Increase In Concentration Of Heavy Metals Research Articles

Biosolids and heavy metals in soils

The application of sewage sludge or biosolids on soils has been widespread in agricultural areas. However, depending on their characteristics, they may cause increase in heavy metal concentration of treated soils. In general, domestic biosolids have lower heavy metal contents than industrial ones. Origin and treatment method of biosolids may markedly influence their characteristics. The legislation that controls the levels of heavy metal contents in biosolids and the maximum concentrations in soils is still controversial. In the long-term, heavy metal behavior after the and of biosolid application is still unknown. In soils, heavy metals may be adsorbed via specific or non-specific adsorption reactions. Iron oxides and organic matter are the most important soil constituents retaining heavy metals. The pH, CEC and the presence of competing ions also affect heavy metal adsorption and speciation in soils. In solution, heavy metals can be present either as free-ions or complexed with organic and inorganic ligands. Generally, free-ions are more relevant in environmental pollution studies since they are readily bioavailable. Some computer models can estimate heavy metal activity in solution and their ionic speciation. Thermodynamic data (thermodynamic stability constant), total metal and ligand concentrations are used by the GEOCHEM-PC program. This program allows studying heavy metal behavior in solution and the effect of changes in the conditions, such as pH and ionic strength and the application of organic and inorganic ligands caused by soil fertilization.

Recent and present sedimentary fluxes of heavy metals and radionuclides in oligotrophic Lake Annecy, France

The present study focuses on two aspects of heavy metals and radionuclide fluxes to lake Annecy: a long term, secular evolution by analysing dated sediment cores, and a short term, seasonal evolution through the analysis of settling particles collected by sediment traps. Compared to background values prior to 1900, sediment cores reveal a two-fold (Cd, Cu, Zn) to a four-fold (Pb) increase in heavy metal concentration after the 40s, and a smaller decrease after the 70s except for Cu, which does not decrease. Sediment traps moored from April 1998 to November 2000 record strong variations of particles (range: 0.5-6.1 g/m 2 .d), organic matter (range 0.03-0.27 g/m 2 .d) and carbonate fluxes (range: 0.2-4.9 g/m 2 .d). The maximum fluxes are observed at the end of spring and summer, related to increased phytoplankton production. Mean annual heavy metal fluxes (0.014 μg/cm 2 .y for Cd, 1 μg/cm 2 .y for Pb and Cu and 2.8 μg/cm 2 .y for Zn) are lower than those recorded in the surface layers of the sediment cores. No relation has been observed between fluxes of heavy metal and of particles. Comparison of heavy metal fluxes in Lake Annecy with two other peri-alpine lakes show that this lake receive more Cu and Pb of anthropogenic origin, in spite of the sewage collector built around the lake.

Reactions of the Heavy Metal Cycle to Industrial Activities in the Deep Sea: An Ecological Assessment

AbstractThis article focuses on possible geochemical consequences of potential industrial activities in the deep sea, such as manganese nodule mining, for the heavy metal cycle of the deep sea and possible reactions of the benthic ecosystem. The metal fluxes induced by sediment resuspension are compared with fluvial, atmospheric, and hydrothermal metal fluxes into the ocean. The results of geochemical laboratory experiments and analyses of deep‐sea benthic organisms are discussed with respect to their ecological importance in case of a seabed disturbance.A limited short‐term increase of heavy metal concentrations in the benthic layer will probably cause only negligible harmful effects on the biota. An essential precondition is that the geochemical milieu remains largely unchanged; especially variations of the redox conditions would result in changes in metal speciation, bioavailability, and toxicity.

Accumulation and fate of selected heavy metals in a biological wastewater treatment system

The aim of this research was to study the accumulation and removal of heavy metals (Cd, Cu, Pb, Zn) by a biological wastewater treatment system. Heavy metal contents in the influent and effluent wastewater were compared. Also, the heavy metal contents in the sludge before and after anaerobic digestion were compared. The results showed: (1) more pronounced variations in the contents of Cu and Zn than that of Cd and Pb, which showed that at 0.02 for Cd and 0.05 mg/l for Pb, the reduction in their contents was insignificant; (2) that removal of heavy metals was directly proportional to their initial contents in the influent wastewater. Corresponding to the influent contents, in increasing order, the reduction in heavy metal contents was: Cd<Pb<Cu<Zn; and (3) that anaerobic stabilization of sludge caused an increase in heavy metal contents on dry weight basis. The order of increase in heavy metal contents in digested sludge (Zn<Pb<Cu<Cd) was opposite to that of their contents removal from influent wastewater.

