小型化土壤微生物燃料电池电信号放大电路的设计与运行

为了提高对小型化的土壤微生物燃料电池(microbial fuel cells,MFCs)产电信号的检测能力,构建了采用加Cu~(2+)处理土壤进行产电的小型化单室MFCs,并设计和制作了基于集成运算的信号放大器,设计放大倍数100倍。将信号放大器与MFCs连接后,采用数据采集卡连续记录土壤产电的原始电压以及放大后的电压。结果显示,土壤产电电压在4 mV附近波动,而放大后的电压升至400 mV左右。统计显示原始电压与放大后的电压相关性达到极显著水平(P0.001)。同时还发现,并非每个电压数值都严格放大100倍,而是倍率存在5%的误差,原因主要在于集成运算放大芯片存在失调误差和温度漂移误差。本研究为实现小型化MFCs产电信号的检测提供了依据。     

两性磁化炭对牧草生长及土壤铜有效性的影响

为了探究材料添加对植物修复过程中的牧草生长和土壤铜有效性特征的影响,采用盆栽试验研究7种土壤Cu~(2+)污染水平[0,100,200,400,800,1 200,1 600 mg/L]下,两性磁化炭表施(0—3 cm)和混施对苏丹草(Sorghum sudanense(Piper)Stapf.)和黑麦草(Lolium multiflorum L.)发芽率、株高和生物量的影响,并分析了盆栽土壤中水溶态和酸提取态铜含量的变化特征。结果表明:(1)在未经Cu~(2+)处理时,表施和混施两性磁化炭都能大幅度提高黑麦草的发芽率和成活率;Cu~(2+)处理后,表施两性磁化炭有利于苏丹草的发芽,但不利于其成活,混施能够提高苏丹草在Cu~(2+)浓度400～800 mg/L内的成活率;(2)各土样上的苏丹草和黑麦草株高前期增长迅速(2 cm/d左右),25 d后趋于缓和。单施两性磁化炭更有利于黑麦草的生长,其中表施的作用尤为显著。(3)混施两性磁化炭能增加苏丹草在Cu~(2+)400～800 mg/L区间中的生物量,而Cu~(2+)浓度低于200 mg/L时,表施和混施两性磁化炭都有利于两种牧草生长;(4)土壤水溶态Cu~(2+)含量和酸提取态Cu~(2+)含量均保持上层高于下层的趋势,黑麦草降低土壤中Cu~(2+)含量的能力强于苏丹草。综上,在铜污染地区表施两性磁化炭并种植黑麦草对土壤的修复效果最佳。     

闽江河口不同淹水频率下湿地土壤全硫和有效硫分布特征

为揭示湿地土壤全硫和有效硫的分布特征对淹水频率差异的响应,对闽江河口湿地近潮沟区域不同淹水频率的藨草(Scirpus triqueter)湿地、短叶茳芏(Cyperus malaccensis)湿地和芦苇(Phragmites australis)湿地以及远潮沟区域的短叶茳芏湿地和芦苇湿地土壤的全硫和有效硫进行测定与分析。研究结果表明:(1)闽江河口湿地土壤全硫和有效硫分别为399.00～3 510.33 mg/kg和4.51～230.55 mg/kg,平均值分别为1 613.20 mg/kg和52.20 mg/kg;(2)近潮沟区域湿地土壤全硫和有效硫均表现出随淹水频率的增加先增大后减小,但远近潮沟区域的同种植物类型湿地间则表现为随淹水频率的增加而增大;(3)盐度是影响闽江河口不同淹水频率下湿地土壤全硫和有效硫变化的最重要的因子;(4)湿地土壤硫储量随淹水频率的增加而增大。     

土壤胡敏素结构特征及对铜离子的吸附特性

以棕壤和赤红壤为供试土壤,在对土壤胡敏素进行结构表征的基础上,采用批量平衡法研究不同反应温度下其对铜离子(Cu~(2+))的吸附动力学和热力学特征,利用同步辐射X-射线吸收光谱技术探测了Cu~(2+)在胡敏素表面吸附的微观局域结构。结果表明:与胡敏酸相比,胡敏素具有较高的脂族性和极性,但其分子中甲氧基碳、羰基碳、木质素类化合物和酚类化合物的比例较低;随溶液Cu~(2+)浓度、接触时间和反应温度的增加,胡敏素对Cu~(2+)的吸附量也增加;吸附动力学曲线符合假二级动力学方程,吸附过程是需要能量和吸热的缔合反应;吸附等温线符合Freundlich和Langmuir方程,吸附反应是自发、吸热和自由度增加的过程;与胡敏酸类似,胡敏素表面吸附态Cu~(2+)是以扭曲的八面体构型存在,第一配位层(Cu-O)由原子间距为1.91～1.97?的4个O原子构成,第二配位层(Cu-C)由原子间距为2.80～2.83?的2个C原子组成,证实Cu~(2+)主要以内层复合物形式吸附在胡敏素表面的有机官能团上。上述结果指出,尽管胡敏素的化学组成不同于胡敏酸,但Cu~(2+)在这两种腐殖物质组分表面的局域配位结构相似。     

