Effect of molecular weight of dissolved organic matter on toxicity and bioavailability of copper to lettuce

To clarify the e ects of molecular weight of dissolved organic matter (DOM) on the toxicity and bioavailability of copper (Cu) to plants, DOM extracted from chicken manure was ultra-filtered into four fractions according to their molecular weights by means of sequential-stage ultrafiltration technique. Lettuce seeds were germinated by being exposed to the solutions containing Cu2+ with or without di erent fractions of DOM. The concentration of copper in roots, leaves, sprouts and the length of roots were investigated. The results showed that not all fractions of DOM could improve copper availability or toxicity. The fraction of DOM with larger molecular weight more than 1 kDa had higher complexation stability with Cu2+ and caused lower concentration of free Cu2+ ion in the solution of copper plus the fraction, resulting in lower availability and toxicity of copper to lettuce, but the fraction with molecular weight less than 1 kDa had the opposite function. Therefore, the molecular weight of 1 kDa may be the division point to determine DOM to increase or decrease copper availability and toxicity.     

莲花山矿区土壤-农作物系统中重金属调控

以广东省莲花山钨矿区耕地为研究点,研究土壤金属含量分布、形态特征及其调控措施。分析耕地土壤中Zn、Cu、Mn、Ni、Pb、Cd、As含量特征,以碱石灰、MnO2、Fe2O3和钙镁磷肥作为改良剂,对矿区污染耕地土壤进行改良,并种植萝卜Raphanus sativus,分析各改良剂对土壤金属形态及其在土壤-农作物界面迁移的影响。研究表明,矿区耕地土壤酸化, Zn、Mn、Pb、Cd和As超过土壤背景值,其中Cd和As污染严重,分别超过背景值的10.2-16.7倍和1.1-1.3倍。碱石灰有效降低耕地土壤pH值,降低土壤Zn、Cu、Mn、Ni、Pb、Cd可溶态含量,减少其在萝卜中积累。萝卜对Pb、Zn、Cd、Cu、Ni累积量与其可溶态含量相关性显著,与总量相关性不显著。Fe2O3、MnO2、钙镁磷肥对耕地土壤Zn、Cu、Ni、Mn、Pb、Cd 生物有效性及其在农作物中累积量无显著影响。矿区耕地土壤分别添加碱石灰、Fe2O3、MnO2,土壤中砷松散结合态含量降低,农作物砷累积量减少。钙镁磷肥对土壤砷形态无显著影响,但能显著降低萝卜中砷的累积量。碱石灰分别与Fe2O3、MnO2、钙镁磷肥相结合改良耕地土壤,比单一改良剂更能有效降低萝卜中砷的累积量。萝卜中砷累积量与松散结合态存在显著正相关性,与Ca-As存在显著负相关性。碱石灰分别和Fe2O3、钙镁磷肥同时加入土壤,能同时地有效降低Zn、Cu、Mn、Ni、Pb、Cd、As的有效性,及其在农作物累积量,因此,这2种改良方式是莲花山矿区土壤金属固定的有效措施。     

镇江市金山湖沉积物磷元素分布特征研究

以镇江市金山湖为研究区域,于2019年1月（冬季）和2019年7月（夏季）采集了10个点位的表层沉积物样品,参照欧洲标准测试测量组织建立的沉积物磷形态分析方法（SMT）测定沉积物总磷（TP）、无机磷（IP）、有机磷（OP）、铁/铝-磷（Fe/Al-P）和钙-磷（Ca-P）质量分数,研究金山湖表层沉积物磷元素及其赋存形态的季节分布特征。结果表明,金山湖表层沉积物中TP质量分数在冬、夏季分别为727.39~1 073.70 mg/kg和700.90~1 002.17 mg/kg,处于中等污染水平;金山湖表层沉积物磷以IP为主,IP在TP中的占比在冬、夏季分别为68.58%~88.86%,73.09%~87.21%;除了Fe/Al-P以外,OP作为生物有效磷源,其冬、夏季质量分数分别为69.37~190.93 mg/kg和108.45~210.42 mg/kg;其平均值分别为129.01,160.15 mg/kg。金山湖冬、夏季沉积物各形态磷质量分数所占比例均表现为Ca-P>Fe/Al-P>OP,表明该研究区域沉积物以Ca-P占优势。金山湖表层沉积物pH值呈现弱碱性,通过Ca-P直接释放到上覆水中的磷较少,故金山湖沉积物磷元素的潜在风险较小。各形态磷的相关性分析结果发现,冬季沉积物TP与Fe/Al-P、IP呈极显著正相关（P<0.01）。夏季沉积物TP与IP、Fe/Al-P之间呈极显著正相关（P<0.01）,与Ca-P呈显著正相关（P<0.05）。此外,金山湖沉积物OP、Fe/Al-P以及Ca-P的来源不一致。pH值对沉积物IP会产生一定影响,而其余磷形态则受pH值的影响程度较小。     

