Pollution assessment and spatial variation of soil heavy metals in Lixia River Region of Eastern China

Purpose

The effect of soil heavy metals on crops and human health is an important research topic in some fields (Agriculture, Ecology et al.). In this paper, the objective is to understand the pollution status and spatial variability of soil heavy metals in this study area. These results can help decision-makers apportion possible soil heavy metal sources and formulate pollution control policies, effective soil remediation, and management strategies.

Materials and methods

A total of 212 topsoil samples (0–20 cm) were collected and analyzed for eight heavy metals (Cd, Hg, As, Cu, Pb, Cr, Zn, and Ni) from agricultural areas of Yingbao County in Lixia River Region of Eastern China, by using four indices (pollution index (PI), Nemerow pollution index (PI_N), index of geo-accumulation (I _geo), E _i /risk index (RI)) and cluster analysis to assess pollution level and ecological risk level of soil heavy metals and combining with geostatistics to analyze the concentration change of heavy metals in soils. GS+ software was used to analyze the spatial variation of soil heavy metals, and the semi-variogram model is the main tool to calculate the spatial variability and provide the input parameters for the spatial interpolation of kriging. Arcgis software was used to draw the spatial distribution of soil heavy metals.

Results and discussion

The result indicated that the eight heavy metals in soils of this area had moderate variations, with CVs ranging from 23.51 to 64.37 %. Single pollution index and Nemerow pollution index showed that about 2.7 and 1.36 % of soil sampling sites were moderately polluted by Cd and Zn, respectively. The pollution level of soil heavy metals decreased in the order of Cd?>?Zn?>?Pb?>?As?>?Cu?>?Cr?>?Ni?>?Hg. The I _geo values of heavy metals in this area decreased in the order of Zn?>?Cd?>?As?>?Pb?>?Cu?>?Cr?>?Hg?>?Ni. According to the E _i index, except Cd that was in the moderate ecological risk status, other heavy metals in soils were in the light ecological risk status, and the level of potential ecological risk (RI) of soil sampling sites of the whole area was light.

Conclusions

The results of four indices and the analysis of spatial variation indicated that the contents of Cd and Zn were contributed mainly by anthropogenic activities and located in the south-east of this study area. However, the contents of Hg, As, Cu, Pb, Cr, and Ni in soils were primarily influenced by soil parent materials.

     

Examining the Effects of the Destroying Ammunition,Mines, and Explosive Devices on the Presence of Heavy Metals in Soil of Open Detonation Pit: Part 1—Pseudo-total Concentration

This paper presents the results of determining the pseudo-total concentration of five heavy metals in the soil on which the destruction of ammunition, mines, and explosive devices is carried out by the method of open detonation. In the analyzed area, the concentrations of cadmium, lead, nickel, copper, and zinc were determined, while from the physical properties of the soil were determined the granulometric composition and the pH. The aim of the study is to determine the origin and total load on heavy metals and, based on that, to assess the dangers and impact of the site in terms of the soil pollution by heavy metals. In accordance with the regulations of Bosnia and Herzegovina, the results of the soil testing showed a significant load of copper (up to seven times) and cadmium (up to six times), and exceeding the allowed values for nickel and zinc in some places. Lead was the only metal whose concentration was within the maximum allowed and according to that the soil was classified as unpolluted. A sample of soil from the edge of the pit is the only sample in which all heavy metals, except Ni, were within the maximum allowable concentration. In regard to the concentration of the examined metals, the soil of the pit is classified as medium polluted from the aspect of copper, cadmium, and nickel and highly contaminated with zinc. The concentrations of copper and zinc in the examination area correspond to contaminated soil that represents ecological risk, which requires soil remediation.     

