Effects of municipal solid waste compost and mineral fertilizer amendments on soil properties and heavy metals distribution in maize plants (Zea mays L.)

Soil amendments based on crop nutrient requirements are considered a beneficial management practice. A greenhouse experiment with maize seeds (Zea mays L.) was conducted to assess the inputs of metals to agricultural land from soil amendments. Maize seeds were exposed to a municipal solid waste (MSW) compost (50 Mg ha⁻¹) and NPK fertilizer (33 g plant⁻¹) amendments considering N plant requirement until the harvesting stage with the following objectives: (1) determine the accumulation of total and available metals in soil and (2) know the uptake and ability of translocation of metals from roots to different plant parts, and their effect on biomass production. The results showed that MSW compost increased Cu, Pb and Zn in soil, while NPK fertilizer increased Cd and Ni, but decreased Hg concentration in soil. The root system acted as a barrier for Cr, Ni, Pb and Hg, so metal uptake and translocation were lower in aerial plant parts. Biomass production was significantly enhanced in both MSW and NPK fertilizer-amended soils (17%), but also provoked slight increases of metals and their bioavailability in soil. The highest metal concentrations were observed in roots, but there were no significant differences between plants growing in amended soil and the control soil. Important differences were found for aerial plant parts as regards metal accumulation, whereas metal levels in grains were negligible in all the treatments.     

Quantitative assessment of the toxic effects of heavy metals on 1,2-dichloroethane biodegradation in co-contaminated soil under aerobic condition

1,2-Dichloroethane (1,2-DCA) is one of the most hazardous pollutant of soil and groundwater, and is produced in excess of 5.44 × 10⁹ kg annually. Owing to their toxicity, persistence and potential for bioaccumulation, there is a growing interest in technologies for their removal. Heavy metals are known to be toxic to soil microorganisms at high concentrations and can hinder the biodegradation of organic contaminants. In this study, the inhibitory effect of heavy metals, namely; arsenic, cadmium, mercury and lead, on the aerobic biodegradation of 1,2-DCA by autochthonous microorganisms was evaluated in soil microcosm setting. The presence of heavy metals was observed to have a negative impact on the biodegradation of 1,2-DCA in both soil samples tested, with the toxic effect being more pronounced in loam soil, than in clay soil. Generally, 75 ppm As³⁺, 840 ppm Hg²⁺, and 420 ppm Pb²⁺ resulted in 34.24%, 40.64%, and 45.94% increase in the half live (t_½) of 1,2-DCA, respectively, in loam soil, while concentrations above 127.5 ppm Cd²⁺, 840 ppm Hg²⁺ and 420 ppm of Pb²⁺ and less than 75 ppm As³⁺ was required to cause a >10% increase in the t_½ of 1,2-DCA in clay soil. A dose-dependent relationship between degradation rate constant (k₁) of 1,2-DCA and metal ion concentrations was observed for all the heavy metals tested, except for Hg²⁺. This study demonstrated that different heavy metals have different impacts on the degree of 1,2-DCA degradation. Results also suggest that the degree of inhibition is metal specific and is also dependent on several factors including; soil type, pH, moisture content and available nutrients.     

Characterization of bacterial communities at heavy-metal-contaminated sites

The microbial community in soil samples from two long-term contaminated sites was characterized by using culture-dependent and culture-independent methods. The two sites investigated contained high amounts of heavy metals and were located in the upper Silesia Industrial Region in southern Poland. The evaluation of the aerobic soil microbial population clearly demonstrated the presence of considerable numbers of viable, culturable bacteria at both sites. A high fraction of the bacterial population was able to grow in the presence of high amounts of metals, i.e. up to 10 mM Zn²⁺, 3 mM Pb²⁺ or 1 mM Cu²⁺. Site 1 contained significantly (P < 0.05) lower bacterial numbers growing in the presence of 10 mM Zn²⁺ than site 2, while the opposite was observed for bacteria tolerating 1 mM Cu²⁺. This coincided with the contents of these two metals at the two sites. Ecophysiological (EP) indices for copiotrophs (r-strategists) and oligotrophs (K-strategists) pointed to high bacterial diversity at both sites. Fluorescence in situ hybridization (FISH) analysis indicated that Actinobacteria and Proteobacteria represent the physiologically active fraction of bacteria at the two sites. Shannon diversity (H′) indices for FISH-detected bacterial phylogenetic groups were not significantly different at the two sites.     

In situ phytoremediation of arsenic- and metal-polluted pyrite waste with field crops: effects of soil management

Sunflower, alfalfa, fodder radish and Italian ryegrass were cultivated in severely As-Cd-Co-Cu-Pb-Zn-contaminated pyrite waste discharged in the past and capped with 0.15 m of unpolluted soil at Torviscosa (Italy). Plant growth and trace element uptake were compared under ploughing and subsoiling tillages (0.3 m depth), the former yielding higher contamination (∼30%) in top soil.Tillage choice was not critical for phytoextraction, but subsoiling enhanced above-ground productivity, whereas ploughing increased trace element concentrations in plants. Fodder radish and sunflower had the greatest aerial biomass, and fodder radish the best trace element uptake, perhaps due to its lower root sensitivity to pollution. Above-ground removals were generally poor (maximum of 33 mg m⁻² of various trace elements), with Zn (62%) and Cu (18%) as main harvested contaminants. The most significant finding was of fine roots proliferation in shallow layers that represented a huge sink for trace element phytostabilisation.It is concluded that phytoextraction is generally far from being an efficient management option in pyrite waste. Sustainable remediation requires significant improvements of the vegetation cover to stabilise the site mechanically and chemically, and provide precise quantification of root turnover.     

