This study focused on determining Arsenic (As), Lead (Pb), Cadmium (Cd) and Zinc (Zn) concentrations of indigenous plants Pteris vittata L. and Eleusine indica L. in greenhouse experiment and some mining sites in Bac Kan province, Vietnam. The results showed that the soils of surveyed mining areas contained 378 – 6753 mgkg-1 As, 3210 - 21312 mgkg-1 Pb, 15.6- 312 mgkg-1 Cd and 1280-25310 mgkg-1 Zn depending on the characteristics of each mining site. In both greenhouse and field, Pteris vittata L. was As hyperaccumulators, containing more than 0.1% As in its shoots. Eleusine indica L accumulate high concentrations of Pb (1234-4316 mgkg-1) and Zn (982-2352 mgkg-1) in their roots. None of two plant species had high Cd accumulating ability in the root and shoot. The amounts of heavy metals in two species under the field condition smaller than in the greenhouse experiment when they grew nearly in the same soil. Both two plants are good candidates for phytoremediation of these mining sites. / Nghiên cứu này nhằm đánh giá hàm lượng Asen (As), Cadimi (Cd), Chì (Pb) và Kẽm (Zn) của hai loài thực vật bản địa là Pteris vittata L. và Eleusine indica L. trong thí nghiệm nhà kính và tại một số điểm khai thác mỏ ở tỉnh Bắc Kạn, phía Bắc Việt Nam. Kết quả chỉ ra rằng, đất vùng mỏ khảo sát có chứa 378 – 6753 mgkg-1 As, 3210 - 21312 mgkg-1 Pb, 15,6- 312 mgkg-1 Cd và 1280-25310 mgkg-1 Zn phụ thuộc vào tính chất của từng điểm lấy mẫu. Trong cả thí nghiệm tại nhà kính và ngoài đồng ruộng, Pteris vittata L. đã được xác định là loài siêu tích lũy As, nó có chứa lượng As nhiều hơn 0.1% ở trong phần trên mặt đất của cây. Eleusine indica L tích lũy cao lượng Pb (1234-4316 mgkg-1) và Zn (982-2352 mgkg-1) trong phần rễ cây. Hai loài thực vật nghiên cứu không có khả năng tích lũy cao lượng Cd ở phần thân và rễ cây. Hàm lượng kim loại nặng tích lũy trong thực vật nghiên cứu ở ngoài thực địa nhỏ hơn trong thí nghiệm khi cùng mọc trên một loại đất ô nhiễm như nhau. Cả hai loài thực vật nghiên cứu là đối tượng tốt cho xử lý ô nhiễm tại các điểm mỏ khảo sát.

In Vietnam, soil contamination with lead and cadmium at very high level was investigated anddiscovered in the surrounding areas of zinc-lead mining and processing factory in Tan Long (Dong Hy district, Thai Nguyen province) and around the lead-recycling smelter in Chi Dao (Van Lam district, Hung Yen province). The survey on soil contaminated by arsenic due to the tin mining and sifting activities in Ha Thuong (Dai Tu district, Thai Nguyen province) was also carried out. In Tan Long, the concentrations of lead and cadmium in the old solid waste dump from zinc-lead factory varied from 1,100 to 13,000 mg·kg-1, and from 11.34 to 61.04 mg·kg-1, respectively. Soil Pollution Indexes (SPI) of lead and cadmium were highest in the old solid waste dump area, followed by the ones in the rice paddy soils. In Chi Dao, the soils of many sites were polluted with lead and cadmium such as in the gardens of lead-recycling households where the concentrations of lead and cadmium were 7,000 - 15,000 mg·kg-1 and 1.8 - 3.6 mg·kg-1. In rice paddies, the soils were also polluted by lead. SPI of lead in paddy soil