Experimental investigation of the inhibition of deep-sea mining sediment plumes by polyaluminum chloride

Deep-sea sediment disturbance may occur when collecting polymetallic nodules,resulting in the creation of plumes that could have a negative impact on the ecological environment.This study aims to investigate the potential solution of using polyaluminum chloride(PAC)in the water jet.The effects of PAC are examined through a self-designed simulation system for deep-sea polymetallic nodule collection and sediment samples from a potential deep-sea mining area.The experimental results showed that the optimal PAC dose was found to be 0.75 g/L.Compared with the test conditions without the addition of PAC,the presence of PAC leads to a reduction in volume,lower characteristic turbidity,smaller diffusion velocity,and shorter settling time of the plume.This indicates that PAC inhibits the entire development process of the plume.The addition of PAC leads to the flocculation of mm-sized particles,resulting in the formation of cm-sized flocs.The flocculation of particles decreases the rate of erosion on the seabed by around 30%.This reduction in erosion helps to decrease the formation of plumes.Additionally,when the size of suspended particles increases,it reduces the scale at which they diffuse.Furthermore,the settling velocity of flocs(around 10^(-2) m/s)is much higher that of compared to sediment particles(around 10^(-5) m/s),which effectively reduces the amount of time the plume remains in suspension.

Predicting the sinkage of a moving tracked mining vehicle using a new rheological formulation for soft deep-sea sediment

The sinkage of a moving tracked mining vehicle is greatly af fected by the combined compression-shear rheological properties of soft deep-sea sediments. For test purposes, the best sediment simulant is prepared based on soft deep-sea sediment from a C-C poly-metallic nodule mining area in the Pacific Ocean. Compressive creep tests and shear creep tests are combined to obtain compressive and shear rheological parameters to establish a combined compressive-shear rheological constitutive model and a compression-sinkage rheological constitutive model. The combined compression-shear rheological sinkage of the tracked mining vehicle at dif ferent speeds is calculated using the Recur Dyn software with a selfprogrammed subroutine to implement the combined compression-shear rheological constitutive model. The model results are compared with shear rheological sinkage and ordinary sinkage(without consideration of rheological properties). These results show that the combined compression-shear rheological constitutive model must be taken into account when calculating the sinkage of a tracked mining vehicle. The combined compression-shear rheological sinkage decrease with vehicle speed and is the largest among the three types of sinkage. The developed subroutine in the Recur Dyn software can be used to study the performance and structural optimization of moving tracked mining vehicles.

Surface Water Sediments Characterization Using Metallic Trace Elements (MTEs): Case of the Artisanal Gold Mining Sites of Kokumbo (Côte d’Ivoire)

The main purpose of this study is to characterize the surface sediments of the Kokumbo artisanal gold mining sites in Metallic trace Elements (MTEs). A total of 12 samples of surface water sediments were collected for this study. The samples were analyzed using the Atomic Absorption Spectrophotometer (AAS). The mean concentrations of Mn (611.37 mg/kg) and Zn (955.86 mg/kg) in the sediments were very high compared to the standard in unpolluted sediments. The enrichment factor (EF) shows that there is an enrichment of Mn at some sites (EF (Mn) > 2). The presence of As, Mn, and Zn is also highlighted by the geo-accumulation index (I-geo) which shows slight pollution in Mn (0 < I-geo (Mn) < 1) on some sites. Moderate pollution for As (1 < I-geo (As) < 2) was determined at the treatment site and high pollution in Zn at some sites in the area (I-geo (Zn) > 3). This study shows that the presence of Zn in the sediments is linked to artisanal gold mining activities. Indeed, Zn is much used for gold recovery. The statistical analysis (PCA) shows, on the one hand, natural mineralization of the sediments and addition of metals linked to anthropic activities corresponding to the erosion of mining discharges. The surface sediments of the Kokumbo mining sites show pollution in As, Mn, and Zn.

