Modeling rhizofiltration: heavy-metal uptake by plant roots

The discovery of phytoaccumulation potential of plant species has led to its application for remediation of heavy-metal-contaminated soil and wastewater, which is termed as phytoextraction/rhizofiltration. For prediction, analysis, planning and cost-effective design of such systems, mathematical models not only are used as a screening tool but also provide optimal parameters like harvesting time, irrigation schedule, etc. Several laboratory and field scale studies have been carried out in the past, and mathematical expressions have been developed by various researchers for different phenomena like metal adsorption in soil, plant root growth with time, moisture and metal uptake by plant root, moisture movement in unsaturated zone, soil moisture relationship, etc. The complete design of any such phytoremediation program would require the knowledge of behavior of heavy-metal movement in soil, water and plant root system. In this paper, a model for simulating heavy-metal dynamics in soil, water and plant root system is developed and discussed. The governing non-linear partial differential equation is solved numerically by implicit finite difference method using Picard's iterative technique, and the formulation has been illustrated using a characteristic example. The source code is written in MATLAB.     

内蒙古某灌域表层土壤六氯环己烷空间分布特征及影响因素

为修复灌区内土壤有机氯农药污染，降低六氯环己烷对土壤环境的危害，对内蒙古某灌域表层土壤进行采样，利用气相色谱测定50个土壤样品中六氯环己烷及其异构体的含量，并利用ArcGIS空间分析技术确定表层土壤中六氯环己烷的分布状况。样本中六氯环己烷的检出率为96%，各样本中六氯环己烷的浓度范围为未检出~23.0 ng/g，平均浓度为4.4 ng/g。4种异构体含量平均值顺序为γ-六氯环己烷>δ-六氯环己烷>β-六氯环己烷>α-六氯环己烷。灌域东北部和西南部残留浓度较高，并由这2个方向向中部地区逐渐递减，表层土壤中的六氯环己烷分布受土壤黏粒量、不同种植种类和灌溉水源的影响较大。虽受人类耕作的影响，但表层土壤中的六氯环己烷污染水平相对较低。     

Assessment of the Heavy Metal Pollution Effects on the Soil Respiration in the Baix Llobregat (Catalonia, NE Spain)

A main goal of investigations is to determine could a soilrespiration be an indicator of the soil pollution. In this case a measured levelof the soil oxygen consumption depends of its pollution. It alsomeans that the pollution reduces biological processes in edaphon.Investigated soil samples were taken from polluted andnon-polluted places in the Baix Llobregat near Barcelona (Catalonia, NE Spain). Soil samples were taken from the top ofsoil (0–5 cm) without a litter. Soil analysis were done, determining percentage shares of coarsefragments, coarse sand, fine sand, coarse silt, fine silt, clay,CaCO₃, organic matter as well as water pH and conductivityCE (1:5 [mS cm^-1]). Also were determined (in mg kg^-1)quantities of heavy metals, as Fe, Al, Mn, Zn, Cr, Ni, V, Cu, Cd, Pb.The soil respiration was investigated in temperatures15 and 30 °C and with controlled humidity.The respiration in 30 °C is number of times greater thenin 15 °C both for polluted and non-polluted soils.Particularly high coefficients of correlation between the soilrespiration and soil pollution in polluted soils were obtainedfor Pb: r = 0.75 in 15 °C and r = 0.98 in30 °C; for Ba: 0.90 and 0.57; for V: 0.99 and 0.81. In non-polluted soils highest correlation coefficients are for Pb: r = 0.70 in 15 °C; Fe: 0.60 and 0.72; Al: 0.68 and0.64; Mn: 0.51 and 0.66; Ba: 0.63 and 0.61; Cr: 0.94 and0.70; Ni: 0.64 and 0.65; Cu: 0.69 and 0.48; as well as V: 0.62in 15 °C; and Cd: 0.69 in 15 °C.This way the soil respiration could be a good indicator of the soil pollution.     

Soil properties and crop productivity as influenced by flyash incorporation in soil

Field experiments were carried out during 1996–97at Gulawathi, Muthiani and Salarpur Villages, IARI Farm, NewDelhi and NCPP Campus, Dadri to evaluate changes in soilcharacteristics and growth of wheat (Triticum aestivum L.),mustard (Brassica juncea L.), lentil (Lence esculentaMoench.), rice (Oryza sativa L.) and maize (Zea mays L.) byvarying amounts of flyash addition (up to 50t ha^-1) in soils atsowing/transplanting time of crops. Flyash addition in areasadjoining NCPP Thermal Power Plant, Dadri, Ghaziabad, U.P.ranged from 5–12 t ha^-1 yr^-1 in 1995–96. Shoot and root growthand yield of test crops at different locations after flyashincorporation resulted in beneficial effects of flyashaddition in most cases. The silt dominant texture of flyashimproved loamy sand to sandy loam textures of the surfacesoils at the farmers' fields. The increased growth in yield ofcrops with flyash incorporation was possibly due tomodifications in soil moisture retention and transmissioncharacteristics, bulk density, physico-chemical characterssuch as pH and EC and organic carbon content. The response offlyash addition in the soil on soil health and cropproductivity needs to be evaluated on long-term sustainableaspects.     

