Analysis of the Fertilizing and Bioremediation Potential of Leaf Litter Compost Amendment in Different Soils through Indexing Method

This research study explored the efficacy of leaf litter compost as a sustainable soil amendment with the objective of promoting soil health and mitigating the accumulation of potentially toxic elements. The investigation encompassed the impact of various organic compost amendments, including leaf compost, cow dung manure, kitchen waste compost, municipal organic waste compost, and vermicompost. The study employed Inductively Coupled Plasma Mass Spectrometry (ICP-MS) to evaluate soil nutrient levels and concentrations of Potentially Toxic Elements (PTEs) such as arsenic, chromium, cadmium, mercury, lead, nickel, and lithium. The fertilization and bioremediation potential of these compost amendments are quantified using an indexing method. Results indicated a substantial increase in overall nutrient levels (carbon, nitrogen, phosphorus, potassium, and sulfur) in soils treated with leaf compost and other organic composts. Fertility indices (FI) are notably higher in compost-amended soils (ranging from 2.667 to 3.938) compared to those amended with chemical fertilizers (ranging from 2.250 to 2.813) across all soil samples. Furthermore, the mean concentrations of PTEs were significantly lower in soils treated with leaf compost and other organic compost amendments compared to those treated with chemical fertilizers amendments. The assessment through the indexing method revealed a high clean index (CI) for leaf compost amendment (ranging from 3.407 to 3.58), whereas the chemical fertilizer amendment exhibits a relatively lower CI (ranging from 2.78 to 3.20). Consequently, leaf compost and other organic composts exhibit the potential to enhance sustainable productivity, promoting soil health and environmental safety by improving nutrient levels and remediating potentially toxic elements in the soil.

Toxic Soil Gets New Life

South China’s Guangxi Zhuang Autonomous Region has one of the country’s biggest reserves of arsenic and lead, which are important resources for industry. Due to contamination by unre-

Effect of acetate on lead toxicity to microbial biomass in a red soil

A laboratory incubation experiment was conducted to elucidate the effect of acetate on lead bioavailability and toxicity to microbial biomass in a red soil. Results indicated that the application of acetate along or at the lower lead levels of 100 and 200 μg/g soil stimulated the soil microbial biomass. The addition of acetate at the higher lead levels of 300, 450 and 600 μg/g soil caused significantly greater reductions in the biomass carbon(C mic ) and the biomass nitrogen (N mic ), compared with the control or the same lead levels applied individually. A greater increase in the biomass C:N ratio occurred by acetate addition at the same lead levels. The concentration of 0.01 mol/L CaCl 2 extractable lead was considerably higher in the lead plus acetate treatments than at the same lead levels with no acetate. Based on these results, it was concluded that the application of acetate might have suppressed the lead adsorption in the soil which in turn resulted in its more bioavailability and hence more toxicity to the soil microbial biomass.

Toxicity Tests of Soil Contaminated by Recycling of Scrap Plastics

The present investigation studied the toxicity of soil contaminated by untreated discharge from a factory that recycles used plastics. The nearby agricultural areas and freshwater fish ponds were polluted with high concentrations of Cu, Ni, and Mn. Water extracts from the contaminated soil retarded root growth of Brassica chinensis (Chinese white cabbage) and Cynodon dactylon (Bermuda grass) where their seeds were obtained commercially. The contaminated populations of C. dactylon, Panicum repen (panic grass), and Imperata cylindrica (wooly grass) were able to withstand higher concentrations of Cu. Ni, and Mn, especially C. dactylon, when compared with their uncontaminated counterparts. 1990 Academic Press, Inc.

Complete stabilization of severely As-contaminated soil by a simple H2O2 pre-oxidation method combined with non-toxic TMT-15 and FeCl3·6H2O

The stabilization of severely As-polluted soil has been a challenge, especially for the extremely toxic As(Ⅲ) contaminants. In this study, soil with a high As concentration(26084 mg/kg) was availably stabilized by a H2O2 pre-oxidation assisted TMT-15(Na3S3C3N3 solution with a mass fraction of 15%) and FeCl3·6 H2O stabilization method. The results showed that the combination of the two stabilizers(i.e., TMT-15 and FeCl3·6 H2O) presented a better stabilization behavior than either stabilizer used individually. The use of the H2O2 pre-oxidation assisted TMT-15 and FeCl3·6 H2O stabilization approach not only converted the As(Ⅲ) to As(Ⅴ) but also reduced the toxic leaching concentration of As to 1.61 mg/L, which is a safe level, when the additions of TMT-15 and FeCl3·6 H2O were 2 mL and 0.20 g, respectively. Thus, using only a simple H2O2 pre-oxidation to combine clean stabilization with non-toxic stabilizers TMT-15 and FeCl3·6 H2O could render the severely As-contaminated soil safe for disposal in a landfill.

