Chromium accumulation, microorganism population and enzyme activities in soils around chromium-containing slag heap of steel alloy factory

The environmental risk of chromium pollution is pronounced in soils adjacent to chromate industry. It is important to investigate the functioning of soil microorganisms in ecosystems exposed to long-term contamination by chromium. 45 soil samples obtained from different places of the slag heap in a steel alloy factory were analyzed for chromium contamination level and its effect on soil microorganisms and enzyme activities. The results show that the average concentrations of total Cr in the soil under the slag heap, adjacent to the slag heap and outside the factory exceed the threshold of Secondary Environmental Quality Standard for Soil in China by 354%, 540% and 184%, respectively, and are 15, 21 and 9 times higher than the local background value, respectively. Elevated chromium loadings result in changes in the activity of the soil microbe, as indicated by the negative correlations between soil microbial population and chromium contents. Dehydrogenase activity is greatly depressed by chromium in the soil. The results imply that dehydrogenase activity can be used as an indicator for the chromium pollution level in the area of the steel alloy factory.

Sorption Characteristics of Hexavalent Chromium in the Soil Based on Batch Experiment and Their Implications to the Environment

The objective of this experimental study was to determine the kinetics and equilibrium sorption of Cr(VI) in soils collected from Hengshui City of Hebei Province, China, based on batch experiments. The main concentration for this paper is on the effect of soil pH, solute concentration and ionic strength as the variable factors in the sorption of Cr(VI) in soils and the assessment of their implications to the environment. Atomic Absorption Spectrophotometer (AAS) was used for Cr(III) analysis;UV-VIS Spectrophotometer for quantification of Cr(VI) in soil samples and determination of electrical conductivity and temperature of the soil samples;and Automatic Laser Particle Size Analyzer LS230 for the determination of soil physical characteristics. Results from this study show that adsorption and reduction are major reactions accounting for removal of Cr(VI) from soil solution. It is concluded that chemical reactions such as reduction, strongly influence Cr(VI) mobility in soil. Adsorption kinetics experiments indicated that Cr(VI) removal from soil solution increases with increasing solute concentration, with decreasing pH and with decreasing ionic strength. Adsorption reactions reached equilibrium within 12 hours in batch reactors. Increasing background electrolyte concentration (KCI) decreases Cr(VI) adsorption on soil. The Cr(VI) adsorption isotherm for this soils conforms well to the Langmuir isotherm at constant pH. Two Cr(VI) adsorption parameters: the maximum sorption capacity (Qo) and Langmuir adsorption constant (KL), were determined as 1.0135 × 10-4 mol/g and 0.0622 mg/L, respectively. The reduction of Cr(VI) into less toxic Cr(III), means reduction of significant environmental problems. Finally, this study advises relevant environmental governing authorities to observeperiodic monitoring of the status of Cr(VI) in soils.

Spatial distribution of chromium in soils contaminated by chromium-containing slag

To evaluate the metal chromium (Cr) contamination of soil at a chromium-containing slag site by ferrochromium production, the contaminated sites, under slag heap, in the vicinity of slag heap and arable soils near the outlet of sewer channel, and unpolluted site 5 km away from one ferroalloy plant in Hunan Province, China, were selected. The concentrations of total Cr and water soluble Cr in bulk soil samples and profile depth samples were determined. The results show that the soils in the vicinity of slag heap have the highest total Cr content followed by the soils under the slag heap and near the outlet of sewer channel of the factory. The mean concentrations of total Cr in the top soils at above three contaminated locations exceed the critical level of Secondary Environmental Quality Standard for Soil in China by 3.5, 5.4 and 1.8 times. In most Cr polluted soils, total Cr has a relative accumulation in soil depth of 40-60 cm, but this trend is not found in unpolluted soils. The average concentrations of water soluble Cr (Ⅵ) in top soils under slag heap and in the vicinity of slag heap are 176.9 times and 52.7 times higher than that in the uncontaminated soils, respectively. However, water soluble Cr (Ⅵ) contents in soils near sewer channel are all low and the values are close to that in the uncontaminated soils. Although water soluble Cr (Ⅵ) content in soil profiles decreases with soil depths, it in soils under slag heap maintains a high level even at a depth of 100-150 cm. The results imply that the transportation of Cr (Ⅵ) can result in a potential risk of groundwater system in this area.

