Elevated Boron Concentrations Research Articles

The Role of Boron in Low Copper Spheroidal Graphite Irons

The effects of boron at concentrations ranging from 5 to 525 ppm in low copper spheroidal graphite iron (SGI) has been studied. At 130 to 140 ppm, no particular effect of boron was observed on the size distributions, number densities, or morphologies of the microparticle populations in the material. Neither was there observed any effects on the size distributions or number densities of graphite nodules. However, boron was observed to lead to a rough surface morphology of the graphite nodules at concentrations as small as 24 ppm. Intercellular carbides were found to form in alloys containing more than 70 ppm boron. Additionally, the graphite shape began to degenerate in alloys with more than 300 ppm of boron. Mass spectrometry analyses revealed these carbides contain relatively high amounts of boron. In an alloy containing 74 ppm boron, it was inferred by using electron backscatter diffraction that these were of the type {{hbox {M}}_{23}({hbox {C}},{hbox {B}})_{6}} borocarbides, where M = Fe, Mn, V, or a combination of them. Mass spectrometry analyses also revealed elevated concentrations of boron in the surface layers of the graphite nodules.

Boron as a contaminant at construction and demolition (C&D) debris landfills

Elevated boron concentrations above the regulatory standard were inadvertently discovered in downgradient groundwater monitoring wells at 22 construction and demolition (C&D) debris landfills in Florida, US. This created a unique opportunity to evaluate whether C&D debris can be considered a plausible source of boron at unlined landfills. Approximately 1200 historical landfill-leachate and groundwater records were surveyed from semi-annual and annual monitoring reports covering a 9-year period. Laboratory leaching experiments were conducted on soils from each of these sites to determine if the source could have been boron mobilized from naturally occurring soils. Historical leachate quality data from lined landfills near four of the unlined C&D debris landfills were examined to determine if leachate from the unlined landfills could be the boron source. The US Environmental Protection Agency (EPA) Method 1312, or Synthetic Precipitation Leaching Procedure (SPLP), and the EPA Method 1316 were performed on materials commonly found in C&D debris to see if these products have the potential to leach appreciable levels of boron. The results of this work indicate leachate from unlined C&D debris landfills as the most plausible source of elevated boron concentrations in downgradient monitoring wells.

The First Find of Oxyborates in Rocks of the Norilsk-1 Intrusion (Northwestern Siberian Platform)

In the taxitic gabbro-dolerites of the upper contact zone of the Norilsk-1 intrusion, five boron minerals were found: kotoite Mg3(BO3)2, suanite Mg2B2O5, warwickite (Mg,Ti,Fe,Cr,Al)2O(BO3), ludwigite (Mg)2Fe3+O2(BO3), and azoproite (Mg,Fe2+)2(Fe3+,Ti,Mg)O2(BO3). This is the first find of oxyborates in the rocks of the Norilsk ore-bearing intrusions and in the Norilsk province as a whole. Oxyborates occur as inclusions in olivine in the recrystallization zones of taxitic gabbro-dolerites. This indicates that they formed at the late-magmatic or postmagmatic stage as result of the interaction between rocks and boron-bearing fluids associated with an ore-bearing intrusion. Microinclusions of boron minerals could be the cause of elevated concentrations of boron in the rocks. This is a characteristic feature of Norilsk PGE–Cu–Ni-bearing intrusions that can be used as a prospecting criterion.

