Metal remediation from partially composted distillery sludge using composting earthworm Eisenia fetida

Distillery sludge, a sugar industry byproduct, has been recommended widely as a potential soil conditioner, but high concentrations of metals limit its continuous use for field crops. In this study we tested the feasibility of earthworm Eisenia fetida (Savigny) in removing metals (Fe, Cu, Zn, Pb) from sludge through vermitechnology. The transfer of metals during the vermicomposting process was also estimate in terms of total metal contents in vermicomposted sludge and earthworm tissues. The sludge processed by worms showed a significant reduction in concentration of metals: Zn (20.5-43.8%), Fe (23.6-34.0%), Mn (18.0-45.7%) and Cu (29.0-58.1%), at the end. The metal reduction in sludge was directly related to the bioaccumulation of metals in the tissues of composting earthworms. The inoculated earthworms showed a considerable level (dry wt basis) of Zn (103.7-143.3 mg kg(-1)), Fe (87.2-146.5 mg kg(-1)), Mn (83.7-138.6 mg kg(-1)) and Cu (16.8-25.5 mg kg(-1)) in their tissues. A higher range of bioconcentration factors (BCFs) for different metals studied further suggest the candidature of earthworm to be used effectively for removal of metals form industrial sludges. The obtained vermicomposts form different vermireactors were rich in nutrients. The feasibility of earthworms to mitigate the metal toxicity and to enhance the nutrient profile in sludge might be useful in sustainable land restoration practices at low-input basis. The ranges of metals in end product were within the standards recommended by different agencies.     

Metal immobilization and phosphorus leaching after stabilization of pyrite ash contaminated soil by phosphate amendments

In this study we would like to show the importance of a holistic approach to evaluation of chemical stabilization using phosphate amendments. An extensive evaluation of metal stabilization in contaminated soil and an evaluation of the leaching of phosphorus induced after treatment were performed. The soil was highly contaminated with Cu (2894 mg kg(-1)), Zn (3884 mg kg(-1)), As (247 mg kg(-1)), Cd (12.6 mg kg(-1)) and Pb (3154 mg kg(-1)). To immobilize the metals, mixtures of soil with phosphate (from H(3)PO(4) and hydroxyapatite (HA) with varying ratios) were prepared with a constant Pb : P molar ratio of 1: 10. The acetic acid extractable concentration of Pb in the mixture with the highest amount of added phosphoric acid (n(H(3)PO(4)) : n(HA) = 3 : 1) was reduced to 1.9% (0.62 mg L(-1)) of the extractable Pb concentration in the untreated soil, but the content of water extractable phosphorus in the samples increased from 0.04 mg L(-1) in the untreated soil sample up to 14.3 mg L(-1) in the same n(H(3)PO(4)) : n(HA) = 3 : 1 mixture. The high increase in arsenic mobility was also observed after phosphate addition. The PBET test showed phosphate induced reduction in Pb bioavailability. In attempting to stabilize Pb in the soil with the minimum treatment-induced leaching of phosphorus, it was found that a mixture of soil with phosphate addition in the molar ratio of H(3)PO(4) : HA of 0.75 : 1 showed the most promising results, with an acetic acid extractable Pb concentration of 1.35 mg L(-1) and a water extractable phosphorus concentration of 1.76 mg L(-1). The time-dependent leaching characteristics of metals and phosphorus for this mixture were evaluated by a column experiment, where irrigation of the soil mixture with the average annual amount of precipitation in Slovenia (1000 mm) was simulated. The phosphorus concentration in the leachates decreased from 2.60 mg L(-1) at the beginning of irrigation to 1.00 mg L(-1) at the end.     

