other information which the researchers deemed to have bearing on the study were obtained such as relative quantity of each gasoline type disposed of in each city within a given period and volume of traffic in each sampling site. A survey questionnaire for gasoline station managers was prepared to determine the relative quantity of each fuel type (diesel, regular gasoline, premium gasoline, and unleaded gasoline) disposed of or sold within a given period in each study area. Results and Discussion Analysis of soil samples for Pb content showed the presence of Pb in all the soil samples collected from the 30 sampling sites in the six cities at varying concentrations ranging from 1.5 to 251 mg kg–1. Elevated levels of Pb in soil (i.e. greater than 25 mg kg–1 Pb) were detected in five out of the six cities investigated. Site 4 recorded the highest Pb concentration (73.9 ± 94.4 mg kg–1), followed by Site 6 (56.3 ± 17.1 mg kg–1), Site 3 (52.0 ± 33.1 mg kg–1), Site 5 (39.3 ± 19.0 mg kg–1), and Site 2 (38.4 ± 33.2 mg kg–1). Soil Pb concentration in Site 1 (16.8 ± 12.2 mg kg–1) was found to be within the estimated natural concentration range of 5 to 25 mg kg–1. Site 1 registered the least Pb concentration. Nonetheless, the average Pb concentration in the soil samples from the six cities studied were all found to be below the maximum tolerable limit according to World Health Organization (WHO) standards. The high Pb concentration in Site 4 may be attributed mainly to vehicular emission. Although Site 4 only ranked 3rd in total volume of vehicles, it has the greatest number of Type B and Type C vehicles combined. Included in these categories are diesel trucks, buses, and jeepneys which are considered the largest contributors of TSP (total suspended particles) and PM10 (particulate matter less than 10 microns) emissions. Conclusion Only one (San Juan in Site 4) of the thirty sampling sites recorded a Pb concentration beyond the WHO permissible limit of 100 mg kg–1. San Juan in Site 4 had a Pb concentration of >250 mg kg–1. On the average, elevated Pb concentration was evident in the soil samples from San Fernando, Olongapo, Malolos, Balanga, and Cabanatuan. The average soil Pb concentrations in these cities exceeded the maximum estimated natural soil Pb concentration of 25 mg kg–1. Average soil Pb concentration in Site 1 (16.8 mg kg–1) was well within the estimated natural concentration range of 5 to 25 mg kg–1. Data gathered from the study areas showed that elevated levels of Pb in soil were due primarily to vehicular emissions and partly to igneous activity. Recommendation and Outlook The findings of this study presented a preliminary survey on the extent of Pb contamination of soils in urban cities in central region of Philippines Island. With this kind of information on hand, government should develop a comprehensive environmental management strategy to address vehicular air pollution in urban areas, which shows as one of the most pressing environmental problems in the country. Basic to this is the continuous monitoring of Pb levels and other pollutants in air, soil, and water. Further studies should be conducted to monitor soil Pb levels in the six cities studied particularly in areas with elevated Pb concentration. The potential for harm from Pb exposure cannot be understated. Of particular concern are children who are more predisposed to Pb toxicity than adults. Phytoremediation of Pb-contaminated sites is strongly recommended to reduce Pb concentration in soil. Several studies have confirmed that plants are capable of absorbing extra Pb from soil and that some plants, grass species in particular, and can naturally absorb far more Pb than others.     

杭州城市土壤重金属污染研究进展及展望

文章综述了杭州城市土壤重金属污染主要来源、重金属污染分布状况、重金属存在形态及相关性,并对下一步土壤重金属研究提出了展望。分析表明,杭州土壤重金属污染主要来源于工业"三废"排放、汽车尾气排放和农业化肥的施用。杭州对蔬菜地、茶园等农业用地、商业居住区、工业区附近土壤污染研究较多,对Cu、Pb和Zn等关注较多,而对Hg和As关注很少。城市土壤已受到一定程度的重金属污染,土壤中Cd、Cr、Cu、N i、Pb、Zn和Mn均有明显的积累,其浓度分布具有一定的地域差异,以工业区和商业区污染较重。土壤中Cd、Co、Cr、N i和Hg以稳定的残余态为主,而Cu、Pb、Zn和Mn以活性较高的非残余态为主,因杭州土壤呈中性偏碱性,正常情况下不会有明显的重金属释放。下一步应重点关注工业企业搬迁后场地重金属污染修复以及Hg和As的污染问题。     

云南省公路路域绿化护坡植物的生态区划与选择

在参考前人研究工作的基础上,以水热因素的地域分异规律为依据,以整体植被景观为参照,以局部环境背景为基础,以有利于公路建设、参考行政区划确定区域界线的原则,将云南全省公路路域分为滇西北北温带寒温针叶林、亚高山草甸区等7个区,西部高山峡谷杉木林、稀疏灌木草丛亚区等17个亚区,德钦维西长苞冷杉、川滇杜鹃、白刺花、扭黄茅、狐茅小区等30个小区.一级分区的7大生态地理单元从宏观上反映了云南全省从东到西、从南到北气候和植被类型的经向、纬向地带性及各生态区域的海拔梯度、地貌特点及土壤类型;二级分区的17个亚区综合反映了一级分区内局部生境的地形地貌特征及微地形环境影响下的植物组合类型;三级分区的30个小区概括反映了全省地县市级行政区域界限与主要护坡绿化植物分布区域的叠合关系.根据植物物种的生态适应性和物种特性,甄别选择了适于不同生态小区环境背景下生长的乔、灌、草等绿化护坡植物.     

