Phosphate fertilizers influence leaching of lead and arsenic in a soil contaminated with lead arsenate

Use of high rates of monoammonium phosphate (MAP) or monocalcium phosphate (MCP) fertilizers has the potential to alter Pb and As mobility in soils contaminated with lead arsenate pesticide residues. A laboratory column experiment was conducted to determine the effects of P amendment source (MAP, MCP), P rate (0, 0.31, 0.62 g column^–1), and amount of leaching (1, 2 pore volume displacements, PVD) on Pb, As, P, pH, and salinity distribution within and leaching from a Burch loam soil containing 1800 mg Pb kg^–1 and 400 mg As kg^–1 Addition of either MAP or MCP significantly increased the amount of As leached from the soil. The P amendments reduced the amount of Pb in the first PVD but enhanced Pb in the second PVD so that the cumulative amount of Pb leached was independent of treatment. Phosphorus source, P rate, and quantity of leaching water influenced the total amount of leachate As, and soil and leachate P, pH, and salinity. Use of phosphate fertilizers on lead arsenate-contaminated soils may temporarily enhance potential for As phytoavailability or As contamination of groundwater.Dept. of Agronomy and Soils Paper No. 9001-11. Project No. 0747, College of Agric. and Home Economics Res. Ctr., Washington State Univ., Pullman, WA 99164.     

利用土壤改良剂固定污染土壤中铅、镉的研究进展

Since the inception of industrial revolution, metal refining plants using pyrometallurgical processes have generated the prodigious emissions of lead (Pb) and cadmium (Cd). As the core target of such pollutants, a large number of soils are nowadays contaminated over widespread areas, posing a great threat to public health worldwide. Unlike organic pollutants, Pb and Cd do not undergo chemical or microbial breakdown and stay likely in site for longer duration after their release. Immobilization is an in-situ remediation technique that uses cost-effective soil amendments to reduce Pb and Cd availability in the contaminated soils. The Pb and Cd contamination in the soil environment is reviewed with focus on source enrichment, speciation and associated health risks, and immobilization options using various soil amendments. Commonly applied and emerging cost-effective soil amendments for Pb and Cd immobilization include phosphate compounds, liming, animal manure, biosolids, metal oxides, and biochar. These immobilizing agents could reduce the transfer of metal pollutants or residues to food web (plant uptake and leaching to subsurface water) and their long-term sustainability in heavy metal fixation needs further assessment.     

Uptake of SigmaDDT, arsenic, cadmium, copper, and lead by lettuce and radish grown in contaminated horticultural soils

Horticultural soils can contain elevated concentrations of selected trace elements and organochlorine pesticides as a result of long-term use of agrichemicals and soil amendments. A glasshouse study was undertaken to assess the uptake of weathered SigmaDDT {sum of the p, p'- and o, p-isomers of DDT [1,1,1-trichloro-2,2- bis( p-chlorophenyl)ethane], DDE [1,1-dichloro-2,2- bis( p-chlorophenyl)ethylene] and DDD[1,1-dichloro-2,2- bis( p-chlorophenyl)ethane]}, arsenic (As), cadmium (Cd), copper (Cu), and lead (Pb) residues by lettuce ( Lactuca sativa) and radish ( Raphanus sativus) from field-aged New Zealand horticultural soils. Concentrations of SigmaDDT, DDT, DDE, Cd, Cu, and Pb in lettuce increased with increasing soil concentrations. In radish, similar relationships were observed for SigmaDDT, DDE, and Cu. The bioaccumulation factors were less than 1 with the exception of Cd and decreased with increasing soil concentrations. Lettuce Cd concentrations for plants grown on four out of 10 assayed soils were equivalent to or exceeded the New Zealand food standard for leafy vegetables of 0.1 mg kg (-1) fresh weight. Concentrations of As, Pb, and SigmaDDT did not exceed available food standards. Overall, these results demonstrate that aged residues of SigmaDDT, As, Cd, Cu, and Pb in horticultural soils have remained phytoavailable. To be protective of human health, site-specific risk assessments and soil guideline derivations for residential settings with vegetable gardens need to consider the produce consumption pathway.     