不同淹水频率下湿地土壤碳氮磷生态化学计量学特征

为了阐明湿地土壤生态化学计量学特征对淹水频率差异的响应,对闽江河口湿地近潮沟区域不同淹水频率的蔗草湿地、短叶茳芏湿地和芦苇湿地以及远潮沟区域的短叶茳芏湿地和芦苇湿地土壤的碳、氮、磷生态化学计量学特征进行了测定与分析.研究结果表明:(1)闽江河口湿地土壤C/N、C/P和N/P比分别为11.46～22.28,25.29～155.62和2.21～8.25,平均值为15.58.73.71和4.67;(2)近潮沟区域土壤C/N、C/P和N/P比均表现出随着淹水频率的增加而减小,但远近潮沟区域的同种植物类型湿地间则表现为随着淹水频率的增加而增大;(3)总体来看,土壤C/N比表现出随着淹水频率和土壤剖面的变化较小,C/P和N/P比的变异性相对较大;(4)盐度是影响闽江河口不同淹水频率下湿地土壤C/N、C/P和N/P比变化的最重要的因子.     

沙柳生物炭对矿区铜离子吸附性能的研究

为研究利用生物炭在草原矿区土壤铜污染修复中的治理效果,研究在外业调查的基础上借以Cu~(2+)为污染源,沙柳生物炭为吸附材料进行了室内模拟试验,探究沙柳生物炭对Cu~(2+)的吸附性能的研究。结果表明:Lagergren准二级动力学模型、颗粒内扩散模型和Freundlich、Temkim等温吸附模型能够较好地描述沙柳生物炭对溶液中Cu~(2+)的动力学吸附过程(R~20.99)及等温吸附过程(R~20.56),可见沙柳生物炭对溶液中Cu~(2+)的吸附并非单层的吸附,而是复杂的吸附过程。沙柳生物炭对溶液中Cu~(2+)的吸附量最大为19.13mg/g,且在弱酸环境下有利于沙柳生物炭的吸附作用;当吸附16h后,沙柳生物炭对Cu~(2+)的吸附量和吸附率均达到峰值后且不再随吸附时间的延长而增加;沙柳生物炭的吸附量、吸附率与吸附时间、溶液pH值均呈显著正相关关系(p0.05)。     

土壤微生物产电信号评价芘污染毒性的研究

通过向土壤中加入葡萄糖促进微生物产电过程,研究了芘污染条件下土壤产电变化规律。利用双室微生物燃料电池(Microbial fuel cells,MFCs),实时、连续记录芘污染土壤产电电压。产电110 h后结束MFCs运行,采用循环伏安法检测芘对土壤微生物电化学活性的影响;结合PCR-DGGE及测序技术,分析芘对MFCs阳极表面细菌群落结构的影响。结果显示,MFCs产电电量随芘浓度增加显著降低。循环伏安检测显示芘降低了土壤微生物的电化学活性。DNA序列分析表明,阳极细菌与已报道的产电细菌高度相似,包括Sporolactobacillus、Clostridium、Enterobacter、Bacillus及Ethanoligenens。芘降低了Bacillus丰度。     