Heavy metal concentrations in Squilla mantis (L.) (Crustacea, Stomatopoda) from the Gulf of Cádiz : Evaluation of the impact of the Aznalcollar mining spill

After the Aznalcóllar mining spill (25th April 1998), considerable social concern arose amongst the inhabitants of the SW Iberian Peninsula concerning the consumption of local seafood. Squilla mantis was collected in four regions of the Gulf of Cádiz with a dual objective: to analyze the heavy metal levels for human consumption and as part of biomonitoring program. Heavy metal concentrations (Fe, Mn, Zn, Cu, Cd and Pb) were analyzed in soft tissues and cuticle. The highest values were found in the soft tissues for zinc, copper and cadmium and in the cuticle for iron, manganese and lead. The mean copper concentration in the soft tissue, corresponding to the edible part, was 27.1 μg·g −1 wet weight. Approximately 80% of stations showed values higher than 20 μg·g −1 wet weight of copper, the Spanish legal limit for the concentration of this metal in the crustacean for human consumption. For Zn and Cu no significant differences were found between regions, probably related with the capacity for regulation of S. mantis. The highest values found for copper in the Gulf of Cádiz compared to other areas is likely to be related with contamination from terrestrial mining activities (copper and pyrites) in the region, dating back to the times of Tartessians and Romans, rather than the effects of mining spill which was shown not to create any significant increases in heavy metal concentrations of organisms of the Guadalquivir River or the adjacent coastal area.

Anthropogenic impact on sediment composition and geochemistry in vertical overbank profiles of river alluvium from Belgium and Luxembourg

The geochemical study of alluvial sediments allows to reconstruct pollution through time. Geochemical and sedimentological variations recorded in 40 vertical overbank sediment profiles from Belgium and Luxembourg can be classified in three dominant pattern types: • type 1 profiles with dominantly non-anthropogenically influenced geochemical distribution patterns. These profiles are devoid of anthropogenic particles such as charcoal, plastic, brick and slag fragments, with the exception, in some cases, of their uppermost parts. Background concentrations thus are displayed throughout the profile (subtype 1A). However, in this group, profiles displaying anomalous values caused by the presence of heavy minerals (subtype 1B) or by base metal mineralisations in the catchment (subtype 1C) also occur; • type 2 profiles displaying clear evidence of anthropogenic influences. Most of these profiles display a gradual increase in heavy metal content in their upper part, with values doubling or tripling (subtype 2A). However, other profiles display a dramatic increase in pollution-related elements caused by past or present-day heavy industrial activities in the catchment (subtype 2B). Here also the sedimentological patterns reflect the influence of the industrial activities; • type 3 profiles contain features related to pedogenetic translocations of mobile elements. Apart from classical pedogenetic features such as illuviation/eluviation, the mobility of As and Cd is of particular importance. From a sedimentological point of view, these profiles do not necessarily differ from type 1 or 2 profiles. It should be noted that in some profiles, pattern types can be superimposed. Type 2B profiles are of particular environmental concern, because the potential release of heavy metals may have consequences for agricultural activities or groundwater contamination in the catchment. Furthermore, reworking of polluted sediments temporarily stored in the alluvial plain can also have negative effects on the ecosystem.