The Fate of Chromium in Weathered Ultramafic Rocks and Their Derivitative Soils in Cuba: Clues from Spectroscopic Studies

In its cationic,trivalent form,Chromium(Cr)it is a micronutrient,and exhibits low environmental mobility.In hexavalent form,however,it is a human carcinogen and also highly mobile.Climate is a key environmental factor controlling weathering rates and stability of primary and secondary Cr-bearing minerals.Knowledge of Cr oxidation state and mineral residence is therefore essential to estimating the risk posed by Cr in serpentinites,chromite mine wastes,and soils developed on these parent materials.X-ray absorption spectroscopy(XAS)is currently the best available technique for determination of the relative abundance of Cr(III)and Cr(VI)in situ(that is,without digestion of solid phases).A brief review of relevant XAS studies of is presented below,focusing on studies in tropical climates1,as they will be most relevant to eastern Cuba’s extensively serpentinized ophiolite belt.Cr(III)-bearing spinels are usually the dominant and most refractory Cr host in ultramafic rocks.Previous XAS studies2 indicate that in tropical climates,Cr-spinels weather rapidly to form Cr(III)-bearing secondary Fe(III)(hydr)oxides(goethite,hematite).Manganese(Mn)is also enriched in ultramafic rocks2;as Mn(IV),it can also co-precipitate with Fe(III)(hydr)oxides,or form its own secondary(hydr)oxides.A previous study found up to 20%Cr(VI)in in a tropical,serpentine soil that contained substantial Mn,and a strong correlation between the*amounts of Cr(VI)and Mn(IV)in the soil profile2.Theresults of several XAS studies suggest that a close association of Mn(IV)and Cr(III)in secondary Fe(hydr)oxides is necessary for oxidation of Cr(III)to Cr(VI)via electron transfer reactions with Mn(IV);however,additional XAS studies have shown that organic matter3and Cr-bearing aluminosilicates4 may also be important sources of Cr(III)to the environment under specific conditions.The stability and fate of Cr has not been studied in detail for these two host phase types,to the best of our knowledge.Access to XAS facilities to perform Cr geochemical experiments is limited and will only become more so in the future.We are working to develop and apply(micro)Raman spectroscopy to evaluate Cr oxidation state and mineral residence(in crystalline and amorphous materials).In addition to standard Raman scattering,we are employing resonance Raman(785 nm laser)to enhance signal from Cr(VI)-bearing phases and laser-stimulated photoluminescence to identify Cr(III)associated with Al-rich alteration products

电动法去除污染土中重金属铬的试验研究

针对土壤铬污染严重的问题,通过自行设置的电动去除装置,研究电动法在不同电压、电解液种类和浓度的条件下对铬去除效果的影响。结果显示:电动法能够有效去除土壤中的重金属铬,并且土壤中铬(Ⅵ)的迁移受电压的影响较大,当电压从10 V增大至40 V时,铬(Ⅵ)的去除率提高了12.25百分点。电解液中加入0.05 mol/L十二烷基苯磺酸钠(Sodium Dodecyl Benzene Sulfonate, SDBS)后铬(总)的去除率提高了5.94百分点,但增大SDBS浓度对提升铬的去除率没有明显效果。柠檬酸(Citric Acid, CA)可显著促进铬的迁移,柠檬酸浓度越大,铬的去除效率越高。在电解液中加入0.15 mol/L柠檬酸后铬(总)的去除率增长幅度达到最大,提高了18.03百分点,铬(Ⅵ)的去除率达到了93.4%,铬(总)的去除率达到了74.96%。其中,弱酸提取态和可还原态铬的去除量占铬(总)去除量的95%左右,CA能够促进残渣态铬向弱酸提取态转换并促进铬的迁移,使各形态铬的残余量均有所下降,进而使铬污染土壤的毒性大幅降低。经电动去除后,土壤表面呈现出针状、絮状或颗粒状,并出现了大量细小的孔隙,结构变得相对松散。

