DTPA-extractable Heavy Metals Research Articles

Modified diatomite for soil remediation and its implications for heavy metal absorption in Calendula officinalis

BackgroundAmong different adsorbents, natural and inorganic compounds such as diatomite are important and advantageous in terms of high efficiency and cost-effectiveness, and function in stabilizing heavy metals in the environment. Calendula officinalis, a plant known as a high accumulator of heavy metals, was cultivated in soil treated with varying concentrations of modified diatomite to demonstrate the efficiency of modified diatomite in stabilizating of heavy metals in soils,ResultsThe modification of diatomite aimed to enhance Calendula officinalis adsorptive properties, particularly towards heavy metals such as lead (Pb), Zinc (Zn), Chromium (Cr), Nickle (Ni), and Copper (Cu), common contaminants in industrial soils. The experimental design included both control and treated soil samples, with assessments at regular intervals. Modified diatomite significantly decreased the bioaccumulation of heavy metals in contaminated soils except Zn, evidenced by decreased DTPA extractable heavy metals in soil and also heavy metal concentrations in plant tissues. Using 10% modified diatomite decreased 91% Pb and Cu, 78% Cr, and 79% Ni concentration of plants compared to the control treatment. The highest concentration of Zn in plant tissue was observed in 2.5% modified diatomite treatment. Remarkably, the application of modified diatomite also appeared to improve the nutrient profile of the soil, leading to enhanced uptake of key nutrients like phosphorus (P) 1.18%, and potassium (K) 79.6% in shoots and 82.3% in roots in Calendula officinalis. Consequently, treated plants exhibited improved growth characteristics, including shoots and roots height of 16.98% and 12.8% respectively, and shoots fresh and dry weight of 48.5% and 50.2% respectively., compared to those in untreated, contaminated soil.ConclusionThe findings suggest promising implications for using such amendments in ecological restoration and sustainable agriculture, particularly in areas impacted by industrial pollution.

Almond shell-derived biochar decreased toxic metals bioavailability and uptake by tomato and enhanced the antioxidant system and microbial community

The effectiveness of almond shell-derived biochar (ASB) in immobilizing soil heavy metals (HMs) and its impact on soil microbial activity and diversity have not been sufficiently studied. Hence, a pot study was carried out to investigate the effectiveness of ASB addition at 2, 4, and 6 % (w/w) on soil biochemical characteristics and the bioavailability of Cd, Cu, Pb, and Zn to tomato (Solanum lycopersicum L.) plants, as compared to the control (contaminated soil without ASB addition). The addition of ASB promoted plant growth (up to two-fold) and restored the damage to the ultrastructure of chloroplast organelles. In addition, ASB mitigated the adverse effects of HMs toxicity by decreasing oxidative damage, regulating the antioxidant system, improving soil physicochemical properties, and enhancing enzymatic activities. At the phylum level, ASB addition enhanced the relative abundance of Actinobacteriota, Acidobacteriota, and Firmicutes while decreasing the relative abundance of Proteobacteria and Bacteroidota. Furthermore, ASB application increased the relative abundance of several fungal taxa (Ascomycota and Mortierellomycota) while reducing the relative abundance of Basidiomycota in the soil. The ASB-induced improvement in soil properties, microbial community, and diversity led to a significant decrease in the DTPA-extractable HMs down to 41.0 %, 51.0 %, 52.0 %, and 35.0 % for Cd, Cu, Pb, and Zn, respectively, as compared to the control. The highest doses of ASB (ASB6) significantly reduced the metals content by 26.0 % for Cd, 78.0 % for Cu, 38.0 % for Pb, and 20.0 % for Zn in the roots, and 72.0 % for Cd, 67.0 % for Cu, 46.0 % for Pb, and 35.0 % for Zn in the shoots, as compared to the control. The structural equation model predicts that soil pH and organic matter are driving factors in reducing the availability and uptake of HMs. ASB could be used as a sustainable trial for remediation of HMs polluted soils and reducing metal content in edible plants.

