植物耐受和解除重金属毒性研究进展

总结了植物细胞及分子水平对重金属耐性和解除其毒性的途径.植物通过避免增加细胞内敏感位点毒物浓度来解除重金属毒性.其途径主要有:一方面通过菌根化、细胞壁吸收及根系分泌物的螯合作用减少根系吸收重金属进入细胞质;另一方面通过体内调节机制解除重金属毒性和提高耐性,主要通过一系列膜蛋白对进入细胞质内的重金属排出细胞质外、隔离于液泡中,或将重金属转变为无毒性形态挥发入大气,或通过细胞质内的植物螯合素、金属硫蛋白、有机酸、氨基酸、多胺等对重金属螯合,解除重金属毒性;同时植物还可以在重金属胁迫下产生热休克蛋白修复胁迫伤害的蛋白质.本文提供了涉及植物重金属解毒和耐性广泛的观点和证据.     

根际环境的调节与重金属污染土壤的修复

根际环境的pH和Eh会产生影响土壤中重金属的化学过程。pH的变化影响到重金属的固定和活化，根际的酸化能够活化大多数重金属，使其毒性增强；反之，则固定大多数重金属，减轻其毒性。Eh的变化可改变重金属的价态和存在形态，使其毒性减弱或增强。根分泌物可从多方面影响金属的毒性和有效性，如改变根际环境的pH值和Eh来改变金属的存在形态和活度；与金属络合或者吸附、包埋金属污染物；通过影响根际微生物特征来改变金属的毒性。根际环境中微生物能改变金属离子存在形态，其代谢产物能对金属离子产生沉淀、螯合等作用。土壤脲酶对重金属污染最敏感，可以用于监测土壤重金属污染。调控根际环境，可以有效地调节土壤中重金属污染物的活度、毒性及其转移，对重金属污染土壤起到修复作用。     

羟基磷灰石对沉积物中重金属释放特性的影响

以羟基磷灰石掺杂前后模拟重金属污染沉积物为研究对象,利用混匀释放实验及化学连续萃取法分析沉积物中重金属的释放特征及形态分布特性,考察了羟基磷灰石对重会属污染沉积物中Cu、zn、Pb、Cd稳定性的影响.结果表明不同来源模拟污染沉积物中松花江沉积物中的重金属最易重新释放,而伊通河沉积物中的重金属释放量最小;同时伊通河沉积物中残渣态重金属的比例较其它沉积物高很多,而可交换态和碳酸盐结合态的重金属比例较其它沉积物低很多,说明同时进入沉积物中的重金属,伊通河沉积物中的重金属相对稳定一些.羟基磷灰石的掺杂不同程度降低了沉积物中重金属的释放能力,促使沉积物中的重金属由较不稳定结合态向较稳定结合态转化,减小了沉积物中重金属的生物可利用性,增强了重金属的稳定性.     

外源铅铜镉在长三角和珠三角农业土壤中的转化

选择了我国经济发达地区的长江三角洲和珠江三角洲10个代表性农业土壤，采用室内培养和化学分级方法研究了加入外源铅、铜、镉在土壤中的动态变化及转化趋势，探讨了碳酸钙、粉煤灰、猪粪和钢渣等土壤改良剂对土壤重金属形态的影响。结果表明，随着土壤重金属负荷的提高，土壤中交换态重金属的比例增大，残余态比例下降，有效性提高，对环境威胁增大。当重金属加入最较低时，重金属优先向氧化物结合态、有机质结合态转化；而当加入最较高时，向交换态和碳酸盐结合态转化的比例明皿增加。pH和土壤组分对重金属在土壤中的转化有显著的影响，土壤pH下降可使交换态Cd、Cu、Pb的比例递增。加入碳酸钙、粉煤灰、猪粪和钢渣等改良剂可显著地降低土壤中交换态重金属比例，增加其它形态的重金属比例。     