Organ heavy-metal accumulation during parenteral nutrition is associated with pathologic abnormalities in rats

OBJECTIVES: Metabolic bone disease, hepatic abnormalities, splenic insufficiency, and nephropathy have been associated with long-term total parenteral nutrition (TPN). We determined the heavy-metal contamination in TPN solutions and investigated whether it was associated with organ deposition and pathologic organ damage. METHODS: Five representative TPN solutions (two adult standard solutions, one renal solution, and one standard pediatric solution to reflect clinical practice) and 28 TPN components were analyzed with inductively coupled plasma mass spectrometry. Twenty-six male Fisher 344 rats were assigned to two groups (chow/NaCl = 8 and TPN = 18). TPN or NaCl was infused at a rate of 50 mL/d. After 14 d, serum, femurs, spine, liver, kidneys, brain, spleen, and testes were analyzed for heavy-metal deposition by using inductively coupled plasma mass spectrometry. Tissues were fixed in formalin, sectioned, and stained with hematoxylin and eosin, periodic acid Schiff, and Masson’s trichrome stain. Kidneys were fixed in gluteraldehyde for ultrastructural examination with scanning electron microscopy. RESULTS: The predominant sources of contaminants in TPN were amino acids (Al, As, Cr, Ge, Pb, Sn), dextrose (As, Ba, Cr, Sn), Ca gluconate (Al), K 2PO4 (Al), lipid emulsion (As, Sn), and vitamins (As). Significant variations in the level of contamination depended on TPN formulation and brand of constituents. In the kidney, Pb, Cr, and Mn concentrations were greater than in controls, although there was no correlation with serum creatinine. Hepatic Cr and Pb concentrations were greater in TPN rats, although there was no correlation with serum aspartate aminotransferase or total bilirubin. Splenic Ba, Cr, Ge, Pb, Mn, and Sn concentrations were greater in TPN rats. Only serum Cr concentration was significantly correlated with splenic concentration ( r = 0.46, P = 0.04). Brain and serum Ba concentrations were significantly correlated ( r = 0.60, P = 0.007). No significant correlations were observed between any other metal in serum and that metal’s respective organ concentration. No increase in heavy-metal accumulation was seen in the femur, spine, or testis. There were no significant depositions of As, Cd, Hg, St, or V in any of the organs examined. Serum Al and Cr concentrations were significantly increased in TPN rats, although there was no correlation with tissue concentrations. No significant increases in heavy-metal concentrations in tissue or plasma were observed for any of the other metals measurable by inductively coupled plasma mass spectrometry. Histologically in the TPN group, 50% of the rats had mild to moderate hepatic steatosis and 33% to 50% developed renal morphologic abnormalties; brains and spleens remained histologically normal. CONCLUSIONS: We found significant heavy-metal contamination of TPN solutions, and this contamination can lead to organ deposition and subsequent histologic abnormalities.

Geochemistry of overbank and high-order stream sediments in Belgium and Luxembourg: a way to assess environmental pollution

A geochemical survey of Belgium and Luxembourg was carried out as part of an international research project entitled `Regional geochemical mapping of Western Europe towards the year 2000'. The aim of this research was to map regional background geochemical patterns based on pristine or at least pre-industrial overbank samples and to deduce regional information on the degree of environmental pollution of floodplain and present-day river sediments. Over the entire study area (about 33,000 km 2), 66 overbank sites have been sampled. Catchment areas range between 60 and 600 km 2. At each site an overbank profile has been dug out in the immediate vicinity of the river and described in detail. A first composite sample was taken 5–25 cm below the surface. This sample is supposed to represent deposition over the last centuries. Human interferences in this interval are often inferable based on changed sedimentary characteristics and the presence of anthropogenic particles such as charcoal, slags and brick fragments. A second composite sample was taken at depth, usually >1.5 m below the surface over an interval of about 20 cm. In most sites, the profile characteristics allowed to assume pre-industrial or even pristine conditions for this lower overbank sample. In some profiles this was confirmed by 14C-dating and/or by the absence of anthropogenic particles. Finally, a present-day stream sediment was sampled on the site to infer the actual pollution status. After drying at 80°C, disaggregation and sieving, the <125 μm fractions of the three sediment samples were analysed by XRF for major elements and several trace elements. Lower overbank samples generally show a direct link with the geological substrate and allow to assess natural background concentrations. Results from the mapping exercise as well as from the statistical analyses display a clear contrast between the northern part of Belgium where Cenozoic unconsolidated sandy and silty formations dominate which are especially vulnerable for erosion, and the southern part of Belgium and Luxembourg where Paleozoic and Mesozoic sandstones, carbonates, marls and shales are the prevalent lithologies. Here the shales are the most intensively eroded lithologies. This is especially reflected in the element patterns of Al 2O 3, MgO, K 2O, Ga, Ni, Rb, Sc and V which negatively correlate with SiO 2. Despite the human related pollution, the geological contrast between north and south Belgium is still recognisable in the geochemical pattern of the upper overbank and present-day stream sediment samples for the above-mentioned elements. Furthermore there is a clear increase in heavy metal contents (Zn, Cd, Pb, Cu), As and in certain locations in Ba from the lower to the upper overbank sediment, as well as to the present-day stream sediment. The relative increase in element content allows to assess the degree of pollution and helps to define those drainage areas where more detailed research is needed.