The transfer of heavy metals to barley plants from soils amended with sewage sludge with different heavy metal burdens

Purpose

Our main aim objective was to evaluate the transfer of Cd, Cr, Cu, Ni, Pb and Zn to barley (Hordeum vulgare) grown in various soils previously amended with two sewage sludges containing different concentrations of heavy metals. This allowed us to examine the transfer of heavv metals to barley roots and shoots and the occurrence of restriction mechanisms as function of soil type and for different heavy metal concentration scenarios.

Material and methods

A greenhouse experiment was performed to evaluate the transfer of heavy metals to barley grown in 36 agricultural soils from different parts of Spain previously amended with a single dose (equivalent to 50 t dry weight ha^?1) of two sewage sludges with contrasting levels of heavy metals (common and spiked sludge: CS and SS).

Results and discussion

In soils amended with CS, heavy metals were transferred to roots in the order (mean values of the bio-concentration ratio in roots, BCF_Roots, in brackets): Cu (2.4)?~?Ni (2.3)?>?Cd (2.1)?>?Zn (1.8)?>?Cr (0.7)?~?Pb (0.6); similar values were found for the soils amended with SS. The mean values of the soil-to-shoot ratio were: Cd (0.44)?~?Zn (0.39)?~?Cu (0.39)?>?Cr (0.20)?>?Ni (0.09)?>?Pb (0.01) for CS-amended soils; Zn (0.24)?>?Cu (0.15)?~?Cd (0.14)?>?Ni (0.05)?~?Cr (0.03)?>?Pb (0.006) for SS-amended soils. Heavy metals were transferred from roots to shoots in the following order (mean values of the ratio concentration of heavy metals in shoots to roots in brackets): Cr (0.33)?>?Zn (0.24)?~?Cd (0.22)?>?Cu (0.19)?>?Ni (0.04)?>?Pb (0.02) for CS-amended soils; Zn (0.14)?>?Cd (0.09)?~?Cu (0.08)?>?Cr (0.05)?>?Ni (0.02)?~?Pb (0.010) for SS-amended soils.

Conclusions

Soils weakly restricted the mobility of heavy metals to roots, plant physiology restricted the transfer of heavy metals from roots to shoots, observing further restriction at high heavy metal loadings, and the transfer of Cd, Cu and Zn from soils to shoots was greater than for Cr, Ni and Pb. Stepwise multiple linear regressions revealed that soils with high sand content allowed greater soil-plant transfer of Cr, Cu, Pb and Zn. For Cd and Ni, soils with low pH and soil organic C, respectively, posed the highest risk.     

Increasing the Knowledge of Heavy Metal Contents and Sources in Agricultural Soils of the European Mediterranean Region

This paper contributes to increase the knowledge of the contents and sources of heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn) to agricultural soils in Castellón province (Spain), a representative area of the European Mediterranean region. The surface horizons of 77 agricultural soils under vegetable crops were sampled and heavy metals were analysed by atomic absorption spectroscopy (AAS) after microwave extraction using the USEPA 3051A method. Mean heavy metal contents were similar to those obtained in other areas of this region. However, heavy metal contents (e.g. Cr, Pb) in some soils were above the maximum limit set in the 86/278/CEE Directive. Multivariate analysis (correlation analysis and principal component analysis – PCA) was performed so as to identify the sources of heavy metals to soils. Co, Fe and Ni were highly correlated amongst them (r?>?0.800; p?<?0.01), whereas Cr and Mn were less correlated with Co, Fe and Ni (r?>?0.500; p?<?0.01). Other relationships among heavy metals (i.e. Cu, Pb and Zn) were also identified, although correlation coefficients were not so high as those among Co, Fe and Ni (r?<?0.500; p?<?0.01). Contents of Co, Fe, Mn and Ni were interpreted to be mainly associated with parent rocks corresponding to the first principal component (PC1). On the other hand, Cd, Cu, Pb and Zn were interpreted to be mainly related to anthropogenic activities and comprised the second (Pb and Zn) and the third (Cd and Cu) principal components (PC2 and PC3, respectively), designated as anthropogenic components. Remarkably, Cr appears to be related in the study area to both the lithogenic and the anthropogenic components. Lithogenic elements were highly correlated with soil properties. Positive relationships with CEC (r?>?0.200; p?<?0.05) and clay (r?>?0.400; p?<?0.01), and negative relationships with carbonates (r?>??0.400; p?<?0.01) and sand (r?>??0.300; p?<?0.01) were observed. Anthropogenic elements were less correlated with soils properties, since these elements are generally more mobile because they form more soluble chemical species associated to anthropogenic sources. Particularly, no correlation was found between Cd and Zn and soil properties. These findings extend results achieved in other parts of the region, highlighting the need to set soil quality standards in order to declare soils affected by anthropogenic pollution, particularly in the case of anthropogenic metals such as Cd, Cu and Pb, and also Cr and Zn in some areas. Further knowledge from other areas in this region would improve the basis for proposing such standards at regional level, which is a priority objective in Europe according to the European Thematic Strategy for Soil Protection.     