闽江河口不同淹水环境下典型湿地植物—土壤系统全硫含量空间分布特征

选择闽江河口鳝鱼滩湿地不同淹水环境下2条样带(A样带,远离主潮沟且退潮后无淹水;B样带,靠近主潮沟且退潮后有淹水)上的短叶茳芏、互花米草和扁穗沙草植被下的湿地为研究对象,探讨了湿地植物-土壤系统全硫(TS)含量的空间分布特征。结果表明,长期淹水环境在导致B样带同种植被类型下的湿地表层土壤的TS含量低于A样带的同时,也增强了不同植被类型下湿地之间0—40cm土层TS含量的水平变异性以及相同类型湿地土壤TS含量的垂直变异性。尽管长期淹水环境降低了B样带3种植被根的TS含量和累积系数,但增加了其地上器官及立枯体的TS含量和累积系数,并提高了其地上器官的硫分配比。对比研究表明,闽江河口3种湿地土壤和植物的TS含量在全国均处于较高水平,其值远高于三江平原淡水沼泽湿地、向海盐沼湿地以及华北海河流域湿地,但略低于南方红树林湿地。研究发现,淹水条件和土壤水分含量是导致A、B 2条样带相同类型湿地土壤TS含量差异的主导因素;淹水条件亦改变了湿地植物的硫分配格局,湿地植物可通过调整自身的硫吸收与累积状况来适应长期淹水环境。     

湿地土壤微生物碳源代谢活性对不同水分条件的动态响应 ——以鄱阳湖为例

为深入了解湿地土壤微生物群落代谢特征对不同水分条件的响应变化,本研究以鄱阳湖湿地表层土壤为研究材料,采用室内控制试验,运用Biolog技术探讨土壤微生物碳源代谢活性在不同水分条件(干燥、湿润、淹水)下连续处理132 d的变化特征。结果表明:湿润组土壤微生物代谢活性最高,其平均光密度值(AWCD)在处理的第72天分别是淹水组和干燥组的1.34倍和3.95倍;同时土壤微生物对不同碳源类型的利用能力也发生了显著的差异性变化,其中干燥组利用的主要碳源为多聚物类和碳水化合物类(占总碳源利用率的39.25%和36.53%),而淹水组对氨基酸类碳源有较高的利用能力(占总碳源利用率的36.33%)。土壤微生物碳源代谢特征在处理的第21天达到稳定状态,而土壤理化性质和土壤微生物群落结构在处理的第72天发生显著变化,同时研究发现淹水条件升高了土壤pH和铵态氮含量,降低了微生物群落多样性。由此可知,水分条件不仅会影响湿地土壤微生物总体碳源代谢活性强度,还会改变对不同碳源的相对利用能力,最终导致土壤环境发生改变。     

强还原和淹水处理对地黄连作障碍的消减效应

地黄是我国著名的大宗中药材,但是在其栽培过程中存在严重的连作障碍现象,至今尚未得到有效解决。为了开发地黄连作障碍消减技术,本文研究了强还原和淹水处理对连作地黄关键生长指标,连作土壤理化性质、细菌群落结构及其生物学功能的影响。结果表明,强还原和淹水处理提高了连作土壤中瘤胃球菌属和肠球菌属等厌氧异养型细菌的相对丰度,形成了富含Fe~(2+)和有机酸等抑制病原菌的土壤环境;其中,强还原处理后土壤中Fe~(2+)和有机酸含量比连作对照分别提高4.73倍和3.54倍,淹水处理后土壤中Fe~(2+)和有机酸含量比连作对照分别提高1.65倍和1.12倍。同时,假单胞菌属等益生菌群落在处理后的土壤中迅速重建。然而,强还原和淹水处理对土壤理化性质和细菌群落结构的影响存在一定差异,二者对地黄连作障碍的消减效果也有所不同:添加秸秆等有机物的强还原处理后连作土壤的有机质含量、碱解氮、速效磷和速效钾含量均有所提高,而淹水处理效果不明显;淹水处理的细菌香农指数和Chao1指数均有所下降,强还原处理的细菌香农指数有所下降,而Chao1指数有所上升,且细菌群落组成的变化也有所不同。强还原和淹水处理均可有效提高连作地黄的存活率和产量,并且以强还原处理效果较优,其存活率和产量比连作对照分别提高1.94倍和4.04倍。因此,强还原和淹水处理能够改善连作土壤的理化性质及其微生物群落结构,达到消减地黄连作障碍的效果,有效提高连作地黄的存活率和产量。     

Using electrical signals of microbial fuel cells to detect copper stress on soil microorganisms