Vertical distribution of lead and arsenic in soils contaminated with lead arsenate pesticide residues

Many deciduous fruit tree orchard sites throughout the world are contaminated with lead (Pb) and arsenic (As) from past use of lead arsenate insecticides. The vertical distribution of Pb and As was examined in six contaminated orchard soils in the State of Washington, USA. Most of the Pb and As was restricted to the upper 40 cm of soil, with Pb concentration maxima ranging from 2.15 to 10.69 mmol/kg, and As concentration maxima ranging from 0.77 to 4.85 mmol/kg. In all cases, there were lower Pb and As concentrations at the soil surface than deeper in the profile. Arsenic was depleted relative to Pb in the topsoils and was enriched relative to Pb in the subsoils, suggesting that there has been preferential movement of As. Absolute soil enrichment with Pb occurred to depths between 15 and 50 cm. Absolute soil enrichment with As occurred to depths between 45 and > 120 cm. At 120 cm, Pb concentrations were < 0.05 mmol/kg, and As concentrations ranged from 0.07 to 0.63 mmol/kg. The deeper movement of Pb and As in the study soils relative to that reported for lead arsenate-contaminated soils elsewhere is attributed to high loading rates of lead arsenate, coarse soil texture, low organic matter content, and use of irrigation. The results indicate that Pb and As concentrations in lead arsenate-contaminated soils are high enough to be of potential environmental concern. The amount of As redistribution appears to be substantial enough to preclude some methods of remediation and to create potential risk of contamination of underlying shallow groundwater.     

Speciation of cadmium,copper, lead,and zinc in contaminated soils

Abstract

To investigate the activity of free cadmium (Cd²⁺), copper (Cu²⁺), lead (Pb²⁺), and zinc (Zn²⁺) ions and analyze their dependence on pH and other soil properties, ten contaminated soils were sampled and analyzed for total contents of Cd, Cu, Pb, and Zn (Cd_T, Cu_T, Pb_T, and Zn_T, respectively), 0.43 MHNO₃‐extractable Cd, Cu, Pb, and Zn (Cd_N, Cu_N, Pb_N, and Zn_N, respectively), pH, dissolved organic matter (DOC), cation exchange capacity (CEC), ammonium oxalate extractable aluminum (Al) and iron (Fe), and dissolved calcium [Ca²⁺]. The activity of free Pb²⁺, Cd²⁺, Cu²⁺, and Zn²⁺ ions in soil solutions was determined using Donnan equilibrium/graphite furnace atomic absorption (DE/GFAA). The solubility of Cd in soils varied from 0.16 to 0.94 μg L^‐1, Cu from 3.43 to 7.42 μg L^‐1, Pb from 1.23 to 5.8 μg L^‐1, and Zn from 24.5 to 34.3 μg L^‐. In saturation soil extracts, the activity of free Cd²⁺ ions constituted 42 to 82% of the dissolved fraction, for Cu²⁺the range was 0.1 to 7.8%, for Pb²⁺ 0.1 to 5.1% and for Zn²⁺2 to 72%. The principal species of Cd, Cu, Pb, and Zn in the soil solution is free metal ions and hydrolyzed ions. Soil pH displayed a pronounced effect on the activity of free Cd²⁺, Cu^2t, Pb²⁺, and Zn²⁺ ions.     

添加物对镉、锌、铅污染土壤上小白菜的生长和养分吸收的影响

A pot experiment was carried out to study the effects of two amendments, lime and calcium magnesium phosphate, on the growth and Cd,Pd,Zn,Cu,Mn,Fe,N,P and K uptake of pakchoi (Brassica chinensis) in a Cd,Pb and Zn polluted acid soil in the southern part of China. The growth of pakchoi was apparently improved by lime and calcium magnesium phosphate application, the uptake of Cd,Pb,Cu and Zn by pakchoi was significantly depressed and the symptom caused by heavy metals pollution was eliminated. Meanwhile, the absorption of N,K and Mn was also inhibited by these amendments. Soil pH was the main factor controlling the uptake of the heavy metals by pakchoi. This suggests that lime and calcium magnesium phosphate could be used as effective amendments for eliminating the toxicity of heavy metals to the vegetable and inhibiting their absorption by the crop.     