The occurrence of heavy metals in irrigated and non-irrigated arable soils,NW Albania

The study analysed the content of heavy metals in surface soil and sediment samples from the Bregu i Matit Plain in NW Albania in relation to irrigation in order to evaluate the soil pollution and the potential risk to human health. Evaluation of soil pollution was performed using the enrichment factor and geo-accumulation index. Contents of cadmium, chromium and nickel of irrigated soils were significantly higher than those of non-irrigated soil, while contents of lead (in three of the irrigated locations), zinc and arsenic (in one of the irrigated locations) were significantly lower. Correlation analysis (CA) and principal component analysis (PCA) indicated that the primary source of the first three metals was irrigation, and the last three metals were originated from other anthropic sources, like the use of chemicals, etc. Enrichment factor (E _f) calculation showed that irrigated soils were most enriched in cadmium, chromium, copper and nickel. Index of geo-accumulation (I _geo) revealed that arable soils of Bregu i Matit are unpolluted to moderately polluted with cadmium, chromium, copper and zinc and moderately to strongly polluted with nickel and arsenic. The presence of heavy metals in the studied soils indicates a potential risk of transfer of these elements in the food chain. Therefore, further studies on the speciation of heavy metals in the studied soils in order to evaluate their mobility are needed.     

Ecotoxicological impact assessment of some heavy metals and their distribution in some fractions of mangrove sediments from Red Sea, Egypt

The total and fraction concentrations of heavy metals (Mn, Cu, Ni, Pb, Co, and Cd) were analyzed in some sediment fractions (Φ2, Φ3, Φ4, Φ5) of selected mangrove ecosystems collected from the Egyptian Red Sea shoreline. The results revealed that manganese had the highest mean value (133?±?97 mg/kg) followed by copper (49.9?±?46.0 mg/kg), nickel (28.1?±?11.8 mg/kg), lead (19?±?13 mg/kg), cobalt (6.7?±?4.0 mg/kg), and cadmium (3.327?±?1.280 mg/kg). The concentrations of heavy metals in the different sediment fractions showed that there was a preferential accumulation of Cu, Co, Mn, and to a lesser degree Cd in the silt and clay fractions rather than in the sand-sized. The sediment quality was performed by using some sediment quality guidelines. Additionally, the contamination and the risk assessment of these heavy metals were achieved by different methods including, potential ecological risk index, contamination factor, pollution load index, and geoaccumulation index. According to the Sediment Quality Guidelines comparisons, the concentrations of Mn and Pb were low and showed no possibility of detrimental effects on the local environment. The levels of Cu and Ni were high, however, could not be considered to present serious threat to the mangrove ecosystem. The data showed that the mangrove ecosystems were affected by the Cd risk.     

Petroleum contaminated soil in Oman: Evaluation of bioremediation treatment and potential for reuse in hot asphalt mix concrete

This paper presents a study that aims at evaluating the leaching characteristics of petroleum contaminated soils as well as their application in hot mix asphalt concrete. Soil samples are environmentally characterized in terms of their total heavy metals and hydrocarbon compounds and leachability. The total petroleum hydrocarbon (TPH) present in the PCS before and after treatment was determined to be 6.8% and 5.3% by dry weight, indicating a reduction of 1% in the TPH of PCS due to the current treatment employed. Results of the total heavy metal analysis on soils indicate that the concentrations of heavy metals are lower when extraction of the soil samples is carried out using hexane in comparison to TCE. The results show that the clean soils present in the vicinity of contaminated sites contain heavy metals in the following decreasing order: nickel (Ni), followed by chromium (Cr), zinc (Zn), copper (Cu), lead (Pb), and vanadium (V). The current treatment practice employed for remediation of the contaminated soil reduces the concentrations of nickel and chromium, but increases the concentrations of all remaining heavy metals.     

State of the marine environment at Little Bay Arm,Newfoundland and Labrador,Canada, 10 years after a "do nothing" response to a mine tailings spill