Application of Rice Husk Biochar and Earthworm on Concentration and Speciation of Heavy Metals in Industrial Sludge Treatment.

The aim of this study was to assess the total concentration and speciation variation of heavy metals (Pb, Cd, Cu and Zn) during composting and vermicomposting of industrial sludge with different addition rations of rice husk biochar. Results indicated that pH, EC, total phosphorus (TP) and total potassium (TK) were increased and total organic carbon (TOC) and total nitrogen (TN) were decreased during the composting of industrial sludge with biochar compared with the control (sludge without biochar). The addition of earthworm to the biochar-amended sludge further decreased pH and TOC but highly enhanced the EC, TN, TP and TK. Comparatively lower concentrations of total and DTPA-extractable heavy metals were observed in biochar-amended sludge treatments mixed with earthworm in comparison with the biochar-amended sludge treatments without earthworm or the control. Sequential extraction methods demonstrated that vermicomposting of sludge with biochar converted more metals bound with exchangeable, carbonate and organic matter into the residual fraction in comparison with those composting treatments of sludge with biochar. As a result, the combination of rice husk biochar and earthworm accelerated the passivation of heavy metals in industrial sludge during vermicomposting. Rice husk biochar and earthworm can play a positive role in sequestering the metals during the treatment of industrial sludge. This research proposed a potential method to dispose the heavy metals in industrial sludge to transform waste into resource utilization.

Vertical distribution of heavy metals in soil profile of peri-urban areas of Haryana

Soil serves as a sink for various heavy metals where they present long period of time in the soil and create a manyharmful effects on soil health. A survey was carried out in peri-urban areas of Mohindergarh and Narnaul city, Haryanairrigated by sewage and tube-well water. Study was conducted on vertical distribution of heavy metals in profile soilsamples. Soil samples were analyzed for initial properties of soil and DTPA extractable heavy metals (Zn, Cu, Cd,Cr, Pb, Ni and Co). The results revealed that the soluble heavy metals, viz. Zn, Cu, Cr, Cd, Pb and Co content in bothsewage and tube-well irrigated profile soil samples decreased with increased depth of soil in both Mohindergarh andNarnaul areas. But, the Ni content increased with depth in both areas of sewage and tube-well irrigated soils. It isconcluded that the profile soil samples were found below the permissible limit of soluble heavy metals concentration.

USING HISTORIC SITES IN DETERMINING PLANT-SOIL INTERACTIONS UNDER LONG TERM CONTAMINATED SOILS

The relationships between heavy metals in soils and crop tissues are critical in understanding the potential risk to crop yields from Zn, Cu and Ni (the principal phytotoxic elements of concern in sludge), and the possible effects on dietary Cd (the critical zootoxic element that is labile in sludge-treated soil and readily absorbed by plants. These relationships cannot be derived from the agronomic trials because the quantities of heavy metals applied to the soil in sludge are small. These are field sites have been treated with sludge for many years in operational practice and where the oncentrations of heavy metals have been significantly raised above background values, representing potentially a worse-case of soil contamination. The purpose of the study was to provide a surrogate for long-term sludge-treated agricultural soil by examining the effects on crops of heavy metals in soil irrigated with raw sewage effluent for periods of more than 80 years and containing significantly elevated concentrations of heavy metals. Methodology: Two surveys of the Gabal El Asfar Old Farm were undertaken to assess the long-term effects of heavy metals in sludge-treated soil on crop quality. In the first survey, the relationships between total and DTPA extractable heavy metals in soil and concentrations in citrus fruit were examined. Concentrations of heavy metals in leaves of citrus were measured in the second survey and related to total and DTPA extractable metals in soil. The heavy metal contents of citrus leaves and fruit (orange - eleven sampling sites; mandarin - four sampling sites), and total and DTPA extractable concentrations in soils were measured in samples collected from different areas of the Farm during two site surveys. Total and DTPA concentrations of heavy metals in the surveyed soils showed significant enrichment by long-term irrigation with sewage effluent. For example, the maximum total concentrations of Zn and Cu were 530 and 366 mg kg-1, respectively, representing a potential risk to crop yields The maximum Cd concentration detected was 9 mg kg-1 and may be a potential risk to the human food chain from uptake into staple crops grown at the farm. DTPA extractable metals were significantly (P<0.001) correlated with the total contents of Zn (r=0.91***), Cu (r=0.83***), Ni (r=0.63***) and Pb (r=0.85***) in soil when data from both surveys were pooled for statistical evaluation. There was also evidence of a weak relationship between DTPA extractable Cd and the total soil Cadmium is the only element of concern in terms of the risk to human health from uptake into food crops grown on sludge-treated soil. The total Cd concentration in soil was raised to a value 3 times the maximum EU limit for this element in sludge-treated agricultural soil. Despite the marked increase in soil Cd content, there was no detectable transfer into citrus leaves or fruit (Figure 1). The absence of Cd uptake into citrus fruit is to be expected because fruits are amongst the least sensitive plant parts to Cd accumulation. These data emphasise the minimal risk to the human diet from Cd in fruit crops grown on sludge-treated soil. . In all cases, leaf tissue concentrations were low and in some cases Cu status was below the deficiency threshold. The Cd content in leaves was small and generally <0.02 mg kg-1 DM.