Heavy Metal Accumulation in Soil Amended with Roadside Pond Sediment and Uptake by Rice (Oryza sativa L.)

The effect of addition of roadside pond sediments on heavy metal contents of flooded rice paddies was studied to investigate the yield of rice and uptake of heavy metal by rice straw and grain. Sequential extraction of heavy metals on sediments shows that the percentage contribution of metals in the labile fraction follows the order lead (Pb, 48%) > copper (Cu, 42%) > zinc (Zn, 31%) > cadmium (Cd, 16%) > chromium (Cr, 9%) > nickel (Ni, 6%). The risk assessment code (RAC) for pond sediment revealed that Cr and Ni were found in the low-risk zone, Zn and Cd in the medium-risk zone, and Cu and Pb in the high-risk zone. However, though the heavy metal concentration in rice grain does not exceed the range acceptable for human consumption, it still represents a significant additional source of heavy metals in the diet. The addition of pond sediment significantly increased the rice yield over control. Therefore, pond sediment would be a valuable resource for agriculture if it is properly used.     

Effects of iron ore tailings on growth and physiological activities of Tagetes patula L.

Purpose

Ornamentals can beautify the environment and resolve heavy metal pollution at the same time. Thus, the present study aimed at studying the growth and physiological response of Tagetes patula on iron ore tailings.

Materials and methods

Pot-culture experiments were conducted to investigate the effect of iron ore tailings both individually as well as in combination with soil (at different proportions) on the growth, pigment production as well as accumulation and translocation of various heavy metals from the tailings.

Results and discussion

The results suggested an increase in growth, chlorophyll content, as well as metal accumulation capacity of T. patula with increasing proportion of tailings in the soil. Furthermore, an increase in antioxidant activities in plants grown on tailings as compared to control was observed which suggests plant efficiency to overcome any stress generated due to excess of heavy metals. The order of accumulation of various heavy metals in the plant parts was observed to be Fe?>?Cr?>?Zn?>?Cu?>?Pb?>?Ni?>?Cd. Both bioaccumulation and translocation values were maximum for Fe and minimum for Ni and Cd, respectively.

Conclusions

The overall study clearly suggests plant ability to grow well on the tailings and survive excess of heavy metals present in the tailings. Thus, the plant qualifies well as a potential tool for phytostabilization of iron ore tailings and probably a source of income generation from wasteland owing to its multiple commercial values.     