In 1989, the tailings pond dam at the site of a former copper mine near Little Bay, Newfoundland and Labrador, Canada, ruptured and tailings spilled into Little Bay Arm. At the time, no action was taken to arrest the flow of tailings or to mitigate the effects of the spill. To date, no action has been taken to repair the dam and tailings continue to flow into Little Bay Arm. As a result, the marine environment around Little Bay Arm has become contaminated with heavy metals from the tailings. However, the tailings are not the only source of heavy metals to the ecosystem. An old slag heap and what is presumably concentrated copper ore spilled during the loading of ore freighters, are also contributing to the ecosystem's metal load. Marine sediment throughout the Arm contained elevated concentrations of Cu, Ni, Zn, As, V, Co, and Mn. Beach material also contained elevated concentrations of metals with material near the slag heap being the most contaminated. At this site, Cu concentrations were in excess of 5000 mg kg(-1) dry weight, Zn greater than 3000 mg kg(-1) and Co concentrations exceeded 700 mg kg(-1). The highest concentrations of metals in biota were found near the slag heap, near the tailings dam breach, and at the site of the former concentrate loading dock. Despite elevated metal concentrations, the tailings and nearby sediment were not devoid of life. Bivalves and seaweed were abundant in the area and there were no obvious signs of tissue damage or disease in soft shell clams (Mya arenaria) living in the tailings. These clams may be suffering from chronic exposure to the tailings, however, evidence of lipid peroxidation in the clams was inconclusive.     

Assessment of heavy metals in some wild edible mushrooms collected from Yunnan Province, China

Eight heavy metals (Cu, Zn, Fe, Mn, Cd, Cr, Ni, and Pb) in 14 different wild-growing edible mushroom species (Coprinus comatus, Voluariella volvacea, Pleurotus nebrodensis, Hypsizigus marmoreus, Hericium erinaceus, Agrocybe aegerita, Lenfinus edodes, Collybia velutipes, Agaricus bisporus, Russula albida, Clitocybe conglobata, Pleurotus eryngii, Lepista sordida, and Pleurotus ostreatus) collected from Yunnan province, China, were determined by inductively coupled plasma-atomic emission spectrometry after microwave digestion. All element concentrations were determined on a dry weight basis. The ranges of element concentrations for copper, zinc, iron, manganese, cadmium, chromium, nickel, and lead were 6.8-31.9, 42.9-94.3, 67.5-843, 13.5-113, 0.06-0.58, 10.7-42.7, 0.76-5.1, and 0.67-12.9 mg/kg, respectively. In general, iron content was higher than other metals in all mushroom species. The levels of zinc, cadmium, and lead in some edible mushroom samples were found to be higher than legal limits. The relative standard deviations were found below 10%. The accuracy of procedure was confirmed by certified reference material.     

Assessment of heavy metal toxicants in the roadside soil along the N-5, National Highway, Pakistan

The assessment of the toxicants in roadside soil on regular basis has become extremely essential with the increase in awareness for the metal toxicity in the environment. The present study investigates the presence of toxic metals along National Highway (N-5), Pakistan. Averages of about 1.3 million per month of automobile vehicles ply on this route. Lead (Pb), zinc (Zn), copper (Cu), nickel (Ni), cadmium (Cd), cobalt (Co), manganese (Mn), mercury (Hg), and iron (Fe) were analyzed by atomic absorption spectrophotometry in roadside soil at the nine selected locations along the highway. Strong Pearson correlations (α = 0.05) were found between Pb and Zn (r(2)?= 0.887), Fe and Mn (r(2)?= 0.880), Hg and Cd (0.864), Cu and Zn (0.838), and Cu and Pb (0.814). The correlation between the elemental compositions of the main automobile components revealed vehicular traffic as the main non-point source of roadside soil pollution. Extremely high level of mercury, 144.05 mg kg(-1), was found at S5. It was revealed that the unregulated incineration and dumping sites of hazardous waste material along N-5 were also responsible for these contaminations. Multivariate analysis on the obtained data also disclosed the same interpretation. Cluster analysis of the data grouped Pb, Zn, and Cu at 85.23% similarity, whereas, Cd, Hg, and Ni were grouped at 78.75% similarity basis. The findings need swift action against the root cause of soil pollution.     

