酸雨条件下黄壤对镉的释放动力学研究

对不同酸雨条件下黄壤对镉释放的研究发现，吸附态镉释放的过程可以分为快反应和慢反应两个阶段。在以常用动力学方程实验数据进行拟合的基础上，创建了反三角函数方程。结果表明，反三角函数方程对多种酸雨条件下黄壤吸附态镉释放过程的拟合度最佳，此外多项式方程、双常数方程也能较好地描述这一过程。     

土壤镉处理对棉花镉吸收及分布规律的影响

用CdCl2将盆栽土壤Cd浓度处理为1mg／kg、5mg／kg、10mg／kg、20mg,／kg、30mg／kg种植棉花，研究棉花对镉的吸收及镉在棉花体内的分布规律。结果表明，当土壤镉浓度小于30mg／kg时，镉在棉花体内的分布呈现不同的规律。当土壤镉浓度小于5mg／kg时，镉主要分布在棉花的地上部；当土壤镉浓度大于20mg／kg时，镉主要分布在棉花的叶片、根、茎中，其中叶片的镉含量最高，棉絮镉含量最低。不同镉污染水平下，棉花的镉富集系数均小于1。当土壤镉污染浓度为5mg／kg时，棉花叶片的镉富集系数为0．76。在同一镉污染水平下，棉花叶片的镉转运系数最高。当土壤镉含量小于20mg／kg时，棉花茎、叶、棉絮的转运系数平均为4．63。     

中国南方酸雨的分布特征及其成因分析

本文阐述了酸雨的危害、近几年中国南方地区酸雨的污染的时空分布状况、酸雨的成因等3方面的内容。研究表明：我国南方酸雨区的酸雨污染状况基本上处在一个稳定的时期。降水pH〈5的区域有从长江中上游向长江中下游发展的趋势;在时间分布上,秋季冬季降水pH低,酸雨发生的频率高;春季夏季降水pH高,酸雨发生的频率低。在酸雨的成因上,着重讨论了大气性质、污染物的迁移和扩散、气候条件、大气中颗粒物浓度以及土壤性质对酸雨形成的影响。     

2006年泸州市酸雨及降水中阴、阳离子浅析

本文对2006年泸州市的酸雨污染状况,以及降水中阴、阳离子成分进行了分析,为确定泸州市酸雨污染原因和酸雨类型提供了依据,并对降低酸雨污染提出了控制措施。     

2006～2020年宁波市沿海酸雨特征及化学组分分析

为了更有针对性地治理酸雨污染，利用宁波市沿海站点2006～2020年降水量、pH及化学组分观测资料，分析了其酸雨污染特征及关键的影响因素。结果表明：宁波市沿海降水年均pH值在4.40～5.37之间，酸化程度总体呈减轻趋势，但酸雨频率没有明显改善，仍呈高发态势。pH值季节变化特征明显：夏季高、冬春季低。2020年宁波市沿海降水中总离子当量浓度为335.31μeq/L,比2006年下降约52%。SO₄^2-、NO^-₃是主要阴离子，两者之和占比约30%～50%;但2016～2019年Cl^-占比最大。NH⁺₄是主要阳离子，占12%～31%,其次是Ca²⁺和Na⁺。阴离子和阳离子浓度年变化升降趋势一致程度高，是酸雨污染状况难以改善的重要因素之一。由于对NO_X的控制力度不及SO₂以及机动车尾气排放的增加，NO^-₃的致酸...     

成都市区酸雨变化及降雨化学组成分析

依据成都市1995～2003年城区酸雨监测统计资料,本文对成都市城区酸雨的变化特征、离子化学组成进行了分析。结果表明:城区降水酸度变化呈现出一定的波动性,酸雨频变化表现出较大的波动性;1999年和2000年酸雨年均酸度及频率情况都较好,之后出现反弹;降水中离子含量高,雨水污染严重;降水中CSO2-的比值正在逐步缩小,酸雨状况转变为硫/CNO-34酸型和硝酸型并重的局面,大气污染物中NOx的贡献率正在升高。灰色关联分析表明:降水pH值与雨水中碱性阳离子的关联序为NH+4>Ca2+>Mg2+>K+>Na+;降水pH′值与雨水中酸性阴离子的关联序为Cl->F->SO2-3。4>NO-     