Toxic metal enrichment characteristics and sources of arid urban surface soil in Yinchuan City, China

To investigate the environmental quality of the urban surface soil in Yinchuan City, the capital of Ningxia Hui Autonomous Region （Ningxia）, China, we sampled surface soil and measured the concentrations of 8 toxic metals （Pb, Cr, Cu, Zn, Co, Bi, Ni and V） using X-ray fluorescence spectrometry. The enrichment characteristics and sources of these toxic metals in the soil were analyzed by the enrichment factor （EF） and multivariate statistical analysis. The results showed that the mean concentrations of these toxic metals in the soil samples were 25.0, 109.1, 16.8, 26.0, 37.2, 2.7, 25.3 and 59.9 mg/kg for Pb, Cr, Cu, Zn, Co, Bi, Ni and V, respectively, which were 1.2, 1.8, 0.8, 0.4, 3.2, 8.7, 0.7 and 0.8 times of the corresponding background values of Ningxia soil, respectively. The variations of Pb, Zn, Co, Bi and Ni concentrations in the surface soil of Yinchuan were larger than those of the other metals. Our results also showed that the toxic metals investigated in the soil had different enrichment levels. Both Co and Bi were significantly enriched, whereas Cr was only moderately enriched in the soil. There was a deficiency or minimal enrichment of the other toxic metals in the soil. Source analysis results based on the concentration, enrichment characteristics and multivariate statistical analysis indicated that Cr, V and Ni originated from a combination of fossil fuel combustion, traffic pollution and natural occurrence. Pb, Cu and Zn were predominantly derived from natural and traffic sources, while Co and Bi primarily originated from construction sources.

Study on the toxicity of acid rain to microbiota in soils

With simulated acid rain and acidification, the soils from both Nanning and Liuzhou municipalities, Guangxi Zhuang Nationality Autonomous Region have been studied to determine the counts of azotobacter, bacteria, actinomyces and the activity of urease in soils, and the changes in respiratory intensity of soil so as to identify the toxicity of acidic substances to microbiota and enzyme in such soils. The concept of the critical pH of toxicity has been developed and used to discuss the representation of the concept, the basis on which the soil treated with simulated acid rain can be taken as an object of study, and the criteria for the identification of toxicity. Based on that as mentioned above, it was found that acid rain behaved to have toxicity to the microbiota in soils from Liuzhou other than from Nanning. The findings may be regarded as an objective basis to study the toxicity of acidic substances to microbiota and enzyme in soils in this region.

A Single-Season Irrigated Rice Soil Presents Higher Iron Toxicity Risk in Tropical Savannah Valley Bottoms

With the aim of finding the geochemical differences and helping to build alleviating strategies against iron toxicity, two hematite dominant valley bottoms irrigating rice soils were investigated in the Tropical Savannah region of Burkina Faso. The first site was Tiefora, a 15-ha modern double-season irrigated rice system and moderately affected by iron toxicity (10% of the area with a toxicity score of 4). The second site was Moussodougou, a 35-ha traditional singleseason irrigated rice valley-bottom, with 50% facing more severe iron toxicity (score 7). Nine soil extracts were taken from three depths—30, 50 and 100 cm—i.e. 27 at Tiefora and 27 at Moussodogou. Five techniques were used to measure the data: 1) the ferrous iron concentration was determined using a reflectometer, 2) a pH-meter yielded the pH, 3) clay-proportions were obtained by United States Department of Agriculture (USDA) grain size analysis and densitometry, 4) the organic matter was determined by oven drying (900℃) and v) the dry bulk density was determined by using undisturbed soil samples. Statistical hypothesis testing of One-way ANOVA and Welch t-test was applied to the data to isolate the similarities and the differences between the two sites. A geochemical analysis followed to find the causes of these differences. The results showed that while oxidation of pyrite leads to a simultaneous increase in Fe2+ concentrations and acidity in the soils of coastal floodplains and mangroves, the oxidation of hematite in Tropical savannah valley bottoms decreases Fe2+ but also increases acidity during the dry season. As a consequence, it was found that the single-season irrigation scheme Moussodougou is significantly (p-value 0.4%) more acidic (pH 5.7) than the double-season system of Tiefora (6.4) with also 750 - 1800 mg/l higher ferrous Fe2+. The ferrous iron reached 3000 mg/l in some layers in Moussodougou. This result is a justification to modernize a traditional single-season spate irrigation schemes into a double-season irrigated rice scheme.

