改性玉米秸秆炭和花生壳炭对溶液中Cd~(2+)的吸附

对玉米秸秆和花生壳炭化制备的生物炭,运用高锰酸钾进行改性,研究其对Cd~(2+)的吸附效果。通过批次吸附实验,考察了两种改性生物炭对Cd~(2+)吸附的初始浓度、pH值、接触时间等因素的影响。结果表明,在pH为6.0,Cd~(2+)浓度为100 mg·L~(-1),温度为20℃,吸附时间为12 h,吸附剂投加量为1.0 g·L~(-1)条件下,改性玉米秸秆炭和花生壳炭对Cd~(2+)的去除率分别为67.03%和46.10%,与未改性的生物炭相比,吸附率分别提高了3.8倍和6.2倍。改性玉米秸秆炭和花生壳炭对溶液中Cd~(2+)的吸附均符合Langmuir和Freundlich等温吸附模型,最大吸附量分别为68.97和55.55 mg·g-1。两种改性生物炭的吸附行为均符合准二级吸附动力学模型,说明其吸附以化学吸附为主。改性玉米秸秆炭和花生壳炭吸附Cd~(2+)后,可用NaOH溶液进行解吸,解吸4次后,对Cd~(2+)仍有较好的吸附效果,吸附量分别为31.40和24.10 mg·g~(-1)。这说明,高锰酸钾改性玉米秸秆炭和花生壳炭是一种吸附性能高且能够重复利用的去除溶液中Cd~(2+)的吸附材料。     

水稻秸秆炭及组合改良剂对石漠化地区土壤-玉米系统中重金属迁移特征影响

化学固定是重金属污染土壤修复及改良技术之一。通过盆栽实验,研究了水稻秸秆炭及其与石灰、磷酸盐组合改良剂对石漠化土壤-玉米体系中As、Zn和Pb 3种重金属迁移的影响,分析了玉米及土壤重金属含量、形态变化。结果表明,几种改良剂均显著促进了玉米生长,地上部分生物量:水稻秸秆炭石灰+水稻秸秆炭石灰秸秆磷酸盐+水稻秸秆炭磷酸盐对照。水稻秸秆炭、石灰及其组合均能够提高土壤pH值,抑制重金属向玉米地上部分迁移。添加改良剂后土壤中As的弱酸提取态和可还原态含量显著降低,均小于3 mg·kg~(-1)。水稻秸秆炭、秸秆与石灰及其组合均能够降低土壤中重金属提取态和还原态量,能够降低玉米籽粒中重金属的含量,但玉米籽实中Pb依然超标。     

玉米秸秆基改性生物质活性炭对Cd的吸附特性

以玉米秸秆为原料,制备了生物质活性炭(以下简称生物炭),用HNO_3、NaOH、沸水、四氢呋喃(THF)对其进行改性,并比较了不同生物炭对Cd的吸附特性,对沸水和THF滤液进行了光谱分析,结果显示:随着Cd初始浓度的增加,玉米秸秆基生物炭及改性产物对Cd的吸附量大体增强;Cd初始质量浓度超过25.0 mg/L时,吸附量表现为碱改性生物炭未改性生物炭THF改性生物炭沸水改性生物炭酸改性生物炭。NaOH通过改变玉米秸秆基生物炭表面官能团和元素构成,增强了其吸附能力。HNO_3使玉米秸秆基生物炭孔隙带正电荷,从而抑制了对Cd的吸附。沸水和THF从玉米秸秆基生物炭孔隙中溶出了有利于吸附反应的部分表面官能团,从而降低了其对Cd的吸附能力。随着Cd初始浓度增加,玉米秸秆基生物炭对Cd的吸附量大体增加,滤液pH大体降低。用玉米秸秆基生物炭处理污水中的Cd时,建议用碱改性法来提高其吸附能力。     

