A simple accelerated rock weathering method to predict acid generation kinetics

The development of effective, and economical pre-development waste rock management plans requires an accurate estimate of the quality of drainage generated during mining. This study was conducted to determine if a simple accelerated rock weathering method with lower capital and personnel costs can be used in lieu of the elaborate and costly ASTM method to predict the quality of drainage generated. It involves subjecting rock samples to a constant relative humidity and temperature for 7 days and leach flooding the weathered samples on the 7th day. The acid production rate from the new weathering method correlates quite well with the net neutralization potential generated from the standard acid-base accounting procedure (R²=0.940) which has been demonstrated to be correct 90% of the time in assessing overburden quality, and a mineralogical method (R²=0.924). For investigators interested in generating weathering kinetic parameters, the simple and less costly accelerated weathering method is proposed.     

地下水中酸性污染羽的自然净化作用数值模拟研究

酸法地浸采铀对铀矿层的地下水环境有极大的破坏作用,当开采结束后将形成酸性地下水污染羽。为恢复含矿含水层的水质,必须采取有效的污染治理措施。自然净化是一种较经济的方法,但是必须对其有效性进行评价。本研究以某退役地浸铀矿采区含矿含水层为研究对象,采用反应溶质运移模拟方法来研究酸性污染羽在含水层中的自然净化作用。研究中使用PHT3D模型模拟污染羽的运移,模拟反应组分共12种、沉淀溶解矿物共6种,模拟时长为5a。模拟结果表明：酸性污染物进入地下水后,形成了由方解石、Al(OH)3（a）和 Fe(OH)3（a）反应所控制的pH缓冲区;随着酸性污染羽的向下游高pH值地下水区域移动,方解石溶解与石膏沉淀反应可使SO42-浓度产生明显下降,其他主要金属离子污染物也有明显的自净作用。     

腐植酸泥浆正交试验优化研究

腐植酸泥浆是非开挖钻进砂层、砾石、卵石以及破碎地层时常用的一种护壁浆液。针对常用的腐植酸泥浆的配方,设计了四因素三水平的正交试验,分析了泥浆性能受各组分影响的主次,然后进行配方优化。把NaCl作为一个正交试验因素,分析了NaCl不同加量对泥浆性能的影响。正交优化后的泥浆性能粘度较高,失水量较小,能较好的满足施工的要求。     

Temporal variation in discharge chemistry and portal flow from the 8-Level adit, Lynx Mine, Myra Falls Operations, Vancouver Island, British Columbia

The Lynx mine, currently inactive, has produced copper and zinc concentrates from massive sulfide deposits on a lease within the rainy, mountainous interior of Vancouver Island. Tailings, used to back-fill a mined-out stope, are being leached by percolating groundwater and the resulting acidic, metal-laden drainage is discharging from the portal of the 8-Level adit. Temporal variations in the flow rate, specific conductance and temperature of the discharge were monitored continuously over a 2-year period while effluent chemistry was sampled weekly. Conductivity was relatively constant throughout most of the year but peaked with the first autumn storm events as accumulated soluble sulfide oxidation products were flushed from the workings. Concentrations of sulfate and most metals were closely correlated with conductivity as were low pH values as stored acidity was released along with dissolved species. Variations in pH controlled the speciation and partitioning of metals between dissolved and particulate phases.     

晶安高科“三废”治理及综合利用

介绍了晶安高科污染源的来源、采取的措施及综合治理、利用方法.使废水指标由PH11～12;SS<1000mg/l;CODcr≤200mg/l;氨氮≤200mg/l降到PH6～9;SS<70mg/l;CODcr≤100mg/l;氨氮≤15mg/l;酸雾指标由HCl500～800mg/m3达到小于25～40mg/m3;炉窑烟气由林格曼黑度5,烟尘浓度2700～5191mg/Nm3降到林格曼黑度1,烟尘浓度小于200mg/Nm3;硅渣可生产复合絮凝剂和白炭黑,不仅可改善环境影响,而且可回收盐酸和利用废资源,可给企业带来经济效益.     

Impact of AMD on water quality in critical watershed in the Hudson River drainage basin: Phillips Mine,Hudson Highlands,New York

A sulfur and trace element enriched U–Th-laced tailings pile at the abandoned Phillips Mine in Garrison, New York, releases acid mine drainage (AMD, generally pH < 3, minimum pH 1.78) into the first-order Copper Mine Brook (CMB) that drains into the Hudson River. The pyrrhotite-rich Phillips Mine is located in the Highlands region, a critical water source for the New York metro area. A conceptual model for derivation/dissolution, sequestration, transport and dilution of contaminants is proposed. The acidic water interacts with the tailings, leaching and dissolving the trace metals. AMD evaporation during dry periods concentrates solid phase trace metals and sulfate, forming melanterite (FeSO₄·7H₂O) on sulfide-rich tailings surfaces. Wet periods dissolve these concentrates/precipitates, releasing stored acidity and trace metals into the CMB. Sediments along CMB are enriched in iron hydroxides which act as sinks for metals, indicating progressive sequestration that correlates with dilution and sharp rise in pH when mine water mixes with tributaries. Seasonal variations in metal concentrations were partly attributable to dissolution of the efflorescent salts with their sorbed metals and additional metals from surging acidic seepage induced by precipitation.     

