Naoharu Mizuno

Metal and metalloid contamination in roadside soil and wild rats around a Pb-Zn mine in Kabwe, Zambia.

Metal (Cr, Co, Cu, Zn, Cd, Pb, Ni) and metalloid (As) accumulation was studied in roadside soil and wild rat (Rattus sp.) samples from near a Pb-Zn mine (Kabwe, Zambia) and the capital city of Zambia (Lusaka). The concentrations of the seven metals and As in the soil samples and Pb in the rat tissue samples were quantified using atomic absorption spectroscopy. The concentrations of Pb, Zn, Cu, Cd, and As in Kabwe soil were much higher than benchmark values. Geographic Information System analysis indicated the source of metal pollution was mining and smelting activity. Interestingly, the area south of the mine was more highly contaminated even though the prevailing wind flow was westward. Wild rats from Kabwe had much higher tissue concentrations of Pb than those from Lusaka. Their body weight and renal Pb levels were negatively correlated, which suggests that mining activity might affect terrestrial animals in Kabwe.

Distribution of Ni and Zn in the leaves of Thlaspi japonicum growing on ultramafic soil

Abstract A Ni-hyperaccumulator, Thlaspi japonicum, grown on ultramafic soil contained large amounts of Ni and Zn in its shoot. The Ni content of the leaves was the highest (3,424 mg kg−1) in the lower epidermis, which had many stomata, followed by the leaf edge, upper epidermis, which had few stomata, and mesophyll. By contrast, the Zn content was the highest (615 mg kg−1) in the upper epidermis followed by the lower epidermis, and was the lowest at the leaf edge. Using a microscope, the dimethylglyoxime-stained Ni-compound was observed as rod-shaped crystals mainly around the stomata and the projections of the leaf edge. In addition, a considerable amount of Ni was excreted via the guttation fluid (0.67 to 1.33 mg L−1), while the concentration of Zn in the guttation fluid was very low (0.01–0.10 mg L−1). In mature leaves, the Ni content was almost constant during the growth period, while the Zn content decreased once around the summer solstice, reached the highest level in midsummer, and decreased thereafter. In young leaves, however, the Ni and Zn contents increased to a level similar to that in mature leaves in midsummer, and decreased after early September. These data suggest that Ni is translocated along with the transpiration stream and concentrated around stomata, and that the excess amount of Ni is excreted via the guttation fluid. This mechanism may not operate for Zn accumulation in this plant. Zn in mature leaves may be supplied to young leaves on demand for rapid growth.

Chemical composition of guttation fluid and leaves of Petasites japonicus v. giganteus and Polygonum cuspidatum growing on ultramafic soil

Abstract Petasites japonicus v. giganteus (Japanese butterbur) and Polygonum cuspidatum (Japanese knotweed) exude a large quantity of guttation fluid from the leaf edge. The concentrations of Ni and Mn in the guttation fluid from Petasites japonicus v. giganteus grown on ultramafic soil were 2.24 (Ni) and 0.32 (Mn) mg L−1, respectively, on the average, whereas those in the guttation fluid from Polygonum cuspidatum were 0.22 (Ni) and 3.13 (Mn) mg −1, respectively. The Ni concentration in the leaves of Petasites japonicus v. giganteus was about 5 times as high as that of Polygonum cuspidatum, especially at the leaf edges, and the Mn concentration in the leaves of Polygonum cuspidatum was about 6 times as high as that of Petasites japonicus v. giganteus. Thus, the concentrations of Ni and Mn in both the guttation fluid and leaves of Petasites japonicus v. giganteus were opposite to those of Polygonum cuspidatum. The contents of K, Mg, and Ca in the guttation fluid from Petasites japonicus v. giganteus were higher than those in the guttation fluid from Polygonum cuspidatum in the ultramafic rock area.

Characteristics of nickel accumulation in native plants growing in ultramafic rock areas in Hokkaido

Abstract Nickel accumulation in the native plants growing in ultramafic rock areas in Hokkaido, Japan was studied. The mean soil pH ranged from 6.1 to 8.0. The content of exchangeable Ni in the soil was only 3 to 13 mg kg−1. The lowest content of total Ni was 1.3 g kg−1, and the highest value was 2.6 g kg−1. Thlaspi japonicum was found to accumulate as much as 1,045 mg Ni (kg dry wt)−1, although this species is not an ultramafic plant. Five other species, Allium schoenoprasum var. sibutuense, Viola yubariana (endemic species on Mt. Yupari), Lagotis takedana (endemic species on Mt. Yupari), Viola sacchalinensis var. alpina, and Draba japonica were identified as strong Ni accumulators based on measurements using dried herbarium specimens. The Ni content in ultramafic plants exceeded 50 mg (kg dry wt)−1 in about half of the native plants growing in ultramafic rock areas. The Ni content of dried plants of Allium schoenoprasum var. sibutuense was 234 mg (kg dry wt)−1, while that of Allium maximowiczii was only 19 mg (kg dry wt)−1. Although Deschampsia caespitosa var. levis, Japonolirion osense var. saitoi, Betula apo iens is , and Primula hidakana are ultramafic plants, the Ni content in these plants was less than 10 mg (kg dry wt)−1. In all the examined ultramafic plant species, the Ni content in plants plotted against the exchangeable Ni content in soil was represented by a regression curve and not a straight line. The Ni content in plants increased markedly with increasing exchangeable Ni content in soil in a low content range, but slightly in a high content range. In common plants, a similar correlation was observed only in one species, a linear correlation in three species and no correlation in two species.