Metallothionein dependent-detoxification of heavy metals in the agricultural field soil of industrial area: Earthworm as field experimental model system

Earthworms are known to reclaim soil contamination and maintain soil health. In the present study, the concentration of DTPA extractable heavy metals, Cd, Cu, Cr, Pb, and Zn in vermicasts and tissues of the earthworms (anecic: Lampito mauritii; epigeic: Drawida sulcata) collected from the soils of four different industrial sites, Site-I (Sago industry), Site-II (Chemplast industry), Site-III (Dairy industry) and Site-IV (Dye industry) have been studied. The heavy metals in industrial soils recorded were 0.01–326.42 mg kg−1 with higher Cu, Cr, and Zn contents while the vermicasts showed lower heavy metal loads with improved physicochemical properties and elevated humic substances. The higher humic substances dramatically decreased the heavy metals in the soil. The bioaccumulation factors of heavy metals (mg kg−1) are in the order: Zn (54.50) > Cu (17.43) > Cr (4.54) > Pb (2.24) > Cd (2.12). The greatest amount of metallothionein protein (nmol g−1) was recorded in earthworms from Site-IV (386.76) followed by Site-III (322.14), Site-II (245.82), and Site-I (232.21). Drawida sulcata can produce a considerable amount of metallothionein protein than Lampito mauritii as the metallothionein production is dependent upon the presence of pollutants. The molecular docking analysis indicates a binding score of 980 for Cd, Cr and Cu, and 372 for Zn. Pb may bind with a non-metallothionein protein of earthworms and bio-accumulated in the internal chloragogenous tissues. Metallothionein neutralizes the metal toxicity and controls the ingestion of essential elements.

River water irrigation with heavy metal load influences soil biological activities and risk factors

The Yamuna is one of the most polluted rivers in India and the land adjacent to river flowing through Delhi city is widely irrigated with its water for growing various food crops. Present study was undertaken to assess the heavy metal load in Yamuna water and surrounding soils of the river bank and its impact on soil enzyme activities. Long term impact of irrigation by Yamuna water on the activities of various soil enzymes namely dehydrogenase (DHA), urease (UA), fluroscein diacetate (FDA), aryl sulphatase (ASA), nitrate reductase (NRA), microbial biomass carbon (MBC) and potentially mineralizable nitrogen (PMN) were assessed. The sensitivity of soil enzymes to heavy metals were observed as DHA>UA>ASA>NRS. Total organic carbon, easily oxidisable soil organic carbon, available phosphorus and available potassium in different sites varied significantly. Total heavy metal contents in soils showed a decreasing order: Fe>Mn>Zn>Cr>Ni>Cu>Pb>Co>As>Cd and the DTPA extractable heavy metal contents followed the order: Mn>Cu>Pb>Zn >Fe>Ni>Cd>Cr>Co>As. Potential ecological risk factors (Er) were under low risk and comprehensive potential ecological risk indices (Ri) were found to be under low, moderate and high risk categories. Copper (Cu) is the main pollutant contributing considerable load to Ri. From (Ri) principal component analysis and cluster analysis, it is evident that the Okhla site (S8) is most contaminated. The water from Yamuna river needs to be cautiously used for growing various food crops on land adjacent to the river as its long-term usage might cross the permissible limits of heavy metals in the soil.