Linking desorption kinetics to phenanthrene biodegradation in soil

The desorption of polycyclic aromatic hydrocarbons (PAHs) often exhibits a biphasic profile similar to that observed for biodegradation whereby an initial rapid phase of degradation or desorption is followed by a phase of much slower transformation or release. Most investigations to-date have utilised a polymeric sorbent, such as Tenax, to characterise desorption, which is methodologically unsuitable for the analysis of soil. In this study, desorption kinetics of ¹⁴C-phenanthrene were measured by consecutive extraction using aqueous solutions of hydroxypropyl-β-cyclodextrin (HPCD). The data indicate that the fraction extracted after 24 h generally approximated the linearly sorbed, rapidly desorbing fraction (F_rap), calculated using a three-compartment model. A good linear correlation between phenanthrene mineralised and F_rap was observed (r² = 0.89; gradient = 0.85; intercept = 8.20). Hence HPCD extraction (24 h) and first-order three-compartment modelling appear to provide an operationally straightforward tool for estimating mass-transfer limited biodegradation in soil.     

Wild fire impact on copper, zinc, lead and cadmium distribution in soil and relation with abundance in selected plants of Lamiaceae family from Vidlic Mountain (Serbia)

Fire has been considered as an improving factor in soil quality, but only if it is controlled. Severe wild fire occurred in the summer 2007 on the Vidlic Mountain (Serbia) overspreading a huge area of meadows and forests.Main soil characteristics and content of heavy metals (Cu, Pb, Cd, Zn) in different fractions obtained after sequential extraction of soil from post-fire areas and from fire non disturbed areas were studied. In four plant species of Lamiaceae family (Ajuga genevensis L., Lamium galeobdolon (L.) L., Teucrium chamaedrys L., Acinos alpinus (L.) Moench.), that grow in typical habitats of the mountain, distribution of heavy metals in aerial parts and roots was investigated too.For all samples from post-fire area cation exchange capacity and soil organic matter content are increased while rH is decreased. Fire caused slightly increased bioavailability of the observed metals but more significant rise happened in metal amounts bound to oxides and organics. The plants showed variable behavior. T. chamaedrys collected on the post-fire area contained elevated concentrations of all analyzed metals. A. alpinus showed higher phytoaccumulation for Zn and Cd, while the other two plant species for Pb and Cd in the post-fire areas.     

Adsorption and thermodynamic parameters of chlorantraniliprole and dinotefuran on clay loam soil with difference in particle size and pH

The behavior of chlorantraniliprole (CAP) and dinotefuran (DNF) insecticides was investigated in clay loam soil, a common type of the Egyptian soil. Effect of temperature, pH and particle size of the soil on the adsorption process was studied. Adsorption isotherm by bulk soil and its constituents; humic acid (HA), clay, silt and sand fractions was measured using batch equilibration technique. The results showed that the adsorption of the insecticides tested was significantly affected by the temperature and was a spontaneous interfacial process in the soil. Freundlich model accurately predicted the adsorption behavior of both insecticides. The interaction between soil and insecticides was endothermic and the highest adsorption for CAP and DNF was obtained at pH 9. However, the effect of pH on the adsorption of DNF was lower than that of CAP. Sorption of CAP and DNF on HA fraction was significantly greater than on clay fraction and bulk soil. In addition, the adsorption was significantly increased with particle size decrease. It could be inferred that the adsorption of CAP and DNF on clay loam soil was physical in nature and greatly influenced by the soil components, pH and temperature.     

三峡水库蓄水至175 m后干流沉积物磷蓄积特征及释放潜力

为揭示三峡水库首次蓄水至175 m后,干流柱状沉积物磷的蓄积特征及其影响因素,于2010年10月下旬采集了三峡水库干流云阳至秭归等5个断面柱状沉积物样品,分析了沉积物粒径、有机质、矿物成分、总磷等理化特征,采用分级提取法分析了柱状沉积物各形态磷分布特征,并对三峡水库柱状沉积物磷的释放贡献率进行估算.结果表明,三峡水库干流柱状沉积物p H在7. 3～7. 8间,总体呈中性.沉积物组成以粉砂为主,含量为49. 4%～78. 6%,黏土为20. 6%～50. 6%,含砂量低于4. 4%,各断面中值粒径沿深度呈现出阶段性地增加或降低趋势.沉积物有机质含量为12. 94～53. 43 g·kg~(-1),从云阳至秭归断面沉积物有机质含量略有增加,碳氮比在4. 00～11. 64之间.三峡水库沉积物总磷为861. 86～1 024. 54 mg·kg~(-1),同一断面沉积物总磷垂向变化较小,且没有随深度变化呈现规律性变化趋势.三峡沉积物磷形态以钙磷为主,约占总磷含量的47. 83%～73. 90%,其余各形态磷所占比例较小.不同断面间磷形态垂向变化趋势差异较大.可交换态磷、铝磷及铁磷在个别断面表层0～4 cm范围内含量相对较高,而在16～20 cm处大部分断面沉积物各形态磷均不随深度发生变化.在同一深度下,不同断面生物可利用磷(可交换态磷、铁磷、铝磷之和,Bio-P)的含量及相对含量沿程分布趋势较为明显,从云阳至秭归断面均表现为沿程增加趋势. Bio-P相对含量为2. 78%～7. 05%,整体而言,三峡水库干流沉积物内源释放风险较小.沉积物生物可利用磷与有机质含量呈显著正相关(P 0. 05,N=50),有机质的分布和转化将影响三峡水库沉积物中磷的迁移和转化.     