北京市得田沟金矿和崎峰茶金矿周边土壤重金属形态分析和潜在风险评价

对密云水库上游已关闭的得田沟金矿和崎峰茶金矿周边土壤中重金属的总量和形态分布进行分析,并通过富集因子法和风险评价编码法（RAC）对其污染状况进行了评价。结果表明,除As和Pb外的重金属平均含量都高于北京市土壤背景值,重金属的空间分布具有一定的差异性。土壤中Pb的铁锰氧化物结合态占总量的50%,其次为残渣态占33%;Cu的残渣态为72%,其次有机结合态为21%;Zn和Mn均以铁锰氧化物结合态和残渣态为主,分别占总量的93%和87%,其他重金属元素则以残渣态为主要形态。大多数重金属含量和可提取态含量的最大值都出现在堆积过尾矿石处（Z8、Z9和Z10）,污染程度较重。基于总量的富集因子结果表明,研究区内Cr有显著污染,Hg、Cu、Cd和Ni为中度污染,其他元素轻微污染或无污染;基于形态的RAC表明该地区重金属元素具有较低的风险水平。     

北京市五环内绿地土壤4种重金属的形态特征及其生物有效性

[目的]了解北京市五环内绿地表层(0—20cm)土壤重金属(Cu,Cd,Pb和Zn)的形态特征及其生物有效性,为北京市绿地土壤重金属污染防治提供比较可靠的参考依据。[方法]在建成时间为2~400a的绿化区内共采集表层土壤样品151个,运用改进BCR提取法分析样品中重金属的赋存形态,而后通过风险评价编码法(RAC)和次生相与原生相分布比值法(RSP)对重金属生物有效性进行评估。[结果]样品中重金属Cu,Cd,Pb和Zn的含量分别为31.42,0.29,29.89,76.78 mg/kg,Cu,Zn在中部和东北部含量较高,Pb在中部地区含量较高,Cd在西北部、东北部和南部存在少量高值区。Cu,Cd,Pb和Zn形态分布的总体规律均为:残渣态可氧化态弱酸溶态可还原态,稳定态含量均远高于有效态,有效态含量比例表明重金属生物有效性大小顺序为:CdZnCuPb风险评价编码法(RAC)表明,Cd和Zn环境风险程度为低风险,Cu和Pb无环境风险。次生相与原生相分布比值法(RSP)显示,Cu,Cd,Pb和Zn元素RSP值分别为0.06,0.49,0.18,0.13,土壤整体上未受到重金属污染,但是有少部分地区存在被污染现象。[结论]北京市五环内绿地土壤总体上不存在重金属Cu,Cd,Pb和Zn污染,环境风险较低,但应对重金属赋存形态保持关注。     

Transfer of Heavy Metals from Soils to Vegetables and Associated Human Health Risks at Selected Sites in Pakistan

Contamination of the food chain with heavy metals is considered as one of the major environmental pathways of human exposure to metals leading to potential health risks. This study aimed to investigate the concentrations of heavy metals such as copper (Cu), zinc (Zn), chromium (Cr), nickel (Ni), and manganese (Mn) in agricultural soils and food crops (fruit, leaf, and root vegetables), and their associated health risks to the local population in selected southern districts of Khyber Pakhtunkhwa Province, Pakistan. The concentrations of the selected metals in soil varied over a wide range, in the following decreasing order: Mn > Zn > Cr > Ni > Cu. The bioaccumulation of metals in vegetables was within the permissible risk limits, except for Cr which showed higher contamination in all the tested food crops. The trend of metal transfer factors for different vegetables was in the order of Cu > Ni > Cr > Mn > Zn, while the calculated daily intake of metals (DIM) in adults and children through consumption of food crops was in the decreasing order of Mn > Zn > Ni > Cr > Cu. The health risk index (HRI) values for the heavy metals for both adults and children were less than 1. Therefore, no significant health risk is anticipated for the local consumers through ingestion of these food crops.     