Study of exchangeable metal on colloidal humic acids and particulate matter by coupling ultrafiltration and isotopic tracers: Application to natural waters

A new method is proposed to characterize the complexation properties of colloids and metal–colloid interactions in natural waters. Based on the association of ultrafiltration with isotopic tracing, this method could quantify the pool of elements in an exchangeable position and also address the kinetic aspects of these exchanges. Basically, it consists of the comparison of isotopic compositions between the bulk sample and a succession of filtrates through time. Exchanges between colloidal humic acids (HA) and metals were first characterized, before applying such manipulations on natural waters. A few elements, representative of a wide range of complexation properties, were chosen: Cu, Zn, Cd, Pb, Sr, Nd, Ni, Th and U. In the case of humic acids, very small (less than 10% of isotopes), but significant isotopic shifts were observed compared to the isotopic equilibrium. It means that more than 90% of the isotopes were exchanged just after addition of isotopic tracers. Experiments on natural organic-rich waters (Mengong and Nyong streams) indicate isotopic composition variations close to those of humic acids. On the contrary, ultrafiltration performed on the total Sanaga River water (including suspended matter “SM”) shows an important isotopic shift between the filtered and unfiltered solutions. It means that in the case of the Sanaga River, a significant part of the chemical elements did not exchange.     

Speciation of aluminum in the stream waters from the Susquehanna River watershed, Chesapeake Bay

 The aim of this paper was to analyze the processing and transport of aluminum speciation through the terrestrial and aquatic ecosystems of the Chesapeake Bay landscape. Stream waters were sampled in 14 different streams from the Susquehanna River watershed to the upper reach of Chesapeake Bay. The basic water quality data were documented and Al speciation was evaluated by modified MINEQL computer model. It was found that the increase in acidity in some of the stream waters near New York were closely linked with a marked decline in basic cation concentrations. In these areas, the sum of the toxic forms of Al³⁺ plus AlOH²⁺ and Al(OH)₂ ⁺ concentrations exceeds the critical level of 5 μmol l^–1. A potential threat from aluminum may occur. Received: 3 January 2000 · Accepted: 21 March 2000     

On the scavenging of SO2 by cloud and raindrops: I. A theoretical study of SO2 absorption and desorption for water drops in air

An extention of our previous theory for trace gas absorption into freely-falling cloud and raindrops is presented. This theory describes the convective diffusion of a trace gas through air and into a water drop with internal circulation, the drop falling at its terminal velocity. Using flow fields for the circulating water inside and for the moving air outside the drop, obtained by numerical solutions to the Navier—Stokes equation of motion, we numerically solved the convective diffusion equation to determine the uptake of SO₂ by water drops of various sizes, time exposure to the gas phase, and concentration of SO₂ in the gas phase. It was found that for drops of radius larger than 1 mm and relatively low gas concentrations (10 ppb (v)), resistance to gas diffusion lies mainly in the gas phase; while for drops of radius less than 500 m and gas concentrations larger than those found in the atmosphere (1% (v)), the resistance to diffusion lies primarily in the liquid phase. With drop sizes and gas concentrations between these limits, the rate of SO₂ uptake is controlled by a coupled resistance to diffusion inside and outside the drop. In addition to our general model, a simplified version was formulated which allows considerable savings in computer time for evaluation and improved ease of handling without significant loss of accuracy. A comparison between our simplified model and that of Barrie (1978) shows that the boundary-layer approach of Barrie may be a useful alternate approach to estimating trace gas absorption by water drops, provided appropriate values are chosen for the thickness of the boundary layers involved.     

Rainwater acidity and ion concentration correlations in a midwest storm system

The pH and the concentrations of sulfate, nitrate, ammonia, and calcium in rainwater were measured for two periods of a single midwest rainstorm which occurred over a mesometeorological network in central Illinois on 24–25 July 1979. Regression analysis was used to compare ion concentrations with rainfall amount, and ion balance was used to compare cation and anion concentrations at individual sites. Only the ions SO₄ ^2- and NO₃ ^- show any significant relationship to rainfall amount, decreasing as rainwater amounts increase (r=–0.57 and –0.60, respectively). During the first period of the rainstorm, a sequential sampler measurements allowed the calculation of detailed temporal variations in SO₄ ^2-, pH, and rain rate. SO₄ ^2- decreased, and pH increased as the rate increased and the opposite temporal pattern occurred as the rain decreased at the end of the period. Reasons for these variations are discussed.Research done while a visiting scientist at the Illinois State Water Survey, Champaign, Illinois, U.S.A.