Environmental Geochemistry of Heavy Metal Contaminants in Soil and Stream Sediment in Panzhihua Mining and Smelting Area,Southwestern China

Mining and smelting activities are the main causes for the in creasing pollution of heavy metals in soil, water body and stream sediment. An e nvironmental geochemical investigation was carried out in and around the Panzhih ua mining and smelting area to determine the extent of chemical contamination in soil and sediment. The main objective of this study was to investigate the envi ronmental geochemistry of Ti, V, Cr, Mn, Cu, Pb, Zn and As in soil and sediment and to assess the degree of pollution in the study area. The data of heavy metal concentrations reveal that soils and sediments in the area have been slightly c ontaminated. Geochemical maps of I\-\{geo\} of each heavy metal show that the co ntaminated sites are located in V-Ti-magnetite sloping and smelting, gangues d am. The pollution sources of the selected elements come mainly from dusts result ant from mining activities and other three-waste-effluents. The area needs to be monitored regularly for trace metal, especially heavy metal enrichment.

Spatial and Temporal Patterns of Variation in Environmental Quality of Water and Sediments of Streams in Mined and Unmined Areas with Emphasis on Mercury (Hg) and Arsenic (As)

Heavy metal pollution from both anthropogenic and natural processes can have significant effect on environmental quality of stream and river systems. However, in Ghana, heavy metal pollution of waterbodies is attributed mainly to mining activities but the role of natural mechanisms in altering stream water and sediment quality in relation to heavy metals has received little attention. Spatial and temporal variation in water quality parameters and heavy metal concentrations in water and sediments were studied comparatively in a river and two streams in a gold-rich watershed impacted by heavy mining activities. Samples were collected monthly over a twelve-month period from November 2010 to October 2011 from upstream (unmined) and downstream (mined) sections of the studied streams. Parameters measured include temperature, dissolved oxygen, conductivity, pH, turbidity, colour, mercury (Hg) and arsenic. High spatial variability of water quality parameters was found. Hg concentrations in water were extremely low in both upstream and downstream areas. Maximum geochemical background levels of Hg in unmined pristine areas were 2.45 mg/g whilst arsenic was 29.10 mg/g. By contrast, gold-mined downstream areas recorded Hg and arsenic concentrations of 8.75 mg/g and 82.53 mg/g in stream sediments respectively. Levels of Hg and arsenic in sediments were several orders of magnitude greater than concentrations in surface water in downstream sections and this may be explained by substances originating from mining activities, upstream transport or remobilized sedimented materials in the overlying water column. Our study showed that both natural and human activities may contribute to heavy metal pollution in the highly mineralized watershed of the Pra River Basin. Human factors are however likely to amplify the natural background levels of heavy metals.

Sediment settlement rate and consolidation time of flling reclamation in coal mining subsidence land

With the continuous growth of the population and the continuous reduction of cultivated land,China’s food security is greatly threatened.In addition,China’s coal mining has been mainly underground mining,causing land subsidence and damaging existing cultivated land.This efect intensifes the contradiction between the growth of the risk population and the reduction of cultivated land.The reclamation of mining subsidence land with Yellow River sediment is often used as an efective way to improve the recovery rate of cultivated land.Shortening the reclamation time and realizing continuous flling are signifcant issues.The work presented in this paper studied the sediment settlement rate and consolidation time by combining theory,feld flling and reclamation tests and numerical simulations.A feld flling test study was carried out in the lowlands of Jibeiwang Village,Qihe County,Shandong Province,China.By calculating the drainage consolidation time,the consolidation factor of 0.015656 m^(2)/d,and the time factor for sediment consolidation of 0.575 were determined.The sediment consolidation time for this test was 9.18 days.The calculation of sediment deposition rate and consolidation time is of great practical signifcance to guide the Yellow River sediment flling,realize continuous flling,and save reclamation time and cost.