A Survey of Trace Metals in Vegetation, Soil and Lower Animal Along Some Selected Major Roads in Metropolitan City of Lagos

The concentration of trace metals (Cd, Cu, Pb and Zn) in a total of 144 samples of grass, soil and lower animal (earthworm, Lybrodrilus violaceous) were collected and analysed for their metallic content. Levels of cadmium ranged from 0.01–0.07 g g^–1; 0.01–0.12 g g^–1 and from trace–0.05 g g^–1 dry weight for plant, soil and animal samples respectively. Mean concentration of copper ranged 0.10–1.48 g g^–1; 0.10–2.90 g g^–1 and 0.01–0.08 g g^–1 for samples in similar order as above. The levels of Pb varied from 0.01–0.14 g g^–1; 0.02–0.23 g g^–1 and from trace–0.07 g g^–1 while that of Zn ranged from 0.19–1.80 g g^–1; 0.51–3.35 g g^–1and 0.01–0.08 g g^–1 also in the same order of samples as mentioned above. Levels of metals in soil samples were higher than the background levels with the exception of Zn but lower than European Union (EU) limits. The results generally revealed the presence of metals in plant and animal samples and metal dynamics up the food chain is highly possible. Acceptable recoveries of the spiking experiment validate the experimental protocol.     

Geostatistical Uncertainty Modelling for the Environmental Hazard Assessment During Single Erosive Rainstorm Events

This paper presents an environmental hazard assessment to account the impacts of single rainstorm variability on river-torrential landscape identified as potentially vulnerable mainly to erosional soil degradation processes. An algorithm for the characterisation of this impact, called Erosive Hazard Index (EHI), is developed with a less expensive methodology. In EHI modelling, we assume that the river-torrential system has adapted to the natural hydrological regime, and a sudden fluctuation in this regime, especially those exceeding thresholds for an acceptable range of flexibility, may have disastrous consequences for the mountain environment. The hazard analysis links key rainstorm energy variables expressed as a single-storm erosion index (EI_sto), with impact thresholds identified using an intensity pattern model. Afterwards, the conditional probabilities of exceeding these thresholds are spatially assessed using non-parametric geostatistical techinques, known as indicator kriging. The approach was applied to a test site in river-torrential landscape of the Southern Italy (Benevento province) for 13 November 1997 rainstorm event.     

IMPACTS OF VISITORS ON SOIL AND VEGETATION OF THE RECREATIONAL AREA “NACIMIENTO DEL RÍO MUNDO” (CASTILLA-LA MANCHA, SPAIN)

This study examines the effects of recreational use on the soil and vegetation at a site of ecological importance (Nacimiento del Río Mundo, Albacete, Spain). The most visited sites showed increased soil compaction of approximately 50%, bare ground increase to 61 ± 10% and a decrease in richness (from 25 ± 2 to 15 ± 2 species), diversity (from 4.0 ± 0.1 to 2.7 ± 0.4) and stratification of plant species (from 80 ± 11 to 21 ± 4%). The most visited sites had 90% less plant species as compared to the least visited. Intense use was associated with the presence of nitrophilous plant and vegetal species with a morphology adapted to heavy trampling. The recreational areas showed a distribution pattern of impact radiating outwards from the most used and degraded point. At the most visited point, Los Chorros (the spring of the river), the impact radiated outwards for about 20 m. A pilot experiment examining the effects of one-year restriction to visitors for access to a formerly impacted area showed a plant cover increase by anthropic and not by native species of 57 percent units.     

苏南地区农村河塘底泥中重金属污染调查与评价

对苏南地区农村河塘底泥中重金属的污染物状况及分布特征进行了调查,分别在镇江、宜兴和常州采集了农村居民生活区、农田附近和养殖厂周围13个底泥样品,对底泥中的5种重金属Zn、Cu、Cd、Pb、Cr质量比进行了分析研究,并利用Hakason生态风险指数法评价了底泥中5种重金属对其所在水域的污染程度,对水域和周围环境造成的潜在风险影响.结果表明,苏南地区部分农村河塘底泥已受到轻度的重金属污染,部分采样点Cd、Cu和Zn已达到中度污染;不同类型底泥的重金属的污染程度趋势为:居民生活区＞养殖厂周围＞农田附近.     

钻井废泥浆中重金属化学形态及潜在生态效应评价

利用化学萃取法对江苏9个油田的不同类型钻井废泥浆的重金属化学形态分布特征进行调查分析,同时选用Hakanson的潜在生态危害指数法对钻井废泥浆中的重金属总量进行生态效应评价。结果表明,钻井废泥浆中Cu、Pb、Zn、Cd、Cr主要以残渣态和有机结合态为主,活性形态含量较低;采用Hakanson的潜在生态危害指数进行评价,发现Cu、Pb、Zn、Cd都属于轻微生态危害水平,而Cr多属于中等水平,产生潜在生态危害的重金属主要为Cr。     

中国土壤中溴,碘的背景含量

通过对全国八百余个表层土样的分析测试,获得了中国土壤中溴、碘背景含量的总体水平及在各土类中的含量,相对于地壳丰度,中国土壤中溴、碘普遍得到了富集,溴、碘含量分异变化较大,并具有明显的地域分异特征,影响中国土壤中溴、碘含量的主要因素是降水量、土壤吸附体的含量以及某些特殊母质。