Geochemical evidence for the origin of vanadium in an urban environment

The city of Salamanca in central Mexico is surrounded by heavy industry, i.e., a refinery, a thermoelectric plant and chemical industries. Variable concentrations of vanadium (V) have been reported in the groundwater, and their presence has been related to particulates so this hypothesis was tested by sampling soil in the urban area and the surrounding uncontaminated country site. The 0-10-cm soil layer in the industrial and rural area was analyzed for V and other metal trace elements found in hydrocarbons, i.e., chromium (Cr), lead (Pb), zinc (Zn), and nickel (Ni). The concentrations of V were higher in the urban rather than in the rural soil, reaching values of >600 mg kg(-1) in the urban soils. In the rural area, V in the soil was related to regional geology, i.e., volcanic rocks such as basalts and rhyolites but not in the urban area where it was related to particulate distribution mostly emitted from the industries burning fuel oil number 6.     

Extractable copper, arsenic and antimony by EDTA solution from agricultural Chilean soils and its transfer to alfalfa plants (Medicago sativa L.)

Following our research on copper, arsenic and antimony in Chilean ecosystems, a study to understand the mobility and transport of these elements from soil to plants was carried out. So, the aim of this study, which follows on from the previous work, was to demonstrate if the total concentrations of these elements or their fractions extracted by 0.05 M EDTA pH 7 from different Chilean soils correlate with the respective total concentrations in the edible tissue of alfalfa plants collected simultaneously from 20 different sites affected or unaffected by mining activities. The highest copper fractions extracted by EDTA solutions were obtained in contaminated soils from the central region (41-69%); however the northern soils presented the highest extractable fractions of arsenic (9-34%). The antimony fraction was low in all soils (0.4-8.0%). Alfalfa plants from all contaminated sites presented high copper, arsenic and antimony concentrations (19-126 mg kg(-1), 5.7-16.3 mg kg(-1) and 0.16-1.7 mg kg(-1), respectively). Statistically significant correlations were obtained between the total contents of copper and arsenic and their respective extractable fractions in soils. Good correlations were found between elements in alfalfa plants. Correlations were also obtained between the total concentrations of three elements in soils and in alfalfa plants. However, excepting for antimony in the northern samples, higher correlation coefficients were evaluated when the extractable fractions were considered. Samples from the north region presented the highest copper transfer factor and the lowest for arsenic, in spite of the high concentration of this metalloid extracted by EDTA solution in these soils. There was not a clear trend on the transfer factor for antimony, probably due to the low content of this element in alfalfa plants and/or the low recovery obtained for this element by EDTA.     

Modelling the Balance of Metals in the Amended Soil for the Case of ‘Atmosphere–Plant–Soil’ System

Changing the concepts of economic development and introducing new amendments can hardly decrease the accumulation in the soil of such pollutants as metals, remaining there for a long time. The predictive models for describing the balance of metals in the soil, which are based on the ‘atmosphere–plant–soil’ system and reflect the complicated physical–chemical nature of the metals’ migration, expressed by coefficients obtained in long-term observations in natural conditions, allow for evaluating long-term concentration of metals in the soil. The model BALANS evaluates self-purification of soil, taking into account the uptake of metals of aerogenic origin by the soil together with amendments, their physical–chemical migration and the type of microrelief determining its intensity as well as the absorbed biomass of plants and the removal of metals with crops. In this model, the half-period of metals’ washing out from the soil, found for the microrelief characteristic of low places, exceeds 200 years for Ni, Cr and Pb and makes 90 and 150 years for Zn and Cu, respectively.     

Survey of four marine antifoulant constituents (copper,zinc, diuron and Irgarol 1051) in two UK estuaries