Evaluation of Bottom Sediment Qualities in Ihetutu Minefield, Ishiagu, Nigeria

Bottom sediment qualities in Ihetutu minefield were assessed to ascertain the impact of Pb-Zn mining activities on the sediments from streams, rivers and ponds in the area. Levels of Cu, Zn, Fe, Ni, Mn, Pb, Cd and Cr and some physico-chemical parameters were measured in bottom sediments taken from four sampling stations (streams/mine pits) within Ihetutu minefield of Ishiagu which receives discharges from mining and human activities, and a control sampling station in Uturu (about 12 km away from study area). The study was conducted in four seasons (Rainy, Late Rainy, Dry, and Late Dry Seasons). Sample digestion was done with a temperature adjustable block digester. Heavy metal analysis was carried out with Flame atomic absorption spectrophotometer (FAAS) while other physico-chemical parameters were determined with standard field and laboratory procedures. Ranges of mean values of results obtained were;pH = 5.81 - 6.44, EC = 269.00 - 1545.00 μS/cm, Cl&#8722 = 43.30 - 112.33 mg/kg, alkalinity = 0.70 - 1.25 mg/kg, NO3-?= 5.90 - 7.90 mg/kg, TOC = 0.81 - 1.75 mg/kg, TOM = 1.40 - 3.02 mg/kg, Cu = 4.74 - 50.93 mg/kg, Zn = 26.78 - 57.07 mg/kg, Fe = 1066.19 - 1764.05 mg/kg, Mn = 36.66 - 42.96 mg/kg, Ni = 4.02 - 17.19 mg/kg, Pb = 38.01 - 162.23 mg/kg, Cd = 1.01 - 25.90 mg/kg, and Cr = 1.23 - 1.62 mg/kg. Assessment of heavy metals pollution, using pollution indices revealed that Contamination factor ranged from moderate to very high degree of contamination while Pollution load index also showed a deterioration of bottom sediment qualities. Geoaccummulation index indicated moderate to very high pollution, especially with Cu, Zn, Pb, and Cd in the mine pit, while Enrichment factor indicated high enrichments and inputs from anthropogenic sources especially, the Pb-Zn mining activities. Pollution of the area by heavy metals was in the order of Fe > Pb > Zn > Mn > Cu > Ni > Cd > Cr. Highest positive correlation (r = 0.992) was between Pb and Cu while the highest negative correlation (r = &#87220.789) was between Ni and Mn. Analysis of variance (ANOVA) at significance level, α = 0.05, showed no statistically significant differences in the sampling stations (p > 0.05). Compared to background (control), DPR and other standard guidelines/values, bottom sediments from Ihetutu minefield were highly polluted with Pb, Zn and Cu especially at the mine site. The overall results from the study revealed that toxic substances released from the prolonged Pb-Zn mining activities in the study area have impacted negatively on the bottom sediments, thereby also possibly deteriorating the quality of lives of the bottom sediments dwelling organisms in the streams, rivers, and pits/ponds in the area.

Mining Implication in the Geochemical Exploration of Fluvial Sediments of the East Nyambaka Volcanic Zone (Adamawa-Cameroon)

Geochemical characterization in stream sediments from Nyambaka locality was carried out on ten samples collected from the study area watershed. The distribution of trace metals in the sediments showed that some lithophiles (Be, Sc, V, Cr, Sr, Th, U), chalcophiles (Cu, Zn, Ga, As) and siderophiles (Mn, Co, Ni, Mo) have high average contents in the sediments compared to their average concentration in the upper crust. From the factorial analysis of the components, the total variance explained made it possible to represent and capture the main information on the data and to represent them in a graphical frame. Thus, using this graphical frame, the trace elements were divided into four groups opposed to each other. They show an enrichment of stream sediments in group 1 (Cr, Cu, Mn, Be, Ni, Co, Zr, Sr, Ba, Mg) and group 2 (Mo, As, Hg, V, Ag) elements more than group 3 (Ga, Sc, U) and group 4 (Au, Th). Rare earth analysis indicates a high abundance of Lanthanide (28.1 ppm to 42.4 ppm), a high concentration of light rare earth (LREE), and depletion of heavy rare earth (HREE). The variable LREE/HREE (7.24 LREE/ HREE 12.22) and (La/Yb)N (6.70 (La/Yb)N 11.72) ratios suggest an effect of heterogeneous sorting of heavy minerals with variable enrichment of dense and resistant minerals.

