Biomineralogy of human urinary calculi (kidney stones) from some geographic regions of Sri Lanka

Kidney stones (urinary calculi) have become a global scourge since it has been recognized as one of the most painful medical problems. Primary causative factors for the formation of these stones are not clearly understood, though they are suspected to have a direct relationship to the composition of urine, which is mainly governed by diet and drinking water. Sixty nine urinary calculi samples which were collected from stone removal surgeries were analyzed chemically for their Na, K, Ca, Mg, Cu, Zn, Pb, Fe and phosphate contents. Structural and mineralogical properties of stones were studied by XRD and FT-IR methods. The mean contents of trace elements were 1348 mg kg⁻¹ (Na); 294 mg kg⁻¹ (K); 32% (Ca); 1426 mg kg⁻¹ (Mg); 8.39 mg kg⁻¹ (Mn); 258 mg kg⁻¹ (Fe); 67 mg kg⁻¹ (Cu); 675 mg kg⁻¹ (Zn); 69 mg kg⁻¹ (Pb); and 1.93% (PO₄³⁻). The major crystalline constituent in the calculi of Sri Lanka is calcium oxalate monohydrate. Principal component analysis was used to identify the multi element relationships in kidney stones. Three components were extracted and the first component represents positively correlated Na-K-Mg-PO₄³⁻ whereas the␣second components represent the larger positively weighted Fe–Cu–Pb. Ca–Zn correlated positively in the third component in which Mn–Cu correlated negatively. This study indicates that during the crystallization of human urinary stones, Ca shows more affinity towards oxalates whereas other alkali and alkaline earths precipitate with phosphates.Contribution from the Environmental Geology Research Group (EGRG), Department of Geology, University of Peradeniya, Sri Lanka.     

Assessment of toxicity of heavy metal contaminated soils by the toxicity characteristic leaching procedure

The concentrations of Cu, Zn, Pb and Cd in soils near a lead–zinc mine located in Shangyu, Zhejiang Province, China, were determined and their toxicity was assessed using the toxicity characteristic leaching procedure (TCLP) developed by the United States Environmental Protection Agency. The TCLP method is a currently recognized international method for evaluation of heavy metal pollution in soils. The available levels of Cu, Zn, Pb and Cd were 8.2–36, 23–143, 6.4–1367 and 0.41–2.2 mg kg⁻¹, respectively, while the international standards were 15, 25, 5 and 0.5 mg kg⁻¹, respectively. Soils around the mine were more polluted with Zn and Pb, followed by Cd and Cu. Moreover, the levels of heavy metals in the soils extracted by TCLP indicated that extraction fluid 2 was more effective than extraction fluid 1 in extracting the heavy metals from the polluted soils and there was a positive correlation between fluids 1 and 2. Available heavy metal contents determined by TCLP were correlated with soil total heavy metal contents.     

Do corals select zooxanthellae by alternative discharge?

Loss of zooxanthellae (dinoflagellate Symbiodinium) from corals will sometimes lead to mass mortality of corals. To detect and quantify Symbiodinium released from corals, we developed a zooxanthellae “trap” and a quantitative PCR (qPCR) system with Symbiodinium clades A–F-specific primer sets. The trap was attached to a branch or the surface of several wild stony corals, and the water samples within the traps, including released Symbiodinium, were subjected to qPCR. All tested corals released clade C Symbiodinium at estimates of ~5,900 cells h⁻¹ cm⁻² of coral surface. Although all tested Pocillopora eydouxi harboured both clades C and D, some of these colonies released only clade C or released a lesser amount of clade D than that in the tissues. Our Symbiodinium quantification system revealed that wild hermatypic corals constantly release Symbiodinium to the environment. Our result suggests that some corals may discharge certain clades of Symbiodinium alternatively.     