A field survey of antifoulant concentrations was undertaken in two UK estuaries (Hamble and Orwell) in 1998 and 1999. The two locations offered variations in physical aspects (Orwell estuary being significantly larger than the Hamble) as well as differences in boat densities (Hamble having almost twice as many vessels moored in the estuary and marinas). Samples were analysed for copper, zinc, diuron and Irgarol 1051, and were collected in summer and winter in order to identify potential seasonal variations in concentrations. The effect that different marina types (e.g. locked marina, one located in a natural inlet and pontooned ones in the open estuary) had on antifoulant concentrations were also investigated. Concentrations of the organic booster biocides, diuron and Irgarol 1051 in the marinas and estuaries were mainly influenced by leaching from antifoulant paints applied to the hulls of leisure craft, and so levels reflected the number of vessels present in the water. As a consequence significantly higher concentrations were found in marinas (up to ca. 900 ng l(-1) for diuron and 240 ng l(-1) for Irgarol 1051) compared with estuaries (up to ca. 400 ng l(-1) for diuron and 100 ng l(-1) for Irgarol 1051) and in summer compared with winter. Sediment concentrations of Irgarol 1051 and diuron were rarely detectable other than in the marinas where high concentrations were detected near slipways assumed to be derived from washed off paint chips. Dissolved concentration profiles for copper and zinc in the estuaries and marinas were different from those for the organic booster biocides partly because other sources of these metals contributed to estuarine and marina loads. In particular, riverine loads and inputs from sacrificial anodes attached to leisure craft, exhibited a major influence of estuarine levels of zinc. Consequently, only in the Hamble estuary for copper was there a clear distinction between summer (typically 3-4 microg l(-1)) and winter dissolved values (typically 1-2 microg l(-1)) that could be largely attributable to the leaching of antifoulant paints. Sediment concentrations for both metals were similar for both estuaries, with little variation between winter and summer values (Zn ranging from 28 to 614 mg kg(-1) and Cu from 6 to 1016 mg kg(-1)) as with the organic booster biocides highest levels were measured at the base of slipways in marinas.     

Bio-monitoring for uranium using stream-side terrestrial plants and macrophytes

This study evaluated the abilities of various plant species to act as bio-monitors for environmental uranium (U) contamination. Vegetation and soil samples were collected from a U processing facility. The water-way fed from facility storm and processing effluents was the focal sample site as it represented a primary U transport mechanism. Soils and sediments from areas exposed to contamination possessed U concentrations that averaged 630 mg U kg(-1). Aquatic mosses proved to be exceptional accumulators of U with dry weight (dw) concentrations measuring as high as 12,500 mg U kg(-1) (approximately 1% of the dw mass was attributable to U). The macrophytes (Phragmites communis, Scripus fontinalis and Sagittaria latifolia) were also effective accumulators of U. In general, plant roots possessed higher concentrations of U than associated upper portions of plants. For terrestrial plants, the roots of Impatiens capensis had the highest observed levels of U accumulation (1030 mg kg(-1)), followed by the roots of Cyperus esculentus and Solidago speciosa. The concentration ratio (CR) characterized dry weight (dw) vegetative U levels relative to that in associated dw soil. The plant species that accumulated U at levels in excess of that found in the soil were: P. communis root (CR, 17.4), I. capensis root (CR, 3.1) and S. fontinalis whole plant (CR, 1.4). Seven of the highest ten CR values were found in the roots. Correlations with concentrations of other metals with U were performed, which revealed that U concentrations in the plant were strongly correlated with nickel (Ni) concentrations (correlation: 0.992; r-squared: 0.984). Uranium in plant tissue was also strongly correlated with strontium (Sr) (correlation: 0.948; r-squared: 0.899). Strontium is chemically and physically similar to calcium (Ca) and magnesium (Mg), which were also positively-correlated with U. The correlation with U and these plant nutrient minerals, including iron (Fe), suggests that active uptake mechanisms may influence plant U accumulation.     

Impacts of epigeic, anecic and endogeic earthworms on metal and metalloid mobility and availability

The introduction of earthworms into soils contaminated with metals and metalloids has been suggested to aid restoration practices. Eisenia veneta (epigeic), Lumbricus terrestris (anecic) and Allolobophora chlorotica (endogeic) earthworms were cultivated in columns containing 900 g soil with 1130, 345, 113 and 131 mg kg(-1) of As, Cu, Pb and Zn, respectively, for up to 112 days, in parallel with earthworm-free columns. Leachate was produced by pouring water on the soil surface to saturate the soil and generate downflow. Ryegrass was grown on the top of columns to assess metal uptake into biota. Different ecological groups affected metals in the same way by increasing concentrations and free ion activities in leachate, but anecic L. terrestris had the greatest effect by increasing leachate concentrations of As by 267%, Cu by 393%, Pb by 190%, and Zn by 429% compared to earthworm-free columns. Ryegrass grown in earthworm-bearing soil accumulated more metal and the soil microbial community exhibited greater stress. Results are consistent with earthworm enhanced degradation of organic matter leading to release of organically bound elements. The degradation of organic matter also releases organic acids which decrease the soil pH. The earthworms do not appear to carry out a unique process, but increase the rate of a process that is already occurring. The impact of earthworms on metal mobility and availability should therefore be considered when inoculating earthworms into contaminated soils as new pathways to receptors may be created or the flow of metals and metalloids to receptors may be elevated.     