Pb concentrations and isotopic compositions in the soil and sediments around the abandoned mine in southwest of Korea

This study was undertaken to investigate the influence of Pb contaminant dispersal from an abandoned mine. For the study, 23 samples of sediment and soil were collected around the abandoned mine located in southwest of Korea. Pb concentrations and isotope ratios of sediment samples were analyzed through ICP-OES (Optima 5300 DV, Perkin Elmer) and MC-ICP-MS (Plasma II, Nu), respectively. The sediment samples collected in the main stream from the mine entrance showed high Pb concentrations of 139 - 1079 mg/kg, while Pb concentrations of the other sites were 19 - 29 mg/kg. Pb isotope ratios of the main stream sediments were 2.4854 - 2.4883 for 208Pb/207Pb and 1.1693 - 1.1740 for 206Pb/207Pb. On the other hand, the Pb isotopic compositions of sediments collected from the other sites were clearly different from those of ore deposits. The Pb isotope ratios versus inverse concentrations plot showed high linear correlation between the main stream, the tributary stream and one of the downstream sites representing the two end member mixing system between these sites. According to the binary mixing equation, the relative contribution of Pb pollutants from the abandoned mine to the downstream area were approximately 33% - 36%.

云南安宁磷矿区水系沉积物磷赋存形态及分布特征

磷污染是水污染的重要组成部分,因其可造成水体富营养化、水质下降,从而引起人们的广泛关注。研究沉积物中不同磷赋存形态及其分布特征有助于了解沉积物中磷的行为特征及迁移能力,从而为水体富营养化防治提供支撑。磷矿的开采、冶炼对矿区内水资源环境可能产生严重影响,本文以安宁磷矿区内河流、水库为研究区域,分析了不同水系沉积物磷元素赋存形态及分布特征,并对其生态风险进行评估。采用X射线荧光光谱法测定研究区水系沉积物总磷(TP)含量,并基于顺序提取及Hupfer改进的磷形态分析方法,将研究区各水系沉积物中磷分为弱吸附态磷(NH4Cl-P)、可还原态磷(BD-P)、金属氧化物结合态磷(NaOH-P)、钙结合态磷(Ca-P)、残渣态磷(Res-P)等5种形态,采用单因子污染指数法对其进行生态风险评估。结果表明:研究区水系沉积物样品中TP含量范围为567.6~48115.5mg/kg,NH4Cl-P含量范围为0.07~115.2mg/kg,BD-P含量范围为8.84~802.5mg/kg,NaOH-P含量范围为21.3~3129.5mg/kg,Ca-P含量范围为12~45098mg/kg,Res-P含量范围为28.5~515.4mg/kg。研究区各水系沉积物样品磷形态具有相似的分布特征,即磷主要以Ca-P和NaOH-P形态存在,其他磷形态的相对含量大小顺序为NH4Cl-P<BD-P<Res-P。单因子污染指数评价结果表明,各水系沉积物中磷以重度污染为主。生物有效磷(BAP)污染评价结果表明,各水系沉积物中磷污染程度有所降低,但河流沉积物中磷仍以重度污染为主,磷释放风险较大,建议加强对磷矿区河流磷污染的监测与评估。