污染土壤中有机质结合态重金属的研究

用物理与化学相结合的方法研究了2个污染土壤剖面中有机质结合重金属（Cd、Cu、Pb和Zn）的分布，把有机质相结合态重金属分为颗粒状有机质（POM）结合的重金属和与细土腐殖质结合的重金属。结果表明，土壤POM对重金属有明品的富集作用，其中〉2mmPOM重金属Cd、Cu、Pb和Zn的富集系数分别在1．4～3．2、2．5～2．6、2．8—3．9和3．0～3．9之间；而0．05～2mmPOM重金属Cd、Cu、Pb和Zn的富集系数分别在2．7～7．8、3．2～6．4、3．2～9．3和3．2～5．6之间，0．05～2mmPOM组分中重金属的平均富集高于〉2mmPOM组分。POM中重金属的富集程度与土壤重金属的积累呈正相关。有机质结合态重金属占土壤重金属总最的比例随土壤有机质积累而增高，表土层约40％以上的重金属以有机质结合态存在。     

重金属Cu,Pb,Zn,Cr,Cd在水稻植株中的富集和分布

研究了外源可溶性重金属进入水稻土环境后，在水稻植株中的迁移、在水稻植株不同部位的分布及其分布随时间的变化。在水稻生长季节，重金属在水稻植株中迁移能力的大小依次为：Cd,Cr＞Zn,Cu＞Pb。重金属在水稻植株不同部位的积累分布是：根部＞根基茎＞主茎＞穗＞籽实＞叶部。水稻分蘖期重金属在根部、茎干部和叶片的积累量达到最大，随着时间的延长，在根部积累的重金属愈来愈少；在茎干部积累的重金属在拔节期降至最小，随后含量又稍微上升；叶片上的重金属含量在拔节期迅速下降，随后趋于稳定。     

Association between heavy metals and antibiotic-resistant human pathogens in environmental reservoirs: A review

Heavy metals can act as co-selecting agents and promote antibiotic resistance. Most frequent resistances to heavy metals are observed for zinc and cadmium. P. aeruginosa and E. coli are commonly resistant to heavy metals and antibiotics. Heavy metals proliferate antibiotic resistance through co- and cross-resistance. Heavy metal and antibiotic resistances are common near anthropogenic activities. Antibiotic resistance in human pathogens can proliferate under selective pressures. Heavy metals in environmental reservoirs may contribute to selecting antibiotic-resistant strains. To determine the associations between heavy metals and antibiotic resistance, a literature review was conducted to systematically collect and categorize evidence for co-occurrence of resistance to heavy metals and antibiotics within human pathogenic bacteria in water, wastewater, and soil. In total, 42 publications adhered to inclusion criteria. Across the reservoirs, zinc and cadmium were the most commonly observed heavy metals associated with resistance to antibiotics. Pseudomonas aeruginosa and Escherichia coli were the most commonly studied bacteria with reported co-occurrence of resistance to several heavy metals and antibiotic classes. As co-selecting agents, prevalence of heavy metals in the environment can proliferate resistance to heavy metals and antibiotics through co-resistance and cross-resistance mechanisms. In comparing different reservoirs, soils and sediments harbor higher heavy metal and antibiotic resistances compared to water environments. Additionally, abiotic factors such as pH can affect the solubility and hence, the availability of heavy metals to bacterial pathogens. Overall, our review demonstrates heavy metals act as co-selecting agents in the proliferation of antibiotic resistance in human pathogens in multiple environmental reservoirs. More studies that include statistical data are needed to further describe the exposure-response relationships between heavy metals and antibiotic resistance in different environmental media. Moreover, integration of culture-based and molecular-based methods in future studies are recommended to better inform our understanding of bacterial co- and cross-resistance mechanisms to heavy metals and antibiotics.     