水旱轮作原位钝化削减技术修复土壤镉污染

为筛选适用于西南地区水旱轮作土壤Cd污染的修复技术,采用水稻-油菜轮作模式和原位钝化实验相结合的方式,比较了施用石灰、生物炭和羟基磷灰石(HAP)3种常见修复剂对土壤基本理化性质、作物产量及籽粒吸收积累镉的影响。结果表明:3种处理均能显著提高土壤pH,与CK相比,使用石灰、生物炭和HAP后,水稻收获期土壤pH分别提高了1.18、 0.51和0.91个单位,油菜收获期土壤pH分别提升了0.29、0.81和0.63个单位,但在油菜收获期施用石灰和HAP处理的土壤pH出现明显回落,降幅为0.91个和0.30个单位,施用生物炭处理的土壤pH则进一步提高了0.28个单位;3种处理在水稻收获期均能提高土壤有机质含量,其中生物炭效果最佳;3种处理均能显著降低水稻收获期土壤有效Cd含量,与CK处理相比,分别降低了21.84%、34.08%和20.12%,但在油菜收获期施用石灰和HAP处理的土壤有效Cd含量较相同处理在水稻收获期时有所回升,而生物炭则进一步降低了41.76%;石灰、生物炭和HAP处理对作物产量影响不大,但与CK处理相比,稻米中Cd含量分别降低了30.00%、43.33%和38.00%,油菜籽中Cd含量分别降低了21.00%、53.57%和55.90%,施用生物炭和HAP处理效果较佳。综上所述,生物炭修复水旱轮作模式下农田Cd污染效果最佳。     

玉米芯生物炭对河岸带土壤中乙草胺和阿特拉津的吸附性能

为改善农药对河岸带土壤污染状况,进而防控农业面源污染,以玉米芯为原料制备生物质炭,利用模拟实验研究其对河岸带土壤中乙草胺和阿特拉津的吸附性能影响,并探讨了其吸附机理。结果表明:河岸带土壤中添加生物炭可使乙草胺和阿特拉津的吸附容量显著增强,其吸附热力学过程与Freundlich和Langmuir模型拟合均有较好的相关性。与对照土壤相比,添加质量分数为1.0%生物炭的土壤对乙草胺的最大吸附量从13.28μg·g~(-1)升高到769.23μg·g~(-1);添加质量分数为0.3%生物炭的土壤对阿特拉津的最大吸附量从70.92μg·g~(-1)升高到333.33μg·g~(-1)。伪二级动力学速率方程对河岸带土壤吸附乙草胺和阿特拉津的过程拟合效果较好,优于一级动力学速率模型的拟合结果,吸附量以及吸附速率均与土壤中生物炭投加量成正比。玉米芯生物炭可作为河岸带土壤的修复剂,降低乙草胺和阿特拉津的迁移性。     

3种生物质炭对活性艳蓝KN-R的吸附简

选择由玉米秸秆、稻壳和稻草秸秆在825℃制成的生物质炭作为吸附剂，通过模拟实验，研究其对溶液中活性艳蓝KN-R的吸附特性，考察了pH值、时间、溶液初始浓度和生物质炭用量对吸附效果的影响。结果表明，当pH为2.0时，玉米秸秆炭和稻壳炭对活性艳蓝的吸附量均达到最大，而pH对稻草秸秆炭的影响不大；三者达到吸附平衡的时间分别为180、300和360 min，最大吸附量分别为114.05、54.60和68.19 mg/g。等温吸附过程可以用Langmuir方程来描述；动力学实验表明，吸附过程更符合拟二级动力学模型；热力学数据分析发现，吸附过程是自发进行的吸热过程。     

油菜秸秆髓芯对水中铜离子吸附作用及其机理

使用单因素实验,分别考察不同溶液p H、油菜秸秆髓芯加入量、溶液初始Cu~(2+)浓度和吸附时间4个因素对油菜秸秆髓芯吸附水中Cu~(2+)影响作用。采用BBD实验设计分析和优化其吸附条件,并得到最佳吸附条件组合。使用吸附等温方程和动力学方程对其吸附Cu~(2+)过程进行评价,运用红外光谱技术对吸附Cu~(2+)前后油菜秸秆髓芯进行分析,初步推断油菜秸秆髓芯吸附水中Cu~(2+)的机理。最佳吸附条件参数组合:在温度为25℃条件下、初始Cu~(2+)浓度为31 mg/L、溶液p H为5.0和油菜秸秆髓芯加入量为1.17 g/L条件组合下吸附120 min,在此组合条件下油菜秸秆髓芯对水中Cu~(2+)最大去除率达到96.86%。吸附等温方程表明,其吸附Cu~(2+)行为更符合Langmuir方程;动力学方程显示,其吸附Cu~(2+)行为符合二次动力学方程。红外光谱显示,油菜秸秆髓芯中的—C=O、酰胺II基团参与Cu~(2+)的络合吸附。油菜秸秆髓芯对水中Cu~(2+)呈现出良好的吸附性能,为油菜秸秆髓芯作为Cu~(2+)吸附剂提供了应用基础与理论依据。     

