Measurement of the leaching behaviour of granular solid wastes

Leaching of granular solids can be described in terms of specific mass transfer functions of a simple mathematical form.

The parameters can be determined by column leaching experiments under well known flow conditions.

Initially available concentrations are obtained from batch experiments at high dilution. Total concentrations in the solids are determined independently to calculate the available fractions.

The determination of the flow pattern is done by radiotracer measurements. Leachates are analyzed by various analytical methods including AAS and INAA. Total concentrations in the solids are determined by INAA preferably.     

Diazinon leaching through a sandy soil amended with different humic materials

The water leaching of diazinon (O,O‐diethyl‐O‐2‐isopropyl‐6‐methylpyrirnidin‐4‐yl phosphoroth‐ioate) through soil columns, was studied after column amendments with two well characterized humic acids (HA), in both liquid and solid state, and with the original raw organic materials, an oxidized coal and a leonardite, from which the HA were extracted. The percolation curves and the pesticide distribution over the soil columns showed that the addition of the raw organic materials and the solid HAs reduced significantly the mobility of the pesticide along the soil column. The oxidized coal was more effective than the leonardite original material; the different origin of the two carbon‐rich materials had an influence on the diazinon movement along the soil columns and such difference was enhanced with increasing addition rates. Moreover, incubation at field capacity for two months of the soil columns treated with raw oxidized coal and leonardite, largely enhanced the described effects on pesticide behaviour. A complete adsorption of diazinon on columns and a practical absence of leaching was observed when the HA from both materials were added in dissolved form. These results were explained with the swelling of the humic micelles in water and the enhanced availability of inner hydrophobic surfaces for the strong adsorption of diazinon. The water diffusion into the solid humic materials after two months incubation, also explains their high pesticide retention capacity. This work indicates the usefulness of either solid o dissolved humic substances, with the proper hydrophobic character, in preventing the vertical leaching of non‐polar organic pesticides in soils.     

模拟酸雨对街道灰尘重金属淋溶的累积释放特征与释放模型

以泉州市交通繁忙区街道灰尘为研究对象,采用模拟酸雨动态淋溶实验和改进的BCR四步提取法研究街道灰尘中重金属元素在不同酸度(pH=3.5、4.5、5.6)模拟酸雨淋溶下的溶出规律及形态变化.结果表明,街道灰尘中重金属元素的累积释放量均随模拟酸雨pH的降低而增加,当pH值为3.5和4.5时,Cu、Pb、Mn、Ni、V、As和Co的释放过程为快速释放阶段,Cr、Zn和Fe的释放过程分为快速释放和相对平稳释放两个阶段;当pH值为5.6时,除Co、V为快速释放过程外,其余重金属都处于相对慢速的释放过程.动力学方程拟合结果表明,双常数速率方程能更好地描述上述重金属元素的累积释放特征.尘样经模拟酸雨淋溶后,弱酸可溶态中Co、Cu、Mn、Zn、Ni百分含量有所增加,Cr、Fe、Pb百分含量变化不明显;可还原态中Cr、Pb、Cu、Ni百分含量有所增加,Mn、Zn、Co百分含量有所下降;可氧化态中上述各元素的百分含量均有所降低;残渣态中除Ni、Mn百分含量有所下降外,其它元素百分含量变化均不显著.     

Does low N-mineralisation rate in soils under grass help limit nitrate leaching in summer?

This paper aimed to confirm the hypothesis that rates of ammonification and net mineral-N production in soils under grass in summer are low and this, rather than nitrate uptake by plants, reduces mineral leaching from soils in summer. Six sets of soil samples were collected from under mown grass on the University of York campus in the UK. Samples were taken from two depths in late summer (August) and late autumn (November) to compare seasonal differences in N species transformations when field-moist soils were incubated for a week at ambient outdoor temperatures after prior removal of vegetation. Ammonification and net mineral-N production rates were low in August in spite of warm temperatures. Net mineral-N production rates were also low in November. The results agreed with those of an earlier study in a different year after considering weather differences between years. They support the hypothesis that litter accumulated over autumn/winter will be minimally mineralised and retain N before the temperature rises in spring. The study shows the merit of measuring concentrations of mineral-N species in both fresh soils and soils incubated at ambient outdoor temperatures after removing plant material to eliminate plant N uptake effects. The results suggest that soil C% and N% are more important than soil C:N ratio alone in understanding controls on N transformations.     

Vertical infiltration of fuel oil hydrocarbons in an agricultural soil

The influence of rainfall, air temperature and soil moisture on the vertical mobility in the soil of fuel oil hydrocarbons (HC) was investigated in a field experiment. A controlled spreading of fuel oil (nC10‐nC25) was performed at a rate of 5 L HCm^‐2 on an agricultural soil in summer and in winter. Concentration, chemical composition of HC and soil moisture were regularly determined at different soil depths between 0 and 140 cm, 1 h, 3, 8and 15 days (d) after the spreading of oil. Sorption of hydrocarbons onto the organo‐mineral matrix of the soil was studied in laboratory experiments. The results showed that in summer, with an air temperature of 24°C and without water leaching in the soil profile, 65% of the initial HC remained trapped in the 0–140 cm soil layer, about 20% of the HC volatilized and around 15% migrated deeper. A vertical selective migration of the lightest (nC10‐nC15) HC (naphthas) was shown lSd after the spreading of fuel oil. Naphthas progressively reached the 120–140 cm soil layers whereas the heavy fractions of oil (nC17‐nC25) migrated and concentrated in the 0–60 cm soil layers. In winter, when soil was regularly watered by rainfalls and at low air temperatures, only 47% of the initial HC remained in the 0–140 cm profile after 15 d. A fast vertical infiltration of naphthas occurred within the first 3 d. After 15 d, all HC were detected in the same relative amounts as in the initial oil in the whole profile. Volatilization was negligible in winter and an increase in the migration of total oil at depth in the soil profile was shown. As inferred from the laboratory experiments, the high soil moisture led to the decrease in HC sorption on the organo‐mineral matter of the soil.     