赤字爱胜蚓对土壤中镉富集的初步研究

将赤字爱胜蚓放在镉浓度分别为0、200、300、400、500、600、700mg·kg^-1的土壤中培养60d后,用原子吸收分光光度计法测定镉在蚯蚓不同部位的分布、蚓粪中镉的含量。结果表明,赤字爱胜蚓对土壤中的镉具有较强的富集能力。当土壤中镉浓度为200mg·kg^-1时,蚯蚓体内镉浓度为305mg·kg^-1,相当于蚯蚓体重的0.03%;土壤镉浓度200～500mg·kg^-1,蚯蚓对镉的富集系数在5以上;蚯蚓第XV体节后的肠道部是镉的主要吸收部位。研究结果表明,蚯蚓对于中轻度镉污染的土壤修复治理效果较为理想。     

2011～2020年昆山市酸雨变化特征及成因分析

酸雨，对人类生活和生产造成了巨大的影响。为了解昆山市酸雨污染状况及其变化特征，根据昆山市2011～2020年降水监测数据，对酸雨的变化特征、变化趋势、离子化学组成、各离子间的相关性及酸雨成因进行了分析。结果表明：2011～2020年昆山市降水的pH年均值总体呈升高趋势，酸雨频率总体呈下降趋势；酸雨呈季节性变化，冬季酸雨频率最高，夏季酸雨频率最低；大气降水中主要阳离子为NH⁺₄和Ca²⁺,主要阴离子为SO₄^2-和NO^-₃;降水中的SO₄^2-和NO^-₃的比值在逐年缩小，从2014年的3.80逐步下降到2020年的0.97,硝酸根离子浓度呈波动变化，但变化不显著，酸雨的特征由硫酸型转化为硫酸-硝酸复合型。因此，加快产业结构调整、优化能源结构、加强工业废气和机动车尾气等的综合治理，从而减少SO₂和NO_X的排放，是...     

1997～2002年成都市区酸雨监测

本文对1997年～2002年成都市区的酸雨污染状况，酸雨分布，以及市区降水中阴离子成分随时间和空间的变化进行了探讨，为成都市区确定酸雨来源、酸雨类型、酸雨分布提供基础数据，并对控制和降低酸雨污染提出了建议。     

沸石粉吸氨性能影响因素研究

研究了粒径、起始氨氮浓度、钾钠等阳离子、pH值、温度、城市污水有机物等因素对沸石粉吸附氨氮能力的影响，为沸石粉的应用奠定理论基础。结果表明粒径、起始氨氮浓度、钾钠阳离子等对沸石粉吸附氨氮有较大影响。     

Heavy metal release from contaminated soils: comparison of column leaching and batch extraction results

Heavy metals in soils may adversely affect environmental quality. In this study, we investigated the release of Zn, Cd, Pb, and Cu from four contaminated soils by column leaching and single and sequential batch extractions. Homogeneously packed soil columns were leached with 67 mL/g 10(-2) M CaCl2 to investigate the exchangeable metal pool and subsequently with 1400 mL/g 10(-2) M CaCl2 adjusted to pH 3 to study the potential of metal release in response to soil acidification. In two noncalcareous soils (pH 5.7 and 5.1), exchange by Ca resulted in pronounced release peaks for Zn and Cd that were coupled to the exchange of Mg by Ca, and 40 to 70% of total Zn and Cd contents were rapidly mobilized. These amounts compared well with exchangeable pools determined in single and sequential batch extractions. In two soils with near-neutral pH, the effluent concentrations of Zn and Cd were several orders of magnitude lower and no pronounced elution peaks were observed. This behavior was also observed for Cu and Pb in all four soils. When the soils were leached at pH 3, the column effluent patterns reflected the coupling of CaCO3 dissolution (if present) and other proton buffering reactions, proton-induced metal release, and metal-specific readsorption within the soil column. Varying the flow rate by a factor of five had only minor effects on the release patterns. Overall, Ca exchange and subsequent acidification to pH 3 removed between 65 and 90% of total Zn, Cd, Pb, and Cu from the four contaminated soils.     