Soil Contamination Due to Heavy Metals from an Industrial Area of Surat, Gujarat, Western India

The pollution of soil is a source of danger to the health of people, even to those living in cities. The anthropogenic pollution caused by heavy industries enters plants then goes through the food chain and ultimately endangers human health. In the context, the knowledge of the regional variability, the background values and anthropogenic vs. natural origin of potentially harmful elements in soils is of critical importance to assess human impact. The present study was undertaken on soil contamination in Surat, Gujarat (India). The aims of the study were: i) to determine extent and distribution of heavy metals (Ba, Cu, Cr, Co, Ni, Sr, V and Zn) ii) to find out the large scale variability, iii) to delineate the source as geogenic or anthropogenic based on the distribution maps and correlation of metals in soils. Soil samples were collected from the industrial area of Surat from top 10 cm layer of the soil. These samples were analysed for heavy metals by using Philips PW 2440 X-ray fluorescence spectrometer. The data reveal that soils in the area are significantly contaminated, showing higher levels of toxic elements than normal distribution. The heavy metal loads of the soils in the study area are 471.7 mg/kg for Ba, 137.5 mg/kg for Cu, 305.2 mg/kg for Cr, 51.3 mg/kg for Co, 79.0 mg/kg for Ni, 317.9 mg/kg for Sr, 380.6 mg/kg for V and 139.0 mg/kg for Zn. The higher concentrations of these toxic metals in soils need to be monitored regularly for heavy metal enrichment.     

Transversal immission patterns and leachability of heavy metals in road side soils

Today there is consensus concerning the road traffic's role as a metal source. However, there are so far only a few studies which focus on the road side immission patterns regarding distance from roads, and especially in combination with the leachability of heavy metals down the soil profile. In this study, the aim was to analyse concentrations of traffic related metals in road side soils, at different depths and distances from roads, both to analyse the immission patterns as well as to explain the importance of the road construction design of the road side terrain. The BCR sequential extraction procedure was performed to be able to address the environmental risk in terms of metal mobility. Approximately 80 soil samples were analysed for seven metals; antimony (Sb), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), nickel (Ni) and zinc (Zn). The results showed that, depending on metal, the total metal concentrations in road side soils have increased 3-16 times compared to regional background during the last decades. Each metal had a limited dispersal distance from the roads as well as down in the soil profile and the road construction significantly affected the metal immission distance. Elevated metal concentrations were mostly found for top soils and down to 10 cm in the soil profiles. The labile fractions counted for more than 40% of the total concentrations for Cd, Cu, Ni, Pb and Zn, indicating a potential mobilization of the metals if the road side soils become disturbed. The present soil metal concentration levels are not alarming, but metals with a high accumulation rate might gradually be an upcoming problem if nothing is done to their emission sources.     

Spatial variability of soil heavy metals in the three gorges area: multivariate and geostatistical analyses

There is a growing concern about environmental contamination in the three gorges area. The objectives of this study were to investigate the spatial variability and the possible influence factors of seven heavy metals (As, Cd, Cr, Cu, Hg, Pb, and Zn) in the center of this area based on multivariate and geostatistical approaches. All analyzed heavy metals were below their background levels, except Cd. The average concentrations of the analyzed elements in topsoil (0-20 cm) were 5.83 mg As kg(-1), 0.21 mg Cd kg(-1), 78.79 mg Cr kg(-1), 21.53 mg Cu kg (-1), 0.049 mg Hg kg(-1), 24.12 mg Pb kg(-1), and 68.5 mg Zn kg(-1). The concentration of As was mostly due to parent materials, whereas the source of Pb was mainly due to vehicle exhaust. The high concentration of Cd was resulted from agricultural practices and parent materials. The concentrations of Cr, Cu, Hg, and Zn were associated with parent materials and human activities.     