Lupinus microcarpus Growing in Arsenic—Agricultural Soils from Chile: Toxic Effects and It Potential Use as Phytoremediator Plant

Arsenic (As) is the most important contaminant of the environment in northern Chile. The purpose of the present work is to study As-toxicity symptoms on Lupino microcarpus (lupine), an annual legume plant that constitutes part of the desert community of the pre-Andean area of the Antofagasta Region, Chile. This plant species is cultivated in As-agricultural soil collected from Chiu Chiu (northern Chile) which is classified as arid soils. Control soil (0 - 20 cm depth) is collected from an area located in the central zone of Chile, which is classified as molli soil. The main physic-chemical characteristics of As-soil and the control soil are determined. Eighteen plastic pots of 1.6 L (fifteen for experimental and three for control) are filled with As-soil and control soil treatments. Two plants are cultivated in each pot and then separated leaves and roots for As-analysis. Visual As-toxicity symptoms such as foliar chlorosis, necrosis of the leaf tips and margins, leaf wilting and stunted are determined. Total As concentrations in soils where lupine is cultivated, reach levels between 5.3 - 14.2 mg·kg-1 d.w. (control soil As-level: 3.1 mg·kg-1). Roots show higher As-concentration than leaves, both experimental plants as control plants (2.28 - 9.1 mg·kg-1 d.w., and 0.76 mg·kg-1 d.w., respectively) and low values of transport index (TI) (0.16 - 0.34). All of visual As-toxicity symptoms determined is showed by lupin cultivated in As-agricultural soils. Neither control lupin plant suffers any toxicity symptoms. The results indicate that lupine plants do not resist contamination and accumulated higher levels of As in roots. Lupine can be used in the phytostabilisation of As immobilizing it by microbial activity in agricultural soil.

Evaluation of Pesticide Toxicity and Chemical Compounds Revealed in Soils of Sikasso and Segou (Mali)

The contaminants of the ground are potentially harmful agents and when they are released in this medium, their persistence becomes an important concern. Because of the expressed interest, a certain number of pesticides and important chemicals and their toxicity are described in this article. The studies went on the determination of the concentration, the lethal amount of the organochlorinated compounds, chemical organophosphates, carbamates and compounds. One summer recorded 3 pesticides in 5 samples of the grounds of Sikasso and Segou (Mali). Their concentration varies from 20 (atrazine) with 45 g/kg of ground. The lethal amounts of the revealed poisons variable from 338 for phtalates to 28.710 mg/kg for hexane (alkane) thus evaluate their impact on the food chain. Organophosphates and the carbamates (insecticidal) involve a reduction of 34.2% of the number of Cyprinus carpio of fresh water. The atrazine contaminates drinking water, but the diuron modifies the behavior and the reproduction of fish by deteriorating their system of olfactive perception of natural substances. Important mortalities of birds are noted around the corn fields of Bougouni treated by the carbofuran. The pesticides involve at the man a reduction in fruitfulness, an increase in the risk of miscarriage of premature birth, congenital malformations and cancers.