螯合剂对大叶井口边草Pb、Cd、As吸收性影响研究

用室内土培试验方法,研究在采自田间的Pb、Cd、As、Zn和Cu复合污染土壤上种植大叶井口边草条件下,外源分别添加0、1.5、3、6、12 mmol/kg乙二胺二琥珀酸（EDDS）、氨三乙酸（NTA）和乙二胺四乙酸（EDTA）对大叶井口边草吸收Pb、Cd和As的影响。结果表明,3种螯合剂处理对大叶井口边草生物量没有显著影响,说明大叶井口边草对3种螯合剂耐性较强;6、12 mmol/kg EDTA处理能极显著提高土壤Pb有效态浓度,进而促进大叶井口边草对Pb的吸收。大叶井口边草地上部Pb吸收量最高达（47.4 ± 1.7）mg/kg,是对照的3.66倍。6、12 mmol/kg EDTA处理能极显著地提高土壤中Cd的有效性,但未促进大叶井口边草地上部对Cd吸收。6 mmol/kg EDDS和3 mmol/kg NTA显著提高了土壤中As有效态浓度,进而提高大叶井口边草地上部对As的吸收,大叶井口边草地上部吸收As最高达（276 ± 10） mg/kg。6 mmol/kg EDTA和6 mmol/kg EDDS处理下大叶井口边草提取的Pb、As量最大,分别为（317 ± 53） μg/盆和（873 ± 41）μg/盆,说明6 mmol/kg EDDS处理下大叶井口边草对复合污染土壤中As的修复具有较大的潜力。     

Redistribution of cadmium,copper, lead,nickel, and zinc among soil fractions in a contaminated calcareous soil after application of nitrogen fertilizers

This study was conducted to evaluate the redistribution of the heavy metals Cd, Cu, Pb, Ni, and Zn among different soil fractions by N fertilizers. In a lab experiment, soil columns were leached with distilled water, KNO₃, NaNO₃, NH₄NO₃, or Ca(NO₃)₂ · 4H₂O. After leaching, soil samples were sequentially extracted for exchangeable (EXCH), carbonate (CARB), organic‐matter (OM), Mn oxide (MNO), Fe oxide (FEO), and residual (RES) fractions. Distilled water significantly increased the concentrations of Cd and Ni in EXCH fraction, while concentration of Cu and Zn did not change significantly. Application of KNO₃, NaNO₃, NH₄NO₃, or Ca(NO₃)₂ · 4H₂O significantly increased the concentrations of Cd and Zn in EXCH fraction, while concentration of Pb and Ni was decreased. Application of all fertilizers caused an increase of Cu in the OM fraction. Moreover, leaching with these solutions significantly increased Cd [except in Ca(NO₃)₂ · 4H₂O], Cu, and Zn concentrations in the CARB fraction, while Pb and Ni concentrations were decreased. With application of all leaching solutions, Zn in the EXCH, CARB, FEO, and MNO fractions was significantly increased, while Zn in the OM fraction did not change. The mobility index indicated that Ca(NO₃)₂ · 4H₂O increased the mobility of Cd, Cu, and Zn in the soil, whereas NaNO₃ decreased the mobility of Pb and Ni in the soil. The mobility index of Pb decreased by all leaching solutions. Thus, these results suggest that applying N fertilizers may change heavy‐metal fractions in contaminated calcareous soil and possibly enhance metal mobility and that N‐fertilization management therefore may need modification.     