Chemical Properties of Soil Influence by Sewage Water Irrigation of Different District of Haryana

The present study deals with the difference of chemical properties between sewage and tube well water irrigated soils. Samples were collected from sewage and tube well water irrigated soil of various site like Kaithal, Narwana and Jind district of Haryana state where these waters are directly used for irrigating the crops. Soil samples (0-15 and 15-30 cm) were also collected from fields irrigated with these waters and from nearby fields irrigated with non-sewage waters to determine the changes in soil chemical properties due to sewage irrigation. Total Zn, Cu, Mn, Fe, Cd, Pb, Co, and Cr along with nitrogen, phosphorus and potassium were estimated form the samples. The mean value of N (200.50 kg ha-1) was found highest in the soils irrigated with sewage water of Kaithal. The mean value of P (35.85 kg ha-1) and K (236.40 kg ha-1) was found highest in the soils irrigated with sewage water of Jind. The mean value of K (236.40 kg ha-1) was found highest in the soils irrigated with sewage water of Jind. The mean value of Zn (4.43 mg kg-1), Cu (3.33 mg kg-1) and Fe (19.43 mg kg-1) was found highest in the soils irrigated with sewage water of Jind. The mean value of Mn (15.13 mg kg-1) was found highest in the soils irrigated with sewage water of Kaithal. The DTPA extractable heavy metals like Cd, Pb and Co were found higher in the soils irrigated with sewage water as compared to soils irrigated with non-sewage water. The value of Cr content was found nil all the soils samples collected from different cities from sewage and non-sewage water irrigated sites.

Impact of Long-Term Application of Sewage on Soil and Crop Quality in Vertisols of Central India.

Shortfall of rain and the decreased groundwater level force farmers to use poor quality water for crop production in developing countries. In this study, the quality of agricultural produce and soil health affected by sewage water (Patranala) irrigation was evaluated. Sewage sediment, soil and crop samples were analyzed for physico-chemical properties. Sewage water found to contain trace concentration of heavy metals. However, long-term application of this water for crop production could build up a significant amount of trace metals in both soil and sediments. The DTPA extractable heavy metals ranged Cu 2.7-7.59, Cd 0.04-0.06, Pb 1.29-2.05, Cr 0.01-0.04, Ni 0.24-1.03 and Zn 0.63-2.59mgkg-1 soil. The heavy metal risk assessment (hazard quotient, HQ) was calculated and found that HQ for these metals in the crops under study was in safe limits. From the study, it is concluded that growing vegetables using sewage water of Patranala is safe, but periodic monitoring to be carried out to avoid food chain contamination.

Simulation of soil heavy metal pollution environmental stress on plant growth characteristics in the presence of wastewater

<p>Soil pollution was simulated by means of artificial heavy metal enrichment, in the presence of treated wastewater, and its effect on the growth characteristics of Beta vulgaris L. (red beets) i.e. on the dry matter yield, and on beet quality expressed in terms of dry matter heavy metal, nitrogen and crude protein content, was investigated in a greenhouse pot experiment. Twelve treatment combinations of heavy metals mixtures composed of Zn, Mn, Cd, Co, Cu, Cr, Ni, and Pb, with each one metal participating in the mixture at 0, 2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22 mg.kg-1 were applied, respectively. It was found that the increase of soil DTPA extractable heavy metal concentrations reflecting high soil pollution, decreased statistically significantly the beet dry matter (dm) yield, but increased the metal and the , the nitrogen concentrations, and consequently, contributed statistisically significantly to the increase of beet crude protein yield.</p>