锑矿周边土-蔬金属元素富集特征与风险评估

为揭示不同锑矿废渣堆放区周围土壤-蔬菜系统中潜在有害重金属元素(PTEs)的富集特征及健康风险,该文以不同种类废渣堆场(锑矿废石、锑矿冶炼渣、锑矿尾砂)周围3处村落及在废渣共同影响下的琏溪河下游的1处村落为采样区,并以采样区域内的土壤-蔬菜系统为研究对象。运用统计学、迁移系数法和体外消化模拟法等方法对土壤和蔬菜样品中的Sb、As、Hg、Pb、Cd和Zn等6种PTE的富集特征及健康风险评估进行讨论。结果表明,6种PTEs在土壤中的平均含量均超过湖南省土壤背景值及风险筛选值。所有蔬菜样品对土壤PTEs的吸收能力弱,生物累积系数平均值低于0.12。蔬菜样品的PTEs中Pb、Cd、Zn的生物转移系数数值均超过1.0,易被蔬菜富集。4个采样区中,锑的暴露风险指数均大于1.0,对人体存在明显的健康风险。用于评价复合污染危害的指数HI在4个采样区均大于2.0,主要PTEs污染因子为Sb和Pb,复合污染已对人体存在健康风险。研究表明,4个采样区的土壤已受到多种PTEs的污染与富集,蔬菜对当地居民均存在健康风险,需要特别关注。

Heavy Metals in Soils Associated with Fertilizers in Trinidad

Heavy metals in agricultural soil pose human health risks through food consumption. In a novel study for Trinidad, concentration and pollution index levels of heavy metals were assessed from 18 agricultural farms using the X-Ray fluorescence technique, then to evaluate the Geo-accumulation and Nemerow’s Integrated Pollution indexes. Toxic elements Pb and As were present but soil quality due to anthropogenic input was found as unpolluted. Overall heavy metal pollution was classified at a precautionary level for 33% of farms, slightly polluted for 61% and moderately polluted for 6% of the farms assessed, thus, regular monitoring and mitigation measures are important for food safety and human health in Trinidad.

基于生态安全的我国土壤镉环境基准研究

土壤镉(Cd)污染的生态安全问题不容忽视,我国目前尚缺乏基于生态风险的土壤Cd环境基准。本研究通过调研国内外关于土壤Cd的生态毒性研究,收集并筛选基于我国土壤的Cd毒性效应数据,采用物种敏感性分布法并结合Cd的生态毒性预测模型,推导不同用地方式下的土壤全量和EDTA提取态Cd生态安全环境基准。共收集与筛选出包含13个物种或生态过程的126个土壤Cd生态毒性数据,其中陆生植物毒性数据60个(6个物种)、无脊椎动物毒性数据39个(3个物种)、生态过程毒性数据27个(4种指标)。土壤Cd生态毒性预测模型研究结果表明,土壤pH是影响Cd生态毒性的最重要因子。自然保护地和农业用地、公园用地、住宅用地、商服及工业用地不同土壤pH值范围的土壤全量Cd生态安全基准分别为1.91~5.25、3.94~11.1、7.59~22.0和10.5~30.8 mg·kg^(-1),基于EDTA提取态Cd的生态安全基准分别为1.13~3.12、2.34~6.62、4.51~13.1和6.24~18.4 mg·kg^(-1)。研究结果可为我国土壤污染风险管控标准的制修订提供依据。

植物适应土壤逆境的分子机制研究进展

土壤逆境泛指对植物生长和生存不利的各种土壤环境因素,如盐碱、酸性、淹水涝害等。植物在长期的进化过程中,对不同土壤逆境会产生一定的适应能力,了解植物对土壤逆境的生理反应和耐性分子机理,对发掘植物生长潜力,提高农业生产效率十分重要。我国植物营养生物学科研人员经过30多年的努力,在植物适应土壤逆境的分子机制研究领域,取得了一批国际领先的研究成果,本文就近年来取得的部分土壤逆境的适应机制的进展(铝毒害、铁毒害和盐碱胁迫)进行简要评述。如以STOP1为核心的植物抗铝调控机制;ALR1作为一个铝离子受体调控植物的抗铝性;根际铁在调控铵态氮耐性和氮素利用效率的分子机制;提升小麦耐盐性且不会影响穗发育的TaSPL6-D基因等。