Human risk assessment of As,Cd, Cu and Zn in the abandoned metal mine site

The cancer risk and the non-cancer hazard index for inhabitants exposed to As, Cd, Cu and Zn in the soils and stream waters of the abandoned Songcheon Au–Ag mine area were evaluated. Mean concentrations of As, Cd, Cu, Pb and Zn in agricultural soils were 230, 2.5, 120, 160, and 164 mg kg⁻¹, respectively. Mean concentrations of As, Cd and Zn of the water in the stream where drinking water was drawn was 246 μg L⁻¹, 161 μg L⁻¹ and 3899 μg L⁻¹, respectively. These levels are significantly higher than the permissible levels for drinking water quality recommended by Korea and WHO. The resulting human health risks to farmers who inhabited the surrounding areas due to drinking water were summarized as follows: (1) the non-cancer health hazard indices showed that the toxic risk due to As and Cd in drinking water were 10 and 4 times, respectively, greater than those induced by the safe average daily dosages of the respective chemicals. (2) the cancer risk of As for exposed individuals through the drinking water pathway was 5 in 1000, exceeded the acceptable risk of 1 in 10,000 set for regulatory purposes.     

Geochemistry of leachates from the El Fraile sulfide tailings piles in Taxco, Guerrero, southern Mexico

Leachates from the El Fraile tailings impoundment (Taxco, Mexico) were monitored every 2 months from October 2001 to August 2002 to assess the geochemical characteristics. These leachates are of interest because they are sometimes used as alternative sources of domestic water. Alternatively, they drain into the Cacalotenango creek and may represent a major source of metal contamination of surface water and sediments. Most El Fraile leachates show characteristics of Ca–SO₄, (Ca+Mg)–SO₄, Mg–SO₄ and Ca–(SO₄+HCO₃) water types and are near-neutral (pH=6.3–7.7). Some acid leachates are generated by the interaction of meteoric water with tailings during rainfall events (pH=2.4–2.5). These contain variable levels of SO₄ ²⁻ (280–29,500 mg l⁻¹) and As (<0.01–12.0 mg l⁻¹) as well as Fe (0.025–2352 mg l⁻¹), Mn (0.1–732 mg l⁻¹), Zn (<0.025–1465 mg l⁻¹) and Pb (<0.01–0.351 mg l⁻¹). Most samples show the highest metal enrichment during the dry seasons. Leachates used as domestic water typically exceed the Mexican Drinking Water Guidelines for sulfate, hardness, Fe, Mn, Pb and As, while acidic leachates exceed the Mexican Guidelines for Industrial Discharge Waters for pH, Cu, Cd and As. Speciation shows that in near-neutral solutions, metals exist mainly as free ions, sulfates and bicarbonates, while in acidic leachates they are present as sulfates and free ions. Arsenic appears as As^(V) in all samples. Thermodynamic and mineralogical evidence indicates that precipitation of Fe oxides and oxyhydroxides, clay minerals and jarosite as well as sorption by these minerals are the main processes controlling leachate chemistry. These processes occur mainly after neutralization by interaction with bedrock and equilibration with atmospheric oxygen.     

Coral mortality following extreme low tides and high solar radiation

Extreme tidal events are one of the most predictable natural disturbances in marine benthic habitats and are important determinants of zonation patterns in intertidal benthic communities. On coral reefs, spring low tides are recurrent disturbances, but are rarely reported to cause mass mortality. However, in years when extremely low tides coincide with high noon irradiances, they have the potential to cause widespread damage. Here, we report on such an event on a fringing coral reef in the central Great Barrier Reef (Australia) in September 2005. Visual surveys of colony mortality and bleaching status of more than 13,000 corals at 14 reef sites indicated that most coral taxa at wave-protected sites were severely affected by the event. Between 40 and 75% of colonies in the major coral taxa (Acropora, Porites, Faviidae, Mussidae and Pocilloporidae) were either bleached or suffered partial mortality. In contrast, corals at wave-exposed sites were largely unaffected (<1% of the corals were bleached), as periodic washing by waves prevented desiccation. Surveys along a 1–9 m depth gradient indicated that high coral mortality was confined to the tidal zone. However, 20–30% of faviid colonies were bleached throughout the depth range, suggesting that the increase in benthic irradiances during extreme low tides caused light stress in deeper water. Analyses of an 8-year dataset of tidal records for the area indicated that the combination of extended periods of aerial exposure and high irradiances occurs during May–September in most years, but that the event in September 2005 was the most severe. We argue that extreme low-tide, high-irradiance events are important structuring forces of intertidal coral reef communities, and can be as damaging as thermal stress events. Importantly, they occur at a time of year when risks from thermal stress, cyclones and monsoon-associated river run-off are minimal.     