A method based on microbial fuel cells (MFCs) was used to evaluate the effects of copper (Cu²⁺) on soil microorganisms. Soil spiked with 50–400 mg kg^?1 of Cu²⁺ as CuCl₂ was incubated for 24 hours before being packed into the MFC anode chambers and assayed for dehydrogenase activity (DHA), substrate‐induced respiration (SIR) and microbial biomass carbon (C_mic). Soil was amended with 5% (w/w) glucose to accelerate ‘start‐up’ and improve power generation, followed by 150 hours of operation. Anode biofilm and soil was extracted to recover total nucleic acids and the 16S rRNA gene was subjected to PCR‐DGGE, sequencing and phylogenetic analysis. Results showed that increases in soil Cu²⁺ concentrations reduced voltage and postponed start‐up. The quantity of generated electrons within 48 hours was 32.5 coulomb (C) in the without‐Cu control and decreased with increasing Cu²⁺ concentrations (11.7, 7.7, 2.0 and 1.3 C under 50, 100, 200 and 400 mg kg^?1 Cu²⁺, respectively). Cyclic voltammetry identified decreased soil electrochemical activity with increasing Cu²⁺ concentrations. The results indicate that Cu²⁺ reduced electrical signals by inhibiting the electrochemical activity, metabolic activity and biomass of microorganisms. The 16S sequences of recovered anodic bacteria were assigned to Firmicutes, including Bacillaceae, Acetobacteraceae, Clostridium, Bacillus and Sporolactobacillus. In general, the DGGE band intensity of anodic bacteria decreased with increasing Cu²⁺ concentrations, except for bands assigned to Firmicutes and Bacillus, which increased with increasing Cu²⁺ concentrations. We suggest that the short‐term electrical signals generated from MFCs with contaminated soil can be used to assess the toxic effect of heavy metal pollutants on soil microorganisms.     

Laboratory Study of Leaching Properties of Mediterranean Forest Species Ashes

For bioremediation of copper-contaminated soils, it is essential to understand copper adsorption and chemical forms in soils related to microbes. In this study, a Penicillium strain, which can tolerate high copper concentrations up to 150 mmol l^?1 Cu²⁺, was isolated from a copper mining area. The objective was to study effects of this fungus on copper adsorptions in solutions and chemical forms in soils. Results from lab experiments showed the maximum biosorptions occurred at 360 min with 6.15 and 15.08 mg g^?1 biomass from the media with Cu²⁺ of 50 and 500 mg l^?1, respectively. The copper was quickly adsorbed by the fungus within the contact time of the first 60 min. To characterize the adsorption process of copper, four types of kinetics models were used to fit the copper adsorption data vs. time. Among the kinetics models, the two-constant equation gave the best results, as indicated by the high coefficients of determination (R ²?=?0.89) and high significance (p?<?0.01). The addition of the fungal strain to autoclaved soil facilitated increases in concentrations of acid-soluble copper, copper bound to oxides, and of copper bound to organic matter (p?<?0.05). However, the inoculation of Penicillium sp. A1 led to a decrease of water-soluble copper in the soil. The results suggested that Penicillium sp. A1 has the potential for bioremediation of copper-contaminated soils.     

铜对土壤中功夫菊酯和氯氰菊酯迁移和扩散的影响

Repeated applications of bordeaux mixture （a blend of copper sulfate and calcium hydroxide） and pyrethroid insecticides （Pys） have led to elevated copper （Cu） and Pys concentrations in vineyard surface soils. To understand the potential influence of Cu on the fate of Pys in the soil environment, we selected two Pys, cypermethrin （CPM） and lambda-cyhalothrin （λ-CHT）, and two typical Chinese vineyard soils, Haplic Acrisol and Luvic Phaeozem, as experimental samples. The dissipation experiment was conducted at room temperature in the dark, and the transport of both Pys through the soils was investigated using soil thin-layer chromatography. The results showed that the transport of Pys in both soils increased as the Cu²⁺ concentration increased from 0 to 100 mg L^-1 , and Pys were more transportable in Haplic Acrisol （HA） than in Luvic Phaeozem （LP） under the same experimental conditions. For CPM, only 100 mg L^-1 of Cu²⁺ significantly （P<0.05） increased Pys transport through both soils relative to water. Lambda-CHT was significantly （P<0.05） transported through HA by all the Cu²⁺ concentrations compared to water, and all but the 1 mg L^-1 of Cu²⁺ significantly （P<0.05） increased the transport of λ-CHT through LP relative to water. However, the dissipation rates of CPM and λ-CHT decreased with the addition of Cu to soils. Our findings suggest that the risk of groundwater contamination by Pys increases in the soils with elevated Cu concentrations.     