土壤环境基准的科学问题与研究方法:以Cd为例

土壤环境基准是土壤环境质量标准制定的科学依据和基础。环境基准是土壤环境保护研究的前沿领域,涉及土壤环境化学、环境毒理学、生物学和风险评估等多学科交叉与基础性科学问题,了解和解决其所涉及的这些科学问题,是土壤环境基准研究的前提。本文针对土壤环境基准研究中影响重金属毒性阈值的非生物因子、生物因子、剂量效应关系测定中等几个关键科学问题进行了阐述,包括土壤老化因子与淋洗因子的矫正,低剂量刺激效应拟合及毒性数据归一化方法等,最后以农田土壤Cd为例,推导出不同性质土壤中Cd环境基准(HC_(5))及其与土壤性质的连续性分布曲线方程(LogHC_(5)=0.132pH+0.083OC+0.008CEC-1.448),以期为农田土壤环境指标基准的研究提供参考与借鉴。

土壤中微塑料:类型、载体效应、迁移行为和潜在风险综述

微塑料(microplastics,MPs)作为一种新兴污染物,广泛存在于土壤中,并不断迁移转化,对土壤生态系统和生物多样性产生潜在风险。为了全面评估土壤MPs的环境风险,加强MPs污染的风险管控,讨论了土壤环境中MPs的类型,系统阐述了土壤MPs的载体效应和迁移行为,并从微生物、植物、动物以及人类四个方面综述了土壤MPs的潜在风险。土壤中MPs并不是单独存在的,MPs的潜在风险一方面来自其本身(颗粒和添加剂)的生物毒性,另一方面是其对共存污染物(有机污染物、重金属和致病菌等)的载体效应。在非生物(淋溶、重力)和生物等作用下,土壤中的MPs时刻都在经历着复杂的迁移过程,从而加剧了其对土壤生态系统的影响。由于粒径小,MPs很容易进入食物链并层层传递,从而对不同营养级生物的正常生理活动产生不利影响,包括影响土壤动植物的新陈代谢,生长,发育和繁殖。此外,MPs不仅在环境中存在,而且也在人体中被发现。MPs可通过饮食、呼吸或皮肤接触等途径进入人体,从而对人体可能产生一系列不良反应。虽然目前仍没有足够的证据证明MPs对人体的直接危害,但其潜在风险仍不容忽视。探讨了土壤MPs污染治理的策略,并对未来土壤微塑料污染的研究方向和重点进行了展望。研究将有助于加深人们对土壤微塑料污染的认识,并为更好地开展微塑料的毒理效应研究和风险评估提供科学线索和理论参考。

微纳米塑料在土壤-植物系统中的迁移机制及毒性效应研究进展

微塑料是指粒径小于5 mm的塑料碎屑和颗粒,其中粒径小于100 nm为纳米塑料。微纳米塑料作为一种新型污染物,具有难以降解、容易发生积累和可长距离迁移等特点,进而对生态环境产生影响。但是,与其他环境中的微纳米塑料相比,人们对土壤环境中的微纳米塑料的认识与了解还比较少。所以,本文详细阐明了微纳米塑料在土壤环境中的生物和非生物迁移过程与机制,系统总结了微纳米塑料从土壤到植物的转运过程,并探讨了微纳米塑料对植物种子萌发和根系发育产生的直接毒性效应,通过改变土壤理化性质和吸附重金属、有机污染物进而成为污染物传输载体而对植物产生的间接毒性作用。最后,提出了土壤-植物系统中微纳米塑料污染目前还需要进一步研究和处理的问题。本文可为土壤-植物系统中微纳米塑料污染的生态风险评估提供科学参考。

纳米颗粒污染土壤的健康评价研究进展

纳米颗粒(nanoparticles,NPs)由于其独特的理化性质在农业上已经被广泛用作纳米肥料以及杀虫剂,部分纳米颗粒也不可避免地进入了土壤环境,对土壤造成污染,其在地球各圈层中循环并进入植物及动物体内,最终可能富集于人体并造成危害.根据文献调研,目前国内外的相关研究大多聚焦于纳米颗粒的生物毒性和环境行为方面,其对土壤性质影响的研究尚不完善,现有的土壤健康评价体系也极少考虑纳米颗粒对土壤环境的破坏.而纳米颗粒会影响土壤力学性能以及pH、氧化还原电位、阳离子交换量等化学性质,并对土壤动物及微生物种群结构及代谢组学特性造成较大影响;同时,纳米颗粒也会通过环境地球化学循环在土壤中迁移、转化和积累,故有必要深入探究其对土壤的污染与生态环境的破坏机理.基于目前的土壤评价体系,未来需针对纳米颗粒产生的污染及风险进行系统性评估,选取不依赖于NPs种类的普适性土壤性质指标,并重点将土壤无脊椎动物生理指标及土壤原生动物性质等生物指标纳入评价体系中;此外,也仍需对纳米颗粒造成的长期污染与空间迁移进行探究,同步借助相关仪器对土壤中纳米颗粒的浓度及种类进行评估,并结合机器学习、模型模拟与地理技术完善评估结果,使评估结果更为客观.