Ecological risk assessment of polymetallic sites using weight of evidence approach

Ecological risk assessment (ERA) of polymetallic contamination in soils has caused extensive solicitude. However, objective and feasible methods suitable for soil ERA are limited. Therefore, in this study, a multidisciplinary and quantitative weight of evidence approach (WOE) specific to soil ecosystems was developed based on the previous WOE for aquatic ecosystems. The framework consisted of four lines of evidence (LOEs): DTPA-extractable heavy metal in soils, bioaccumulation in earthworms, integration of biomarker responses and expected community effect (multi-substance Potentially Affected Fraction, msPAF). These four LOEs were initially evaluated by each hazard quotient (HQ) of them based on the ratio to the reference (RTR) of each parameter. Then, Environmental risk index (EnvRI) integrated by HQs with different weights was calculated. At last, three sites, one for reference (N1) and two for contaminated soils (N2 and N3) were chosen to apply the modified WOE approach. Results showed that heavily contaminated site, N3 had higher HQ classification for each LOE and its EnvRI was classified as Major levels, while the EnvRI of N2 was assigned into Moderate. What's more, HQ of biomarker response (HQbiomarker) integrated by RTRs of biomarkers increased gradiently with the increase of heavy metal levels in soils though irregular changes were observed for most of those biomarkers. Overall, our results indicated that the quantitative WOE framework specific to soil ERA had the advantage of obtaining a comprehensive and objective risk assessment.

Influence of biochar on heavy metals and microbial community during composting of river sediment with agricultural wastes

Studies were performed to evaluate influence of biochar addition on physico-chemical process, heavy metals transformation and bacterial community diversity during composting of sediment with agricultural wastes. Simultaneously, the relationships between those parameters including heavy metals and bacterial community compositions were evaluated by redundancy analysis (RDA). The results show that the extraction efficiency of DTPA extractable heavy metals decreased in both piles, and reduced more in pile with biochar addition about 0.1–2.96%. Biochar addition dramatically influenced the bacterial community structure during the composting process. Moreover, the bacterial community composition was significantly correlated with C/N ratio, water soluble carbon (WSC), and organic matter (OM) (P<0.05) in pile with biochar addition; while significantly correlated with temperature, WSC, and C/N ratio in pile which was free of biochar. This study would provide some valuable information for improving the composting for disposal of river sediment with heavy metals contamination.

Erratum to: Organic fertilization in nectarine (Prunus persica var. nucipersica) orchard combines nutrient management and pollution impact

Recycled organic fertilizers may be used to replace chemical source of nutrients; however, some nutrients such as nitrogen and heavy metals released by mineralization can become potential pollutants. The objective of this experiment was to compare, over a 3-year-period of time, the effectiveness of two organic fertilizers (cow manure and compost) with a traditional mineral fertilizer on soil fertility, tree nutritional status, heavy metal concentration in soil and plant in a mature nectarine orchard. Trees were subjected, since their plantation (made in 2001) to the following treatments: (1) mineral fertilization (including nitrogen at 130 kg ha−1 year−1); (2) cow manure (5 t DW year−1 ha−1); (3) compost (5 t DW year−1 ha−1). Soil organic matter and total nitrogen concentration increased as a consequence of compost application. Soil nitrate concentration was increased by mineral fertilizer and compost applications. In summer, macro and micro nutrient concentrations in leaves were not affected by treatments with the exception of N that was increased by mineral fertilization. At the end of the season, leaf N, K and Zn were remobilized to storage organs, while Ca, Mg, Cu, Fe and Mn accumulated in abscised leaves and returned to the soil, with no differences among treatments. Nitrogen and K were found principally in fruit flesh. With the exception of Cu and Zn, the concentration of heavy metals in leaves and fruits was below detection limits. Total and DTPA-extractable heavy metals in soil were not increased by organic fertilization if compared with mineral fertilizer.