Modeling of arsenic immobilization by zero valent iron

Ground waters in geothermal regions contain arsenic concentrations that exceed the recommended drinking water standards. In addition, when these regions have agricultural activities, the waters also contain high levels of nitrates and phosphates. These contaminants can be removed from the water with the use of filters containing zero valent iron (ZVI). The objective of this study was to model the removal of arsenate (As(V)) and arsenite (As(III)) by ZVI and to model the effect of competing ions (phosphate and nitrate) on arsenate removal. Arsenic immobilization by ZVI columns was simulated by the HM-1D chemical transport and speciation model and an one-dimensional analytical solution model. Laboratory column studies were conducted in order to obtain representative experimental data for simulation with both models. Arsenic speciation and the presence of competing ions greatly affect arsenic removal by ZVI. Most arsenic is precipitated/co-precipitated on ZVI and on the corrosion products formed on ZVI. The simulations suggested that As(V) process parameters are higher than the As(III) parameters and that they are affected by the presence of nitrates and phosphates in the system. Such models can be used to design treatment units by incorporating the impact of nitrates and phosphates in the removal of arsenic by ZVI as well as the impact of temperature on the process.     

Accumulation of lead and arsenic by peanut grown on lead and arsenic contaminated soils amended with broiler litter ash or superphosphate

Accumulation of lead (Pb) and arsenic (As) in peanut grown on Pb/As-contaminated soils amended with two sources of phosphorus (P) was investigated. An urban soil and an orchard soil with Pb concentrations of 1120 and 272, and As concentrations of 6.9 and 90 mg kg^-1, respectively, were amended with three rates (0, 56, and 112 kg ha^-1) of P supplied as broiler litter ash or superphosphate and planted with peanuts. At harvest, peanut kernel As concentration was 2.9 mg kg^-1 on the orchard soil and 0.003 mg kg^-1 on the urban soil. Kernel As was not significantly affected by P source and was not significantly different between the normal and high P rates. Kernel Pb concentration was below the instrument detection limit in all cases. Land with history of arsenic or lead-arsenate application should be tested for As before used for peanut production.     

Effect of soil application of cadmium contaminated lime on soil cadmium distribution and cadmium concentration in strawberry leaves and fruit

Heavy metal environmental pollution which occurs as a result of lime contaminated with cadmium (Cd) poses a potential health hazard. This investigation was undertaken to study uptake of Cd by strawberry plants grown in soil amended with three different sources and two different rates of industry waste lime containing 3.4, 14.3, and 60.0 mg Cd/kg, respectively. The effects of Cd applied to the soil were investigated, including its distribution in the soil and effect on Cd concentration in strawberry cv. Senga Sengana (Fragaria anassa) leaves and fruit in response to soil organic matter content and lime rates. Cadmium accumulated mainly in the plough layer, increasing from 0.170 mg Cd/kg (background level) to a maximum of 1.2 mg Cd/kg. Fruit had very high, hazardous Cd concentrations regardless of its content in the soil. This indicates that Cd was easily taken up by strawberry plants and accumulated in upper plant parts, including the fruit. Soil Cd content had no effect on concentration of this element in strawberry fruit. However, plant Cd uptake and fruit concentration was increased in acid soils even when soil Cd concentration was low.     

Heavy metals immobilization in contaminated soil by grape-pruning-residue biochar

To investigate the influence of grape-pruning-residue (GPR) biochar on cadmium (Cd), lead (Pb), copper (Cu) and zinc (Zn) immobilization in a contaminated soil, a laboratory study was conducted with different rates of GPR biochar (0, 2, 5 and 10% w/w) at 25°C. After 1, 2, 4, and 8 weeks of incubation, the Tessier sequential extraction procedure was performed and metal mobility factor (MF) and metal stability index (I_R) were calculated. The exchangeable (EX) and carbonate (CAR) fractions of the metals decreased significantly (p ≤ 0.05) with the biochar addition. The EX metal fractions decreased by 23 to 72%, and the CAR fractions decreased by 51 to 67% in the 10% biochar treatment after 8-week incubation. The MF values of Cd, Pb, Cu and Zn decreased by 47, 62, 70 and 49%, respectively, with addition %10 of the biochar. Biochar addition favored the metal redistribution into more stable fractions and resulted in an increase in I_R values. The results demonstrated that the GPR biochar, especially at high application rate (10%), can effectively immobilize the heavy metals, thereby reducing their mobility in contaminated soils.     