Boron exposure through drinking water during pregnancy and birth size

BackgroundBoron is a metalloid found at highly varying concentrations in soil and water. Experimental data indicate that boron is a developmental toxicant, but the few human toxicity data available concern mostly male reproduction. ObjectivesTo evaluate potential effects of boron exposure through drinking water on pregnancy outcomes. MethodsIn a mother-child cohort in northern Argentina (n=194), 1–3 samples of serum, whole blood and urine were collected per woman during pregnancy and analyzed for boron and other elements to which exposure occurred, using inductively coupled plasma mass spectrometry. Infant weight, length and head circumference were measured at birth. ResultsDrinking water boron ranged 377–10,929μg/L. The serum boron concentrations during pregnancy ranged 0.73–605μg/L (median 133μg/L) and correlated strongly with whole-blood and urinary boron, and, to a lesser extent, with water boron. In multivariable-adjusted linear spline regression analysis (non-linear association), we found that serum boron concentrations above 80μg/L were inversely associated with birth length (B−0.69cm, 95% CI −1.4; −0.024, p=0.043, per 100μg/L increase in serum boron). The impact of boron appeared stronger when we restricted the exposure to the third trimester, when the serum boron concentrations were the highest (0.73–447μg/L). An increase in serum boron of 100μg/L in the third trimester corresponded to 0.9cm shorter and 120g lighter newborns (p=0.001 and 0.021, respectively). ConclusionsConsidering that elevated boron concentrations in drinking water are common in many areas of the world, although more screening is warranted, our novel findings warrant additional research on early-life exposure in other populations.

Assessing the suitability of saline wastewaters for irrigation of Citrus spp.: Emphasis on boron and specific-ion interactions

Many ground waters and recycled municipal wastewaters contain elevated concentrations of boron (B) and salts but are nonetheless potential irrigation water sources for agricultural production. Unlike most agricultural crops, Citrus spp. is among the most sensitive to B and salinity. Here, an extensive review of the literature from 1928 to present on Citrus spp. tolerance to B and specific ions has been conducted. The overall suitability of such water supplies largely depends upon the salt and B concentration in the irrigation water, irrigation management, rainfall, soil and climatic conditions and orange rootstock. Since salinity and B stresses often occur together, the overall suitability may depend on interactive abiotic stresses as well. The combination and potential interaction of these constituents, combined with the soil and climatic conditions, can affect the overall suitability of B in irrigation water over the long-term. And there is evidence of internal tolerance mechanisms (i.e. B transport/compartmentation; B complexation) present allowing leaves to tolerate higher B concentrations than they would otherwise and that certain amendments can reduce uptake and transport from rootstock to scion. Regardless, new research does not provide any more information to suggest that the existing B tolerance guidelines for orange (0.50–0.75mg/L in the soil solution, Bss) should be adjusted upwards or downwards. The challenge comes in determining the maximum B concentration in the irrigation water (Bw) that would result in these Bss tolerance values. Two steady-state approaches that were used here suggest that the maximum Bw for the protection of orange falls between 0.3 and 0.5mg/L over the long term provided good water management, adequate leaching and no additional stresses are affecting the tree. For lemon, maximum Bw concentrations would be less. The presence of specific ions and ion interactions makes water quality assessment difficult.