Leaching from organic matter-rich soils by rain of different qualities: I. Concentrations

Soil monoliths from an area exposed to acid precipitation and from an unpolluted area were used in a lysimeter experiment to study effects of different rain qualities on the chemical composition of the leachate from shallow soils rich in organic matter. The vegetation was either dominated by moorgrass [Molinia caerulea (L.) Moench] or heather [Calluna vulgaris (L.) Hull]. The lysimeters received either "acid rain" (pH 4.3) or "normal rain" (pH 5.3). High concentrations of dissolved organic carbon (DOC) were characteristic of the leachate. The different "rain" qualities had no significant influence on the DOC concentration. More DOC was, however, leached from lysimeters with heather vegetation. Roughly 50% of the aluminum (Al) was in complex with organic material and the Al charge was calculated to be between +1.4 and +2.0. Sulfate (SO4(2-)) was the only component that was significantly influenced by the treatment, as more was leached from lysimeters receiving "acid rain." Sulfate was poorly correlated with pH, suggesting that reduced SO4(2-) input would not necessarily lead to reduced acidity. Differences in the pH of the leachate due to the treatments were less than 0.15 pH units. Nitrate (NO3-) was only leached in very low concentrations and of little consequence for the leachate acidity. Some observations do, however, suggest that NO3- may contribute to acidification in episodes with high precipitation. High concentrations of Cl- in the leachate and a significant positive correlation between Cl-, H+, and base cations indicate that sea salt episodes may be important for soil acidification and acidity of the leachate.     

Response of soil microbiological activities to cadmium,lead, and zinc salt amendments

Heavy metal pollution of soil has been recognized as a major factor impeding soil microbial processes. From this perspective, we studied responses of the soil biological activities to metal stress simulated by soil amendment with Zn, Pb, and Cd chlorides. The amounts of heavy metal salts added to five metal-polluted soils and four nonpolluted soils were selected to match the total metal concentrations typically found in polluted soils of the Silesia region of Poland. From the perspective of soil quality, metal mobility in amended soils could not be described by simple functions of pH or organic matter. Reaction of Pb with the soil caused strong immobilization with less than 1% of the Pb amendment recovered by 0.01 M CaCl2 extractions. Immobilization of Cd was also significant, whereas immobilization of the Zn amendment was much weaker than that of Cd or Pb. The Zn amendment had substantial inhibitory effect on soil dehydrogenase, acid and alkaline phosphatase, arylsulfatase, urease, and nitrification potential. Generally, Cd and Pb had limited or stimulatory effect on most of these biological activities, with an exception of Pb strongly inhibiting soil urease. The effect of the metal amendments on biological activities could not be satisfactorily accounted for by metal toxicity because no strong relationship was observed between extractable metal content and the degree of inhibition. The Zn amendment had a significant effect on soil pH, resulting in confounding effects of pH and Zn toxicity on activities. Metal amendment experiments seem to be of limited utility for meaningful assessment of metal contamination effects on soil quality.     

Effect of chloride in soil solution on the plant availability of biosolid-borne cadmium

Increasing chloride (Cl) concentration in soil solution has been shown to increase cadmium (Cd) concentration in soil solution and Cd uptake by plants, when grown in phosphate fertilizer- or biosolid-amended soils. However, previous experiments did not distinguish between the effect of Cl on biosolid-borne Cd compared with soil-borne Cd inherited from previous fertilizer history. A factorial pot experiment was conducted with biosolid application rates of 0, 20, 40, and 80 g biosolids kg(-1) and Cl concentration in soil solution ranging from 1 to 160 mM Cl. The Cd uptake of wheat (Triticum aestivum L. cv. Halberd) was measured and major cations and anions in soil solution were determined. Cadmium speciation in soil solution was calculated using GEOCHEM-PC. The Cd concentration in plant shoots and soil solution increased with biosolid application rates up to 40 g kg(-1), but decreased slightly in the 80 g kg(-1) biosolid treatment. Across biosolid application rates, the Cd concentration in soil solution and plant shoots was positively correlated with the Cl concentration in soil solution. This suggests that biosolid-borne Cd is also mobilized by chloride ligands in soil solution. The soil solution CdCl+ activity correlated best with the Cd uptake of plants, although little of the variation in plant Cd concentrations was explained by activity of CdCl+ in higher sludge treatments. It was concluded that chlorocomplexation of Cd increased the phytoavailability of biosolid-borne Cd to a similar degree as soil (fertilizer) Cd. There was a nonlinear increase in plant uptake and solubility of Cd in biosolid-amended soils, with highest plant Cd found at the 40 g kg(-1) rate of biosolid application, and higher rates (80 g kg(-1)) producing lower plant Cd uptake and lower Cd solubility in soil. This is postulated to be a result of Cd retention by CaCO3 formed as a result of the high alkalinity induced by biosolid application.     