含铁介质用于修复砷污染土壤研究综述

原位固化/稳定化技术被认为是当前土壤砷污染修复中相对经济、高效的技术之一,含铁介质是土壤固砷的一类上佳材料。从含铁材料修复砷污染土壤的研究现状出发,阐述其固砷机理,主要包括吸附、络合作用以及沉淀/共沉淀作用。介绍了5种常用的固砷效果评价方法,分别为化学形态连续提取法、毒性特征浸滤法、植物指示法、体外消化模拟法以及现代物理学方法。阐述了土壤环境条件,如酸碱条件、氧化还原条件以及土壤中共存离子和有机质的变化对固砷效果的影响。总结了目前含铁材料用于修复砷污染土壤的不足之处,并指出了今后的研究重点。     

稻壳和稻壳生物炭对镉污染土壤肥力及镉有效性的影响

在镉(Cd)污染土壤中添加等碳量的稻壳及稻壳生物炭,研究不同材料对Cd污染土壤理化性质、肥力、酶活性及重金属Cd有效态含量的影响。共设置4个处理组,未被Cd污染土壤(CK)、Cd污染土壤(CD)、添加2%生物炭的Cd污染土壤(BO)、添加等碳量的稻壳Cd污染土壤(DK)。试验结果表明,BO和DK组的土壤总有机碳含量较CD组分别提高10.05%和5.02%,DK组的可溶性有机碳含量在第60 d,比CD组高出43.90%,BO组培养第90 d时,比CD组高13.00%;BO组的碱解氮含量对比CD显著降低,DK组的碱解氮含量对比CD组显著升高。不同处理组对酶活性有不同影响,第45 d时,BO和DK组的脲酶活性较CD组显著提高,分别提高10.14%和8.61%;施加稻壳和稻壳生物炭均能显著提高土壤中的蔗糖酶活性,但BO组显著低于DK组。不同处理对土壤理化性质有不同的影响,DK和BO组均显著提升土壤的孔隙度、初始孔隙比和土壤中砂粒、黏粒的比例;土壤重金属有效态试验结果表明,DK组中Cd污染土壤中的酸可提取态Cd的含量显著降低。对比施入稻壳生物炭,施加稻壳能够短期提升土壤肥力;生物炭和稻壳均能提升土壤的孔隙度和比重,使土壤中的黏粒占比上升;稻壳生物炭及稻壳均能缓解Cd对酶活性的抑制作用;相比生物炭而言,稻壳更能显著降低土壤中酸提取态的Cd含量。     

Flooding-enhanced immobilization effect of sepiolite on cadmium in paddy soil

Purpose  

Little is known of the effect of sepiolite on the transformation of Cd in anthropogenically contaminated paddy soil under different moisture conditions; therefore, we studied the effects of sepiolite and flooding on the extractability and fractionation of Cd in paddy soils.     

Daily intake of arsenic, cadmium, mercury, and lead by consumption of edible marine species

The daily intake of arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) through the consumption of 14 edible marine species by the general population of Catalonia, Spain, was estimated. Health risks derived from this intake were also assessed. In March-April 2005, samples of sardine, tuna, anchovy, mackerel, swordfish, salmon, hake, red mullet, sole, cuttlefish, squid, clam, mussel, and shrimp were randomly acquired in six cities of Catalonia. Concentrations of As, Cd, Hg, and Pb were determined by ICP-MS. On the basis of recent fish and seafood consumption data, the daily intake of these elements was calculated for eight age/sex groups of the population. The highest As concentrations were found in red mullet, 16.6 microg/g of fresh weight, whereas clam and mussel (0.14 and 0.13 microg/g of fresh weight, respectively) were the species with the highest Cd levels. In turn, swordfish (1.93 microg/g of fresh weight) and mussel and salmon (0.15 and 0.10 microg/g of fresh weight) showed the highest concentrations of Hg and Pb, respectively. The highest metal intake through fish and seafood consumption corresponded to As (217.7 microg/day), Cd (1.34 microg/day), and Pb (2.48 microg/day) for male seniors, whereas that of Hg was observed in male adults (9.89 microg/day). The daily intake through fish and seafood consumption of these elements was compared with the provisional tolerable weekly intakes (PTWI). The intakes of As, Cd, Pb, and total Hg by the population of Catalonia were below the respective PTWI values. However, the estimated intake of methylmercury for boys, 1.96 microg/kg/week, was over the PTWI.     