土壤作物系统镉污染及其防治研究

选择我国北方主要粮食作物冬小麦和夏谷进行盆栽试验，研究了土壤镉污染对作物生长发育和产量的影响及泥炭、羊粪两种不同类型的有机肥缓减土壤镉污染危害的作用；分析了镉在两种作物不同器官中的迁移效率和累积规律；认为施加有机肥是缓减土壤镉污染危害的有效措施，且施羊粪的效果比施泥炭好。     

湘江霞湾港段底泥的含镉量分布研究

为了研究湘江霞湾港段底泥中镉的含量分布和释放特性,对该河段底泥采样以测定含镉量,并采用Tessier连续提取法对镉形态进行分析测定.结果表明,湘江霞湾港段受到严重的镉污染,其底泥含镉量最高达359.8μg/g.湘江底泥和间隙水中含镉量的吸附-解吸平衡可采用Freundlich吸附等温式描述.对新霞湾和老霞湾排污口附近河流底泥的镉形态分析表明,镉污染物以有机质-硫化物结合态为主,分别占总量的73.3%(质量分数,下同)、65.3%,其次是残渣晶格结合态,分别占总量的26.5%、34.4%.     

紫茉莉修复镉污染土壤的研究

研究了紫茉莉在镉污染土壤中的生长特征、对镉的富集能力和体内分布规律。紫茉莉对镉的耐性较强，富集浓度最高可达92．82mg／kg，镉在紫茉莉的分布为根〉茎〉叶。紫茉莉在中、低浓度镉污染土壤中可取得较好的修复效果。     

Biochar- and phosphate-induced immobilization of heavy metals in contaminated soil and water: implication on simultaneous remediation of contaminated soil and groundwater

Long-term wastewater irrigation or solid waste disposal has resulted in the heavy metal contamination in both soil and groundwater. It is often separately implemented for remediation of contaminated soil or groundwater at a specific site. The main objective of this study was to demonstrate the hypothesis of simultaneous remediation of both heavy metal contaminated soil and groundwater by integrating the chemical immobilization and pump-and-treat methods. To accomplish the objective, three experiments were conducted, i.e., an incubation experiment was first conducted to determine how dairy-manure-derived biochar and phosphate rock tailing induced immobilization of Cd in the Cd-contaminated soils; second, a batch sorption experiment was carried out to determine whether the pre-amended contaminated soil still had the ability to retain Pb, Zn and Cd from aqueous solution. BCR sequential extraction as well as XRD and SEM analysis were conducted to explore the possible retention mechanism; and last, a laboratory-scale model test was undertaken by leaching the Pb, Zn, and Cd contaminated groundwater through the pre-amended contaminated soils to demonstrate how the heavy metals in both contaminated soil and groundwater were simultaneously retained and immobilized. The incubation experiment showed that the phosphate biochar were effective in immobilizing soil Cd with Cd concentration in TCLP (toxicity characteristics leaching procedure) extract reduced by 19.6 % and 13.7 %, respectively. The batch sorption experiment revealed that the pre-amended soil still had ability to retain Pb, Zn, and Cd from aqueous solution. The phosphate-induced metal retention was mainly due to the metal–phosphate precipitation, while both sorption and precipitation were responsible for the metal stabilization in the biochar amendment. The laboratory-scale test demonstrated that the soil amended with phosphate removed groundwater Pb, Zn, and Cd by 96.4 %, 44.6 %, and 49.2 %, respectively, and the soil amended with biochar removed groundwater Pb, Zn, and Cd by 97.4 %, 53.4 %, and 54.5 %, respectively. Meanwhile, the metals from both groundwater and soil itself were immobilized with the amendments, with the leachability of the three metals in the CaCl₂ and TCLP extracts being reduced by up to 98.1 % and 62.7 %, respectively. Our results indicate that the integrated chemical immobilization and pump-and-treat method developed in this study provides a novel way for simultaneous remediation of both metal-contaminated soil and groundwater.     

