Dissolution of slag fertilizers in a paddy soil and Si uptake by rice plant

Abstract

Maize (Zea mays L.) cv. Ganga 2 was grown in refined sand at three levels of copper: deficient (0.00065 mg L^-1), adequate (0.065 mg L^-1), and excess (6.5 mg L^-1), each at three levels, deficient (0.00065 mg L^-1), adequate (0.065 mg L^-1), and excess (6.5 mg L^-1) of zinc. Excess Cu magnified the zinc deficiency effects in maize by lowering further the biomass, the concentration of leaf Zn, activities of carbonic anhydrase, aldolase, and ribonuclease and intensified the visible foliar symptoms of Zn deficiency. The effects of Cu deficiency, low dry weight, the concentration of leaf Cu and activities of cytochrome oxidase and polyphenol oxidase were enhanced by excess Zn. Synergism was observed between combined deficiency of Cu and Zn and Cu or Zn deficiency, because the depression in the parameters characteristic of Cu or Zn deficiency was more pronounced when both Cu and Zn were deficient than when Cu or Zn was deficient. Antagonism was observed in some parameters between combined excess of Cu and Zn and Cu or Zn excess. Dry weight was decreased further when both Cu and Zn were in excess than when either Cu or Zn was in excess. After the infiltration of Cu and Zn together to the leaf discs from deficient Cu-deficient Zn treatment, the increase in the concentration of leaf Zn and the activities of aldolase, carbonic anhydrase, polyphenol oxidase, and cytochrome oxidase was more pronounced than after the infiltration of Cu or Zn singly. Discontinuance of excess Zn supply from the excess Zn-deficient Cu treatment increased the concentration of leaf Cu and activities of polyphenol oxidase and cytochrome oxidase and lowered the concentration of Zn. Similarly the discontinuance of excess Cu supply from the leaf discs in the “excess Cu-deficient Zn” treatment increased the leaf Zn concentration and the activities of carbonic anhydrase and aldolase.     

Copper stress affects grain filling in rice

Abstract

Rice (Oryza sattva L.) cv. Jaya was grown in refined sand at graded levels of copper (Cu) viz. 0.00065, 0.0065, 0.013, 0.065, 0.13, 0.65, and 6.5 mg L^‐1. In acute Cu deficiency (0.0065, 0.00065 mg L^‐1), the visible foliar symptoms appeared on young leaves as chlorosis changing to necrosis, later affected leaves appeared papery and withered. The biomass and grain yield were highest at 0.065 mg L^‐1 and compared to this, the decrease in both parameters was significant at low and high Cu supply. The concentration of Cu in grains increased from 0.4 in acute deficiency to 47.4 ppm at excess Cu. In rice leaves, concentration of sugars and activities of polyphenol oxidase and ascorbic acid oxidase were decreased both by low and excess Cu. Both low and high Cu also retarded the grain formation as well as their quality by decreasing the grain yield and the concentration of starch, sugars and proteins in grains and activities of amylase, invertase and starch phosphorylase at the time of grain filling in seeds. In young leaves, 3.9, 6.8, 32, and 48 μg Cu g^‐1dry weight were indicative of deficiency, threshold of deficiency, threshold of toxicity, and toxicity values of Cu, respectively, in rice.     

Phosphorus and acid phosphatase enzyme activity in leaves of tomato cultivars in relation to zinc supply

Abstract

Tomato cultivars Blizzard and Liberto were grown hydroponically in a controlled temperature (C.T.) room for 35 days. The objective was to investigate the relationship between phosphorus (P) concentration and acid phosphatase enzyme [EC.3.1.3.2.] (APE) activity in leaves in relation to zinc (Zn) concentration in nutrient solution. Zinc was added at concentrations of 0.01,0.5, and 5 mg L^‐1. The 0.01 and 5 mg L^‐1 Zn treatments led to a significant reduction in dry matter and total chlorophyll content compared with 0.5 mg L^‐1 for both cultivars. Zinc concentration was considered inadequate in the leaves of plants subjected to 0.01 mg L^‐1 Zn, while it was at toxic level in those in the 5 mg L^‐1 Zn treatment according to values stated for tomato plants. Optimal results for all criteria tested in this experiment were for plants grown in 0.5 mg L^‐1 Zn treatment. In the leaves of plants grown at 0.01 mg L^‐1 Zn, APE concentrations were significantly the lowest and concentrations of P were at a toxic level. The APE activity was noticeably higher in the P‐deficient plants of both cultivars grown in the solutions with high Zn (5 mg L^‐1).     