Temporal variation of total and DTPA-extractable heavy metal contents as influenced by sewage sludge and perlite in a calcareous soil

ABSTRACTContinuous application of sewage sludge (SS) as a source of organic matter, may increase available heavy metals (HMs) up to their critical levels. As a consequence their uptake by plants, risks of accumulation in food chain and groundwater pollution increases. To evaluate the effects of perlite and SS on total content and available fraction of iron (Fe), manganese (Mn), lead (Pb), copper (Cu), nickel (Ni), cadmium (Cd) and zinc (Zn) over 45 and 90 days a completely randomized pot experiment was conducted. Treatments consisted of SS (0, 2 and 4%) and combined SS and perlite levels (1:1, 1.5:0.5 and 0.5:1.5% SS:perlite). Mean available Fe, Ni, Cd, Mn and Zn fractions decreased over time by 7–27%, whereas, total contents did not change. Available HMs in SS-treated soils increased by 0.5–25%; whereas, only total Zn, Cu and Pb concentrations increased with SS application (although concentrations fall in the range of critical levels). The lowest (1.6 fold) and highest (22.1 fold) increases obtained for available Cu and Zn, respectively. Perlite could mitigate the adverse effect of high rate application of SS on amplification of HMs extractability. Therefore, their concomitant applications can be suggested considering the perlite durability and its positive effects on soil physical properties.

Heavy metal extraction by weeds in wheat and cauliflower irrigated with sewage water

The weed species emerged in wheat and cauliflower were screened for heavy metal accumulation ability under sewage water contaminated sites in Jabalpur and adjoining areas. It was observed that nearly 2–10 times higher accumulation of DTPA extractable heavy metals, viz. 0.42–6.30 μg/g cadmium, 2.43–24.1 μg/g lead, 3.06–89.43 μg/g copper, 88.9–226 μg/g manganese and 30–200 μg/g iron were recorded in sewage water soils than the tube well irrigated soils containing 0.69 μg/g Cd, 2.85 μg/g Pb, 62.8 μg/g Mn, 7.36 μg/g Cu, and 37.7 μg/g Fe. Relatively crops accumulated metals to lower extent than the weed species. Among weed species, Avena ludoviciana removed higher 69.6–122.3 μg/g manganese and 48.9–104 μg/g copper, Parthenium hysterophorus extracted 1065–2507 μg/g iron whereas Sonchus arvensis extracted 3.07 μg/g cadmium which were higher than the metal hyperaccumulating Brassica juncea (43.5 μg/g Mn, 19.0 μg/g Cu, 1352 μg/g Fe, 1.40 μg/g Cd). Thus, information on the build up of heavy metal concentration in soil and their removal by seasonal weed species grown on sites receiving sewage water indicate risk of metal entry in animal food chain as these weed species except Parthenium are used as a feed for animals. Besides this these weed species can be exploited for phyto-extraction of heavy metals under abiotic stress situation of metalliferrous sites.

Agricultural use of wastewater sludge from various sources with special emphasis on total and DTPA-extractable heavy metal content

Agricultural use of wastewater sludge from various sources with special emphasis on total and DTPA-extractable heavy metal content

Effect of the application of various wastewater sludges on the properties of sandy soil.

This research was conducted to determine the effect of various wastewater sludge (domestic type (B), mixture of industry and domestic type (L), aerobic food industry (P), anaerobic food industry (M)) levels on the properties of sandy soil, including pH, electrical conductivity (EC), and the levels of available N (NH4 and NO3) and P, diethylenetriamine pentaaceticacid (DTPA)-extractable microelements and heavy metals. An incubation experiment was performed in which sludges were applied at rates of 0, 40, 80, 120, and 160 tons ha(-1), and the effects on the soil properties were measured over a period of 150 days. Soil pH decreased and electrical conductivity increased with increasing levels of sludge application. The levels of NH4-N, NO3-N, available P, and DTPA-extractable heavy metals also increased with the application rate of the sludge. NO3-N content increased and NH4-N content decreased over time. The most unfavorable effects on soil properties were observed with the B sludge. Other soil characteristics changed according to the sludge properties.