Metal concentrations, growth, and yield of potato produced from In Vitro plantlets or microtubers and grown in municipal solid‐waste‐amended substrates

In vitro plantlets or microtubers (in vitro produced tubers) of ‘Spunta’ potato (Solanum tuberosum L.) were planted in a 3 soil: 2 peat moss: 1 sand substrate (by volume) amended with municipal solid waste (MS W) compost at 0, 10, 20, or 30 g 4‐1 L pot. Three months later, plant growth and tuber yield were evaluated and concentrations of shoot and tuber tin (Sn), arsenic (As), copper (Cu), zinc (Zn), nickel (Ni), lead (Pb), manganese (Mn), cadmium (Cd), and iron (Fe) were determined. Amending with MSW resulted in significant increases in concentrations of all tested metals in the substrate. Number of proliferated shoots of plants started from rooted plantlets was greatest at 10 g pot‐1 MSW, whereas shoot weight of plants started from microtubers was greatest at 10 and 20 g pot‐1 MSW. Tuber yield of plants started from rooted plantlets or microtubers was greatest at 10 or 30 g pot‐1 MSW, respectively. In all instances, amending with MSW at 30 g pot‐1 resulted in significant increases in concentrations of all tested metals in shoots and tubers. Concentrations of shoot Ni and tuber Zn and Fe for plants started from rooted plantlets and concentrations of shoot Fe and tuber As, Cu and Pb for plants started from microtubers increased consistently with increasing MSW percentage of the substrate. Plants started from rooted plantlets produced shoots with sufficient Zn, Mn, and Ni concentrations regardless of the substrate but with toxic Cu content at 30 g pot‐1 MSW. Plants started from microtubers produced shoots with sufficient Mn and Ni concentrations regardless of the substrate but with low Zn and deficient Cu in unamended substrates. All plants had shoot Fe content higher than the sufficiency range. Although there were significant differences in concentrations of some nutrients among MSW treatments, no symptoms of nutrient toxicity or deficiency were observed. In all instances, tested elements did not accumulate in tubers to levels hazardous to human health. Concentrations of Cd, the most hazardous element, in potato tubers was not high enough to pose a threat to human. Our results indicate that there is a potential use of MSW in satisfying the needs of potato growth with negligible increases in heavy metal concentrations in tubers.

Soil heavy metal concentrations, microbial biomass and enzyme activities in a contaminated grassland ecosystem

Soil enzyme activities and microbial biomass were measured in a grassland ecosystem with a wide range of heavy metal concentrations ranging from 7.2 to 48.1 mmol kg −1 (As, Cd, Cr, Cu, Ni, Pb and Zn) in portions of the U.S. Army's Aberdeen Proving Ground, Maryland, U.S.A. Total and fluorescein diacetate active (FDA) fungal biomass, FDA-active bacterial biomass, substrate-induced respiration (SIR), the activity of N-acetylglucosaminidase, β-glucosidase, endocellulase, and acid and alkaline phosphatases were also measured. Most measures of microbial biomass were lower in polluted soils. Significant reductions (10- to 50-fold) in the activities of all enzymes closely paralleled the increase in heavy metal concentrations. These results demonstrate that heavy metal contamination of soil has adversely affected the abundance and activity of microorganisms involved in organic matter decomposition and nutrient cycling in this site.