Adsorption of Pb(II) on variable charge soils amended with rice-straw derived biochar

Two Ultisols and one Oxisol from tropical regions of southern China were incubated with rice straw biochar to investigate the effect of biochar on their surface charge and Pb(II) adsorption using batch methods. The incorporation of biochar induced a remarkable increase in soil cation exchange capacity after 30 d of incubation. The incorporation of biochar significantly increased the adsorption of Pb(II) by these variable charge soils; the enhancement of adsorption of Pb(II) by these soils increased with the addition level of biochar. Adsorption of Pb(II) involved both electrostatic and non-electrostatic mechanisms; however, biochar mainly increased Pb(II) adsorption through the non-electrostatic mechanism via the formation of surface complexes between Pb²⁺ and functional groups on biochar. There was greater enhancement of biochar on the non-electrostatic adsorption of Pb(II) by the variable charge soils at relatively low pH. Therefore, the incorporation of biochar decreased the activity and availability of Pb(II) to plants through increased non-electrostatic adsorption of Pb(II) by acidic variable charge soils.     

添加天然沸石和石灰对土壤镉形态转化的影响

采用土壤培养实验,研究镉污染土壤中添加沸石、石灰及两者配施对土壤pH值和土壤镉形态变化的影响。结果表明,土壤pH值随沸石用量的增加而增加,随培养时间呈现先增加后下降并逐渐趋于稳定的趋势,但均高于对照。高剂量石灰的处理对土壤pH的影响最大,与对照相比土壤pH提高了3.33个单位。在土壤5~50 d培养过程中,石灰处理的土壤交换态镉含量呈现先逐渐降低而后略有升高的趋势,其余处理均呈下降趋势。培养50 d后,高剂量的沸石、石灰及高剂量沸石与石灰配施处理的土壤交换态镉含量从5 d时的67.54、61.95和55.56 mg/kg降低至54.65、49.93和45.96mg/kg。相关分析表明,不同培养时期交换态镉含量与土壤pH值呈负相关关系。在10个处理中,L2Z3(石灰2 g/kg土和沸石60 g/kg土)组合处理效果最好,使土壤交换态镉含量下降了34.68%,碳酸盐结合态镉含量上升了4.30%,铁锰氧化结合态镉含量上升了16.97%,有机结合态镉含量上升了1.31%,残渣态镉含量上升了12.11%。     

Effect of culturing temperatures on cadmium phytotoxicity alleviation by biochar

Biochar produced from rice straw at 400 °C (RS400) was prepared to determine its alleviating effect on Cd phytotoxicity to wheat seedlings under different cultivation temperatures and pH. A hydroponic system (pH 4.3) and a loam soil slurry system were designed to respectively simulate acidic and neutral soil condition, and cultivation at increasing temperatures (20, 25, and 30 °C) were performed to evaluate the greenhouse effect. The root and shoot elongation and the Cd concentration in root and solution were measured; furthermore, batch experiments for Cd adsorption were undertaken. An increasing inhibition of the root by Cd addition was observed at increasing temperatures. The inhibition rate was 50.50 and 20.80% in hydroponic system and slurry system at 25 °C, respectively; however, the corresponding inhibition rates of root were significantly decreased to 25.5 and 3.5% with addition of RS400. This is mainly attributed to the reduction of Cd migration into the roots by RS400, which decreased Cd bioavailability. The mechanism behind the reduced Cd bioavailability is attributed to the Cd adsorption and the strong buffering capacity of acidity by RS400. Therefore, biochar could be a potential amendment for the remediation of Cd-contaminated soil even at increasing culturing temperatures.

