Chemical composition and seasonal variation of acid deposition in Guangzhou, South China: comparison with precipitation in other major Chinese cities

With the aim of understanding the origin of acid rains in South China, we analyzed rainwaters collected from Guangzhou, China, between March 2005 and February 2006. The pH of rainwater collected during the monitoring period varied from 4.22 to 5.87; acid rain represented about 94% of total precipitation during this period. The rainwater was characterized by high concentrations of SO₄²⁻, NO₃⁻, Ca²⁺, and NH₄⁺. SO₄²⁻ and NO₃⁻, the main precursors of acid rain, were related to the combustion of coal and fertilizer use/traffic emissions, respectively. Ca²⁺ and NH₄⁺ act as neutralizers of acid, accounting for the decoupling between high SO₄²⁻ concentrations and relatively high pH in the Guangzhou precipitation. The acid rain in Guangzhou is most pronounced during spring and summer. A comparison with acid precipitation in other Chinese cities reveals a decreasing neutralization capacity from north to south, probably related to the role and origin of alkaline bases in precipitation.     

Soil acidification and foliar nutrient status of Ontario's deciduous forest in 1986 and 2005

To assess the impacts of the decline in sulphur (S) deposition over the past 20 years in Ontario, soil chemistry and sugar maple (Acer saccharum Marsh) foliar chemistry were measured at 17 sites in south and central Ontario in 2005 and compared with archived samples collected in 1986. Foliar S concentrations were lower in 2005, reflecting the decline in S deposition whereas foliar N remained unchanged, reflecting the lack of change in N deposition in Ontario. Mineral soil pH, exchangeable base cations were lower in 2005 whereas total S, N and cation exchange capacity (CEC) were unchanged. Foliar concentrations of Ca were positively related to soil Ca levels in the A-horizon and were lower in 2005. Despite evidence of increasing soil acidity and losses of calcium, foliar base cation concentrations at most sites were adequate for sugar maple and forest health in terms of canopy appearance (Decline Index) improved.     

Ion activity and distribution of heavy metals in acid mine drainage polluted subtropical soils

The oxidative dissolution of mine wastes gives rise to acidic, metal-enriched mine drainage (AMD) and has typically posed an additional risk to the environment. The poly-metallic mine Dabaoshan in South China is an excellent test site to understand the processes affecting the surrounding polluted agricultural fields. Our objectives were firstly to investigate metal ion activity in soil solution, distribution in solid constituents, and spatial distribution in samples, secondly to determine dominant environment factors controlling metal activity in the long-term AMD-polluted subtropical soils. Soil Column Donnan Membrane Technology (SC-DMT) combined with sequential extraction shows that unusually large proportion of the metal ions are present as free ion in the soil solutions. The narrow range of low pH values prevents any pH effects during the binding onto oxides or organic matter. The differences in speciation of the soil solutions may explain the different soil degradation observed between paddy and non-paddy soils.     

油页岩循环流化床锅炉底渣和飞灰中重金属元素浸出毒性研究

为了研究我国桦甸油页岩65 t/h循环流化床锅炉的底渣和飞灰中重金属元素Cr、Cu、Pb和Zn的赋存状态及不同酸度条件下的浸出特性,分别进行了逐级提取实验和分批浸出的淋滤实验。逐级提取实验结果表明,这4种元素在底渣和飞灰中具有基本相当的赋存状态。硫化物结合态和稳定的残渣态是各元素的主要赋存状态,元素的潜在浸出能力大小表现为:PbCrCuZn,飞灰中各元素的潜在浸出能力大于底渣中的。浸出实验结果表明,元素的赋存状态决定了其浸提能力,浸提液的pH值对各元素浸出能力的影响不尽相同,各元素的浸出能力随浸提时间的延长都会趋于平衡,Cr和Pb的浸出浓度都高于地表水和饮用水的国家标准。     

采用响应面优化酸浸法回收报废三元电池中有价金属的研究

为简化传统报废锂离子电池(LIBs)处理工艺,对报废镍钴锰三元(NCM)电池正极材料进行浸出处理,在单因素试验的基础上,利用响应面分析法分析浸出温度、抗坏血酸浓度、固液比和浸出时间对正极材料中Co、Li、Mn、Ni浸出率的影响。建立数学回归模型,分析因素间的交互作用。结果表明,各金属的回归方程模型均显著(p<0.05),R^2≥0.88,信噪比N>4,C.V.较低,可用于报废NCM电池中Co、Li、Mn、Ni浸出工艺的分析与预测,其中浸出温度和抗坏血酸浓度的交互作用对Li和Ni的浸出率影响最大。各金属浸出率的最佳工艺条件为:浸出温度69.26℃,抗坏血酸浓度1.24 mol/L,固液比31.30 g/L,浸出时间59.79 min。在此条件下,Co、Li、Mn、Ni浸出率分别为96.35%、92.53%、89.28%、56.32%。结合回归分析及可操作性原则,进行3次平行试验,试验结果与模型理论预测值接近。试验过程简单,处理方法对环境友好,有利于工业化生产。     