Effect of Cadmium on Microbial Activity and a Ryegrass Crop in Two Semiarid Soils

Soil pollution with Cd is an environmental problem common in the world, and it is necessary to establish what Cd concentrations in soil could be dangerous to its fertility from toxicity effects and the risk of transference of this element to plants and other organisms of the food chain. In this study, we assessed Cd toxicity on soil microorganisms and plants in two semiarid soils (uncultivated and cultivated). Soil ATP content, dehydrogenase activity, and plant growth were measured in the two soils spiked with concentrations ranging from 3 to 8000 mg Cd/kg soil and incubated for 3 h, 20 days, and 60 days. The Cd concentrations that produced 5%; 10%;, and 50%; inhibition of each of the two soil microbiological parameter studied (ecological dose, ED, values) were calculated using two different mathematical models. Also, the effect of Cd concentration on plant growth of ryegrass (Lolium perenne, L.) was studied in the two soils. The Cd ED values calculated for soil dehydrogenase activity and ATP content were higher in the agricultural soils than in the bare soil. For ATP inhibition, higher ED values were calculated than for dehydrogenase activity inhibition. The average yields of ryegrass were reduced from 5.03 to 3.56 g in abandoned soil and from 4.21 to 1.15 g in agricultural soil with increasing concentrations of Cd in the soil. Plant growth was totally inhibited in abandoned and agricultural soils at Cd concentrations above 2000 and 5000 mg/kg soil, respectively. There was a positive correlation between the concentration of Cd in the plants and the total or DTPA-extractable concentrations of Cd in the soil.     

Predicting cadmium concentrations in wheat and barley grain using soil properties

The entry of Cd into the food chain is of concern as it can cause chronic health problems. To investigate the relationship between soil properties and the concentration of Cd in wheat (Triticum aestivum L.) and harley (Hordeum vulgare L.) grain, we analyzed 162 wheat and 215 barley grain samples collected from paired soil and crop surveys in Britain, and wheat and barley samples from two long-term sewage sludge experiments. Cadmium concentrations were much lower in barley grain than in wheat grain under comparable soil conditions. Multiple regression analysis showed that soil total Cd and pH were the significant factors influencing grain Cd concentrations. Significant cultivar differences in Cd uptake were observed for both wheat and barley. Wheat grain Cd concentrations could be predicted reasonably well from soil total Cd and pH using the following model: log(grain Cd) = a + b log(soil Cd) - c(soil pH), with 53% of the variance being accounted for. The coefficients obtained from the data sets of the paired soil and crop surveys and from long-term sewage sludge experiments were similar, suggesting similar controlling factors of Cd bioavailability in sludge-amended or unamended soils. For barley, the model was less satisfactory for predicting grain Cd concentration (22% of variance accounted for). The model can be used to predict the likelihood of wheat grain Cd exceeding the new European Union (EU) foodstuff regulations on the maximum permissible concentration of Cd under different soil conditions, particularly in relation to the existing Directive and the proposed new Directive on land applications of sewage sludge.     

Mapping the probability of exceeding critical thresholds for cadmium concentrations in soils in The Netherlands

The probability of exceeding critical thresholds of Cd concentrations in the soil was mapped at a national scale. The critical thresholds in soil were based on food quality criteria for Cd in crops or in organs of cattle (Bos taurus), and were calculated by inverting a regression model for the Cd concentration in the crop, with the Cd concentration in soil, soil organic matter (SOM) content, clay content, and pH as predictors. The probability of exceeding the critical threshold for Cd in soil per node of a 500- x 500-m grid was approximated by Monte Carlo simulation, using the estimated cumulative distribution functions (cdf) of SOM, clay, pH, and Cd as input. The cdfs were estimated by simple indicator kriging with local prior means. For SOM, clay, and pH, detailed maps of soil type and land use were used to define subregions with assumed constant local means of the indicators (a priori distributions). The cdfs were sampled by Latin hypercube sampling. We accounted for correlation between the actual and critical Cd concentrations in soil by drawing Cd values from cdfs conditional on SOM and clay. The estimated probability for grassland is negligible, even in areas with high Cd concentrations in soil, and for maize (Zea mays L.) land the probability is almost everywhere smaller than 5%. For arable soils, however, these probabilities commonly are larger than 5% when sugar beet (Beta vulgaris L.) or wheat (Triticum aestivum L.) is taken as a reference crop, and locally exceed 50%.     