水稻重金属污染研究进展

从水稻植株和籽实对重金属的吸收富集规律、重金属的分析方法、重金属的赋存形态、受重金属污染后水稻的生理生化效应等四个方面，介绍了水稻中重金属污染的研究进展，并对今后控制水稻受重金属污染的方向提了一些建议。     

沉积物再悬浮-重金属释放机制研究进展

水-沉积物界面重金属迁移和转化行为已成为水环境质量研究的热点。因自然、生物、人为活动等驱动的沉积物再悬浮使得沉积物颗粒吸附和结合的重金属可能通过吸附-解吸平衡和氧化还原反应而释放进入上覆水体。随着外在污染源输入逐步得到控制,沉积物再悬浮释放重金属将成为水体重要的内在污染源而对水环境质量和水生生物产生影响。本文综述了最近几年的相关研究文献,对沉积物再悬浮的动力来源及发生机制、再悬浮-重金属释放机制及主要影响因素进行了阐述,探讨了该领域未来可能的研究方向。相关研究发现,当干扰切应力大于沉积物的临界切应力值时,沉积物再悬浮发生,且再悬浮颗粒量随干扰切应力的增强而增大;再悬浮使还原态沉积物暴露于有氧环境,有机质和硫化物的氧化是沉积物结合态重金属释放的主要机理,而沉积物颗粒电性吸附的重金属则通过解吸进入水体;切应力大小、再悬浮水体理化性质、沉积物理化性质以及微生物活性等因素调控着沉积物吸附态或结合态重金属的释放。本文指出再悬浮沉积物释放重金属的去向（再分配机理）以及再悬浮-重金属释放的动力学过程、沉积物悬浮-重金属释放复合预测模型的建立、沉积物悬浮-释放重金属的生物可利用性及生物毒害评价将是本领域需要进一步研究的重点。     

猪粪混合堆肥过程中重金属含量的变化

在猪粪混合堆肥中，采用不同的通风方式和填充料，分析该过程中重金属总量和DTPA提取的重金属含量变化。结果表明，通过猪粪混合堆肥，重金属总量不会降低，但重金属生物有效性可降低；在猪粪与木屑混合堆肥中，加入树叶或鸡粪均能显著降低重金属的生物有效性，强制通风 机械翻堆比单一机械翻堆更能降低重金属的生物有效性。     

Sulfur mediated heavy metal biogeochemical cycles in coastal wetlands: From sediments,rhizosphere to vegetation

• In sediments, the transformation of sulfides may lead to the release of heavy metals. • In the rhizosphere, sulfur regulates the uptake of heavy metals by plants. • In plants, sulfur mediates a series of heavy metal tolerance mechanisms. • Explore interactions between sulfur and heavy metals on different scales is needed. The interactions and mechanisms between sulfur and heavy metals are a growing focus of biogeochemical studies in coastal wetlands. These issues underline the fate of heavy metals bound in sediments or released into the system through sediments. Despite the fact that numerous published studies have suggested sulfur has a significant impact on the bioavailability of heavy metals accumulated in coastal wetlands, to date, no review article has systematically summarized those studies, particularly from the perspective of the three major components of wetland ecosystems (sediments, rhizosphere, and vegetation). The present review summarizes the studies published in the past four decades and highlights the major achievements in this field. Research and studies available thus far indicate that under anaerobic conditions, most of the potentially bioavailable heavy metals in coastal wetland sediments are fixed as precipitates, such as metal sulfides. However, fluctuations in physicochemical conditions may affect sulfur cycling, and hence, directly or indirectly lead to the conversion and migration of heavy metals. In the rhizosphere, root activities and microbes together affect the speciation and transformation of sulfur which in turn mediate the migration of heavy metals. As for plant tissues, tolerance to heavy metals is enhanced by sulfur-containing compounds via promoting a series of chelation and detoxification processes. Finally, to further understand the interactions between sulfur and heavy metals in coastal wetlands, some major future research directions are proposed.     

Co-pyrolysis of sludge and kaolin/zeolite in a rotary kiln: Analysis of stabilizing heavy metals