     

Inhibition of rainbow trout acetylcholinesterase by aqueous and suspended particle-associated organophosphorous insecticides

Cadmium (Cd) adsorption on 14 non-calcareous New Jersey soils was investigated with a batch method. Both adsorption edge and isotherm experiments were conducted covering a wide range of soil composition, e.g. soil organic carbon (SOC) concentration ranging from 0.18% to 7.15%, and varying Cd concentrations and solution pH. The SOC and solution pH were the most important parameters controlling Cd partition equilibrium between soils and solutions in our experimental conditions. The Windermere humic aqueous model (WHAM) was used to calculate Cd adsorption on soils. The effect of solution chemistry (various pH and Cd concentrations) on Cd adsorption can be well accounted for by WHAM. For different soil compositions, SOC concentration is the most important parameter for Cd binding. Only a fraction of SOC, the so-called active organic carbon (AOC), is responsible for Cd binding. We found a linear relationship between SOC and AOC based on the adsorption edge data. The linear relationship was validated by the independent data sets: adsorption isotherm data, which presumably can be used to predict Cd partition equilibrium across a wide range of soil compositions. The modeling approach presented in this study helps to quantitatively predict Cd behavior in the environment.     

鼠李糖脂协助下的土壤中镉电动修复

实验研究了重金属Cd在生物表面活性剂鼠李糖脂协助下的电动修复过程,通过不同方式、不同浓度、不同酸碱度的鼠李糖脂溶液的添加与空白处理对比,探讨了鼠李糖脂协助下电动修复过程中的Cd在土壤介质中的迁移转化和机理,分析了鼠李糖脂溶液作为电动修复添加剂的可行性。结果表明,中等浓度酸性的鼠李糖脂溶液(pH=4.78,浓度为0.5、1和2 g/L)能对土壤中的重金属Cd进行有效的富集,富集量均在初始值的4倍以上,且其可交换态比重均大于42.07%,非常有利于土壤进行二次修复。此外,以pH=4.78,浓度为0.5 g/L的鼠李糖脂溶液作为预处理剂的Ex-08中的重金属Cd并未出现富集现象,但其对重金属的Cd的总去除效率达到了49.27%。表明利用鼠李糖脂溶液作为电动修复添加剂进行土壤重金属修复是可行的。     

Effect of biochars on adsorption of Cu(II), Pb(II) and Cd(II) by three variable charge soils from southern China

The purpose of this study is to compare the relative contribution of different mechanisms to the enhanced adsorption of Cu(II), Pb(II) and Cd(II) by variable charge soils due to incorporation of biochars derived from crop straws. The biochars were prepared from the straws of canola and peanut using an oxygen-limited pyrolysis method at 350 °C. The effect of biochars on adsorption and desorption of Cu(II), Pb(II) and Cd(II) by and from three variable charge soils from southern China was investigated with batch experiments. Based on the desorption of pre-adsorbed heavy metals, the electrostatic and non-electrostatic adsorptions were separated. EDTA was used to replace the heavy metals complexed with biochars and to evaluate the complexing ability of the biochars with the metals. The incorporation of biochars increased the adsorption of Cu(II), Pb(II) and Cd(II) by the soil; peanut straw char induced a greater increase in the adsorption of the three metals. The increased percentage of Cd(II) adsorption induced by biochars was much greater than that for the adsorption of Cu(II) and Pb(II). Cu(II) adsorption on three variable charge soils was enhanced by the two biochars mainly through a non-electrostatic mechanism, while both electrostatic and non-electrostatic mechanisms contributed to the enhanced adsorption of Pb(II) and Cd(II) due to the biochars. Peanut straw char had a greater specific adsorption capacity than canola straw char and thus induced more non-electrostatic adsorption of Cu(II), Pb(II) and Cd(II) by the soils than did the canola straw char. The complexing ability of the biochars with Cu(II) and Pb(II) was much stronger than that with Cd(II) and thus induced more specific adsorption of Cu(II) and Pb(II) by the soils than that of Cd(II). Biochars increased heavy metal adsorption by the variable charge soils through electrostatic and non-electrostatic mechanisms, and the relative contribution of the two mechanisms varied with metals and biochars.     