Absorption of various types of chelated copper in a low concentration range by cucumber

Two experiments were conducted to compare absorption of copper (Cu) from cupric chloride (CuCl₂) and various types of chelated Cu in a low concentration range by cucumbers. In the first experiment, two varieties of cucumber were grown on rockwool for 40 days in a glasshouse with standard nutrient solution which contained six different concentrations of CuCl₂ (0, 0.05, 0.10, 0.20, 0.40, and 0.80 μmol/L). Copper deficiency symptoms were examined during the growing period, and the total nitrogen (N), iron (Fe), manganese (Mn), zinc (Zn), and copper contents of young fully grown leaves were measured. There were no differences among treatments in the leaf contents of N and Mn. Copper contents increased and Zn decreased with increasing Cu levels. The content of Cu at the three low Cu treatments (including no Cu addition) were in the deficient range (48–65 μmol/kg dry matter). The zero Cu level had paler green leaves than other treatments. No differences were apparent between varieties. The second experiment was carried out under exactly the same conditions as the first, but on the basis of the results of the first experiment, Cu treatments were 0, Cu‐EDDHA at 0.4, Cu‐DTPA at 0.4, Cu‐EDTA at 0.4, Cu‐NTA at 0.4, CuCl₂ at 0.4 μmo/L as Cu²⁺. After the experiment, the total N, Fe, Mn, Zn, and Cu contents of young, fully grown leaves were measured. There were no differences between treatments in the leaf contents of Cu except zero Cu level. They were in the range of 101–119 μmol/kg dry matter. At no Cu addition treatment, the Cu content was only 31 μmol/kg dry matter which is considered to be the deficiency level. For the other examined elements, there were no differences among the treatments and varieties. From these data it was concluded that the availability of these chelated Cu types were the same as CuCl₂ under the conditions of the experiments conducted.     

Effect of excess zinc and arbuscular mycorrhizal fungus on bioproduction and trace element nutrition of Tomato (Solanum lycopersicum L. cv. Micro-Tom)

ABSTRACT

The effect of excess Zn and arbuscular mycorrhizal (AM) fungus on bioproduction and trace element nutrition were investigated in tomato. In a completely randomized factorial design, the experimental treatments – Zn addition at 0 (normal) and 300 (excess) mg Zn kg^?1 soil, and AM inoculation (non-AM and Rhizophagus irregularis) – were set up in a growth chamber for 10 weeks. Generally, AM effects on the available Zn, Mn, Cu, and Fe in the rhizosphere soil were in tandem with the effects in host tissues. Under normal Zn condition, AM enhanced Cu availability in the rhizosphere, optimized the Cu:Zn balance in shoots, and increased the host biomass production. Excess Zn reduced mycorrhizal colonization in AM plants and the total plant biomass in both AM and non-AM plants. Although AM decreased the Zn concentrations in soil and host tissues under excess Zn, the distortions in host TE balance were not significantly ameliorated by the fungus. While Zn in fruit was within the safety threshold, Mn deficiency in the fruit was observed under excess Zn, alongside increased root-to-fruit Fe and Cu translocations. Mycorrhizal reductions in soil and tissue Mn concentrations were considered a minus in terms of probable symbiont amelioration of Mn:Zn in-balance under excess Zn. Additional microbe(s) that can enhance Mn homeostasis might be helpful in tomato under elevated soil Zn.     