Pathological and Hormonal Changes in Freshwater Fishes Due to Exposure to Heavy Metals Pollutants

The concentrations of major heavy metals in organs of two cyprinid fish and in water collected from three sections of the Kor River, Iran, were determined using the induction coupled plasma method. The concentrations of heavy metals in tissue of fish from the middle sampling zone were significantly higher (p?<?0.05) than those from the other two sampling zones, whereas no significant differences (p?>?0.05) were detected between the two sexes and species. Estradiol in females and progesterone and testosterone in males from the middle study site were significantly (p?<?0.05) lower than values from the other two sites. Pathological changes in blood cells, liver, and kidneys of fishes were significantly higher in highly polluted areas (middle sampling zone). So heavy metals exposure can effectively decreases estrogenic and androgenic secretion in fish. These results show that industrial activities have polluted the river and that heavy metals exposure can induce pathological changes in fish organs.     

Behaviors of Organic and Heavy Metallic Pollutants during Supercritical Water Oxidation of Oil-Based Drill Cuttings

Oil-based drill cuttings (OBDCs), which contain various petroleum hydrocarbons, heavy metals, and alkaline salts, will significantly affect the local ecosystem if left untreated. Supercritical water oxidation (SCWO) is regarded as a potential end-of-pipe technology that is able to degrade organic compounds, stabilize heavy metals, and neutralize alkaline salts simultaneously. In this paper, SCWO of OBDCs was carried out using a batch reactor. Six organic compounds and eight elements were selected as representatives of the petroleum hydrocarbons and heavy metals, respectively, in OBDCs. The effects of the oxygen coefficient (OC), temperature (T), and reaction time (t) on the degradation of petroleum hydrocarbons and the stabilization of heavy metals were evaluated in detail. The results indicated that nearly 100% of naphthalenes and more than 97% of alkanes could be destroyed when T?>?475 °C, t?>?2 min, and OC?>?2.5. The elements Ba, Cr, and Pb were almost completely stabilized in the solid products, and small amounts of Zn and Cu were detected in the liquid products. More than the original contents of Fe, Cr, and Ni were found in the solid products due to the corrosion of the SCWO reactor. The content of alkaline salt in the feed was too low to affect the pH of the liquid products. The results of X-ray diffractometer (XRD) and scanning electron microscope (SEM) analyses suggested that SCWO can efficiently remove organic pollutants from OBDCs but does not obviously affect the microstructure and composition of the inorganic compounds.     

Heavy metals in the soil–plant system of the Don River estuarine region and the Taganrog Bay coast

Purpose

The aim of this work was to study the level and degree of mobility of heavy metals in the soil–plant system and to perform bioindication observations in the Don River estuarine region and the Russian sector of the Taganrog Bay coast.

Materials and methods

The objects of the study included samples of zonal soils (chernozem) and intrazonal soils (alluvial meadow and alluvial-stratified soils, Solonchak, sandy primitive soil) from monitoring stations of the Don river estuarine region and the Taganrog Bay coast, as well as their higher plants: Phragmites australis Cav., Typha angustifolia L., Carex riparia Curtis, Cichorium intybus L., Bolboschoenus maritimus L. Palla, and Rumex confertus Willd. The total concentrations of Mn, Ni, Cd, Cu, Zn, Pb, and Cr in the soils were determined by X-ray fluorescent scanning spectrometer. The concentration of heavy metal mobile forms exchangeable, complex compounds, and acid-soluble metal were extracted using the following reagents: 1 N NH₄Ac, pH 4.8; 1 % EDTA in NH₄Ac, pH 4.8; 1 N HCl, respectively. Heavy metals in plants were prepared for analysis by dry combustion at 450 °C. The heavy metal concentration in extracts from plants and soils was determined by AAS.

Results and discussion

The total contents of heavy metals in the soil may be described with a successively decreasing series: Mn?>?Cr?>?Zn?>?Ni?>?Cu?>?Pb?>?As?>?Cd. The total concentrations of As, Cd, and Zn in the soil exceed the maximum permissible concentrations levels. Contamination of alluvial soils in the estuarine zone with mobile Сu, Zn, Pb, and Cd has been revealed, which is confirmed by the high bioavailability of Cu and Zn and, to a lesser degree, Cd and Pb accumulating in the tissues of macrophytic plants. Data on the translocation of elements to plant organs have showed their predominant accumulation in the roots. Bioindication by the morphofunctional parameters of macrophytic plants (with a Typha L. species as an example) can be used for revealing the existence of impact zones with elevated contents of metals in aquatic ecosystems.