• Adding kaolin/zeolite promotes the formation of stable heavy metals. • The potential ecological risk index of co-pyrolysis biochar is extremely low. • Increasing the pyrolysis temperature reduces the leaching toxicity of heavy metals. • The toxicity of biochar reduces with the increasing content of stable heavy metals. Pyrolysis is a promising technique used for treating of sewage sludge. However, the application of pyrolysis products is limited due to the presence of heavy metals. In this study, sewage sludge mixed with kaolin/zeolite was pyrolyzed in a rotary kiln, aiming to improve the immobilization of heavy metals in pyrolytic carbon. The total concentrations, speciation distributions, leaching toxicities, and potential ecological risk indices of heavy metals in pyrolysis biochar were explored to examine the effects of kaolin/zeolite and pyrolytic temperature on immobilizing heavy metals. Further, mineral composition and surface morphology of biochar were characterized by X-ray diffraction and scanning electron microscopy to reveal the potential mechanism of immobilizing heavy metals. Increasing pyrolysis temperature facilitated the stabilization of heavy metals in pyrolysis biochar. The proportions of stable heavy metals in biochar obtained at 650℃ were 54.50% (Cu), 29.73% (Zn), 79.29% (Cd), 68.17% (Pb) and 86.70% (Cr). Compared to sewage sludge, the potential contamination risk index of pyrolysis biochar obtained at 650℃ was reduced to 17.01, indicating a low ecological risk. The addition of 7% kaolin/zeolite further reduced the risk index of co-pyrolysis biochar prepared at 650℃ to 10.86/15.28. The characterization of biochar revealed that increase in the pyrolysis temperature and incorporation of additives are conducive to the formation of stable heavy metal-inorganics. This study demonstrates that the formation of stable mineral compounds containing heavy metals is the key to stabilizing heavy metals in pyrolysis biochar.     

Terrigenous Inputs and Accumulation of Trace Metals in the Southeastern Taiwan Strait

Abstract

Terrigenous inputs and sedimentary fluxes of trace metals were studied to understand the metal sources, transport and sinks in the southeastern Taiwan Strait. the major terrigenous metals come from seven major rivers in the southwestern Taiwan, even though significant fractions of most metals were retained in estuaries. the net fluxes of river borne metals contributed from 65% (Pb) to 92% (Fe, Zn) of total inputs. the remainder was attributed to marine sewage discharges (0.6–6.9%) and atmospheric inputs (5.3–31.5%). Sedimentary fluxes of trace metals were spatially variable as a result of derivation from site-specific sedimentation rates and metal distributions in sediments. in spite of imbalance between sources and sinks of trace metals, an accumulation of metals in the sediment of southeastern Taiwan Strait was found for sites close to Taiwan Island. Surface enrichment of metals in near-shore sediments beginning around 1976 was coincident with a time of industrial boom in Taiwan. the metal enrichment hierarchy was found as (Cd, Pb < Cu < Zn < Mn, Fe).     

干旱区绿洲土壤中重金属的形态分布及生物有效性研究

测定了Cd、Pb、Zn和Ni等重金属在不同处理土壤中的全量和各赋存形态,以及它们在盆栽试验油菜（Brassica cole）中的质量分数,并利用Pearson相关系数分析了该区土壤-油菜体系的生物有效性。结果表明,供试绿洲土壤原状土中,Cd、Pb、Zn和Ni均以稳定的残渣态形式存在;而在处理土壤中,重金属被钝化的量有限,Cd的存在形式主要以碳酸盐态为主,Pb、Zn和Ni则主要以铁锰氧化态为主。根据相关性分析,油菜根部和叶部的Ni质量分数均与土壤中Ni的各非残渣态分布系数有相关性,表明当土壤中Ni以非残渣态存在时,活动性Ni的质量分数较高,其被生物吸收利用的可能性也较大;油菜根部的Zn质量分数与土壤中Zn的碳酸盐结合态分布系数显著的正相关性;油菜各部位Cd和Pb的质量分数与土壤中Cd和Pb的各形态分布系数之间无显著相关关系。     

填埋场内重金属总量及其形态分布对迁移性的影响

以杭州市天子岭填埋场为例,对不同深度填埋层中的重金属总量、重金属迁移率和重金属形态分布进行了研究．结果表明,尽管填埋层中的重金属总量是土壤背景值的数十倍,超出土壤环境质量标准,但是重金属的迁移率却很低．另外,重金属迁移率与可交换态含量相关;Cd,Cu,Pb,Cr,Ni和Zn在填埋层中均以残渣态为主,填埋场中重金属都得到了有效固定,迁移性很差;各元素的易还原态与难还原态是重金属除残渣态之外主要的结合态(除Cr),铁锰氧化物循环是控制填埋场中重金属转化行为的主要机制之一;Cu的酸可溶态与易还原态具有较好的相关性,说明cu这两种形态的转化行为相似．     