Total Contents and Sequential Extraction of Heavy Metals in Soils Irrigated with Wastewater,Akaki, Ethiopia

The Akaki River, laden with untreated wastes from domestic, industrial, and commercial sources, serves as a source of water for irrigating vegetable farms. The purpose of this study is to identify the impact of waste-water irrigation on the level of heavy metals and to predict their potential mobility and bioavailability. Zn and V had the highest, whereas Hg the lowest, concentrations observed in the soils. The average contents of As, Co, Cr, Cu, Ni, Zn, V, and Hg of both soils; and Pb and Se from Fluvisol surpassed the mean + 2 SD of the corresponding levels reported for their uncontaminated counterparts. Apparently, irrigation with waste water for the last few decades has contributed to the observed higher concentrations of the above elements in the study soils (Vertisol and Fluvisol) when compared to uncontaminated Vertisol and Fluvisol. On the other hand, Vertisol accommodated comparatively higher average levels of Cr, Cu, Ni, Zn, etc V, and Cd, whereas high contents of Pb and Se were observed in Fluvisol. Alternatively, comparable levels of Co and Hg were found in either soil. Except for Ni, Cr, and Cd in contaminated Vertisol, heavy metals in the soils were not significantly affected by the depth (0–20 and 30–50 cm). When the same element from the two soils was compared, the levels of Cr, Cu, Ni, Pb, Se, Zn, V, Cd at 0–20 cm; and Cr, Ni, Cu, Cd, and Zn at 30–50 cm were significantly different. Organic carbon (in both soils), CEC (Fluvisol), and clay (Vertisol) exhibited significant positive correspondences with the total heavy metal levels. Conversely, Se and Hg contents revealed perceptible associations with carbonate and pH. The exchangeable fraction was dominated by Hg and Cd, whereas the carbonate fraction was abounded with Cd, Pb, and Co. conversely, V and Pb displayed strong affinity to reducible fraction, where as Cr, Cu, Zn, and Ni dominated the oxidizable fraction. Cr, Hg, Se, and Zn (in both soils) showed preference to the residual fraction. Generally, a considerable proportion of the total levels of many of the heavy metals resided in non residual fractions. The enhanced lability is generally expected to follow the order: Cd > Co > Pb > Cu > Ni > Se > V and Pb > Cd > Co > Cu > Ni > Zn in Vertisol and Fluvisol, respectively. For the similar wastewater application, the soil variables influence the status and the distribution of the associated heavy metals among the different soil fractions in the study soils. Among heavy metals that presented relatively elevated levels and with potential mobility, Co, Cu, Ni (either soil), V (Vertisol), Pb, and Zn (Fluvisol) could pose health threat through their introduction into the food chain in the wastewater irrigated soils.     

青海湖沉积物重金属分布及其潜在生态风险分析

青海湖是我国最大的闭口咸水湖.近年来随着工农业及旅游业的迅速发展,湖泊受人为活动影响不断增加,引起广大学者关注.为了深入了解青海湖表层沉积物中的重金属分布情况,在调查Zn、 Cu、 Pb、 Co、 Ni、 As、 Cd和Cr这8种重金属含量的基础上,对其赋存形态进行了分析,并对其进行来源解析和生态风险评价.结果表明：（1）青海湖表层沉积物重金属除ω（As）(13.21 mg·kg^-1)和ω（Cd）(0.21 mg·kg^-1)超出环境背景值1.13倍和1.53倍,其余6种重金属均不同程度低于环境背景值,从空间分布来看,除As外其他7种重金属元素空间分布特征极为相似,高值主要分布在湖泊西北部及151码头附近;（2）除Cd外其他7种重金属的主要存在形态为残渣态,而Cd主要以生物有效态形式存在,对水生生物具有较高的潜在生物毒性;（3）结合相关性分析和主成分分析,沉积物中Zn、 Cu、 Pb、 Co、 Ni、 Cd和Cr的来源以自然源为主,As的来源则受到农业生产等人为因素影响;（4）根据潜在风险分析结果,青海湖沉积物重金属整体处于轻微生态危害水平,但...