Plant growth,phosphorus nutrition,and acid phosphatase enzyme activity in three tomato cultivars grown hydroponically at different zinc concentrations

Three tomato cvs., Blizzard, Liberto, and Calypso, were grown hydroponically in a controlled temperature (C.T.) room for six weeks at three zinc (Zn) concentrations (0.01, 0.5, and 5.0 mg Zn L^‐1) in the nutrient solution. There were significant reductions in the dry matter and chlorophyll contents of all three cultivars grown at both low (0.01 mg L^‐1) and high (5 mg L^‐1) Zn as compared to 0.5 mg Zn L^‐1. The concentration of Zn at 0.01 mg L^‐1 was not sufficient to provide for optimal plant growth, while 5 mg Zn L^‐1 in the nutrient solution was detrimental to plant growth for all three cultivars. The best results for all parameters tested were for the plants grown at 0.5 mg Zn L^‐1. The concentration of phosphorus (P) was at an excess level in leaves of plants grown in 0.01 mg Zn L^‐1, while it was deficient in the 5 mg Zn L^‐1 treatment. Acid Phosphatase Enzyme [EC.3.1.3.2.] (APE) activity was significantly higher in both the leaves and roots of P‐deficient plants, i.e., plants receiving high (5 mg L^‐1) Zn. Acid Phosphatase Enzyme activity was slightly higher in the mature leaves than those in developing leaves, where P concentration was higher. Concentration of P and, in particular Zn, increased in the roots with increasing Zn in the nutrient solution. The APE activity increased in the roots of P‐deficient plants receiving high Zn (5 mg L^‐1).     

Accumulation of Metals in the Sediment and Reed Biomass of a Combined Constructed Wetland Treating Domestic Wastewater

This study assessed the accumulation of Al, Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn in the sediment and biomass of P. australis (Cav.) Trin. ex Steud. in a combined constructed wetland (CW) designed for the treatment of domestic wastewater of 750 population equivalents. The CW consists of two vertical subsurface flow (VSSF) reed beds followed by two horizontal subsurface flow (HSSF) reed beds. The sediment in the VSSF reed bed was contaminated with Cu (201 ?±? 27 mg kg^?1 DM) and Zn (662 ?±? 94 mg kg^?1 DM) after 4 years of operation. Concentrations of Cd, Cu, Pb and Zn in the sediment generally decreased along the treatment path of the CW. On the contrary, higher Al, Cr, Fe, Mn and Ni concentrations were observed in the sediment of the inlet area of the HSSF reed bed. Redox conditions were presumably responsible for this observed trend. Metal concentrations in the reed biomass did not show excessive values. Accumulation in the aboveground reed biomass accounted for only 0.5 and 1.4% of, respectively, the Cu and Zn mass load in the influent. The sediment was the main pool for metal accumulation in the CW.     

Varietal tolerance to Zinc deficiency in wheat and barley grown in chelatorbuffered nutrient solution and its effect on uptake of Cu,Fe, and Mn

Tolerance to zinc (Zn) deficiency was examined for three wheat (Triticum aestivum L.) and three barley (Hordeum vulgare L.) varieties grown in chelator‐buffered nutrient solution. Four indices were chosen to characterize tolerance to Zn deficiency: (1) relative shoot weight at low compared to high Zn supply (“Zn efficiency index”), (2) relative shoot to root ratio at low compared to high Zn supply, (3) total shoot uptake of Zn under deficient conditions, and (4) shoot dry weight under deficient conditions. Barley and wheat exhibited different tolerance to Zn deficiency, with barley being consistently more tolerant than wheat as assessed by all four indices. The tolerance to Zn deficiency in the barley varieties was in the order Thule=Tyra>Kinnan, and that of wheat in the order Bastian=Avle>Vinjett. The less tolerant varieties of both species accumulated more P in the shoots than the more tolerant varieties. For all varieties, the concentrations of Mn, Fe, Cu, and P in shoot tissue were negatively correlated with Zn supply. This antagonism was more pronounced for Mn and P than for Cu and Fe. Accumulation of Cu in barley roots was extremely high under Zn‐deficient conditions, an effect not so clearly indicated in wheat.     