高潜水位采煤沉陷区微塑料赋存特征及风险评估

为探明高潜水位采煤沉陷区微塑料污染赋存特征及其环境风险,选取安徽省淮南市春申湖、舜耕湿地公园两个典型采煤沉陷区为研究区域,采集了表层水体,底泥及周边农田土壤样品,采用体视显微镜、扫描电镜、红外光谱对微塑料尺寸、形状、颜色及丰度等赋存特征进行表征.结果表明:采集的样本中多为纤维微塑料和薄膜微塑料,类型主要以聚乙烯,聚丙烯为主,颜色以黄色和透明为主,粒径大多小于500μm.采煤沉陷区的地表水丰度范围为0.77~7.1pcs/L,沉积物微塑料的丰度范围为540~2800pcs/kg,周边农田土壤微塑料的丰度范围为380~2380pcs/kg.采用污染负荷指数(PLI)模型进行评估,地表水和农田土壤的风险评估都为于Ⅰ级,属于轻微污染,而沉积物中的微塑料风险评估为Ⅱ级,属于中度污染.

重金属污染水体背景下的底质反射率光谱特征及其对离水反射率贡献影响分析

水体重金属遥感反演是水环境遥感领域中的难题,目前仍有相当多的基础性问题有待解决,而浅水区底质对离水反射率贡献规律是将来遥感反演模型精度其中一个重要影响因素,尤其在重金属污染这种特殊的背景下,揭示其贡献规律对提升水体重金属遥感模型精度有重要作用,测量结果对研究重金属尾矿底泥的反射率光谱特征以及区分常见水底底质有参考意义。首先利用光谱仪测量获得广东大宝山尾矿底质反射率,发现其在波长755、 1 280、 1 620和2 200 nm存在反射峰,有明显光谱特征,并与河床常见的粗沙、淤泥和石头三类底质反射率进行了对比分析,结果表明:一方面,粗沙和淤泥反射率呈一缓慢上升的曲线,与存在多个特征反射峰的矿区底泥有明显区别;另一方面,石头反射率则在波长范围550~650 nm出现一个宽而扁平的反射峰后随即在波长675 nm处出现波谷然后增大至波长750 nm后趋于平缓,其特征波长与矿区底泥均不一样。上述特征波长可作为重金属污染背景下底泥光谱的重要区分波段。测量水深为1 cm、 10 cm和深水区的离水反射率,结合水质遥感模型计算出1 cm水深情况下底质反射光、水体散射光,并将其对离水反射率贡献进行讨论。离水反射率测量结果表明,底质对浅水区影响极大,随着水深变浅,离水反射率总体不断被抬升。而水底反射光和水体散射光对离水反射率贡献规律则以波长515 nm为分界线,向短波方向以水体散射光贡献为主,向长波方向则以水底反射光为主,贡献量由底质反射能力和水体散射能力共同决定。对考虑了底质反射光后的遥感模型精度进行评价,模型计算得到波长范围350~950 nm内的离水反射率与野外测量值对比结果,二者具有显著的线性相关(R^(2)=0.964 2),相对误差在波长范围560~830 nm低于10%,甚者可低于5%,模型总体模拟精度较好,远比在不考虑底质影响时精度高,模型满足将来水中重金属遥感反演要求。研究结果对今后水体重金属遥感反演时处理底质影响提供了重要的参考数据和理论依据,有助推动该领域进一步发展。

履齿结构对深海沉积物扰动分析

为探究集矿车在行进过程中履带运动对深海沉积物的扰动机理,并建立适用于机械结构与沉积物作用的仿真模型,结合水槽实验和模拟分析,设定对照试验,研究机械结构运动对沉积物的扰动作用和羽状流扩散现象。实验与仿真结果表明:偏置一字形履齿低扰动性能较好,扰动最大速度在1.5 m/s以下;扰动源的下陷深度和转速对水槽中的浊度变化有显著影响,浊度计最大和最小测量值为4 381.3 mg/L和3 073.3 mg/L,相差29.9%,峰值时间相差超过50%。搭建欧拉多相流模型,设定参数和边界条件,仿真与试验结果接近,可用于后续开展小范围内的机械扰动研究。