Arsenic contamination in water,soil, sediment and rice of central India

Arsenic contamination in the environment (i.e. surface, well and tube-well water, soil, sediment and rice samples) of central India (i.e. Ambagarh Chauki, Chhattisgarh) is reported. The concentration of the total arsenic in the samples i.e. water (n=64), soil (n=30), sediment (n=27) and rice grain (n=10) were ranged from 15 to 825 μg L⁻¹, 9 to 390 mg kg⁻¹, 19 to 489 mg kg⁻¹ and 0.018 to 0.446 mg kg⁻¹, respectively. In all type of waters, the arsenic levels exceeded the permissible limit, 10 μg L⁻¹. The most toxic and mobile inorganic species i.e. As(III) and As(V) are predominantly present in water of this region. The soils have relatively higher contents of arsenic and other elements i.e. Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, As, Ga, Zr, Sn, Sb, Pb and U. The mean arsenic contents in soil of this region are much higher than in arsenic soil of West Bengal and Bangladesh. The lowest level of arsenic in the soil of this region is 3.7 mg kg⁻¹ with median value of 9.5 mg kg⁻¹. The arsenic contents in the sediments are at least 2-folds higher than in the soil. The sources of arsenic contamination in the soil of this region are expected from the rock weathering as well as the atmospheric deposition. The environmental samples i.e. water, soil dust, food, etc. are expected the major exposure for the arsenic contamination. The most of people living in this region are suffering with arsenic borne diseases (i.e. melanosis, keratosis, skin cancer, etc.).     

Risk assessment of heavy metal contamination in shrimp farming in Mai Po Nature Reserve, Hong Kong

An ecological survey was carried out to determine the sediment concentrations of nutrients and heavy metals and bioaccumulation of heavy metals in fish and shrimp including tilapia (Oreochromis mossambicus×O. nilotica), grey mullet (Mugil cephalus), gei wai shrimp (Metapenaeus ensis) and caridean shrimp (Macrobrachium nipponensis) in the traditional tidal shrimp ponds (gei wais) of Mai Po Nature Reserve, Hong Kong. The sediments collected from the landward sites contained higher nutrient contents, as well as zinc (Zn), chromium (Cr), copper (Cu), nickel (Ni) and cadmium (Cd) than those collected from the seaward sites, but vice versa for lead (Pb) and mercury (Hg). However, the concentrations of all metals were exceptionally high in the two sites located outside the reserve, suggesting that waters from Deep Bay might be the possible source of metal contamination affecting the reserve. All metals studied seemed to accumulate in the viscera of fish. Body size was the determining factor for the accumulation of heavy metals in caridean shrimp and gei wai shrimp but not fish. Concentrations of the metals studied in tissues of grey mullet and gei wai shrimp were found to be safe for human consumption. Concentrations of Cr in tilapia whole body (0.68–1.10 mg kg⁻¹ wet weight) were close to or over the guideline value of 1 mg kg⁻¹ set by the Food Adulteration (Metallic Contamination) Regulations of Hong Kong. Tilapia flesh and small caridean shrimp collected from gei wais were contaminated by Cr and Pb but still fit for human consumption. Caution is required if large caridean shrimp is to be consumed in large amounts continuously because the concentration of Pb exceeded the maximum permitted concentration (6 mg kg⁻¹). The rather high Cr concentrations in tilapia whole body should not be overlooked as the fish will serve as a food source for migratory birds visiting the site.     