EFFECT OF LANTHANUM ON RICE PRODUCTION,NUTRIENT UPTAKE,AND DISTRIBUTION

ABSTRACT

Split root solution culture experiments were conducted to study the effects of the rare earth element lanthanum (La) on rice (Oryza sativa) growth, nutrient uptake and distribution. Results showed that low concentrations of La could promote rice growth including yield (0.05 mg L^?1 to 1.5 mg L^?1), dry root weight (0.05 mg L^?1 to 0.75 mg L^?1) and grain numbers (0.05 mg L^?1 to 6 mg L^?1). High concentrations depressed grain formation (9 mg L^?1 to 30 mg L^?1) and root elongation (1.5 mg L^?1 to 30 mg L^?1). No significant influence on straw dry weight was found over the whole concentration range except for the 0.05 mg L^?1 treatment. In the pot and field experiments, the addition of La had no significant influence on rice growth.Lanthanum had variable influence on nutrient uptake in different parts of rice. Low concentrations (0.05 mg L^?1 to 0.75 mg L^?1) increased the root copper (Cu), iron (Fe), and magnesium (Mg), and grain Cu, calcium (Ca), phosphorus (P), manganese (Mn), and Mg uptake. High concentrations (9 to 30 mg L^?1) decreased the grain Ca, zinc (Zn), P, Mn, Fe and Mg, and straw Ca, Mn, and Mg uptake. With increasing La concentration, root Zn, P, Mn, Cu, and Ca concentrations increased, and grain Ca and Fe, and straw Mn, Mg, and Ca concentrations decreased. Possible reasons are discussed for the differences between the effects of La in nutrient solutions and in pot and field experiments.     

ALLEVIATION OF CADMIUM-TOXICITY BY APPLICATION OF ZINC AND ASCORBIC ACID IN BARLEY

ABSTRACT

Effect of cadmium (Cd) on biomass accumulation and physiological activity and alleviation of Cd-toxicity by application of zinc (Zn) and ascorbic acid in barley was studied, using semisolid medium culture including 15 treatments [four Cd concentration treatments: 0.1, 1, 5, 50?µmol?L^?1, four treatments with addition of 300?µmol?L^?1 Zn or 250?mg?L^?1 ascorbic acid (ASA) based on these four Cd concentrations, respectively, and three controls: basic nutrient medium, and with Zn or ASA, respectively]. Cadmium addition to semisolid medium, at a concentration of 1, 5, and 50?µmol?L^?1, inhibited biomass accumulation and increased malondialdehyde (MDA) content of barley plants, while the addition of 0.1?µmol?L^?1 Cd increased slightly dry mass. There was a tendency to a decrease in Zn, copper (Cu) concentrations both in shoots and roots and iron (Fe) in shoots of barley plants exposed to 1 to 50?µmol?L^?1 Cd. In addition, there were indications of a stress repose characterized by increased superoxide dismutase (SOD) and peroxidase (POD) activities relative to plants not subjected to Cd. The physiological changes caused by Cd toxicity could be alleviated to different extent by application of 300?µmol?L^?1 Zn or 250?mg?L^?1 ASA in Cd stressed plants. The most pronounced effects of adding Zn or ASA in Cd stressed medium were expressed in the decreased MDA and increased biomass accumulation, e.g., MDA contents were reduced (p≤0.01) by 4.8%–17.8% in shoots and 0.5%–19.7% in roots by adding 300?µmol?L^?1 Zn, in 50?µmol?L^?1 Cd stressed plants, and by 1.3%–7.4% in shoots and 2.6%–4.5% in roots by application of 250?µmol?L^?1 ASA, respectively. However, ASA addition may enhance Cd translation from root to shoot, accordingly, ASA would be unsuitable for the edible crops grown in Cd contaminated soils to alleviate phytotoxicity of Cd.     