Conclusions

The results revealed that increased content of Zn, Pb, Cu, Ni, and As in soil have anthropogenic sources. The high content of Cr in the soils is related to the lithogenic factor and, hence, has a natural source.

     

Geochemical Mobility and Bioavailability of Heavy Metals in a Lake Affected by Acid Mine Drainage: Lake Hope, Vinton County, Ohio

Sandy Run (Vinton County, southeastern Ohio, USA) is a stream receiving acid mine drainage (AMD) from an abandoned coal mine complex. This stream has been dammed to form Lake Hope. The heavy metal composition of waters (benthic and pore), sediments, and macroinvertebrates in the lake reservoir sediments were analyzed. Lake waters contained Mn as the heavy metal present in higher concentrations followed by Fe, Al, and Zn. Depletion of Fe and Al occurred from precipitation of less soluble Fe and Al oxides and hydroxides along Sandy Run before entering the lake, producing a high Mn water input into the reservoir. Concentrations of heavy metals in the sediments increased toward the dam area. Sequential extraction of metals in the sediments showed that the highest fractions of metals corresponded to the detrital fraction or eroded material from the watershed and metals associated with iron and manganese hydroxides. Heavy metals in the organic sediment fraction were low. Heavy metals from the AMD source, as well as sediments rich in heavy metals eroded from the watershed, were transported to the downstream dam area and stored at the bottom, producing the observed chemistry. Heavy metals in benthic waters also were sourced from the diffusion of ions from sediments and lake waters as variation in pH and redox conditions determined the flux at the sediment–water interface. Metal concentrations were measured within two deposit feeders, oligochaetes and chironomids, and compared to trends in physical metal concentration across the lake. For the four heavy metals with higher concentration in both benthic animals, the concentrations followed the trend: Fe?>?Al?>?Mn?>?Zn, which were similar to the bioavailable metals in the sediments rather than the pore or the benthic water where Mn was the most abundant heavy metal. Ingestion of sediment, not exposure to pore or benthic waters, appeared to be the main transfer mechanism for metals into the biota. Trends and patterns in animal metal concentrations across the lake were probably a complex process controlled by metabolic needs and metallic regulation and tolerance. Even when Mn was the highest concentration heavy metal in the pore waters, it was the lowest to bioconcentrate in the organisms. In comparison, Cd, the lowest concentration metal in the sediments, presented one of the highest bioaccumulation factors.     

Reaction of sewage farm soils to different irrigation solutions in a column experiment 2. Heavy metals and their leaching

Heavy metal polluted soils from a recent and a former sewage farm were studied in a 2.5 years‐column experiment under various irrigation regimes and/or liming treatment. The copper (Cu), zinc (Zn), lead (Pb), and cadmium (Cd) concentrations in the soil and the leaching of these elements were studied. The amounts of the metals leached differed markedly between both soils, however, the effect of various irrigation treatments was less pronounced. The heavy metal content in the soil solid phase depended on the organic carbon content, however these dependencies differed for both soils as well as for particular metals. In lower soil horizons, the amount of heavy metals bound by unit mass of organic carbon was constant. It was assumed that the same amount of the heavy metals can be bound by the unit mass of the DOC. Under this assumption the amount of the DOC in the former sewage farm soil was in general too small to carry all heavy metals leached. Therefore leaching of their cationic forms has been postulated. The amount of the DOC in the present sewage farm soil could carry more heavy metals than these being leached. Therefore, an undersaturation of the DOC in heavy metals could occur in this soil.<?show $6#>     

Municipal Waste and Poultry Manure Compost Affect Biomass Production,Nitrate Reductase Activity and Heavy Metals in Tomato Plants