Determination of heavy metal profiles in dated sediment cores from Sai Kung Bay, Hong Kong

Eight sediment cores from Sai Kung Bay area were sampled and analysed for Cd, Cr, Cu, Fe, Ni, Pb, Zn, Ca, and organic matters. The cores were dated from an overall consideration of the 210Pb and maximum 137Cs activities, and historical records of previous land use, past heavy typhoon and rainstorm activities. Contamination by Cd, Cr, Cu, Pb, and Zn was found at coastal cores with a mean Enrichment Factor of 5.0, 1.0, 1.7, 1.4, and 1.3, respectively. The overall mass sedimentation rates were found varying from 0.111 – 0.454 g/cm 2·y and recent average anthropogenic fluxes in μg/cm 2·y for coastal/offshore cores were estimated as 0.52 0.028 (Cd) , 2.0 0.26 (Cr) , 7.6 0.92 (Zn) , 2.8 1.4 (Cu) , and 2.9 2.3 (Pb) , respectively. The major problem is Cd and Cr, in particular at coastal cores. The heavy metal input to the Sai Kung Bay areas was found to change considerably over the past 50 y starting from a low background level, via an intermediate period with cottage industries discharging Cr and Cd, to recent years with rapid urbanization and heavy boating activities emitting Cu, Pb, and Zn in addition to Cr and Cd. A rapid increase in heavy metal contents and a significant decrease in biological activities were found at the recently deposited coastal sediments, indicating a problem requiring urgent remedial action to stop further deterioration of the coastal environment of the beautiful resort area at Sai Kung Bay.

The induction of stress proteins (hsp) in Oniscus asellus (Isopoda) as a molecular marker of multiple heavy metal exposure: I. Principles and toxicological assessment

The induction of stress-70 (hsp70) and stress-60 (hsp60, chaperonin 60) in the terrestrial woodlouse, Oniscus asellus, after exposure to various heavy metals and heavy metal combinations was investigated by means of standard Western-blot using monoclonal antibodies. The expression of stress-70 was found to react much more sensitively to metal contamination than that of stress-60. The general course of the stress-70 response to increasing metal concentration was found to be similar for all treatments. Based on the obtained results, this course could be divided into three zones: in the first zone, the expression of stress-70 proteins was only marginally increased by comparatively low metal concentrations; in the second zone, strong induction of stress-70 occurred and the ability of the heat shock system to react to increased metal concentrations reached its climax; and in the third, non-compensation zone, a further increase in heavy metal concentration resulted in a decline of stress-70 levels, which can be interpreted as a result of pathological tissue damage. Combinations of metals were found to increase the stress- 70 level more intensely than related concentrations of singularly applied metals. Based on these studies, a ranking scheme of increasing toxicological impact of a variety of heavy metal combinations was composed

A comparison of heavy metal deposition in selected Eastern European countries using the moss monitoring method, with special emphasis on the ‘Black Triangle’

The paper describes the use of moss analyses to compare heavy-metal pollution in Germany, Poland, the Czech Republic and the Slovak Republic. Special emphasis is placed on the regions where three countries meet within the area covered by the survey. In the countries participating, samples of Pleurozium schreberi, Scleropodium purum, Hypnum cupressiforme and Hylocomium splendens, Polytrichum formosum and Dicranum scoparium were collected at a total of 831 sampling points and analyzed for the elements Cd, Cr, Cu, Fe, Ni, Pb and Zn. The results were then presented in the form of coloured contour maps using the geographic information system (GIS) ARC-Info. The values found for heavy metals document the level of technical development in the countries concerned, which is generally characterized by a low standard in respect of emission-reducing systems. Moreover, the heavy-metal concentrations reflect the sources of emissions characteristic of the areas in which they occur. Above all, these are the primary use of coal (both hard coal and lignite) as an energy source, the chemical industry and ferrous- and non-ferrous metal working, which produce considerable emissions of particulate and fly ash, and also the use of leaded petrol. In most cases the moss method made it possible to identify the areas affected by the various industrial locations. The results show an increase in heavy-metal concentrations and higher average levels in the eastern parts of the countries compared. The paper also discusses the possibility of including the ‘three-country triangle’ further east in studies of Eastern Europe on the grounds that it constitutes another ‘Black Triangle’ in addition to the already familiar one.