Short‐term relationships between membrane permeability and growth parameters in three tomato cultivars grown at low and high zinc

Abstract

An experiment was carried out in a controlled temperature (CT) room for five weeks with tomato cvs., Moneymaker, Liberto, and Calypso, to investigate possible relationships between zinc (Zn) deficiency or toxicity and electrolyte leakage in plant leaves. The concentrations of Zn in nutrient solution were 0.01, 0.5, and 5.0 mg L^?1, respectively. There were significant reductions in the dry matter and chlorophyll content of all three cultivars grown both at 0.01 (low) and 5 mg L^?1 (high) Zn compared to 0.5 mg L^?1. The concentration of Zn at 0.01 mg L^?1 was not sufficient to provide for optimal plant growth, while 5 mg L^?1 in nutrient solution was detrimental to plant growth for all three cultivars. Dry matter production was generally lowest in the plants grown at low (0.01 mg L^?1) Zn except for Moneymaker where the lowest biomass was in the high Zn treatment. Zinc concentration was increased in the leaves and roots with increasing Zn concentration in nutrient solution. Phosphorus concentration was toxic in the leaves of the plants grown at low (0.01 mg L^?1) and was deficienct at high Zn (5 mg L^?1). The electrolyte leakage (%) gradually increased in the plants grown at low and high Zn concentrations and these increases were greatest in the leaves of plants grown at low Zn (except for Moneymaker grown at high Zn where reduction in dry matter was less). The best results for all growth parameters tested were for the plants grown at 0.5 mg L^?1 Zn. The results of this short‐term experiment show that electrolyte leakage which is relatively simple and easy to measure may be a good indicator of cultivar tolerance to Zn deficiency and toxicity.     

Aluminum effects on micronutrient uptake by annual ryegrass

Abstract

Four ryegrass (Lolium multiflorumLam.) cultivars were grown in 1/5 Steinberg nutrient solution supplemented with six Al levels (0, 37, 74, 148, 296, or 592 umol L^‐1) at pH initially adjusted to 4.2. Average net Fe influx was stimulated at low nutrient solution Al levels. This stimulation was larger for more Al‐tolerant cultivars Marshall and Gulf. Decreases in average net Mn and Zn influxes were brought about by increasing Al levels in the nutrient solution. The average net influx of Fe, Mn, and Zn was positively correlated with the root tolerance index (relative root yield of plants grown with and without Al added to the nutrient solution). For more Al‐tolerant cultivars, increased total uptake of Fe and Cu was brought about by increased nutrient solution Al levels up to 74 umol L^‐1. Decreases in total uptake of Mn and Zn were generally noted with increased nutrient solution Al levels. Percentage inhibition of total Fe, Mn, Zn, and Cu uptake was negatively correlated with the mean pH of the Al‐containing nutrient solutions. The higher average net influx and the smaller percentage inhibition of total Fe uptake at nutrient solution Al levels up to 74 umol L^‐1can be used as indicators in ranking ryegrass cultivars as more Al‐tolerant     

Behavior of Metals Under Different Seasonal Conditions: Effects on the Quality of a Mexico–USA Border River

Spatial and seasonal mobilization trends of metals in surface water were evaluated in the US–Mexico San Pedro River (SPR). Water samples were collected at five sampling stations for the analysis of dissolved oxygen, pH, electric conductivity, sulfates, and metals (Cd, Cu, Fe, Mn, Pb, and Zn). Quality of the water was characterized through Ecological Criteria of Water Quality (ECWQ) established in Mexico and Water Quality Criteria (Environmental Protection Agency (EPA)). High total metal concentrations were detected as follows: Fe?>?Cu?>?Mn?>?Zn?>?Pb?>?Cd. Metal concentrations were slightly higher in dry season than in rainy season: Cd (below detection limit (BDL)–0.21 mg L^?1), Cu (BDL–13 mg L^?1), Fe (0.16–345 mg L^?1), Mn (0.12–52 mg L^?1), Pb (BDL–0.48 mg L^?1), and Zn (0.03–17.8 mg L^?1). Low pH and dissolved oxygen values as well as high sulfate content were detected in both seasons. High values of metals (Cd, Cu, Fe, Mn, Pb, Zn) were detected at station E1 representing pollution source, as well as at stations E2 (Cd, Cu, Fe, Mn), E3 (Fe, Mn, Pb), and E4 and E5 (Fe, Mn). Detected concentrations exceeded maximum permissible established in ECWQ and Water Quality Criteria (EPA). Efflorescence salts on sediments in the dry season could increase levels of metals in water column. This study provides valuable information on the potential mobility of metals in surface water of SPR located in an arid environment where transport processes are strongly linked to climate. The information derived from this study should help the regional and national authorities to address present environmental regulations.     