骨粉生物质炭对酸性土壤的改良作用

以猪、鸡、牛和羊骨为原材料厌氧热解制备成生物质炭(骨炭)作为改良剂,探究骨炭最佳制备条件及其对酸性土壤改良效果,并从土壤固相和液相二个角度探究骨炭对酸性土壤铝(Al)形态的影响。结果表明:高温厌氧热解制备的骨炭富含CaO、CaCO_(3)和Ca_(5)(PO_(4))_(3)(OH),同时含有NaO、MgO等碱性物质及-OH等多种官能团。但骨炭碱含量受热解温度影响较大,鸡骨和牛骨在800℃、猪骨和羊骨在900℃时其炭碱含量接近峰值并保持稳定,约为生石灰的90%,是最佳制备温度。此温度下制备的四种骨炭均可有效地提高pH<6.0的酸性红黏土、红砂土和砖红壤pH。骨炭中的碱性物质主要以H+缓冲剂的形式存在,从而导致其提高土壤pH的幅度与初始土壤pH成反比。pH=4.40的红黏土中添加5 g·kg^(-1)猪、鸡、羊和牛骨炭后土壤溶液Al浓度分别较对照降低33%、34%、47%和41%,固相有机结合态Al含量无显著变化(P>0.05)。骨炭增加了酸性土壤阳离子交换量,并通过促进活性Al向土壤固相吸附态羟基Al和更稳定态Al转化从而降低土壤溶液Al及交换态Al含量。骨炭富含植物生长所需营养元素,具备无机和有机改良剂的双重特性,是可替代传统石灰作为酸性农田土壤改良剂的优质材料。

改性黄麻纤维协同水泥固化重金属铅污染土的强度及毒理性分析

改性纤维兼具良好的吸附能力和机械强度,在污染土治理方面具有广泛的应用前景。优选黄麻作为纤维材料,分别采用均苯四甲酸二酐、聚苯胺和双氧水进行改性,结合无侧限抗压强度、土体阳离子交换量(cation exchange capacity,CEC)、电导率(electrical conductivity,EC)、pH值等指标探究改性黄麻纤维协同水泥的固化效能,并借助醋酸缓冲溶液法分析其毒理性演变规律。结果表明,适宜的改性黄麻纤维协同水泥固化铅污染土可同步实现强度提升和毒性释放的控制,协同固化污染土较单一水泥固化污染土,无侧限抗压强度提高了76.78%,浸出毒性量降低了64.73%,且10次冻融循环作用下浸出毒性的波动缩小至1/3。黄麻纤维水解所生成碱性纤维素会引起水泥固化污染土pH的增大,羧基类酸性官能团的改性有助于借助中和作用进一步促进水化反应,增强水化硅酸钙(calcium silicate hydrate,CSH)凝胶的生成。黄麻特别是改性纤维的引入对于EC和CEC的增益显著,纤维水泥协同固化作用下EC提高量可达单一水泥固化提高量的2.25倍,是增强吸附固化稳定性的关键。但由于纤维团聚、微粒间聚合及金属离子间静电斥力的影响,固化污染土强度和浸出毒性与纤维掺量及纤维长度并非呈正相关关系,3种改性方式中酸酐改性黄麻纤维吸附固化效果受纤维长度和掺量影响较小,且在强度和毒性控制指标方面均表现良好,统筹考虑工程应用和生态发展需求,纤维掺量0.9%+纤维长度18 mm的酸酐改性黄麻纤维适合用于协同水泥进行重金属污染土的固化处置。