Organic wastes can be usefully recovered to produce organic amendments, for example, compost, to be used for crop production, thus reducing impacts through efficient waste management. The aim of this work was to study the effects of compost obtained from municipal waste in combination with poultry manure on plant growth, nitrate reductase (NR) activity and absorption and distribution of heavy metals (HM) in plant tissues of tomatoes, grown in pots in greenhouses. Two compost types obtained from municipal waste mixed with poultry manure (C1?=?3:2 and C2?=?2:3) were used at two different ages (105 d and 173 d) and at two mix rates with soil (32.5?g pot^?1 and 65?g pot^?1); soil with no compost amendment was used as control. The experiment was conducted using tomato plants in pots and plant growth and nutrient plant uptake was determined after 65?days from plant transplanting. Results obtained indicated that compost type and compost rate affected biomass production. However, compost age did not influence the development of plants. Nutrient status of tomato plants was also investigated with reference to the N cycle. Nitrite accumulation in the leaves increased with the increase in compost doses. The accumulation of NO₂^? was associated with a significant increase in NR activity. HM content in leaves decreased with compost use. HM accumulated preferentially in roots and leaves and the soil to root metals transfer was in this order: Fe (1.08–2.14)> Co (0.53–4.10)>Cu (0.28–2.28) >Mn (0.3–1.34) >Zn (0.87–1.21)>Cr (0.12–1.64). The highest and lowest dynamic bioaccumulation factors (BAF_dyn) were observed in roots and stems, respectively. The root system acted as a barrier for Cd and Pb. It was concluded that compost use is beneficial for tomato plants, with particular reference to the compost obtained by using a higher amount of poultry manure (C2) in the mix.     

Accumulation of Heavy Metals in Wheat (Triticum aestivum L.) Seedlings Grown in Soils Amended with Electroplating Industrial Sludge

A glasshouse study was undertaken to evaluate the effect of lime-treated (0, 0.5, and 1%) industrial sludge amendments (10 and 20%) on wheat (Triticum aestivum L.) seedling growth and heavy metal accumulation in soils as well as in wheat seedlings. Industrial sludge–amended soil samples were filled in earthen pots (2 kg pot^?1) one week before planting and 7-day-old seedlings were transplanted in pots (3/pot) and were kept in a glasshouse. Diethylenetriamine pentaacetic acid (DTPA)-extractable metals and metals in seedlings increase with increasing doses of industrial sludge. Biomass and growth have been found to increase with increasing rates of sludge. It also enhanced heavy metal concentrations in wheat seedlings and followed the trend zinc (Zn) > lead (Pb) > copper (Cu) > cadmium (Cd). Lime enhanced the biomass and reduced the heavy metal concentrations in wheat seedlings. Although 20% treatments in both soils showed a significant enhancement in shoot length, metals like Pb reached beyond permissible limits.     

Heavy Metals in Water Percolating Through Soil Fertilized with Biodegradable Waste Materials

The influence of manure and composts on the leaching of heavy metals from soil was evaluated in a model lysimeter experiment under controlled conditions. Soil samples were collected from experimental fields, from 0- to 90-cm layers retaining the layout of the soil profile layers, after the second crop rotation cycle with the following plant species: potatoes, spring barley, winter rapeseed, and winter wheat. During the field experiment, 20 t DM/ha of manure, municipal sewage sludge composted with straw (SSCS), composted sewage sludge (SSC), dried granular sewage sludge (DGSS), “Dano” compost made from non-segregated municipal waste (CMMW), and compost made from municipal green waste (CUGW) was applied, i.e., 10 t DM/ha per crop rotation cycle. The concentrations (μg/dm³) of heavy metals in the leachate were as follows: Cd (3.6–11.5)?<?Mn (4.8–15.4)?<?Cu (13.4–35.5)?<?Zn (27.5–48.0)?<?Cr (36.7–96.5)?<?Ni (24.4–165.8)?<?Pb (113.8–187.7). Soil fertilization with organic waste materials did not contaminate the percolating water with manganese or zinc, whereas the concentrations of the other metals increased to the levels characteristic of unsatisfactory water quality and poor water quality classes. The copper and nickel content of percolating water depended on the concentration of those metals introduced into the soil with organic waste materials. The concentrations of Cd in the leachate increased, whereas the concentrations of Cu and Ni decreased with increasing organic C content of organic fertilizers. The widening of the C/N ratio contributed to Mn leaching. The concentrations of Pb, Cr, and Mn in the percolating water were positively correlated with the organic C content of soil.     