The Effect of Heavy Metals on the Isoenzymes of Amylase and Peroxidase During Germination of Lentil (Lens esculenta L.) Seeds

Lentil seeds were treated with 10-100 mg/l Cu, Cd, Hg and 50-200 mg/l Zn. The seed germination rate was gradually decreased with respect to the increase in heavy metal concentrations. New isoperoxidases which were not in the control were found in cotyledons and plumule-radicles due to the effects of the heavy metals. The Isoperoxidase number in the plumule-radicle was increased in Cu and Cd, but in the cotyledon in Zn and Hg, compared with other metal treatments. It was found that the number of amylase isoenzymes was also increased by the heavy metals in the cotyledons and the plumule-radicle.

Nutrient Concentrations, Growth, and Yield of Tomato and Squash in Municipal Solid-waste-amended Soil

The effects of municipal solid waste (MSW) materials on growth, yield, and mineral element concentrations in tomato (Lycopersicon esculentum Mill.) (1991 and 1992) and squash (Cucurbita maxima Duch. Ex Lam.) (1992 and 1993) were evaluated. Agrisoil compost (composted trash), Eweson compost (co-composted trash and sewage sludge), or Daorganite sludge (chemically and heat-treated sewage sludge) were incorporated into calcareous limestone soil of southern Florida. The control had no MSW material added to the soil. The effect of MSW on crop growth, yield, and mineral element concentrations varied considerably between years for tomato and squash. In 1991, tomato plants grown in soil amended with Eweson or Daorganite had a greater canopy volume than plants in the control treatment. Tomato plants grown in Daorganite had greater total fruit weight (1991) than plants in Agrisoil and more marketable fruit (1992) than control plants. In both years, tomato plants in Agrisoil had higher root Zn concentrations than plants in the other treatments. In 1992, tomato plants in Eweson had lower root Mn concentrations than plants in the other treatments, whereas Mg concentrations in the roots were higher in the Daorganite treatment than in Eweson. Tomato plants in Agrisoil had higher Pb concentrations in the roots than plants in all other treatments. In 1991, leaves of tomato plants in Agrisoil had lower Ca concentrations than leaves of plants in the control treatment. In 1992, leaf Zn concentrations were greater for tomato and squash in Agrisoil than in the control or Daorganite. In 1992, canopy volume and yield of squash were greater for plants in Daorganite than for plants in the control and other MSW treatments. Although canopy volume and total squash fruit weight did not differ among treatments in 1993, plant height was greater for squash plants in the MSW treatments than for those in the control. In 1993, leaf Mg concentrations were greater for squash grown in Daorganite than for plants in the control or Agrisoil. In 1993, fruit Cd concentration was higher for plants with Eweson than for plants in the control or Agrisoil. However, the fruit Cd concentration in squash grown in Eweson compost (1.0 mg/kg dry weight) was far below a hazardous level for human consumption. Our results indicate that amending calcareous soils with MSW materials can increase growth and yield of tomato and squash with negligible increases in heavy metal concentrations in fruit.

A filtration system for the size separation of freshwater samples

A system to filter freshwater samples in situ in the field is described, using polycarbonate membranes. It was developed and tested with respect to the conventional filtration method, both for its efficiency and for the effect on heavy metal concentrations in the filtrates. A marked reduction of filtration time is obtained and the possibility to carry out one stage filtrations that otherwise would need the filter to be changed. PIXE analysis generally shows an increase of heavy metal concentrations in the filtrates; this is accompanied by a smaller data spread in sub-samples obtained by repeated filtrations, indicating a higher capability in maintaining the nominal membrane pore size during operations, which produces a better dimensional selection. The system is suitable to perform immediate filtration of numerous fresh water samples to be treated in heavy metal pollution assessments.