中国东部太湖地区酸性水稻土团聚体上铜的专性和非专性吸附动力学研究

The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper(Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy metals in the biological environment. In this study, the kinetics of Cu2+sorption by the bulk soil and the aggregate size fractions of an acidic paddy soil collected from the Taihu Lake region, the effects of temperature on Cu2+sorption, and the p H changes of the solution were investigated by static sorption and magnetic stirring. The aggregate size fractions were prepared by low-energy ultrasonic dispersing and freeze-drying. The total sorption amounts of the bulk soil and the aggregate size fractions for Cu2+followed a descending order of clay > coarse sand > bulk soil > silt> sand, corresponding to those of organic matter content, free iron oxide content, free aluminum oxide content, and cation exchange capacity. The kinetic sorption curves of Cu2+by the bulk soil and the aggregates, which were divided into two stages(rapid and slow sequentially), were well fitted by the first-order equation, the diffusion equation, and the Elovich equation, showing significant correlations(P < 0.05). Specific and non-specific sorption dominated in the fast and slow stages, respectively, and the former was predominant throughout the sorption process. The specific sorption accelerated and the non-specific sorption decelerated with rising temperature. The p H of the solution decreased significantly during the specific sorption and remained unchanged or increased slightly during the non-specific sorption. When the specific sorption terminated, the p H of the solution was minimized nearly simultaneously.The sorption progress of Cu2+by the bulk soil significantly preceded that by the aggregates. Therefore, heavy metal contamination may be another factor reducing soil p H and metal sorption forms should be taken into consideration in studies of mitigating soil heavy metal pollution or determining environmental capacity of heavy metal in soil.     

Flooding effects on soil phenol oxidase activity and phenol release during rice straw decomposition

Phenol oxidase (Pox) plays a key role in soil C cycle and its presence may affect soil C mineralization during crop residue decomposition. To examine soil dynamics and relationships between Pox, phenols, Fe²⁺, and C mineralization, we designed a 53‐d laboratory experiment conducted with and without rice straw addition and under non‐flooded and flooded conditions. The results demonstrate that rice straw can indeed decompose faster under flooded conditions. The addition of rice straw significantly increased soil Pox activity (up to 15‐fold), but only under flooded conditions. Rice straw application increased alkali extractable phenol (AEP) concentration by 129% at day 4. However, flooded conditions reduced soil AEP by 61% and 49% at day 53 with and without rice straw application, respectively. Phenol oxidase activity was positively correlated with dissolved organic C and Fe²⁺, while negatively related to AEP, which itself was positively correlated with C mineralization (i.e., CO₂ emission rates). Also, all relationships between soil Pox, AEP, Fe²⁺, and C were stronger under flooded conditions. We therefore conclude that flooded conditions in paddy soil may promote straw decomposition as a result of the stimulation of Pox activity and phenol decomposition.     

Copper Release, Speciation, and Toxicity Following Multiple Floodings of Copper Enriched Agriculture Soils: Implications in Everglades Restoration

This study characterizes the effects of water–soil flooding volume ratio and flooding time on copper (Cu) desorption and toxicity following multiple floodings of field-collected soils from agricultural sites acquired under the Comprehensive Everglades Restoration Plan (CERP) in south Florida. Soils from four field sites were flooded with three water–soil ratios (2, 4, and 6 [water] to 1 [soil]) and held for 14 days to characterize the effects of volume ratio and flooding duration on Cu desorption (volume ratio and flooding duration study). Desorption of Cu was also characterized by flooding soils four times from seven field sites with a volume ratio of 2 (water) to 1 (soil) (multiple flooding study). Acute toxicity tests were also conducted using overlying waters from the first flooding event to characterize the effects of Cu on the survival of fathead minnows (Pimephales promelas), cladocerans (Daphnia magna), amphipods (Hyalella azteca), midges (Chironomus tentans), duckweed (Lemna minor), and Florida apple snails (Pomacea paludosa). Acute tests were also conducted with D. magna exposed to overlying water from the second and third flooding events. Results indicate that dissolved Cu concentrations in overlying water increased with flooding duration and decreased with volume ratio. In the multiple flooding study, initial Cu concentrations in soils ranged from 5 to 223 mg/kg (dw) and were similar to Cu concentration after four flooding events, indicating retention of Cu in soils. Copper desorption was dependent on soil Cu content and soil characteristics. Total Cu concentration in overlying water (Cu_w) was a function of dissolved organic carbon (DOC), alkalinity, and soil Cu concentration (Cu_s): log(Cu_w)?=?1.2909?+?0.0279 (DOC)?+?0.0026 (Cu_s)???0.0038 (alkalinity). The model was validated and highly predictive. Most of the desorbed Cu in the water column complexed with organic matter in the soils and accounted for 99% of the total dissolved Cu. Although total dissolved Cu concentrations in overlying water did not significantly decrease with number of flooding events, concentrations of free Cu²⁺ increased with the number of flooding events, due to a decrease in DOC concentrations. The fraction of bioavailable Cu species (Cu²⁺, CuOH⁺, CuCO₃) was also less than 1% of the total Cu. Overlying water from the first flooding event was only acutely toxic to the Florida apple snail from one site. However, overlying water from the third flooding of six out of seven soils was acutely toxic to D. magna. The decrease in DOC concentrations and increase in bioavailable Cu²⁺ species may explain the changes in acute toxicity to D. magna. Results of this study reveal potential for high Cu bioavailability (Cu²⁺) and toxicity to aquatic biota overtime in inundated agricultural lands acquired under the CERP.     