Zinc uptake kinetics in the low and high‐affinity systems of two contrasting rice genotypes

Rice (Oryza sativa L.) cultivars differ widely in their susceptibility to zinc (Zn) deficiency. The physiological basis of Zn efficiency (ZE) is not clearly understood. In this study, the effects of Zn‐sufficient and Zn‐deficient pretreatments on the time and concentration‐dependent uptake kinetics of Zn were examined at low (0–160 nM) and high Zn supply levels (0–80 μM) in two contrasting rice genotypes (Zn‐efficient IR36 and Zn‐inefficient IR26). The results show that ⁶⁵Zn²⁺ influx rate was over 10 times greater for the Zn‐deficient pretreatment plants than for the Zn‐sufficient pretreatment plants. At low Zn supply, significant higher ⁶⁵Zn²⁺ influx rates were found for the Zn‐efficient genotype than for the inefficient genotype, with a greater difference (over three‐fold) at Zn supply > 80 nM in the Zn‐deficient pretreatments. At high Zn supply levels, however, a difference (2.5‐fold) in ⁶⁵Zn²⁺ influx rate between the two genotypes was only noted in the Zn‐deficient pretreatments. Similarly, the ⁶⁵Zn²⁺ accumulation in the roots and shoots of Zn‐efficient IR36 pretreated with Zn‐deficiency were sharply increased with time and higher than that in the Zn‐inefficient IR26 with an over four‐fold difference at 2 h absorption time. However, with Zn‐deficient pretreatments, the Zn‐efficient genotype showed a higher shoot : root ⁶⁵Zn ratio at higher Zn supply. Remarkable differences in root and shoot ⁶⁵Zn²⁺ accumulation were noted between the two genotypes in the Zn‐deficiency pretreatment, especially at low Zn level (0.05 μM), with 2–3 times higher values for IR36 than for IR26 at an uptake time of 120 min. There appear to be two separate Zn transport systems mediating the low and high‐affinity Zn influx in the efficient genotype. The low‐affinity system showed apparent Michaelis–Menten rate constant (K_m) values ranging from 10 to 20 nM, while the high‐affinity uptake system showed apparent K_m values ranging from 6 to 20 μM. The V_max value was significantly elevated in IR36 and was 3–4‐fold greater for IR36 than for IR26 at low Zn levels, indicating that the number of root plasma membrane transporters in low‐affinity uptake systems play an important role for the Zn efficiency of rice.     

The effect of different production systems on the content of micronutrients and trace elements in potato tubers

The aim of this study was to determine the effect of different production systems (conventional, integrated and organic) on the content of micronutrients and trace elements in the tubers of very early, early and medium-early maturing potato cultivars. Five Polish potato cultivars were grown in three production systems under field conditions. In plant material selected microelements (chemical elements essential for living organisms) were analysed: boron (B), copper (Cu), iron (Fe), manganese (Mn) and zinc (Zn) as well as some trace elements (not regarded as essential element for living organisms): chromium (Cr), nickel, (Ni) and lead (Pb). The content of micronutrients and trace elements in potato tubers was modified by production system, genotype and weather conditions during the growing season. Organically grown potatoes had a higher content of B (8.6–8.9?mg kg^?1) and Cu (2.8–3.1?mg?kg^?1), and a lower content of Fe (47.0–47.1?mg?kg^?1), Mn (6.0–6.4?mg?kg^?1) and Zn (11.9–12.2?mg?kg^?1), than potatoes grown in conventional and integrated systems. Potatoes grown in the conventional system had the highest Pb content. Organic cultivation can assure better alimentation of potato tubers with B and Cu, which are important microelements often deficient in the soils. On the contrary, when cultivating potato in conventional system, one should supply this element with fertilisers.     