Behaviour of Dioxins,Furans and Metals Associated with Stabilized Msw Combustor Ash in Sea Water

This report presents the results of a research programme designed to examine the engineering and environmental acceptability of stabilizing municipal solid waste (MSW) combustor ash for artificial reef construction. Municipal solid waste combustor ash was combined with Portland cement to form solid blocks using conventional construction block making technology. the resultant stabilized combustor ash (SCA) blocks were used to construct an artificial habitat in Conscience Bay, Long Island Sound, New York and compared to identical concrete blocks, fabricated using natural aggregates. Over a 4.5 year period divers periodically returned to the site to monitor the interaction of SCA blocks with the marine environment and compare the performance of these blocks with the concrete control blocks. Results show that the SCA blocks retain their strength after prolonged sea water exposure. Contaminants of environmental concern, including metals, dioxins and furans, were retained within the cementitious matrix of the SCA blocks after prolonged sea water submersion. in addition, organisms growing on the surfaces of the SCA blocks did not accumulate contaminants from the blocks.     

细胞冻融破碎对城市污泥中重金属浸出浓度的影响

利用反复冻融的方法对污泥细胞进行破碎,考察处理前后污泥重金属的浸出浓度和形态分布的变化,并通过扫描电镜和红外光谱分析污泥中微生物细胞形貌和有机化合物含量的变化.结果显示,经过细胞破碎处理后,污泥中重金属的浸出浓度增大,锌、镍、铬、镉和铜的浸出浓度比原始污泥分别增加了9.7%、5.1%、25%、9%和50%.不稳定态增加,锌和镍的不稳定态分别增加了20.4%和37.9%,锌、镍、铬和铜的有机态分别减少了4.2%、8.2%、1.2%和5.1%.细胞发生了形貌上的变化,细胞体破碎程度严重.细胞EPS以及污泥中的蛋白质、羧酸、多聚糖等有机基团含量明显减少.细胞破碎后污泥浸出浓度增加的主要原因是污泥中有机态的重金属转化成了其他不稳定态的重金属.     

含砷废物资源化产品中砷的浸出特性与环境风险分析

分别以我国某地2种含砷废物(污泥和废渣)为研究对象,用EA NEN 7371实验方法分析其不同资源化产品(烧制砖、免烧砖和含砷水泥等)中As的有效量浸出特性,从环境风险的角度探讨了含砷废物资源化利用的可行性. 结果显示:含砷污泥进行烧砖处置后,其产品中As的有效量浸出率从15%左右升至60%～70%;含砷废渣与水泥进行混合粉磨共处置后,含砷水泥产品中As的有效量浸出率从60%～70%降至4%以下;含砷废渣制成免烧砖后,As的有效量浸出率从60%～70%降至10%左右. 表明含砷污泥不宜进行烧砖处置;而含砷废渣可根据含砷量,在控制掺加比例的条件下与水泥熟料共处置生产混合水泥或作为原材料生产免烧砖.      

浸取方式对废物水泥窑共处置产品中Pb,Cd和Ni浸出的影响

模拟煅烧试验制取含Pb,Cd和Ni的水泥熟料,并将其制成混凝土样品,通过水槽浸出试验研究间歇浸取方式对混凝土中Pb,Cd和Ni释放的影响. 结果表明:间歇碳化保存处理浸出液的pH为9.5～10.4,低于连续浸取处理浸出液的pH(10.3～11.0),而间歇自然保存处理的浸出液pH则与连续浸取处理浸出液的pH相近;间歇浸取过程的碳酸化作用增加了混凝土中Pb和Cd的释放,表现为间歇浸取碳化保存处理的累积浸出量最大(Pb和Cd分别为686和332 mg/m2),连续浸取处理的累积浸出量最低(Pb和Cd分别为480和203 mg/m2);间歇处理对Ni的释放影响与Pb和Cd的不同,连续浸取处理的累积浸出量最大,为155 mg/m2,而间歇碳化保存处理的累积浸出量(85 mg/m2)最小.      

菇渣用作无纺布容器育苗成型机配套基质的研究

为探讨菇渣在无纺布容器育苗成型技术中作为配套容器基质应用的可行性,研究了育苗成型机制备的菇渣(发酵后)和草炭容器基质的基本理化性质、盐分淋洗特征及其对火炬树和侧柏出苗及生长的影响。结果表明:菇渣基质的容重、通气状况与草炭基质之间无显著差异,pH值虽显著高于草炭基质,但适宜多数植物生长;相对于草炭基质,菇渣基质的持水能力不足,保肥性能较差;菇渣基质的适宜水分范围(36.1%~143.5%)明显小于草炭基质(41.9%~193.8%),有效水绝对含量较低;菇渣基质的电导率(3.71 mS.cm-1)虽高于安全育苗的临界值(≤2.6 mS.cm-1),但随着浇水次数的增加可逐渐降到安全值以下;菇渣基质的全氮、全磷和全钾含量显著高于草炭基质。在充足的水分和养分条件下,菇渣和草炭容器基质对侧柏和火炬树出苗及成活的影响基本一致,但菇渣基质对火炬树的育苗效果优于草炭基质。可见,只要保证充足水分,菇渣基质在无纺布容器育苗成型技术中可以替代草炭基质用于火炬树和侧柏的育苗。