areas within 300 m radius from the lead smelter were from 3.6 to 100 fold higher than the safe limit. The sediment from the ditch near the lead smelters contained extremely high levels of lead (7,000 - 110,000 mg·kg-1) and cadmium (3.8 - 17.7 mg·kg-1). The tin mining and sifting activities in Ha Thuong was the cause for the arsenic contamination of the soil in this area. The arsenic contents in soils at all locations investigated were higher than 320 mg·kg-1 (dry weight) and up to 3,809 mg·kg-1. / Tại Việt Nam, đất bị ô nhiễm bởi chì và ca-đi-mi với hàm lượng cao đã được điều tra phát hiện ở các khu vực phụ cận của nhà máy khai thác và chế biến kẽm/chì thuộc địa phận xã Tân Long, huyện Đồng Hỷ, tỉnh Thái Nguyên và các khu vực phụ cận của lò tái chế chì thuộc địa phận xã Chỉ Đạo, huyện Văn Lâm, tỉnh Hưng Yên. Sự khảo sát đất bị ô nhiễm bởi a-sen do các hoạt động khai thác và tuyển thiếc ở xã Hà Thượng, huyện Đại Từ, tỉnh Thái Nguyên cũng đã được tiến hành. Tại xã Tân Long, nồng độ chì và ca-đi-mi trong bãi chất thải rắn cũ từ nhà máy sản xuất kẽm chì là 1.100 - 1.300 mg.kg-1 và từ 11,34 đến 61,04 mg.kg-1, tương ứng. Chỉ số ô nhiễm đất (SPI) của chì và ca-đi-mi cao nhất trong khu vực đổ chất thải rắn cũ, tiếp theo sau là ở các ruộng lúa. Tại xã Chỉ Đạo, đất ở nhiều địa điểm đã bị ô nhiễm chì và ca-đi-mi chẳng hạn như trong khu vườn của các hộ gia đình tái chế chì, nồng độ chì và ca-đi-mi là 7.000 - 15.000 mg.kg-1 và 1,8 - 3,6 mg.kg-1. Trong cánh đồng lúa, đất cũng bị ô nhiễm bởi chì. Chỉ số ô nhiễm đất của chì (SPI-Pb) trong cánh đồng lúa trong vòng bán kính 300 m từ lò tái chế chì cao hơn giới hạn của đất an toàn từ 3,6 đến 100 lần. Trầm tích thu từ kênh gần lò tái chế chì chứa hàm lượng chì rất cao (.7000 - 110.000 mg.kg-1) và ca-đi-mi (3,8 - 17,7 mg.kg-1). Việc khai thác và tuyển thiếc tại xã Hà Thượng đã gây ra ô nhiễm a-sen trong đất tại khu vực này. Hàm lượng a-sen trong đất tại tất cả các địa điểm nghiên cứu cao hơn 320 mg.kg-1 (trọng lượng khô), đặc biệt là lên đến 3809 mg.kg-1.

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The effect of trampling on vegetation and soil, as a result of recreational pressure, was studied in the Buffalo campground of the Targhee National Forest, Idaho. Site deterioration was most evident in the forty-two year old site. The tree stand had matured, but there were few young trees and tree reproduction had been reduced to ten seedlings per acre for Pinus contorta. Only two shrub species were sampled with a combined population of eight individuals per acre. Most of the grass species had been seeded; forbs provided 20% of the ground cover, 13% was bare ground and 71% litter. The soil had become compacted, and a hard-pan had formed. Similar deterioration was found in the six-year old site, but to a lesser degree. The year-old site was most similar to the control area, but site deterioration had occurred. It is difficult to reverse or halt site deterioration and still maintain the area as a public facility. Seeding and rest-rotation could improve the oldest site; younger sites could be maintained by restrotation, to allow existing vegetation to re-stock the depleted areas.