螯合剂与低分子有机酸复配淋洗修复Cr(Ⅵ)污染土壤

为探究可生物降解螯合剂氨三乙酸(NTA)替代乙二胺四乙酸二钠(EDTA)在复配淋洗剂中的作用,本文研究了NTA和EDTA与草酸和酒石酸所配制的复配淋洗剂在不同浓度、固液比、pH值和淋洗时间下对Cr(Ⅵ)污染土壤淋洗效果的影响及淋洗动力学,此外还使用顺序提取方案(BCR)分析了淋洗前后土壤中重金属的形态、迁移率和稳定性变化。结果表明:混合等体积的0.25 mol·L^(-1)NTA和0.3 mol·L^(-1)草酸在固液比为1∶9、pH为3、淋洗时长为240 min条件下达到最大Cr(Ⅵ)去除效率82.94%,这与使用EDTA淋洗时的效率相近;该复配淋洗剂淋洗Cr(Ⅵ)污染土壤时的动力学符合拟二级动力学方程;BCR实验结果表明,NTA和草酸复配淋洗后土壤中Cr的弱酸可提取态、可氧化态和残渣态组分含量分别从6346.67、4280.00、2387.67 mg·kg^(-1)下降至1161.67、433.35、741.00 mg·kg^(-1),可还原态组分从2746.67 mg·kg^(-1)上升至6016.67 mg·kg^(-1),污染土壤重金属迁移率下降。淋洗后土壤有机质含量从13.47%上升至30.56%,脲酶和脱氢酶活性分别从46.32、329.09μg·d^(-1)·g^(-1)降低至29.36、131.98μg·d^(-1)·g^(-1),土壤结构基本与原土一致。因此,NTA与草酸复配淋洗剂是一种高效且对土壤影响较小的淋洗剂。

不同材料复合添加对土壤铬形态的影响

以铬污染黄壤为研究对象,选择有机材料(泥炭)、pH值调节剂(沸石)、生物炭(鸡粪)3种不同种类的土壤重金属污染改良剂,采用正交试验L_(9)(3^(4))设计和室内盆栽试验,考察不同复合材料组对土壤中重金属铬形态、pH值、有机质含量的影响。结果表明:沸石的添加提高了土壤pH值、有机质含量,增加了土壤可还原态、可氧化态铬含量;鸡粪的添加通过提高土壤pH值从而增加土壤可还原态铬的含量;泥炭的添加提高了土壤有机质含量、土壤可氧化态铬含量,降低了土壤可交换态铬含量。

煤基半焦对重金属土壤中铬和镉的原位钝化及作用机制分析

工业化和城市化的快速发展对土壤造成严重的重金属污染,其中由于铬、镉的毒性强,对环境的危害极大。以资源丰富的石河子煤和乌鲁木齐煤为原料经热解制得半焦,将其作为铬和镉污染土壤的钝化材料,以实现重金属污染土壤的修复和改良。利用热重分析得到两种煤样热解的特征温度;采用N_(2)等温吸附法对半焦的孔隙结构进行了表征。通过重金属浸提实验,研究了半焦钝化剂作用时间和添加量对单一污染土壤及复合污染土壤中重金属有效态含量的影响。结果表明:乌鲁木齐煤基半焦具有较适宜重金属钝化的表面特征,孔径主要集中在1.8 nm~4.0 nm,单位面积酸性官能团和碱性官能团数量较多,分别为0.0026 mmol/m^(2)和0.0164 mmol/m^(2);在其添加量为5%,粒径为300μm~500μm,与土壤作用时间为90 d的条件下,铬和镉的有效态含量分别下降了78%和21%。相比于单一污染土壤,竞争作用使得复合污染土壤中铬和镉的钝化效果略有下降。此外,土壤中添加半焦后,土壤的pH值保持在稳定的弱碱性范围内,其有机质含量和阳离子交换量均有提高,改善了土壤的理化性质,可增强土壤肥力。