국내육성 주요 딸기 품종에서 발생하는 붕소 과잉 증상 및 영양진단을 위한 식물체 내 한계농도

미량원소인 붕소(B)의 시비농도를 인위적으로 조절한 관비용액으로 '금향', '매향' 및 '설향' 딸기를 재배하면서 시비수준이 생육에 미치는 영향, 생육을 우수하게 유지할 수 있는 식물체의 한계농도, 그리고 B 과잉시비로 유발되는 생리장해의 특징을 구명하기 위하여 본 연구를 수행하였다. 0.25mM B 시비구에서 세 종류 딸기 품종의 생체중 및 건물 중이 가장 무거웠고 관부직경도 가장 굵었지만 B 시비농도가 높아짐에 지상부 생장량이 급격하게 감소하였다. B가 과다하게 시비되면 신생엽에서는 황화현상, 중간에 위치한 잎들에서는 잎 가장자리의 갈변 및 괴사현상, 그리고 하위엽들이 괴사하면서 안쪽으로 말리는 증상이 나타났다. 하위엽에서 나타나는 증상은 '금향'의 경우 2mM 이상의 처리구, '매향'과 '설향'은 0.5mM 이상의 시비구에서 잎 선단부의 갈변 및 괴사, 그리고 잎 내부에 갈변 및 괴사현상이 나타났다. B 시비농도가 증가하여도 다량원소중 양이온인 K, Ca 및 Mg 함량에는 차이가 나타나지 않았으며, 음이온인 인산 함량이 감소하는 경향을 나타냈다. B 시비농도가 증가할 때 '금향'과 '설향' 딸기에서 Fe 함량이 감소하였으며, Zn 함량이 증가하는 경향을 보였다. 건물중에 기초한 지상부 생장량의 90%와 이 때의 B 함량을 정상생육을 위한 최대한계점으로 간주할 때 '금향', '매향' 및 '설향' 딸기에서 식물체내 B 함량이 각각 25.1, 44.2 및 <TEX>$62.5mg{\cdot}kg^{-1}$</TEX> 이하를 유지하도록 B 시비농도를 조절하여야 과잉피해를 방지할 수 있다고 판단하였다. Diagnosis of nutrient disorders in cultivating crops is based on the visual symptoms and results of soil and plant analysis. This study was carried out to investigate the influence of B concentrations in fertilizer solution on the growth of and nutrient uptake by domestically bred strawberries. Tissue analysis based on the dry weight were also conducted to determine the threshold levels in plants when toxicity developed in boron. The growth was seriously restricted in the three strawberry cultivars as the B concentrations in fertilizer solution were elevated. The fresh and dry weights were heavier and crown diameters were thicker in the 0.25 mM boron treatment than the other treatments tested. The toxicity symptoms of boron appeared on the older leaves of three strawberry cultivars while interveinal chlorosis symptoms appeared on the young leaves of 'Keumhyang' and 'Seolhyang' strawberries. The toxicity symptoms in lower leaves were developed when B concentrations in fertilizer solution were higher than 2 mM in 'Keumhyang' and 0.5 mM in 'Maehyang' and 'Seolhyang' strawberries. The elevated boron concentrations in fertilizer solution did not influence the tissue K, Ca, and Mg contents, but influenced the phosphorus contents with decreasing tendency. The tissue Fe and Zn contents decreased and increased, respectively, as the B concentrations in fertilizer solution were elevated. When the concentration of boron at which the growth of a plant is retarded by 10% is regarded as a upper threshold level, the boron contents based on dry weight of above ground plant tissue should be lower than 25.1, 44.2, and 62.5 <TEX>$mg{\cdot}kg^{-1}$</TEX> in 'Keumhyang', 'Maehyang', and 'Seolhyang' strawberries, respectively.

Boron removal and recovery from concentrated wastewater using a microwave hydrothermal method

Boron compounds are widely-used raw materials in industries. However, elevated boron concentrations in aqueous systems may be harmful to human and plants. In this study, calcium hydroxide (Ca(OH)2) alone and Ca(OH)2 with phosphoric acid (H3PO4) addition (P-addition) were used to remove and recover boron from wastewater using hydrothermal methods. A microwave (MW) hydrothermal method was used and compared with the conventional heating (CH) method in batch experiments. Physicochemical properties of the precipitates obtained from both methods were analysed by XRD, SEM with EDX and BET. For the case of Ca(OH)2 alone and the MW method, experimental results showed that boron recovery efficiency reached 90% within 10min, and crystals of Ca2B2O5·H2O were found in the precipitates as indicated by the XRD analysis. For the case of P-addition and the MW method, boron recovery efficiency reached 99% within 10min, and calcium phosphate species (CaHPO4·H2O, CaHPO4 and Ca10(PO4)6(OH)2) were formed. The experimental results of this study indicate that the required reaction time of the MW method was much less than that of the CH method, and the MW method is an effective and efficient method for boron removal and recovery from concentrated wastewater.

Comparative Sensitivity of Feeding and Nonfeeding Stages of Heligmosomoides bakeri (Nematoda) to Boron

Boron compounds are increasingly recognized as important industrial pollutants. We examined whether elevated concentrations of boron would exert toxic effects on different life cycle stages of the rodent gastrointestinal nematode Heligmosomoides bakeri and established toxicity in feeding and nonfeeding stages. All stages except eggs responded in a dose-dependent manner to boron. Reduced motility of first-stage larvae immediately after hatching and of the larvae exposed to boron only at the third larval stage were observed. Moreover, exposure of third-stage larvae to high concentrations of boron reduced their infectivity to mice. Survival of first- and second-stage larvae and of fourth-stage larvae and adults cultured in vitro in boron was impaired. Interestingly, adult males were more sensitive to boron than adult females. Finally, per capita fecundity of females cultured in vitro decreased with increasing boron concentration. Together, these results show that high boron concentrations are harmful to free-living stages and to parasitic stages in vitro and support our hypothesis that nonfeeding stages (eggs and third-stage larvae) are more resistant to boron than feeding stages (first-, second-, and fourth-stage larvae and adult worms).