Estimating Sorption Affinities of Heavy Metals on Humic Acid and Silica using a Constant Capacitance Model

The adsorption of heavy metals [cadmium (Cd ²⁺), cobalt (Co²⁺), nickel (Ni²⁺), zinc (Zn²⁺), and lead (Pb)] and calcium (Ca²⁺) on humic acid and silica were investigated to understand the adsorptive selectivities of heavy metals on the constituents of soil. The experiments for the adsorption of Cd and Pb were carried out in a 0.1 mol L^?1 (M) sodium nitrate (NaNO₃) background solution, whereas those for the other metals were done in a 0.1 M sodium chloride (NaCl) solution. The adsorptive affinities of the metal ions on the humic acid and silica were ranked by the intrinsic surface complexation constants [K _m ¹(int)] that were calculated approximately from the adsorptive data using a constant capacitance model. The log [K _m ¹(int)] values of the metals were in the order Zn²⁺(?2.29) > Cd²⁺(?2.41) > Co²⁺(?2.74) > Ni²⁺(?2.92) ?> Ca²⁺ (?3.33) for the humic acid and Zn²⁺(?4.23) > Cd²⁺(?4.49) > Ni²⁺(?4.51) ? Co²⁺ (?5.99) > Ca²⁺(?6.37) for silica.     

Use of Single Extraction Methods to Predict Bioavailability of Heavy Metals in Polluted Soils to Rice

Human exposure to toxic heavy metals via dietary intake is of increasing concern. Heavy-metal pollution of a rice production system can pose a threat to human health. Thus, it was necessary to develop a suitable extraction procedure that would represent the content of metal available to rice plants (Oryza sativa L.). The aim of this study was to predict, on the basis of single extraction procedures of soil heavy metals, the accumulation of heavy metals (cadium, lead, copper, and zinc) in rice plants. Six extracting agents [Mehlich 1, Mehlich 3, EDTA (ethylenediaminetetraacetic acid), DTPA–TEA (diethylenetriaminepentaacetic acid–triethanolamine), ammonium acetate (NH₄OAc), and calcium chloride (CaCl₂)] were tested to evaluate the bioavailability of heavy metals from paddy soils contaminated with lead–zinc mine tailings to rice. The extraction capacity of the metals was found to be of the order EDTA > Mehlich 3 > Mehlich 1 > DTPA–TEA > NH₄OAc > CaCl₂. The correlation analysis between metals extracted with different extractants and concentrations of the metals in the grain and stalk of the plant showed positive correlations with all metals. The greatest values of correlation coefficients were determined between the NH₄OAc- and CaCl₂-soluble fractions of soil and contents in plants in all four metals studied. Therefore, NH₄OAc and CaCl₂ were the most suitable extractants for predicting bioavailability of heavy metals in the polluted soils to rice. The results suggested that uptake of heavy metals by rice was mostly from exchangeable and water-soluble fractions of the metals in the soils. Soil-extractable metals were more significantly correlated with metal accumulation in the stalk than in the grain. The pH had more significant influence on availability of heavy metals in the soils than total content of metals and other soil properties. The bioavailability of metals for rice plants would be high in acidic soils.