不同价态铬的定量分析综述

从铬的形态、价态开展了具体分析,综述了铬的检测分析方法。根据水样的差异性、土壤污染程度、食品安全标准等采用不同的检测方法,确保检测方法的准确性与灵敏度。随着铬在不同环境中检测技术的成熟发展,展望了磷矿石中不同价态铬的检测方法。

铬污染土壤的电动修复研究

通过调控电动修复阴极pH值及添加增强剂,提升电动修复技术对Cr污染土壤的总Cr去除率,并探究了电动修复工程的能耗变化及Cr迁移分布规律。结果表明,乙二胺四乙酸(EDTA)、柠檬酸和盐酸等增强试剂能显著提升电动修复过程的总Cr去除率。不调控电动修复阴极pH值,电动修复土壤7d,向土壤分别添加EDTA、柠檬酸时,总Cr去除率分别为24.47%、23.24%;不调控阴极pH值,会发生较明显的偏极效应。控制电动修复阴极pH值,电动修复土壤7d,向土壤分别添加盐酸、柠檬酸时,总Cr去除率分别为44.20%(是空白电动修复组的4.9倍)、36.80%;控制阴极pH值,能有效阻止阴极区域Cr发生沉淀作用,提高Cr的去除率;控制阴极pH值不会显著增加电动修复过程能耗。该方法大幅提升了电动修复对土壤中总Cr的去除率,对重金属污染土壤的修复具有指导意义。

污染土壤稳定化处理后铬返溶影响因子的研究

探究了稳定化处理后污染土壤中Cr的返溶影响因子。结果表明,对返溶释放促进作用最大的条件为:水淹、水溶液pH为1、40℃、一周鼓3 d氧气,这时土壤中Cr(VI)由10.00 mg/kg增至31.47 mg/kg,浸出液中总铬由0.15 mg/L增至0.36 mg/L。40℃、水淹、水溶液pH=1、水溶液pH=12、一周鼓3天氧气处理后Cr的有效态质量分数分别增加0.02%、1.46%、2.12%、0.03%、0.85%。含水率是影响污染土壤稳定化处理后Cr返溶的主要因素,pH为次要因素。在不同pH条件下,稳定化处理后的土壤中Cr的释放量皆与二级动力学方程拟合度最高。

高原山区茶园土壤pH和重金属铬的空间异质性研究——以贵州省贵定县为例

【目的】探究高原山区茶园土壤pH及重金属铬(chromium,Cr)含量的空间异质性及其驱动因素,为茶树高产优质栽培提供科学依据。【方法】采集贵州省贵定县423个茶园土壤样品,采用地统计学和半方差函数模型法探究茶园土壤pH和Cr的空间异质性,并利用随机森林算法研究不同pH下Cr含量变化的驱动因素。【结果】高原山区茶园土壤pH值为4.5~6.0的样品占74%,适宜茶树生长。研究区域内土壤Cr含量处于安全水平。土壤pH值自西南向东北逐渐减小,呈明显的带状分布。土壤重金属Cr含量的空间分布呈现自北向东南逐渐降低的趋势,低值斑块多出现在东南区域,高值斑块集中在中西部。【结论】不同土壤pH值对Cr含量的影响不同。在pH≤5.5的茶园土壤中,土壤pH对Cr含量影响最大;在5.5<pH≤6.5的茶园土壤中,土壤颗粒对Cr含量影响最大。