Column- and catchment-scale transport of cadmium: effect of dissolved organic matter

In the Ellen catchment on the Pinjarra Plain, NE of Perth in Western Australia, cadmium from fertilisers is starting to leach from soils. About 70% of surface soils in the Ellen catchment are sandy and often on top of a shallow ephemeral water table. Adsorption of Cd in the sandy soils of the Ellen catchment was studied by batch adsorption and by leaching small columns of soil. Adsorption of Cd increases linearly with increasing soil organic matter content and exponentially with increasing pH. Cadmium is significantly mobilised in the sandy soils by dissolved organic matter.The capacity of most of the sandy soils in the Ellen catchment to adsorb phosphate from fertiliser has been saturated. Resulting concentrations in Ellen Brook average 500 μg L⁻¹ P. Cadmium is adsorbed more strongly in the sandy soils than phosphate and is just starting to leach into Ellen Brook. From a comparison of Cd/P ratios in water, soils and fertiliser, cadmium concentrations in Ellen Brook are estimated to be at 10–30% of their maximum for complete breakthrough from soils. Present concentrations of Cd in Ellen Brook average 0.1 μg L⁻¹ and are estimated to approach the maximum for complete breakthrough in 100 yr. Maximum Cd concentrations in Ellen Brook could range from 0.6 to 2 μg L⁻¹, depending on rates of input with fertiliser and future increases in agricultural land use in the catchment.Breakthrough curves, resulting from leaching Cd through small columns of sandy soil, indicate that adsorption significantly increases the effective hydrodynamic dispersion of Cd. Longitudinal dispersivities, measured at pore-water velocities of 0.7–14 m day⁻¹, were 5 cm for Cd and 0.1–0.2 cm for chloride. The much greater dispersion of Cd in the sandy soils than of chloride is shown not to be caused by non-equilibrium adsorption.     

Monometal and competitive adsorption of heavy metals by sewage sludge-amended soil

Sewage sludge-amended soils may alter their ability to adsorb heavy metals over time, due to the decomposition of sludge-borne organic matter. Thus, we studied Cd, Ni, and Zn adsorption by a sewage sludge-amended soil (Typic Xerofluvent) before and after one-year incubation in both monometal and competitive systems. In the monometal system, the order of decreasing sorption was Zn>Cd>Ni. Competition significantly reduced metal K(d), especially that of Cd which decreased by nearly 50%. Over the course of the incubation there was a 31% reduction of soil organic matter content. At the same time, in competitive systems Cd K(d) significantly decreased, while Zn K(d) significantly increased, and Ni K(d) remained unaffected. This study shows that sewage sludge-amended soils may change in their ability to sorb heavy metals over time at high metal concentrations. The data suggest that Cd is likely to be of most environmental significance in such soils, since it exhibited decreased sorption under competitive conditions and as the organic matter content of the soil was reduced. The potential for long-term release of metals should be considered in the risk assessment associated with sewage sludge addition to soils, particularly in climates where degradation of organic matter is likely to be enhanced.     

Characteristics of heavy metals in soils and grains of wheat and maize from farmland irrigated with sewage

The farmland irrigation with the sewage is a common and better pathway to save the resource of groundwater in Northern China. The investigation was conducted in the farmland along the Fuhe River to explore characteristics of heavy metals in soils and grains of wheat and maize from a long-term sewage-irrigated area of Baoding region. The results showed that the topsoil with long-term sewage irrigation accumulated more Cd, Pb, and Hg compared with that of soil irrigated with groundwater and their corresponding natural background values. Cd concentrations in 48% of sewage-irrigated soil samples exceeded the Chinese safety limitation at 0.6 mg/kg, but less Cd accumulated in crop grains and did not pose the potential health risk. On the contrary, Pb levels in soils irrigated with sewage were lower than the safety limitation but Pb concentrations in 24% of wheat grain samples exceeded the Chinese national safety limit. Long-term sewage irrigation did not increase As, Cr, and Ni concentrations in soils or crop grains. The target hazard quotient (THQ) of heavy metals in edible grains of crops was selected to assess their risk to human health. Total THQ values were higher than 1.0 for the wheat samples from sewage-irrigated area and both sewage-irrigated and smelter-impacted areas, and As is the main contributor to the total THQ and posed the potential risk to human health. Therefore, the accumulation of Cd, Pb, Hg, and As in soils and crops in sewage-irrigated area should be monitored continuously to ensure food safety and security.