Mechanisms of degassing at Nevado del Ruiz volcano, Colombia

Nevado del Ruiz volcano is an andesite stratovolcano located in the northern Andes of Colombia. The volcano erupted on 11 September 1985, 13 November 1985, and 1 September 1989. The last two eruptions emitted juvenile solid material. This paper examines the volatile and light lithophile trace element contents of melt inclusions and matrix glasses from this juvenile material, and proposes a model for degassing within the volcano. Major element distributions in the glasses show two evolutionary trends, with subsidiary points that lie between the two trends. The data suggest the existence of two separate magmas, which have interacted, mingled, and mixed during their ascent and eruption. Water contents in melt inclusions, as determined by secondary ionization mass spectrometric analysis, are generally low, averaging between 1.6 and 3.3 wt.%. Halogen concentrations in the glasses range from 400 to 1200 ppm for fluorine and from 1100 to 1500 ppm for chlorine. Sulphur contents are low, not exceeding 500 ppm, with most glasses containing &lt;200 ppm. Lithium concentrations range from 20 to 40 ppm, beryllium from 1.5 to 2 ppm, and boron exhibits high variability from 30 to 100 ppm. The only significant difference between melt inclusions and matrix glasses is for water, with matrix glasses having significantly lower concentrations (&lt;0.5 wt.%) than the melt inclusions. The generally elevated concentrations of boron in the magma may be a consequence of enrichment in the source region of the magma, i.e. by subduction of altered oceanic crust and/or sediments. Yet the large degree of boron heterogeneity in both melt inclusions and matrix glasses necessitates subsequent addition of boron at shallower depths as well, by the assimilation of crustal sedimentary rocks or by interaction with hydrothermal fluids. Evidence for pre-eruptive magma emplacement at shallow levels is provided by (1) anhydrous mineral assemblages of plagioclase and pyroxene, (2) high silica contents of glasses, and (3) low water contents in melt inclusions. When combined, these observations suggest a period of magma residence at shallow depths, probably &lt;3 km beneath the summit of the volcano. A multistage model of magma transport and degassing involves alternating periods of magma ascent and magma ponding. Initially, volatile-bearing magma ascends from depths of 9–15 km, driven by buoyancy. During decompression, the magma loses gas, particularly CO 2 and sulphur. The magma eventually ponds at its neutral buoyancy level. At this point, the gas-saturated magma cools and crystallizes, thereby liberating gas under isobaric conditions. As a result, CO 2 is depleted from the magma whereas H 2 O and SiO 2 are enriched. The H 2 O enrichment is caused by its increased solubility in the magma as CO 2 is degassed, whereas SiO 2 is enriched by fractional crystallization. The density of the magma decreases as the level of dissolved H 2 O increases, eventually causing the magma to become buoyant once more and to continue its ascent, either to erupt or to freeze at shallow depths.

Naturalized salmonid populations occur in the presence of elevated trace element concentrations and temperatures in the firehole river, Yellowstone National Park, Wyoming, USA

We investigated the effects of geothermally influenced waters on the distribution of rainbow trout, Oncorhynchus mykiss, and brown trout, Salmo trutta, in the Firehole River and its tributaries in Yellowstone National Park (WY, USA) from June 1997 to June 1998. Geothermal features in the Firehole River basin elevate mineral content and temperature in portions of the river and its tributaries. We found concentrations of boron and arsenic to be elevated in geothermally influenced areas compared with upstream sites. Boron concentrations occasionally exceeded 1,000 microg/L, a proposed limit for the protection of aquatic organisms. Arsenic concentrations occasionally exceeded 190 microg/L, the chronic ambient water quality criterion. Temperatures in geothermally influenced sites ranged up to 30 degrees C and were consistently 5 to 10 degrees C higher than upstream sites unaffected by geothermal inputs. Rainbow trout occurred at sites with elevated concentrations of boron, arsenic, and other trace elements and elevated water temperatures. Rainbow trout inhabited and spawned at sites with the most elevated trace element concentrations and temperatures; however, brown trout were absent from these sites. Water temperature may be the major factor determining brown trout distributions, but we cannot exclude the possibility that brown trout are more sensitive than rainbow trout to boron, arsenic, or other trace elements. Further investigations are needed to determine species-specific tolerances of boron, arsenic, and other trace elements among salmonids.