还原菌Staphylococcus sp.修复六价铬污染土壤的中试研究

为探索微生物修复的工程化应用前景,开展六价铬污染土壤的微生物还原修复中试研究。通过采集废弃电镀厂场地污染土壤,筛选出1株具有六价铬还原作用的功能菌Staphylococcus sp.。Staphylococcus sp.对六价铬的耐受质量浓度高于200 mg/L,最适pH值为7,适宜温度为25~35℃。研究发现,当土壤六价铬初始质量比为98.00 mg/kg、水土比(mL∶g)为2∶1、添加肉膏蛋白胨(Luria-Bertani,LB)培养基的条件下,Staphylococcus sp.能在21 d内将六价铬全部还原。在污染土壤的微生物治理中试研究中,污染土壤的用量为200 kg,水土比(mL∶g)为2∶1,且周期性地添加LB培养基。土壤中六价铬初始质量比为65.42 mg/kg,Staphylococcus sp.在6 d内对六价铬的还原率达到92.59%,后续24 d土壤中六价铬质量比在2.97~10.85 mg/kg呈现波动状态。结果表明,污染场地筛选出的土著功能菌Staphylococcus sp.具有潜在的工程应用价值。中试研究确定的相关参数能为后期工程化应用提供技术支撑。

一种新型重度铬污染土壤修复技术

我国退役铬化工企业的土壤铬污染严重,部分土壤六价铬浓度可高达10^(3)~10^(4)mg·kg^(-1),对植物生长、人类活动产生了不良影响。常用的铬污染土壤修复方法有还原修复技术、生物修复技术、酸淋洗-还原联合修复技术,用稀酸溶液加上还原剂将土壤中的六价铬浸出、还原。但酸溶液对难提取六价铬的溶解效果有限,且易引起土壤侵蚀等次生环境问题。碱性条件下重度铬污染土壤淋洗和还原的修复工艺能有效解决酸淋洗存在的土壤溶蚀、钙流失、含盐量大幅增加以及其他重金属浸出浓度超标等次生环境问题,且该技术通过碱淋洗还原工艺显著提高难提取六价铬的提取和还原效率,该研究形成经济可行、易于推广的铬污染土壤修复技术路线。

硫化物与铁系还原剂还原土壤重金属Cr(Ⅵ)的成效及影响因素研究

为了探究不同化学还原剂对淮南市新庄孜矿区土壤重金属Cr(Ⅵ)的去除效率的影响,构建土壤、还原剂、投加比例和pH值的正交试验,模拟土壤在不同的pH值以及其他因素影响下,Cr(Ⅵ)的去除率变化情况及土壤水溶液的稳定性情况,同时探究最佳还原剂投入比值。研究结果表明:待修复土壤中铬含量超出了规定第一类,第二类建设用地为用途的铬含量的4.065和1.560倍。土壤水溶液比值在1∶5(g·mL^(-1))时候,Cr(Ⅵ)的浸出率最高。还原剂FeCl_(2)·4H_(2)O与Na_(2)S·9H_(2)O的组合较其他还原剂取得更优异的还原Cr(Ⅵ)的效果,还原剂FeCl_(2)·4H_(2)O与Na_(2)S·9H_(2)O反应生成FeS是其取得优异还原效果的原因。还原剂FeCl_(2)·4H_(2)O与Na_(2)S·9H_(2)O联用摩尔比值为1∶1.5时,Cr(Ⅵ)的去除率达到最佳效果。催化剂过氧化氢溶液和二氧化锰的加入也进一步提高了Cr(Ⅵ)去除率。联用还原剂四水氯化亚铁和九水硫化钠修复后的土壤水溶液pH值呈中性,避免了对土壤酸碱度的破坏。综上所述,还原剂FeCl_(2)·4H_(2)O与Na_(2)S·9H_(2)O的联用对土壤重金属Cr(Ⅵ)的去除效果显著,催化剂的加入进一步提高了Cr(Ⅵ)的去除率,联用还原剂中和了土壤水溶液的pH值。