Prediction of subsurface migration of contaminant through soils involves analyses of unsaturated and saturated flow of water and advective dispersive transport of contaminant species. A finite element model is developed here for such an analysis. It is based on the transient nonlinear Richard's equation for the unsaturated flow and the mass transport equation using advective dispersive transport phenomenon. The model makes it possible to make advance predictions of the spread of the contaminant with respect to time and space, into the ground water system. The hydraulic properties of the unsaturated soils and the dispersion characteristics need to be obtained for such an analysis. The unsaturated flow parameters are obtained from a functional relationship between capillary pressure head and moisture saturation, and can be determined from laboratory tests on simple column samples of soils. A general expression is assumed to account for the effect of velocity dependence of the hydrodynamic dispersion coefficient in the mass transport problem. A computer program POLUT2D is developed based on the above assumptions. Pre and post processors for the computer program POLUT2D are also developed for interactive input of data and graphics displays of results. The computer program is first evaluated by comparing the results of a problem given in the literature with the results obtained by POLUT2D. The factors affecting the contaminant movement and distribution such as dispersivities, hydraulic conductivities and the effect of cutoff walls in controlling the spread of contaminant plume are studied. Also in this regard, the movement and spread of a contaminant at a landfill site in New Castle County, Delaware, is studied by comparing the simulated pattern of plume with the observed pattern. / Master of Science

An assessment of heavy metal and pesticide pollution was conducted at a commercial airport in Pietermaritzburg, which is the base for a local crop spraying operation, as well as a small-scale aircraft maintenance centre. The study investigated the presence of heavy metals from the aircraft activities (tyre wear, emission and aircraft body attrition) along the edges of the runway. In addition, the study assessed the pollution of the soil in different parts of the airport (areas adjacent to the crop sprayer hangar and maintenance hangars drainage ditch) caused by organic chemicals (pesticides) originating from the washing and maintenance of the crop spraying aircrafts. A total of 37 samples were taken from the top soil (0-15 cm) adjacent to both sides of the runway, approximately 100 meters apart, for heavy metal assessment. Total metal concentrations were determined on a 1:1 HNO3 acid extract analysed using inductively coupled plasma spectroscopy and the results compared with the baseline concentrations of heavy metals in the soils of South Africa. The average levels of the heavy metals in the soils were: Cd - 4.4, Co - 76, Cr - 142, Mn - 6580, Pb - 64 and Zn - 70 mg/kg. The Cd and Co concentrations of all samples and the Pb and Zn concentrations of 86% of the samples were above the South African guidelines for the maximum permissible contents of these metals (2 mg/kg Cd, 20 mg/kg Co, 6.6 mg/kg Pb, 46.5 mg/kg Zn) in soils. In addition, the concentration of Cr was significantly above these guidelines (80 mg/kg Cr ) in 51% of the samples. All the metals, except zinc, were highly correlated with one another indicating the source for these heavy metals is the same. In addition the concentration of these metals was high at sampling points adjacent to the runway where pronounced aircraft tyre wear marks were observed, suggesting that the aircraft activities are the sources of these heavy metals. A total of 13 samples were collected from areas adjacent to the crop sprayer hangar and the drainage ditch (at the maintenance hangars) in order to determine the qualitative presence of organic pollutants. The samples were prepared using soxhlet extraction. Cypermethrin, deltamethrin, azoxystrobin, fusillade and fluazifop-p-butyl as well as fuel oils Jet Al and Avgas were qualitatively determined using GC/MS. Only fusillade and fluazifop-p-butyl were detected, in some of the samples. No quantitative analysis of the organic chemicals was attempted due to time constraints. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2004.

Volcanic tuffs and tuffaceous sediments are frequently associated with elevated As groundwater concentrations even though their bulk As contents (~ 5 mg kg-1; Savoie, 2013) are only marginally greater than the average crustal abundance of 4.8 mg g-1 (Rudnick & Gao, 2003). Thus, As mobilization must be facilitated by conditions particular to these rocks. Alkaline desorption, anionic competition, reactive glass dissolution, and reductive dissolution of iron oxides are proposed processes of As release from volcanic rocks. Geogenic As contamination of groundwater in the southern Willamette Valley in western Oregon has been well-documented since the early 1960s, and previous studies have identified the Little Butte Volcanics Series and Fisher and Eugene Formations as the source of As contamination. This study examines 19 samples from 10 units of ash flow tuffs and tuffaceous sediments within the Fisher Formation and Little Butte Volcanics Series, representing a range of weathering and devitrification, to determine conditions of mobilization and mineralogical constraints that control As release into solution. Leachate studies were conducted over a range of pH from 7 to 11, phosphate concentrations from 10 μM to 100 mM, and in time series from 4 to 196 hours. Results demonstrate that silicic volcanic tuffs are capable of mobilizing As in concentrations above regulatory limits at pH conditions produced naturally by the tuffs (pH 8-9) or with moderate concentrations of P (10-100 μM). Alteration products, e.g. zeolites and clays, appear to be the primary host phases for mobile As. Samples that do not contain these alteration products tend to produce concentrations of As well below regulatory limits and often below the instrument detection limits of this study. The type of alteration may influence As mobilization: tuffs containing more clays tend to mobilize As through surficial desorption, and tuffs containing more zeolites tend to mobilize As by dissolution or formation of colloids. Additionally, one volcaniclastic sample demonstrates that extremely elevated concentrations of As, up to 1000 μg/L are possible as a result of oxidative dissolution of As-bearing sulfide phases.