Effects of boron and nitrate on hatching success of amphibian eggs.

As part of a land-application wastewater disposal system in central Pennsylvania, vernal ponds are commonly exposed to wastewater effluent containing high levels of boron and nitrate. We examined the individual effects of these compounds on the eggs of amphibians breeding in these ponds. Wood frog (Rana sylvatica), Jefferson salamander (Ambystoma jeffersonianum), spotted salamander (A. maculatum), and American toad (Bufo americanus) eggs were exposed to boron (0, 50, and 100 mg L-1) and nitrate (0, 10, 25, and 40 mg L-1) under laboratory conditions. There was no difference in the hatching success or proportion of deformed larvae among the four nitrate levels in any of the species. High boron concentrations reduced the hatching success of B. americanus and produced more deformed offspring in R. sylvatica, A. jeffersonianum, and A. maculatum. Deformed R. sylvatica and A. jeffersonianum hatchlings displayed a "curling defect" in which the larvae had a crescent body shape and expressed difficulty in swimming. A. maculatum larvae from high boron treatments displayed a different abnormality, possibly because of longer times to hatching, characterized by a swelling of the thoracic region and altered gill morphology. Although the concentrations of boron and nitrate tested were within the range measured in wastewater effluent, maximum levels of boron and nitrate in breeding ponds were only 1.5 mg L-1 and 26.7 mg L-1 respectively, likely due to rainwater dilution and biological and chemical processes reducing the levels of these compounds in vernal ponds. Nonetheless, these studies are the first to examine the effects of boron and nitrate on amphibian egg hatching success, and to demonstrate that elevated boron concentrations can detrimentally affect the development of amphibian embryos.

Ecological risk assessment of a wetland exposed to boron

A wetland located in the southeastern portion of the United States was the site of an investigation to determine the potential ecological risk of elevated boron concentrations to the flora and fauna living in the wetland. The conceptual model identified the vegetation as the primary receptor of concern, and thus the vegetation is the focus of this article. Samples of surface water, sediments, and selected vegetation were collected from the study wetland and several nearby reference sites and were analyzed for boron. Concentrations of boron in all three media exceeded reference site concentrations. Boron concentrations were highest near the suspected source but decreased almost to reference-site concentrations near the outer perimeter of the wetland. Some plants appeared stressed with yellowing and necrotic leaves; however, a correlation between tissue boron concentrations and the plant's visual appearance was not apparent for all species studied. Modeling of the fate of boron indicated that the wetland has likely been at a steady state for many years and that boron concentrations were not expected to increase. It was concluded that no observable adverse ecological impacts to the vegetation could be attributed to boron, nor is it likely that the boron poses an unacceptable risk to the surrounding areas.

ECOLOGICAL RISK ASSESSMENT OF A WETLAND EXPOSED TO BORON

A wetland located in the southeastern portion of the United States was the site of an investigation to determine the potential ecological risk of elevated boron concentrations to the flora and fauna living in the wetland. The conceptual model identified the vegetation as the primary receptor of concern, and thus the vegetation is the focus of this article. Samples of surface water, sediments, and selected vegetation were collected from the study wetland and several nearby reference sites and were analyzed for boron. Concentrations of boron in all three media exceeded reference site concentrations. Boron concentrations were highest near the suspected source but decreased almost to reference-site concentrations near the outer perimeter of the wetland. Some plants appeared stressed with yellowing and necrotic leaves; however, a correlation between tissue boron concentrations and the plant's visual appearance was not apparent for all species studied. Modeling of the fate of boron indicated that the wetland has likely been at a steady state for many years and that boron concentrations were not expected to increase. It was concluded that no observable adverse ecological impacts to the vegetation could be attributed to boron, nor is it likely that the boron poses an unacceptable risk to the surrounding areas.