The Effects of Copper and Lead on Growth and Zinc Accumulation of Thlaspi Caerulescens J. and C. Presl: Implications for Phytoremediation of Contaminated Soils

Thlaspi caerulescens J. and C. Presl is a Zn-hyperaccumulatingplant which has aroused considerable interest with respect to its possible use for phytoremediation of Zn-contaminated soils. In this work, a British population of T. caerulescens, from a soil which was found to have relatively high concentrations of water-extractable Cu (0.22 mg L^-1), Pb (0.99 mg L^-1) and Zn (6.49 mg L^-1), was studied. Its ability to grow and accumulate Zn from hydroponic nutrient solution in the presence of elevated concentrations of Cu and/or Pb was investigated. The chosen concentrations of Cu, Pb and Zn were based on reported water-soluble concentrations of these heavy metals in contaminated soils. When supplied with 32.7 mg L^-1 Zn, plants accumulated 19 780 mg kg^-1 Zn in their shoot dry matter. This concentration declined by 9.3, 87 and 84% respectively when 5.0 mg L^-1 Pb, 1.0 mg L^-1 Cu or 2.0 mg L^-1 Cu were included in the nutrient solution. Despite the apparent adaptation of this population of T. caerulescens to a Zn/Pb/Cu-contaminated soil, these Cu treatments strongly inhibited growth, but the Pb treatment did not affect growth significantly.     

大棚菜田种植年限对土壤重金属含量及酶活性的影响

为了探讨大棚种植年限对大棚菜田土壤重金属累积、土壤酶活性的影响以及二者的关系,采集不同种植年限(0、5、10、15、20、25、30 a)大棚菜田土壤样品共140份,测定土壤样品中重金属的含量以及土壤酶活性。结果表明:大棚菜田土壤中重金属Zn、Pb、Cu的含量和种植年限极显著相关;重金属Cd、Ni、Mn的含量和种植年限显著相关;重金属Cr的含量和种植年限不相关。大棚菜田土壤中过氧化物酶、多酚氧化酶、淀粉酶活性和种植年限极显著相关,磷酸酶、蔗糖酶活性和种植年限显著相关,过氧化氢酶、脲酶、蛋白酶活性和种植年限相关性不显著。随着种植年限的延长重金属Zn、Cu含量对多酚氧化酶、过氧化物酶活性有抑制作用,其敏感性顺序为:过氧化物酶对Zn敏感性>多酚氧化酶对Zn敏感性>过氧化物酶对Cu敏感性>多酚氧化酶对Cu敏感性。土壤中过氧化物酶、多酚氧化酶可以作为重金属Zn污染的指示酶,过氧化物酶可以作为重金属Cu污染的指示酶。该文为设施污染土壤环境质量评价提供依据。     

Deposit of zinc and manganese in an aqueous environment mediated by microbial mats

Microbial mats have been developed to sequester heavy metals from contaminated water. Mixed populations of photosynthetic and heterotrophic bacteria, dominated by Scillatoria spp., were developed for metal tolerance and integrated into a durable, self-sustaining community of microbes stimulated by and attached to ensiled grass. The mat was immobilized on glass wool and layered in flow-through baffled tanks. After allowing 8 weeks for the maturation of the mat, mixed solutions of Zn and Mn (15–16 mg L^?1) were passed through a three-tank experimental series. Effluent from each tank was first sampled and then applied to the next tank. This procedure was repeated in triplicate and with six applications of new metal solution per three-tank series. By the third tank, the target metal concentration <1 mg L^?1 was always achieved. Mean percentages of the initial influent concentration removed by tanks 1, 2 and 3, respectively, were 72, 93 and 98 for Zn and 78, 97 and 99 for Mn. Mean metal concentrations in the effluents (average of 6 applications) were, for tank 1: Zn (mg L^?1) 5.0, Mn (mg L^?1) 4.2; for tank 2: Zn 1.6, Mn 0.75; for tank 3: Zn 0.53, Mn 0.19. Mean effluent concentrations from each of the three sequential treatments (average of 6 applications per tank) were for Zn (mg L^?1) 5.0, 1.6 and 0.53; for Mn (mg L^?1) were 4.2, 0.75 and 0.19. Thus target concentrations were reached in experimental tank 2 for Mn and tank 3 for Zn. Metal removal in the control tank series, containing glass wool only, was 37% for Zn and 5% for Mn (average of 6 applications). Oxygen and redox potential analyses of the mat/glass wool matrix revealed a heterogenous structure of anoxic and oxic zones. Zeta potential analysis of the mat samples identified a mat surface charge ranging from ?12.3 to ?69.2 mV. Various metal removal mechanisms possibly involved with metal sequestering include surface binding to the mat or to mat exudates trapped within the glass wool, precipitation of the metals with anions present in the oxic/anoxic zones, mat mediation of the water conditions in favor of metal-oxide precipitation and active transport of the metals into the cell.     