A contaminação dos solos por elementos potencialmente tóxicos provoca alterações na estrutura e no funcionamento dos ecossistemas, além de oferecer riscos à saúde pública. Embora os metais pesados ocorram naturalmente, fontes antropogênicas contribuem para o aumento das taxas de redistribuição desses elementos entre os compartimentos do ambiente. O coeficiente de distribuição ou partição sólido-solução (Kd) permite observar a afinidade entre os metais e os colóides do solo. O Kd é peça-chave em muitos modelos para definição de valores orientadores e para previsão de riscos ambientais, e seu valor é dependente das condições edafoclimáticas das regiões onde se assentam os solos. Os valores de Kd de metais pesados ainda não foram determinados para solos da região Amazônica. Nesse estudo objetivou-se determinar os valores de Kd de metais pesados em solos do Estado do Pará. Para tanto foram conduzidos experimentos de adsorção, tipo batch, nos quais foram adicionados 0,5; 1,0; 2,5; 5,0 mg L-1 de Cd, Co, Cr, Cu, Hg, Ni, Pb, e Zn em amostras de 21 solos paraenses. As menores variações nos valores absolutos de Kd foram registradas para o Pb (uma ordem de magnitude - 196,4 a 5.572,5 L kg-1) e para o Cu, Hg e Ni (duas ordens de magnitude 50,5 a 7.368,7; 24,9 a 4.191,6; 4,7 a 524,2 L kg- 1, respectivamente). Variações de três ordens de magnitude foram observadas para: Cd (6,0 a 2.471,9 L kg-1), Co (2,7 a 4.604,1 L kg-1), Cr (2,5 a 1.811,6 L kg-1) e Zn (1,4 a 7.933,0 L kg-1). Obteve-se a seguinte ordem de afinidade: Pb > Cu > Hg > Cr > Cd Co > Ni > Zn. O pH, os teores dos óxidos de Fe e de Mn e a CTC foram os atributos dos solos que mais se correlacionaram com os valores de Kd, que foram inferiores aos estabelecidos por Agências Internacionais e para o Estado de São Paulo. / Soil contamination by potentially toxic elements affects the structure and the functioning of the ecosystems and pose risks to public health. Although heavy metals occur naturally, anthropogenic sources contribute to increased rates of redistribution of these elements between the compartments of the environment. The solid-solution coefficient of distribution or partition (Kd) shows the affinity between metals and soil colloids. Kd is a key componentt in many models for defining and guiding values for prediction of environmental hazards, and its value is dependent on environmental conditions in the regions where they settle the soil. Kd values for heavy metals have not been determined for soils in the Amazon region. In this study, these values were obtained for 21 soils of the State of Pará, Brazil. Adsorption experiments were conducted, type \"batch \", by means of the adition of 0.5, 1.0, 2.5, 5.0 mg L-1 of Cd, Co, Cr, Cu, Hg, Ni, Pb, and Zn to the soils. The small variations in the absolute values of Kd were recorded for Pb (an order of magnitude 196.4 to 5,572.5 L kg-1) and for Cu, Hg and Ni (two orders of magnitude 50.5 to 7,368.7; 24.9 to 4,191.6; 4.7 to 524.2 L kg-1, respectively). Variations of three orders of magnitude were observed for: Cd (6.0 to 2,471.9 L kg-1), Co (2.7 to 4,604.1 L kg-1), Cr (2.5 to 1,811.6 L kg-1), and Zn (1.4 to 7,933.0 L kg-1). We obtained the following order of affinity: Pb > Cu > Hg > Cr > Cd Co > Ni > Zn. The pH, the contents of Fe and Mn oxides, and CEC were the soil attributes that correlated significantly with the values of Kd, which were lower than those set by international and the State of São Paulo, Brazil, agencies.