Flame absorption spectroscopic determination of cadmium, copper, iron, lead, and zinc in mussels

A rapid method is proposed for determination of Cd, Cu, Fe, Pb, and Zn in mussel samples. The elements are extracted with concentrated nitric acid in borosilicate glass tubes at 90 degrees C for 1 h, and determined by flame atomic absorption spectroscopy. Detection limits for a 300 mg sample corresponded to 0.3 microgram Cd/g, 0.7 microgram Cu/g, 33 microgram Fe/g, 0.7 microgram Pb/g, and 6 micrograms Zn/g. The coefficient of variation for 20 independent analyses was 7% for Cd, 7% for Cu, 6% for Fe, 14% for Pb, and 8% for Zn. Recoveries were 107 +/- 3% for Cd, 90 +/- 3% for Cu, 94 +/- 1% for Fe, 90 +/- 5% for Pb, and 96 +/- 3% for Zn. The accuracy of the method was determined by analyzing NBS Oyster Tissues.     

Simultaneous differential pulse polarographic determination of cadmium, lead, and copper in milk and dairy products

The contents of potentially toxic elements lead and cadmium and the essential element copper in various milk and dairy products consumed in Turkey were determined by differential pulse polarography (DPP), primarily to assess whether the intakes comply with recommended desired concentrations for essential and permissible levels for toxic elements. A simple and rapid DPP method has been developed for the simultaneous determination of cadmium, lead, and copper in samples. Using the differential pulse mode, half-wave peak potentials as E(1/2) were -0.58, -0.40, and -0.07 V for cadmium (Cd), lead (Pb), and copper (Cu), respectively. Marketed formulations of dairy products have been analyzed by calibration and standard addition methods. Recovery experiments were found to be quantitative. The linear domain ranges were 0.00-674.28 microg/L for Cd (R2 = 0.9999), 0.19-2.94 mg/L (p < 0.01) for Pb (R2 = 0.9997), and 0.41-133.46 microg/L for Cu (p < 0.01) (R2 = 0.9999). The studies have shown that the method is a rapid, reproducible, and accurate determination of these elements in milk and dairy products and can be used in the analysis of marketed formulations in the milk and dairy industry.     

Effects of various cooking processes on the concentrations of arsenic, cadmium, mercury, and lead in foods

The effects of cooking processes commonly used by the population of Catalonia (Spain) on total arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb) concentrations in various foodstuffs were investigated. All food samples were randomly acquired in local markets, big supermarkets, and grocery stores of Reus (Catalonia). Foods included fish (sardine, hake, and tuna), meat (veal steak, loin of pork, breast and thigh of chicken, and steak and rib of lamb), string bean, potato, rice, and olive oil. For each food item, two composite samples were prepared for metal analyses, whose levels in raw and cooked (fried, grilled, roasted, and boiled) samples were determined by inductively coupled plasma-mass spectrometry (ICP-MS). The highest concentrations of As, Hg, and Pb (raw and cooked samples) were mainly found in fish, with a clear tendency, in general, to increase metal concentrations after cooking. However, in these samples, Cd levels were very close to their detection limit. In turn, the concentrations of metals in raw and cooked meat samples were detected in all samples (As) or only in a very few samples (Cd, Hg, and Pb). A similar finding corresponded to string beans, rice, and olive oil, while in potatoes, Hg could not be detected and Pb only was detected in the raw samples. In summary, the results of the present study show that, in general terms, the cooking process is only of a very limited value as a means of reducing metal concentrations. This hypothetical reduction depends upon cooking conditions (time, temperature, and medium of cooking).