两种铁改性水热炭对土壤中铬固化效能及其形态影响

本实验采用机械球磨法分别制备零价铁(ZVI)、黄铁矿负载水热炭,通过土壤提取实验和土柱淋溶实验,对比添加不同材料后土壤中铬(Cr)含量的变化,分析淋溶液中Cr累积释放规律及Cr在土柱中的纵向迁移行为.实验结果表明,与其他材料相比,施加ZVI改性水热炭(ZBC)和黄铁矿改性水热炭(HBC)对土壤中Cr均有优秀的固化效果.在低投加量(5 g·kg^(-1))下ZBC、HBC使土壤浸出液中总铬浓度分别降低35.8%、39.6%,而土壤中有效铁含量涨幅均小于0.1%,解决了使用ZVI和黄铁矿引起的土壤铁含量过度增加的问题.在土柱淋溶实验中,施加ZBC、HBC后淋溶液总铬含量较CK(未加改性水热炭的对照组)分别下降27.3%、39.3%;土柱下部未污染土壤总铬含量分别降低31.4%、56.3%,Cr(Ⅵ)浓度分别降低51.7%、44.4%.结合表征可得,土壤中的Cr可被ZBC、HBC吸附,水热炭负载的Fe可将Cr(Ⅵ)还原成Cr(Ⅲ)并附着在土壤中,HBC中的FeS_(2)有效参与了对Cr(Ⅵ)的还原.总的来看,HBC对土壤中Cr的固化效果更好,可为水热炭修复重金属污染土壤的应用提供思路与探索.

砖红壤中铬的溶出和外源三价铬的氧化转化

砖红壤铬(Cr)的背景值和锰氧化物的含量均较高,当土壤中Cr溶出或者受到Cr(Ⅲ)污染,可能被氧化生成毒性较高的Cr(Ⅵ),从而对周围环境造成威胁。为考察砖红壤中Cr的环境风险,以云南、海南和广东采集的部分砖红壤为对象,研究土壤中Cr的溶出和外源Cr(Ⅲ)的氧化。连二亚硫酸钠-柠檬酸钠-重碳酸钠法提取和电子探针扫描分析的结果表明,砖红壤中的Cr主要与铁氧化物和硅酸盐矿物结合,呈非活性状态。盐酸和柠檬酸的酸化和络合作用促进了Cr的溶出,但即使1 mol·L^(-1)的盐酸也仅使海南3和广东9砖红壤中3.68%和3.54%的Cr溶出。向砖红壤中添加Cr(Ⅲ)并培养42d,发现少量添加的Cr(Ⅲ)氧化为Cr(Ⅵ),但不同土壤中Cr(Ⅵ)的生成量与亚锰的净产生量不一致,说明土壤中Cr(Ⅲ)氧化生成的Cr(Ⅵ)可能会被土壤有机质重新还原为Cr(Ⅲ)。去除土壤有机质后,一次平衡实验中观察到外源添加的Cr(Ⅲ)氧化为Cr(Ⅵ),氧化量与土壤易还原锰的含量一致。随着溶液pH的增加,Cr(Ⅲ)的氧化量呈先上升后降低的趋势,在pH4.5时Cr(Ⅲ)氧化量达最大值,但Cr(Ⅲ)的氧化转化量在Cr(Ⅲ)添加量中的占比很小,外源Cr(Ⅲ)在土壤中氧化转化的风险也很低。虽然砖红壤的背景Cr和易还原锰的含量较高,但自然条件下Cr的溶解和Cr(Ⅲ)的氧化反应很难发生,Cr(Ⅲ)不易转化为Cr(Ⅵ),因此无需过度担忧砖红壤中Cr的环境风险。