Micronutrient status of calcareous paddy soils and rice products: implication for human health

Modern agricultural systems have to provide enough micronutrient output to meet all the nutritional needs of people. Accordingly, knowledge on micronutrient status in soil and crop edible tissues is necessary. This study was carried out to investigate zinc (Zn), iron (Fe), manganese (Mn), and copper (Cu) concentration of calcareous paddy soil and the relative rice grain. Rice crops (straw, hull, and grain) and associated surface soils (0–25 cm) were collected from 136 fields and analyzed for total and diethylene triamine pentaacetic acid (DTPA) available Zn, Fe, Mn, and Cu. The DTPA-Zn concentration in more than 50% of paddy soils was less than its critical deficiency concentration (2 mg kg⁻¹), while the concentrations of DTPA Fe, Mn, and Cu were sufficient. The grain Zn concentration of more than 54% of the rice samples was less than 20 mg kg⁻¹. About 55% and 49% of the rice samples were deficient in Mn and Cu, respectively, while the Fe concentration in rice grains was sufficient. A significant negative correlation was found between the CaCO₃ content and soil DTPA-extractable Zn, Fe, Mn, and Cu. There were significant relationships between the total soil phosphorus and DTPA-extractable micronutrient concentrations. By considering the average daily rice consumption of 110 g per capita, the Zn, Fe, Mn, and Cu intake from rice consumption was estimated to be 2.4, 7.7, 1.6, and 0.7 mg for adults, respectively.     

Evaluation of the Mehlich 3 soil extractant for upland Malawi soils

Abstract

The Mehlich 3 (M3) universal soil extraction method was compared with the ammonium acetate (AA), Bray 1, and DPTA extraction procedures for the analysis of calcium (Ca), magnesium (Mg), potassium (K), phosphorus (P), zinc (Zn), copper (Cu), manganese (Mn), and iron (Fe). Upland Malawi soils from 112 smallholder farmers’ fields of the Alfisol, Ultisol, and Oxisol soil orders were analyzed by the four procedures. Calcium, Mg, and K extracted by the M3 and AA procedures were highly correlated (r² = 0.98, 0.98, and 0.99 for the respective elements). The M3 extractant also correlated well with the DPTA procedure for Zn and Cu (r² = 0.88 for both elements) and the Bray 1 method for P (r² = 0.80). Amounts of Mn and Fe extracted by M3 and DPTA were poorly correlated (r² = 0.28 and 0.47, respectively), with both elements testing high in all soils. The high levels suggest that Mn and Fe deficiencies are likely to be rare, and that analysis for these elements is not generally necessary. Special precautions for Zn and Cu analyses are advised due to the low conentrations of these elements in the M3 extract and various laboratory sources of Zn contamination. The use of soil pH along with M3‐extractable Zn is recommended in the identification of potentially Zn‐deficient soils. The preference for expressing analytical results on a volume rather than weight basis is discussed. Based on a review of literature relating to the M3 extractant, the following critical M3 soil test values are tentatively recommended for maize on upland Malawi soils: Ca, 50 mg/dm³; Mg, 75 mg/dm³ and Mg:Ca ratio >0.067; K, 70 mg/dm³; P, 20 mg/dm³; Zn, 1.0 mg/dm³; and Cu, 0.5 mg/dm³. These suggested values should not preclude in‐country correlation studies. Because the M3 procedure is well correlated with the AA, DPTA, and Bray 1 methods, and because it is a rapid procedure, the M3 method can be highly recommended as a replacement for the three current procedures for Malawi upland soils. Caution is advised in extending the results to Malawi lowland soils, which are characterized by higher pH values.