Correlation of cadmium distribution coefficients to soil characteristics

Cadmium (Cd) distribution between the soil solid phase and the soil solution is a key issue in assessing the environmental effect of Cd in the terrestrial environmental. Previous studies have shown that many individual minerals and other components found in soils can bind Cd, but most studies on whole soil samples have shown that pH is the main parameter controlling the distribution. To identify further the components that are important for Cd binding in soil we measured Cd distribution coefficients (Kd) at two fixed pH values and at low Cd loadings for 49 soils sampled in Denmark. The Kd values for Cd ranged from 5 to 3000 L kg(-1). The soils were described pedologically and characterized in detail (22 parameters) including determination of contents of the various minerals in the clay fraction. Correlating parameters were grouped and step-wise regression analysis revealed that the organic carbon content was a significant variable at both pH values. Cation exchange capacity (CEC) and gibbsite were important at the low pH (5.3) while iron oxides also were important at the high pH (6.7). None of the other clay minerals present in the soils (illite, smectite, kaolinite, hydroxy interlayered clay minerals [HIM], chlorite, quartz, microcline, plagioclase) were significant in explaining the Cd distribution coefficient.     

Prediction of zinc, cadmium, lead, and copper availability to wheat in contaminated soils using chemical speciation, diffusive gradients in thin films, extraction, and isotopic dilution techniques

To predict the availability of metals to plants, it is important to understand both solution- and solid-phase processes in the soil, including the kinetics of metal release from its binding agent (ligand and/or particle). The present study examined the speciation and availability of Zn, Cd, Pb, and Cu in a range of well-equilibrated metal-contaminated soils from diverse sources using several techniques as a basis for predicting metal uptake by plants. Wheat (Triticum aestivum L.) was grown in 13 metal-contaminated soils and metal tissue concentrations (Zn, Cd, Pb, and Cu) in plant shoots were compared with total soil metal concentrations, total soluble metal, and free metal activities (pM2+) in soil pore waters, 0.01 M CaCl2-extractable metal concentrations, E values measured by isotope dilution, and effective metal concentrations, C(E), measured by diffusive gradients in thin films (DGT). In the DGT technique, ions are dynamically removed by their diffusion through a gel to a binding resin, while E values represent the isotopically exchangeable (labile) metal pools. Free metal activities (Zn2+, Cd2+, and Pb2+) in soil pore waters were determined using a Donnan dialysis technique. Plant Zn and Cd concentrations were highly related to C(E), while relationships for Zn and Cd with respect to the other measures of metals in the soils were generally lower, except for CaCl2-extractable Cd. These results suggest that the kinetically labile solid-phase pool of metal, which is included in the DGT measurement, played an important role in Zn and Cd uptake by wheat along with the labile metal in soil solution. Plant Pb concentrations were highly related to both soil pore water concentrations and C(E), indicating that supply from the solid phase may not be so important for Pb. Predictions of Cu uptake by wheat from these soils by the various measures of Cu were generally poor, except surprisingly for total Cu.     

Adsorption of cadmium on biosolids-amended soils

Debate exists over the biosolid phase (organic or inorganic) responsible for the reduction in phytoavailable Cd in soils amended with biosolids as compared with soils amended with inorganic salts. To test the importance of these two phases, adsorption isotherms were developed for soil samples (nine biosolids-amended soils and their five companion controls) and two biosolids samples from five experimental sites with documented histories of biosolids application. Subsamples were treated with 0.7 M NaClO to remove organic carbon. Cadmium nitrate was added to both moist soil samples and their soil inorganic fractions (SIF) in a 0.01 M Ca(NO3)2 solution at three pH levels (6.5, 5.5, and 4.5), and equilibrated at 22 +/- 1 degrees C for at least 48 h. Isotherms of Cd adsorption for biosolids-amended soil were intermediate to the control soil and biosolids. Decreasing pH did not remove the difference between these isotherms, although adsorption of Cd decreased with decreasing pH level. Organic matter removal reduced Cd adsorption on all soils but had little influence on the observed difference between biosolids-amended and control soils. Thus, increased adsorption associated with biosolids application was not limited to the organic matter addition from biosolids; rather, the biosolids application also altered the adsorptive properties of the SIF. The greater affinity of the inorganic fraction of biosolids-amended soils to adsorb Cd suggests that the increased retention of Cd on biosolids-amended soils is independent of the added organic matter and of a persistent nature.