Concentration of Cd, Cu, Pb, Zn, Al, and Fe in soils of Manresa, NE Spain

The aims of this study were to determine the contents of cadmium (Cd), copper (Cu), lead (Pb), zinc (Zn), aluminium (Al), and iron (Fe) (aqua regia-extractable) in 27 soil plots (54 samples) from Manresa, NE Spain, and to establish relationships between heavy metals and some soil properties. The main soil types were surveyed and the median concentrations (mg kg(-1)) obtained were Cd 0.28, Cu 20.3, Pb 18.6, Zn 67.4, Al 22,572, and Fe 21,551. Element concentrations for these soils were lower than the published values for the Valencia region (Spain) and Torrelles and Sant Climent municipal districts (Catalonia, Spain). In terms of soil properties, the results of this study suggest that, in Manresa soils, both trace element adsorption and retention are influenced by several properties such as clay minerals, carbonates, organic matter, and pH. All element contents were positively correlated with clay content. Pb and Zn were negatively correlated with pH and CaCO(3).     

乌鲁木齐市米东污灌区农田土壤重金属污染评价

对米东污灌区农田土壤重金属含量进行监测分析,利用不同的评价方法和标准对土壤重金属的环境质量进行评价。结果表明:米东污灌区农田土壤重金属含量分别为Cd(0.12±0.06)mg/kg,Cu(40.43±5.30)mg/kg,Zn(78.38±11.04)mg/kg,Pb(11.66±11.79)mg/kg,Ni(20.24±8.05)mg/kg,Cr(75.81±8.05)mg/kg。以国家土壤环境质量标准(二级)为标准评价,各元素的污染指数排序为Cu>Ni>Cr>Zn>Cd>Pb,综合污染指数为0.337,污染程度为安全。以食用农产品产地土壤环境质量要求为标准评价,各元素的污染指数排序为Cu>Ni>Cr>Zn>Cd>Pb,综合污染指数为0.343,污染程度为安全。表明米东污灌区农田土壤重金属含量尚能达到食用农产品产地土壤环境质量要求。Pb、Cu、Zn的平均含量超过乌鲁木齐市土壤背景值,这说明污灌区土壤重金属Pb、Cu、Zn近年来已有所累积,存在一定的污染风险。     

Matrix-bound phosphine and phosphorus fractions in paddy soils

Phosphine (PH(3)) is a natural gaseous carrier of phosphorus (P) in its geochemical cycles, and it might be important to the P balance of natural ecosystems. Paddy fields are thought to be one of the main sources responsible for the production and emission of PH(3) in to the environment. The relationships between matrix-bound PH(3) (MBP) and different P fractions, as well as selected metals were investigated to explore the possible production of MBP and its link to P cycle in the paddy soils. MBP range from 20.8 (-1) to 502 ng kg(-1) with an average of 145 ng kg(-1). Concentrations at the milk stage are significantly higher than at the jointing stage. The total P range from 333 mg kg(-1) to 592 mg kg(-1). Average P fractions decrease in the order: Ca-P (69.9%) > Organic P (16.5%) > occluded P (6.50%) > Fe-P (5.93%) > dissolved P (0.80%) > exchangeable P (0.32%) > Al-P (0.02%). Different levels of nitrogen fertilizer have little effect on the contents of MBP, P fractions and metals. A significant positive correlation between MBP and Ca-P (p = 0.002), as well as between MBP and Ca (p = 0.008) could be observed, suggesting that Ca-P mainly affects the production of MBP in the paddy soils. It is suggested that soil MBP is strongly linked to Ca-P fertilizer use because soil spiked with P-fertilizer produced an additional 758 ± 142 ng of MBP per kg of soil, compared to only 81.7 ± 12.3 ng of MBP per kg of unspiked soil. No correlations are found between MBP and other P fractions, or between MBP and Al, Fe and Mn.