Heavy metal pollution in sediment from the Seto Inland Sea, Japan

To discuss the geochemical and environmental behaviors of heavy metals in the Seto Inland Sea which is the largest semi-closed coastal sea in Japan, (1) distributions of heavy metals concerning pollution were examined and (2) mass balances of Zn and Cu were studied by applying a simple box model. Increase in heavy metal contents of core sediments already started in the late 1800s and is considered to be due to human activities. Recently, the pollution of sediment in Osaka Bay which is most contaminated sea area in the Sea, seems to have tended to decrease. In 1980, total sedimentary loads of Cu and Zn over the whole area of the Sea were estimated to be 630 and 3,500 tons/yr, respectively. Further, the sedimentary loads without and with human activities were estimated separately to be, respectively, 320 and 310 tons/yr for Cu and 1,800 and 1,700 tons/yr for Zn. Total inputs of Cu and Zn into the Sea were estimated to be 870 and 4,250 tons/yr and about one half of this being the results of human activities. 70% of the Cu input and 80% of the Zn input are accumulated into the sediments.

Accumulation of Heavy Metals in Sewage Sludge‐Treated Soils

AbstractThe accumulation of Cd, Cr, Cu, Ni, Pb, and Zn in sewage sludge‐treated soils was studied after 6 y of continued annual sludge application at a cropland disposal site. Soil samples were taken at 15‐cm depth increments from Greenfield sandy loam (coarse‐loamy, mixed, thermic, Typic Haploxeralf) and Domino loam (fine‐loamy, mixed, thermic Xerollic Calciothid) that received 0 (control), 22.5, 45, and 90 Mg ha−1 y−1 of composted sludges or 0 (control), 3.75, 7.5, and 15 cm y−1 of liquid sudges since 1976. Samples were also obtained from areas where liquid sludge treatment was terminated after 1978. Heavy metals in soils were extracted by 4M HNO3 and analyzed by atomic absorption spectroscopy. Over 90% of the deposited heavy metals were found in the 0‐ to 15‐cm soil depth where sludges were incorporated; no statistically significant increase in heavy metal contents of the soil was detected below the surface 30 cm of the soil profile. Although crop absorption of heavy metals has increased with the sludge application rates, the total uptake amounted to &lt; 1% of the metal introduced through sludge application. Through a material balance calculation, it was found that recovered heavy metals were low relative to amounts added due to incomplete extraction of metals from soils by 4M HNO3 and changes in soil bulk density.

Sewage sludge effects on soil: Heavy metal accumulation and movement

Abstract Treated municipal sewage sludge at 0, 11.2, 33.6, and 67.2 metric tons/ha was applied each year for two consecutive years and incorporated into a Byler loam soil (Typic Fragiudalf) having an initial pH of 5.6. Sorghum (Sorghum vulgare L.) was grown in replicated plots (6.1m × 4.6m). Soil samples were taken at 0 to 20 cm and 20 to 40 cm depth at the end of each year and analyzed for DTPA‐extractable Cu, Zn, Cd, and Ni. Surface soil exhibited significant increases in heavy metal concentrations in the first year at the 67.2 metric tons/ha rates. Heavy metal concentrations increased with continued sludge application. However, this increase was not in proportion to the amount of sludge applied suggesting some immobilization of metals with time. After two years, downward movement and significant increases in Cu, Zn, and Ni levels were noted at the 20 to 40 cm depth at the higher rates. Heavy metal levels in the surface soil did not appear to be phytotoxic as judged from sorghum grain and dry matter yie...

Protective effects of certain environmental factors on the toxicity of zinc, mercury, and methylmercury to Chlorella vulgaris

The specific growth rate and final yield of Chlorella vulgaris treated with zinc, mercury, and methylmercury declined with increase in metal concentration. Methylmercury was most toxic and at 1 × 10 −3 mg/liter concentration it reduced survival by about 50%. Approximately 50% mortality occurred at 25 and 0.4 mg/liter concentration of zinc and mercury, respectively. The total chlorophyll content decreased and the carotenoids/chlorophyll ratio increased with increase in heavy metal concentration. Of the various factors investigated, pH, phosphate, and calcium produced a highly significant ( P < 0.001) effect on metal toxicities, and magnesium produced a less significant effect ( P < 0.1). The present study suggests that alkaline and hard eutrophic waters might help protect freshwater organisms against heavy metal toxicity.