Chemical characterization of conducive and suppressive soils for potato scab in Hokkaido, Japan

Absract Potato common scab induced by Streptomyces scabies is a serious constraint for potato-producing farmers and the incidence of potato scab depends on the soil chemical properties. We examined the chemical characteristics of conducive and suppressive soils to potato common scab with reference to the chemical properties of nonallophanic Andosols, recently incorporated into the classification system of cultivated soils in Japan. Allophanic Andosols with a ratio of pyrophosphate-extractable aluminum (Alp) to oxalate-extractable aluminum (Alo) of less than 0.3–0.4 were “conducive” soils with a high allophane content of more than 3%. On the other hand, nonallophanic Andosols with a Alp/Ala ratio higher than this critical value were “suppressive” soils, and their allophane content was less than 2%. The concentration of water-soluble aluminum (AI) was also a useful index for separating conducive from suppressive soils as well as the Alp/Ala value and allophane content. The suppressive soils showed a much hi...

Serpentine Plants in Hokkaido and their Chemical Characteristics

Abstract In the serpentine area in Hokkaido, 46 taxa of serpentine plant species were recognized, and 44 of them were endemic to Hokkaido. The P concentration in the serpentine plants was lower, while the concentrations of K, Ca, and N were higher, than those in nonserpentine plants and trees. The Ni concentration of the serpentine plants increased proportionally to that of the exchangeable Ni concentration in the soil up to 10 mg kg-1 soil, but did not increase further. Among the plants investigated, a nonserpentine plant, Thlaspi japonicum, was recognized for its extraordinary Ni accumulation (1300 mg kg-1 on average), indicating that this plant is the first Ni-hyperaccumulator identified in Japan.

Cloning and characterization of phytochelatin synthase from a Nickel hyperaccumulator Thlaspi japonicum and its expression in yeast

Abstract Phytochelatin {γ-(EC) n G} is a group of peptides that chelate and detoxify heavy metals in plants. However, the relationship between the phytochelatin function and metal-hyperaccumulating plants has not been elucidated. In the current study, we cloned the phytochelatin synthase (PCS) gene, designated as TjPCS, from a Ni-hyperaccumulator plant Thlaspi japonicum, and examined its ability to detoxify Cd2+. The RT-PCR product of 1,745 bp, which contained the open reading frame of the TjPCS was isolated, and cloned. The deduced amino acid sequence of TjPCS (475 amino acid length) showed a 90% identity with the sequence of PCS from Arabidopsis thaliana. The yeast transformed with the TjPCS produced PCS and showed an obvious Cd2+ tolerance after the induction of gene expression by galactose.

Method of judging copper deficiency from the concentration of soluble copper in soils and the copper: Iron ratio in wheat plants

Abstract With the increasing acreage of wheat in Hokkaido, Cu deficiency has become a problem in various parts of Hokkaido since 1979. Cu deficiency was found in some brown forest soils, peat soils and andosols, whose total Cu concentration ranged from 5.5 to 22 ppm. Sterility of wheat plants was seen in soils whose soluble Cu concentration (soil: 0.1 N HOratio, 1 : 5) was lower than 0.15 ppm (mineral soils) or 0.2-0.25 ppm (peat soils). No clear relationship was observed between the humus content and concentration of soluble Cu. It was difficult to determine Cu deficiency from the concentration of Cu in the tops of wheat plants. On the other hand, it was found that wheat plants deficient in Cu tended to have a high concentration of Fe. The Cu : Fe ratio in all wheat plants which were made sterile through Cu deficiency was 0.003 to 0.01, whereas the same ratio in fructified wheat plants was mostly 0.01 to 0.1. Thus, the Cu :Fe ratio in wheat plants can serve as a useful parameter in judging whether or not...

Efficacy of single application ammonium sulfate in suppressing potato common scab.

Abstract The objective of this study was to suppress potato common scab by lowering the soil pH and increasing the concentration of water-soluble aluminum (Al) in soil with a single application of ammonium sulfate into each row. Superphosphate (P) and potassium sulfate (K) were applied to the surface soil horizon and ammonium sulfate (N) was applied only into the rows along which potato plants were to be planted. By this application method, the soil pH was lowered and the concentration of water-soluble Al was increased in the soil of the rows where potato tubers were grown. Potato common scab was suppressed in the soil containing water-soluble Al in concentrations of 0.2 to 0.3 mg L−1 or higher. The pH of the soil fertilized as indicated above remained lower than that of the control soil to which the mixture of N, P, and K was uniformly applied. In soil types such as Haplic Andosols containing allophane at high concentrations of 71 g kg−1 in Memanbetsu, the suppression of potato common scab by this single application of ammonium sulfate was less effective due to the low soluble Al concentration. In other soil types, the soil pH was easily controlled and common scab was suppressed by this method. The advantages of this method are that (a) it minimizes the use of fertilizers, thus reducing the adverse effects of unnecessary fertilizers on the soil; and (b) it lowers the cost by eliminating additional agricultural chemicals and extra fertilizers.

DISTRIBUTION OF HEAVY METALS IN SERPENTINE SOIL

Abstract It is known that an abnormally high nickel content in the serpentine soils, seriously affects the crops as a result of metal toxicity (1, 2). However, when it contains a high quantity of chromium comparable to that of nickel, no affect of the metal toxicity is seen in the crops (3, 4). With special regards to this, it has been suggested that the harmlessness of chromium was closely related to its low solubility, Manganese content in the serpentine soils, likewise, shows the same tendency; in the serpentine soils, the content of the metal is higher than in general soils in the same area (5).