Iron Toxicity in Lowland Rice

Lowland rice is a staple food for more than 50% world population. Iron toxicity is one of the main nutritional disorders, which limits yield of lowland rice in various parts of the world. The toxicity of iron is associated with reduced soil condition of submerged or flooded soils, which increases concentration and uptake of iron (Fe^{2 +}). Higher concentration of Fe^{2 +} in the rhizosphere also has antagonistic effects on the uptake of many essential nutrients and consequently yields reduction. In addition to reduced condition, increase in concentration of Fe^{2 +} in submerged soils of lowland rice is associated with iron content of parent material, oxidation-reduction potential, soil pH, ionic concentration, fertility level, and lowland rice genotypes. Oxidation-reduction potential of highly reduced soil is in the range of –100 to –300 mV. Iron toxicity has been observed in flooded soils with a pH below 5.8 when aerobic and pH below 6.5 when anaerobic. Visual toxicity symptoms on plants, soil and plant tissue test are major diagnostic techniques for identifying iron toxicity. Appropriate management practices like liming acid soils, improving soil fertility, soil drainage at certain growth stage of crop, use of manganese as antagonistic element in the uptake of Fe^{2 +} and planting Fe^{2 +} resistant rice cultivars can reduce problem of iron toxicity.     

不同土地利用方式土壤对铜、镉离子的吸附解吸特征

采用一次平衡法对Cu²⁺、Cd²⁺在城市及城郊农田、林地、草地3种土地利用方式土壤中的吸附解吸过程进行比较研究, 结果表明: Cu²⁺、Cd²⁺在3种土地利用方式土壤中的吸附量均随平衡液浓度的增加而增大, Cu²⁺、Cd²⁺在农田土壤上的吸附量均高于林地和草地土壤。分别用Langmuir和Freunlich两种等温吸附方程对吸附过程进行拟合, 3种土壤对Cu²⁺的吸附过程运用Langmuir方程拟合效果好, 而对Cd²⁺的吸附过程运用Freunlich方程拟合效果更好。Cu²⁺在3种土壤的解吸量大小顺序为农田>林地>草地, Cd²⁺在3种土壤的解吸量大小顺序为农田>草地>林地。两种离子在3种土壤中的动态吸附是个快速反应的过程, 随时间延长, 吸附反应趋于平衡。运用双常数函数方程和Elovich方程能较好地拟合重金属在土壤上的吸附动力学过程。Cu²⁺、Cd²⁺的吸附与土壤黏粒含量、有机质含量、CEC和pH均有关。     

Sorption of cupric,dichromate and arsenate ions in some New Zealand soilds

Concentrated solutions of copper (Cu²⁺), dichromate (Cr₂O^2? ₇) and aresenate (AsO₄ ^3?) ions (CCA solutions) are used extensively in the New Zealand timber preservation industry. These ions are therefore, potential soil pollutants at timber treatment sites. Sorption of these three ions was examined by the surface and sub-surface horizons of two free-draining New Zealand soils over a range of soil solution pH values. Copper sorption by both soils increased substantially with increasing pH and was greater in the surface compared with the sub-surface horizons. Less dichromate was sorbed than the other two ions and wa similar in both surface and sub-surface horizons for each soil. Dichromate sorption increased with decreasing pH. Arsenate sorption from solutions containing all three ions was not greatly different to influenced by changes in soil solution pH. Arsenate sorption was generally greater in the sub-surface horizons of both soils. Sorption from solutions containing all three ions was not greatly different to sorption from solutions containing the single metal ions. Sorption behaviour for each ion is related to its chemistry and the soil chemical properties of each horizon. Results suggest that in the event of soil contamination by CCA solution, the immediate leaching potential of the initial ions species present would increase in the following order: Cu²⁺ < HAsI ₄ ^? ? Cr₂O ₇ ^2? .