氯盐对汞化合物污染土壤热脱附过程的影响

对HgCl₂、HgS、Hg(NO₃)₂·H₂O、HgO、HgSO₄ 5种试剂分别添加MgCl₂、CaCl₂和NaCl 3种氯盐,采用热重分析法进行热挥发性对比研究,以期选择对汞化合物热脱附有促进作用的氯盐,并将其添加到内蒙古2块不同污染场地的汞污染土壤样品(A、B)中,进行低温热脱附修复研究. 结果表明:5种汞化合物试剂热脱附温度由低到高依次为HgCl₂＜HgS＜Hg(NO₃)₂·H₂O＜HgO＜HgSO₄. 在汞化合物中加入MgCl₂、CaCl₂和NaCl后的热重分析发现,MgCl₂对HgS、Hg(NO₃)₂·H₂O、HgO、HgSO₄热脱附过程影响最大,降低了汞化合物热脱附的初始温度. A、B 2个污染土壤样品加入MgCl₂热脱附后,汞的去除率分别从无药剂处理的65.67%、70.74%升至81.35%、84.91%. 表明MgCl₂可以促进汞污染土壤中汞化合物的转化,有利于土壤汞污染的热脱附修复,应用前景较好.      

环境因子对香溪河库湾淹没土壤磷释放的影响

三峡工程建成后大量的耕地良田被淹没,淹没土壤对水体环境的影响问题受到各方关注,该研究针对不同利用类型的土壤进行磷释放研究,评价淹没土壤的营养释放对三峡支流水体富营养化进程的影响。采集香溪河库湾的3种不同利用类型的土壤,通过静态淹水模拟实验,研究3种土壤的磷释放特点,结果表明:施肥次数多且土质松软的菜地土对上覆水TP含量影响最大,柑橘园土其次。菜地土的磷释放量为柑橘园土的1.7倍。林地土其自身磷含量较小,上覆水无明显影响。TP累积释放量为:不同pH下,TP累积释放量之间的大致关系为:pH=11.02时,TP累积释放量最大,为4.710 mg/kg;pH=3.98时次之,为3.645 mg/kg;pH=7.01时最小,为2.235 mg/kg。水温的升高能够有效加速受淹土壤内源磷的释放,在30℃条件下,土壤的TP最大释放量分别约为10℃,20℃时的1.7倍、4.2倍。因此冬季淹没土壤的释放对水体TP的影响较小;而夏季库区水温升高,引起淹没土壤磷的释放。     

西南高镉地质背景区农田土壤与农作物的重金属富集特征

为探明高地质背景区农田土壤与农作物系统中重金属富集与转运特征,通过对采自重庆黑色岩系高镉地质背景区的土壤和农作物样品进行分析,并与其他典型黑色页岩区域进行对比研究.发现研究区部分农田土壤pH极低; Cd、Cr、Ni和Zn显著富集.土壤样品Cd的超标率为100%,其次为Cr和Ni,91. 3%的土壤样品Cd污染级别为严重污染及以上.土壤Zn、Cu、Cr和Ni的残渣态占比为80%以上,Cd和Pb较低;弱酸提取态Cd占比27. 0%±6. 4%,Zn和Ni次之.黑色岩系母质风化导致研究区土壤重金属富集,Cd是区域内的特征污染元素,其生物有效性较高,并易于在农作物中富集. Cd的转运系数高于其他元素,农作物中Cd的富集和污染程度最高,特别是叶类蔬菜,平均Cd含量(干重)高达11. 5 mg·kg~(-1),不适于种植和食用;部分农作物Cr超标,存在一定风险.因此,有必要对研究区农田土壤进行污染等级划分,实行科学管控,并进行农作物种植结构调整,以保障当地人群健康.     

乌鲁木齐市水磨河底泥及污灌区土壤中有机氯农药的分布

用GC-ECD定量测定了乌鲁木齐市水磨河底泥及污灌区土壤中有机氯农药的含量.结果表明:底泥样品中HCHs和DDTs的含量为0.107-111.69ng·g-1和0.476-66.512ng·g-1,有机氯农药总量为0.583-178.202ng·g-1;土壤中为0.194-6.974ng·g-1和0.520-10.438ng·g-1,有机氯农药总量为0.714-17.412ng·g-1.底泥中HCHs的α/γ比值约为4,底泥和土壤中DDT/(DDE DDD)的比值较大.     

东江流域农村土壤中多环芳烃的分布特征及其健康风险评估

为了解东江流域农村土壤多环芳烃的分布特征与人类健康风险,采集了30个不同土地利用类型农村表层土壤样品,进行采用索氏抽提法,硅胶/氧化铝（2：1）层析柱分离纯化,最后加内标经气相色谱-质谱仪定量解析的方法测定16种多环芳烃的含量。同时,测定了土壤中不同形态有机质包括总有机碳（TOC）、非水解性有机碳（NHC）、黑碳（BC）以及无定形有机碳（AOC）的含量。结果表明,土壤多环芳烃质量分数在24-238μg·kg-1之间,平均质量分数为107±60μg·kg-1。在16种多环芳烃中,萘、菲、荧蒽和苯并（b）荧蒽的含量最高,占总多环芳烃含量的比重依次为16%、20%、10%和10%。土壤中多环芳烃含量与TOC、NHC以及BC均具有极显著的线性关系（p〈0.01）,三者斜率的大小顺序为BC〉NHC〉TOC（p〈0.01）,表明土壤有机碳中的非水解性有机碳和黑碳在控制土壤中多环芳烃的分布、积累中发挥着重要的作用。土壤中多环芳烃含量与AOC的相关性不显著（p=0.29）。另外,健康风险评价表明儿童暴露的增量终身致癌风险（ILCRs）在可接受的安全范围内（ILCRs 〈10-6）,而成人暴露的增量终身致癌风险则相对较高（10-6皮肤接触〉呼吸;而成人则为：皮肤接触〉误食土壤〉呼吸。