超声处理对煤泥组分沉降速度的影响

这是一篇矿业工程领域的论文。高岭石与蒙脱石是煤泥中存在的主要黏土矿物,而黏土矿物是影响煤泥沉降的主要因素。本文以精煤、高岭石和蒙脱石作为研究对象,首先探索了超声强度、作用时间、超声脉冲间隔三类超声条件对其沉降效果以及絮团直径的影响,实验结果表明:当超声密度为0.4 W/cm^(3),超声作用时间为2 min时,高岭石和蒙脱石的沉降速度都得到了改善,选择合适的超声脉冲间隔时间对样品进行间断超声可以进一步提高其的沉降效果,但是超声处理反而不利于精煤沉降。将精煤、高岭石和蒙脱石试样按2∶1∶1的比例混合制样,改变超声脉冲间隔时间对其进行超声处理,结果表明:对于混合试样,未经超声处理时沉降速度为2.67 cm/min,在超声密度为0.2 W/cm^(3),超声脉冲间隔时间为4 s时作用2 min,沉降速度提高到5.41 cm/min。图像分析与电位表征显示,适当的超声脉冲间隔时间使药剂作用发挥更充分,进而双电层得到最大程度压缩,最终提高了颗粒凝聚和絮团生长效果。

基于Burger’s蠕变模型的采矿车行驶海底稀软底质下陷研究

在陆地矿产资源日渐枯竭的今天,深海矿产资源已成为全球各个国家争相开采与利用的焦点,深海采矿车是实现深海矿产资源开采的重要装备。海底稀软底质是一种承载力与抗剪强度极低的特殊底质,在采矿作业中,深海稀软底质的物理力学特性直接影响采矿车行走的稳定性。文章选取Burger’s接触模型作为深海稀软底质的本构模型,对某海域海底稀软原状土开展室内三轴试验,通过PFC3D颗粒流数值模拟实验对比实际三轴试验,对稀软底质的Burger’s蠕变模型进行参数标定,同时依据标定结果改变相应参数,针对5种不同底质条件的工况,建立海底采矿车的数字仿真模型,模拟各工况下采矿车在不同行驶速度时的下陷深度。结果显示,下陷深度会随行驶速度呈非线性变化,在一定范围内随着行驶速度的增大而减少并逐渐趋于稳定。同时结果还表明,该区域海底稀软底质具有更高的黏粒含量(38.1%~48.4%)、含水率(88.13%~137.79%)和压缩性(压缩系数:1.86~3.73 MPa^(-1),压缩模量:1.26~2.13 MPa),具有更低的密度(1.3~1.5 g/cm^(3))和强度特性(贯入阻力:0.19~1.32 N,黏聚力:3.7~6.9 kPa,内摩擦角:2.4°~3.9°),即承载力较低,蠕变性能较强。本研究在宏观上做了一般的探讨,为类似参数的稀软底质下海底采矿车的运行安全控制提供了较好借鉴与依据。

水牛蹄型深海集矿机履齿设计及牵引性能研究

作为深海采矿系统的重要组成部分,深海集矿机的技术研究和开发一直是许多国家的难题。为了提高深海集矿机在稀软沉积物上的牵引性能,基于水牛蹄的曲面结构特征和特殊几何结构,设计了一款仿水牛蹄蹄型履齿。以该款履齿的结构参数为研究对象,通过对朗肯被动土压力理论的优化,得到了仿水牛蹄蹄型履齿的牵引力解析解,建立了对应的履齿仿生参数对履齿牵引力的影响公式。结合正交试验方法进行了不同形式履齿在沉积物上运动的单、多履齿剪切试验,将仿水牛蹄蹄型履齿与直型履齿、仿水牛蹄轮廓履齿(另一种仿生履齿)进行对比试验,并通过模型车试验验证了该款履齿的可行性。结果表明:3种履齿中,仿水牛蹄蹄型履齿提供的最大牵引力最高。研究可为进一步优化仿水牛蹄蹄型履齿结构参数和提高深海稀软底质机械的牵引性能提供参考依据。