Impact of heavy metal pollution on the hemogram and serum biochemistry of the Libyan jird, Meriones libycus

The stress profiles of the hemogram and serum biochemistry were determined in the context of heavy metal (Cd, Cu, Hg, Ni and Pb) exposure in the wild libyan jird, Meriones libycus, from one of Riyadh’s polluted areas versus a reference site. Coupling the pronounced drop in platelets (PLT) (28%) and mean platelet volume (MPV) (17%) with the insignificant responses of other red blood cell indices, suggests bone marrow suppression that is characterized by thrombocytopenia as an initial abnormality. The species-specific stress leukogram for M. libycus is expressed by leukocytosis (66%), monocytosis (40%), lymphocytosis (23%) with eosinopenia (81%) and neutropenia (42%). Hyperglycemia (50%), hyper-low-density-lipoproteinemia (38%), hypocortisolism (85%) and hypotriglyceridemia (55%) depicted serum biochemistry profile. In polluted jirds, the elevated activities of pseudocholinesterase (PChE) and serum marker enzymes (alanine aminotransferase ALT, aspartate aminotransferase AST and creatine kinase CK) strongly suggest functional damage of the liver and/or heart. A potential role of PChE in low-density lipoprotein (LDL) metabolism is implied in the joint rise of both indices and in the recognized relationship between PChE and lipid metabolites. While increased utilization in lipid metabolism and energy synthesis could rationalize the inhibition of the normal patterns of triglycerides and lactate dehydrogenase (LDH), the inhibited activities of LDH could additionally be attributed to its hormetic behavior towards low and high metal concentrations. The overall findings presented here documented the relevance of M. libycus in biomonitoring and predicting the risk imposed on human populations living in polluted areas.     

Metal sorption by peat and algae treated peat: kinetics and factors affecting the process

The article presents a new approach that can be used for the purification of water contaminated by heavy metals. The treatment of peat with microalgae showed to be an effective way of increasing metal uptake by peat. Metal sorption was studied for a multimetal solution containing Cu, Cd, Ni, Zn, Cd, and Pb. Cu and Pb were found to be the metals having the highest affinity to peat. Water hardness has a strong effect on the uptake of borderline metals (Cd, Ni, Zn, Cd) from a solution. The use of algae for peat treatment resulted in less time to reach an equilibrium (24 h vs. 72 h for pure peat), and the effect of water hardness (Ca²⁺) on metal uptake was considerably reduced. Both peat and algal-treated peat were able to take up metals from rather acidic solutions (pH 3.0). pH had less influence on the metal uptake compared with water hardness. The affinity of heavy metals to peat was the following: Pb > Cu > Ni > Cd > Zn > Co. It slightly changed to Pb > Cu > Ni > Cd ≈ Co ≈ Zn when the combined sorbent, peat treated with microalga, was applied.     

Immobilization of potentially toxic metals using different soil amendments

The in situ stabilization of potentially toxic metals (PTMs), using various easily available amendments, is a cost-effective remediation method for contaminated soils. In the present study, we investigated the effectiveness of apatite and a commercial mixture of dolomite, diatomite, smectite basaltic tuff, bentonite, alginite and zeolite (Slovakite) on Pb, Zn, Cu and Cd stabilization by means of decreasing their bioavailability in contaminated soil from an old lead and zinc smelter site in Arnoldstein, Austria. We also investigated the impact of 5% (w/w) apatite and Slovakite applications on soil functionality and quality, as assessed by glucose-induced soil respiration, dehydrogenase, acid and alkaline phosphatase and β-glucosidase activity. Both amendments resulted in increased soil pH and decreased PTM potential bioavailability assessed by diethylenetriamine pentaacetic acid extraction and by sequential extractions in the water-soluble and exchangeable fractions. The efficiency of stabilization was reflected in the soil respiration rate and in enzymatic activity. The β-glucosidase activity assay was the most responsive of them.     

污泥低温热解技术在德国的应用实践

本文介绍污泥低温热解技术的原理和工程应用。德国的工程实践表明,这项技术在经济性、可再生能源回收以及设备稳定性方面具有明显的优势。这对我国的污泥处置有较好的借鉴作用。     

Exposure of an anoxic and contaminated canal sediment: Mobility of metal(loid)s

A derelict canal contains an estimated 9800 tonnes of anoxic sediment with highly elevated concentrations of trace elements. Lack of maintenance, reduced water levels and vegetation colonization threaten the stability of pollutants by removing existing waterlogged reduced conditions. A column leaching study of the sediment under increasingly oxidized conditions showed reductions in As mobility but increased heavy metal concentrations. In a reduced state, As mobility was higher (as a consequence of enhanced Fe and organic carbon solubility) whilst heavy metal concentrations in leachates were lower (due to markedly higher pH). Over 10 contiguous wetting and drying cycles, the consequences were profound; all trace elements were continuously leached with enhanced flushing of Fe, As, Zn and Cu. This raises concern over possible mobilization of pollutants to the wider environment, including groundwater. Options for management to stabilize contaminants are discussed that point to the importance of limiting water flow through the sediment.