Assessment of EDTA heap leaching of an agricultural soil highly contaminated with heavy metals

The efficiency of heavy metal removal from soil by EDTA leaching was assessed in a column leaching experiment at the laboratory scale and field heap leaching at the pilot scale using a sandy loam sierozem agricultural soil contaminated with Cd, Cu, Pb, and Zn. Soil amendment and aging were conducted to recover leaching soils. The percentages of Cd, Cu, Pb, and Zn removed by column leaching were 90%, 88%, 90%, and 67%, respectively, when 3.9 bed volumes of 50mM EDTA were used. At the pilot scale, on-site metal removal efficiencies using the selected leaching procedure were 80%, 69%, 73% and 62% for Cd, Cu, Pb and Zn, respectively. EDTA leaching decreased soil CEC, total P, total K and available K concentrations but increased organic matter and total Kjeldahl N concentrations. The subsequent amendment and soil aging further reduced the DTPA-extractable heavy metals in the leached soils. Growth of the first crop of pak choi in the leached soil was inhibited but the second crop grew well after the soil was aged for one year and the concentrations of Cd and Pb in the edible parts were below the Chinese statutory limits. The results demonstrate the potential feasibility of the field leaching technique using EDTA combined with subsequent amendment and soil aging for the remediation of heavy metal-contaminated agricultural soils.

Phytotreatment of Sewage Sludge Contaminated by Heavy Metals and Pahs by Co-Planting Sedum Alfredii and Alocasia Marorrhiza

High concentrations of heavy metals and organic pollutants in municipal sewage sludge are key factors limiting its use in agriculture. The objectives of this study were to decrease the heavy metal and polycyclic aromatic hydrocarbon concentrations in sewage sludge by phytotreatment and to determine, in a field experiment, whether co-planting is more effective than using a mono-crop of Sedum alfredii. Four treatments were used in the plot experiment: no sludge, no plants, S. alfredii and co-planting S. alfredii and Alocasia marorrhiza. The results showed that co-planting produced tubers and shoots of A. marorrhiza that were suitable as a safe animal feed and good organic K fertilizer, respectively. Co-planting was more effective than mono-planting at reducing concentrations of total Zn and diethylenetriaminepentaacetic acid (DTPA)-extractable Zn, Cd, and Cu in the sludge. Co-planting decreased the concentrations of DTPA-extractable heavy metals and benzo[a]pyrene (B[a]P) in the sludge significantly compared with the unplanted sludge. Decreases of 87, 75, 85, 31, and 64% were obtained for B[a]P and DTPA-extractable Zn, Cd, Cu, and Pb, respectively, compared with the fresh sludge. These results indicate that co-planting can reduce significantly the environmental risks associated with heavy metals and B[a]P in sewage sludge for further disposal.

Influence of temperature on the heavy metals accumulation of five vegetable species in semiarid area of northwest China

The aim of the present study was to investigate the possible effects of temperature on cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) accumulation in five vegetable species collected at different sites (Shuichuan, Beiwan, Dongwan and Wufe) in northwest China. The meteorological data of air and soil temperatures were recorded daily during the period from sowing to harvest for the five vegetables. The air and soil temperatures affected the capacity of pumpkin, cabbage, brassica napus and Chinese cabbage to accumulate Zn, Cd, Cu and Pb. Principal component analysis showed that temperature, photosynthetic and physiological factors all contributed to the soil–plant transfer properties of DTPA-extractable heavy metals. Temperature played a more important role in Cd, Pb, Cu and Zn accumulation in four vegetables in this semiarid area. However, the enormous surface area of spinach was likely to elevate heavy metal loads owing to atmospheric deposits. For most vegetables studied, there was a striking dissimilarity in the uptake and translocation ability of Cd, Zn and Cu in soil, but similar accumulation to translocation for Pb in soil.