原子吸收光谱法和分光光度法测定土壤六价铬对比研究

土壤六价铬监测在耕地保护中具有重要意义,不同原理测定方法结果的一致性是准确测定土壤中六价铬及研制土壤六价铬标准物质的技术基础,目前国内测定土壤六价铬的唯一标准是HJ 1082—2019《土壤和沉积物六价铬的测定碱溶液提取-火焰原子吸收分光光度法》,但土壤中六价铬的测定存在较为严重的基体效应。为建立准确测定土壤中六价铬的方法,采用氢氧化钠-碳酸钠碱溶液、磷酸盐缓冲溶液-氯化镁体系提取土壤六价铬,用原子吸收光谱法(AAS)和分光光度法(UV-Vis)测定,研究了基体效应对两种方法测定结果的影响。AAS测定土壤六价铬,基体干扰较为严重,制作标准曲线需要进行基体匹配,在线性范围0~2 mg/L线性良好,检出限0.42 mg/kg,方法精密度为2.1%;UV-Vis测定土壤六价铬几乎不受基体效应影响,以水为溶剂制备标准曲线,在线性范围0~0.2 mg/L线性良好,检出限0.12 mg/kg,方法精密度为3.4%。对分别来自安阳、安顺、兰州的低、中、高3种含量的实际样品测定,两种方法平行测定6次,经t检验两种方法无显著性差异,一致性较好,邀请国内十家高水平实验室进行协作定值实验,两种方法测定结果与其他实验室测定结果一致。通过基体匹配、稀释待测液和添加高锰酸钾等方法可显著减小基体效应、颜色及有机质对两种方法测定土壤六价铬的影响,两种方法均具有良好的精密度和正确度,适用于土壤六价铬的测定。

镉对高山松和高山栎盆栽中土壤动物多样性的影响

为了解金属镉污染过的土壤在种植不同高山木本后对土壤动物多样性的影响,本研究以三种浓度的金属镉对土壤进行处理,分别种植高山松和高山栎90 d后,用干漏斗法分离土壤动物。共捕获土壤动物2门7纲20目,其中真螨目、弹尾目为优势类群。结果表明:高山栎盆栽比高山松盆栽土壤中的物种丰富度更大,土壤动物数量更多。金属镉处理土壤后导致土壤动物群落结构趋于简单,土壤动物数量和土壤动物多样性降低。研究发现,一定浓度的金属镉处理后的土壤中,弹尾目和真螨目的动物在土壤动物群落中的数量变化不显著,说明弹尾目和真螨目动物可能对重金属镉具有一定的耐受性。

基于网格搜索优化CatBoost模型的GF-5卫星影像铬离子含量反演研究

高光谱遥感技术以其低成本、高效率、广泛覆盖范围、宏观性强和动态监测能力等优势而受到关注。利用高光谱遥感技术,对安图县新合乡尾矿库土壤中六价铬离子污染状况进行有效监测;以高分五号(GF-5)卫星的高光谱遥感影像及实测土壤样本为数据源,基于皮尔逊相关系数、波段加法和比值指数,提取与土壤重金属含量变化相关的特征,构建反演模型。首先,剔除预处理后的遥感影像中饱和、噪声和水汽吸收波段,同时利用各波段反射率进行代数运算构建加法和比值指数,计算其与实测铬离子含量数据的皮尔逊相关系数;然后,基于皮尔逊相关系数得到的前50最高相关特征变量,采用网格搜索优化的CatBoost回归,建立土壤六价铬离子含量反演模型,并使用SHAP方法评估特征重要性,探究影响GF-5反演土壤重金属重要波段。结果显示,在相同光谱变换条件下,与偏最小二乘回归(PLSR)、随机森林回归(RFR)、支持向量机回归(SVMR)、卷积神经网络(CNN)和多元逐步线性回归模型相比,网格搜索优化的CatBoost模型效果最好,训练集拟合优度为0.92,验证集为0.88。利用网格搜索优化CatBoost回归模型对吉林省安图铬渣填埋场进行了土壤六价铬离子含量反演,结果显示该区域尾矿库开采区域周边六价铬离子污染严重,这与该地矿山开采和尾矿堆放实际情况基本一致。该研究为土壤重金属污染监测和环境管理提供了重要的技术手段和科学依据。