Spatial and temporal trends in heavy metal concentrations in mussels from Northern Ireland coastal waters

Data are presented on the heavy metal concentrations in mussels, Mytilus edulis (L), sampled over a 1 yr period (August 1980–August 1981) from Northern Ireland coastal waters. The study was aimed at investigating the spatial extent and temporal trends in heavy metal contamination and highlighting any areas with exceptionally high levels of toxic metals. With the exception of two sites with high values for mercury and chromium, respectively, contamination by metals was relatively low. Significant spatial and temporal differences in the concentrations of several metals were found. There were also significant spatial x temporal interactions for all the metals studied. Significant negative correlations between the percentage dry matter content of mussels and the concentrations of several metals were found. There were also significant positive correlations between certain pairs of metals. It is proposed that small variations in contamination of the marine environment can be detected by subtle differences in the concentration of metals in mussels and that mussel condition may be adversely affected by metal contamination.     

中国蔬菜地土壤重金属健康风险基准的研究

对我国目前土壤和蔬菜中重金属污染评价情况进行了综述,根据全国已报道蔬菜地土壤和蔬菜中重金属含量的数据和相关资料,探讨了蔬菜地土壤和蔬菜中重金属含量之间的关系以及不同的蔬菜种类和品种中重金属的积累差异,并在已有土壤和蔬菜中重金属污染的评价指标基础上,对蔬菜地土壤和蔬菜中重金属的健康风险基准值进行了讨论,尤其对我国各地区蔬菜地土壤中重金属的污染指标值进行了统一的限定,可为制订蔬菜地土壤重金属健康风险标准提供科学依据.     

矿区周围土壤中重金属危害性评估研究

分别用总量法和连续萃取法对广东大宝山矿周围土壤、植物和沉积物中重金属的总量和化学形态进行了详细分析。结果发现，矿山废水流入的横石河沉积物中Pb、Zn、Cu和Cd的质量分数分别为1841．02、2326．28、1522．61和10.33mg／kg；经此河水灌溉的稻田中重金属(Cu、Cd、Pb和Zn)的质量分数也远远超出了土壤环境二级标准值，其中Cu、Cd超标倍数分别为14．01和4．17倍。结果还表明，生长在矿区周围的植物也受到不同程度重金属的污染且不同植物吸收和积累重金属的能力相差很大。用Tessier连续法对土壤中重金属进行萃取发现，虽然重金属主要存在于残余态中，但在Fe-Mn氧化态、有机结合态中的质量分数也很高．说明这些土壤确实受到了有毒有害重金属元素的严重污染。     

Uncommon heavy metals,metalloids and their plant toxicity: a review

Heavy metals still represent a group of dangerous pollutants, to which close attention is paid. Many heavy metals are essential as important constituents of pigments and enzymes, mainly zinc, nickel and copper. However, all metals, especially cadmium, lead, mercury and copper, are toxic at high concentration because of disrupting enzyme functions, replacing essential metals in pigments or producing reactive oxygen species. The toxicity of less common heavy metals and metalloids, such as thallium, arsenic, chromium, antimony, selenium and bismuth, has been investigated. Here, we review the phytotoxicity of thallium, chromium, antimony, selenium, bismuth, and other rare heavy metals and metalloids such as tellurium, germanium, gallium, scandium, gold, platinum group metals (palladium, platinum and rhodium), technetium, tungsten, uranium, thorium, and rare earth elements yttrium and lanthanum, and the 14 lanthanides cerium, dysprosium, erbium, europium, gadolinium, holmium, lutetium, neodymium, promethium, praseodymium, samarium, terbium, thulium and ytterbium.     

太湖表层沉积物中重金属的形态分析

采用BCR三步分级提取法和ICP-AES测定了太湖沉积物中8种重金属不同形态的含量，初步评估了太湖沉积物中重金属的生物有效性，探讨了沉积物总有机碳（TOC）与重金属不同形态之间的关系。