Leaching of metals on stabilization of metal sludge using cement based materials

Toxicity characteristic leaching procedure(TCLP) of zinc plating sludge was carried out to assess the leaching potential of the sludge and the leachates were analyzed for heavy metals. The concentration of zinc, chromium, and lead in the leachate were 371.5 mg/L, 1.95 mg/L and 1.99 mg/L respectively. Solidification of zinc sludge was carried out using four different binder systems consisting of cement mortar, fly ash, clay and lime and cured for 28 d, The ratio of sludge added varied from 60% to 80% by volume. The solidified products were tested for metal fixing efficiency and physical strength. It was observed that the volume of sludge added that resulted in maximum metal stabilization was 60% for all the combinations, above which the metal fixation efficiency decreased resulting in high values of zinc in the leachate. Addition of 5% sodium silicate enhanced the chemical fixation of metals in all the binder systems. Among the four fixing agents studied, mixture of fly ash: lime, and cement mortar: lime stabilized zinc and other metals in the sludge effectively than other combinations. Addition of lime increased the stabilization of zinc whereas cement mortar increased the strength of the solidified product.     

煤矸石与粉煤灰淋溶渗出液对水环境影响研究

试验表明,煤矸石与粉煤灰淋溶渗出液pH值将会稳定在煤矸石和粉煤灰本身pH值附近,淋溶渗出液的重金属离子含量及酸碱度符合<一般工业固体废物贮存、处置场污染控制标准>(GB18599-2001),不会对地下水环境造成污染.试验还表明煤矸石和粉煤灰对淋溶水中高含量的重金属有一定的吸附作用.     

螯合剂和生物表面活性剂对 Cu、Pb污染塿土的淋洗修复

螯合剂和生物表面活性剂由于其具有较强的螯合、增溶等特征而被广泛用于土壤中重金属、有机物污染的修复,为探明其对石灰性土壤中重金属污染的修复效果,选用螯合剂乙二胺四乙酸(EDTA)和柠檬酸(CIT)以及生物表面活性剂二鼠李糖脂(RL2)作为淋洗剂,采用批实验和柱实验方法,研究了3种淋洗剂以及生物表面活性剂与螯合剂复合对塿土中Cu、Pb的淋洗修复效果.结果表明,不同淋洗剂对塿土中Cu、Pb的淋洗百分率大小表现为EDTA>CIT>RL2,在淋洗剂浓度为0.02mol.L-1时,3种淋洗剂淋洗Cu的百分率分别为62.74%(EDTA)、52.28%(CIT)和15.35%(RL2),淋洗Pb的百分率分别为96.10%(EDTA)、23.08%(CIT)和14.42%(RL2).当RL2浓度在100 CMC时,其对EDTA、CIT淋洗Cu具有协同增溶作用;而当RL2浓度在200 CMC时,对EDTA和CIT淋洗Cu表现为拮抗作用.RL2与EDTA复合对Pb的淋洗影响类似于对Cu的影响;而RL2的存在抑制了CIT对Pb的淋洗作用.EDTA、CIT能有效去除污染塿土中交换态、吸附态、碳酸盐结合态和有机结合态的Cu、Pb;RL2可以去除塿土中交换态、吸附态结合的Cu、Pb.     

甘肃白银东大沟铅锌镉复合污染场地水泥固化稳定化原位修复

以甘肃白银东大沟Pb、Zn、Cd复合污染土壤为研究对象,通过毒性浸出、形态提取、微观分析等手段,研究了水泥对重金属污染场地的固化稳定化效果及适用性.毒性浸出结果表明,水泥对污染土壤中Cd、Zn能够起到较好的固化稳定化作用,在5%的添加量下,水泥对Cd、Zn的修复效率分别达到99.5%~100%、96.6%~98.8%,而Pb的浸出浓度提高了2.6~5.8倍;在8%的添加量下,水泥对Cd、Zn的修复效率分别达到99.6%~100%,94.4%~97.9%,而Pb的浸出浓度提高了1.9~12.5倍.形态分析结果表明,水泥能够使土壤中的酸可提取态Cd、Zn向残渣态转化,可还原态Pb向可氧化态、残渣态转化,稳定性增强.微观特征分析结果表明,Pb~(2+)、Zn2+、Cd2+这3种离子可以参与水泥的水化反应,生成相应的硅酸盐矿物和氢氧化物,进而对其起到固化稳定化作用.综上,水泥在重金属污染场地修复工程中具有良好的优势,但在具体应用过程中需注意场地及环境条件的特殊性.     

太湖典型地区蔬菜地土壤磷素淋失风险

以太湖典型地区宜兴市大浦镇湖滨公路以东沿太湖50hm2老蔬菜基地为研究对象,采用网格法(50m×50m)采集表层(0～20cm)土壤样品156个.地统计学分析表明:土壤P(全P、Bray P、CaCl2浸提水溶P)呈明显空间变异,土壤高P区出现在朱渎港、林庄港两村庄附近.土壤Bray P低于60mg·kg-1,几乎没有检测到CaCl2浸提水溶P,而当土壤速效P大于60mg·kg-1后,CaCl2浸提水溶P随Bray P增加而直线增加.以土壤Bray P含量60mg·kg-1为研究地土壤发生P淋溶的临界值,研究范围内土壤发生P淋溶面积占总调查面积28%.针对目前土壤状况,提出控制蔬菜地P淋溶对策.