Effects of Cadmium on Nutrient Uptake and Translocation by Indian Mustard

Plants that hyperaccumulate metals are ideal subjects for studying the mechanisms of metal and mineral nutrient uptake in the plant kingdom. Indian Mustard (Brassica juncea) has been shown to accumulate moderate levels of Cd, Pb, Cr, Ni, Zn, and Cu. In this experiment, 10 levels of Cd concentration treatments were imposed by adding 10–190 mg Cd kg^–1 to the soils as cadmium nitrate [Cd(NO₃)₂]. The effect of Cd on phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), and the micronutrients iron (Fe), manganese (Mn), copper (Cu), and zinc (Zn) in B. juncea was studied. Plant growth was affected negatively by Cd, root biomass decreased significantly at 170 mg Cd kg^–1 dry weight soils treatment. Cadmium accumulation both in shoots and roots increased with increasing soil Cd treatments. The highest concentration of Cd was up to 300 mg kg^–1 d.w. in the roots and 160 mg kg^–1 d.w. in the shoots. The nutrients mainly affected by Cd were P, K, Ca, Fe, and Zn in the roots, and P, K, Ca, and Cu in the shoots. K and P concentrations in roots increased significantly when Cd was added at 170 mg kg^–1, and this was almost the same level at which root growth was inhibited. Zn concentrations in roots decreased significantly when added Cd concentration was increased from 50 to 110 mg kg^–1, then remained constant with Cd treatments from 110 to 190 mg kg^–1. However, Zn concentrations in the shoots seemed less affected by Cd. It is possible that Zn uptake was affected by the Cd but not the translocation of Zn within the plant. Ca and Mg accumulation in roots and shoots showed similar trends. This result indicates that Ca and Mg uptake is a non-specific process.     

Assessment of As and Heavy Metal Contamination in the Vicinity of Duckum Au-Ag Mine, Korea

In order to assess the potential of As and heavy metal contamination derived from past mining activity and to estimate the human bioavailability quotients for As and heavy metals. Tailings, soils and crop samples were collected and analysed for As, Cd, Cu, Pb and Zn. The mean concentrations of As, Cd, Cu, Pb and Zn in the tailings were 68.5, 7.8, 99, 3,754 and 733 µg g^–1, respectively. Maximum Pb concentration in tailings was up to 90 times higher than its tolerable level. The concentrations of these metals were highest in the soils from the dressing plant area, and decreased in the order: farmland soil to paddy soil. In particular, some of the soils from the dressing plant area contained more than 1% of Pb and Zn. The pollution index ranged from 0.19 to 1.93 in paddy soils, and from 1.47 to 3.60 in farmland soils. The average concentrations of heavy metals in crops collected from farmland were higher than those in rice stalks or rice grains, and higher than the internationally accepted limits for vegetables. Element concentrations extracted from farmland soils within the simulated human stomach for 1 h are 9.4 mg kg^–1 As, 3.8 mg kg^–1 Cd, 37 mg kg^–1 Cu, 250 mg kg^–1 Pb and 301 mg kg^–1 Zn. In particular, the extracted concentrations of Cd, Pb and Zn are in excess of the tolerable levels. The results of the simple bioavailability extraction test (SBET) indicate that regular ingestion (by inhalation and from dirty hands) of soils by the local population could pose a potential health threat due to long-term toxic element exposure.     

Coral bleaching, bleaching-induced mortality, and the adaptive significance of the bleaching response

Coral bleaching events are often associated with higher levels of coral mortality but when this occurs in the chronology of individual bleaching events is poorly documented. Knowing when mortality occurs is important for understanding molecular mechanisms and the putative adaptive significance of the response (the Adaptive Bleaching Hypothesis). In a detailed study of a coral bleaching event on the Great Barrier Reef, involving weekly and twice weekly repetitive observations of >200 individually marked corals over an 18 month period (∼16,000 observations), it is shown that bleaching in Acropora latistella, A. subulata and Turbinaria mesenterina was an acute, rapid response, occurring within days of a peak in seawater temperatures exceeding previously described thresholds. Subsurface light levels, measured over the duration of the event, were not anomalous. Full bleaching (i.e. whole colonies turning bone-white) and partial bleaching (white patches) was observed in the Acropora spp. whilst the T. mesenterina colonies typically paled to a light brown colour. Algal densities in bleached corals were 10–30% of those of normally pigmented corals (∼2.5 × 10⁶ algae per cm²), and in this instance bleaching was clearly a sudden, isolated, stress event and not an extreme low-point in the seasonal fluctuation of the density of symbiotic algae. Bleached corals were associated with high levels of partial and whole-colony mortality, but mortality was exclusively limited to the two Acropora spp. Importantly, most of this mortality was recorded in surveys conducted 1 and 2 weeks after bleaching was first observed, and for A. latistella as little as 1 week after bleaching was first observed. This suggests that in this particular bleaching event, for the Acropora species, that bleaching and mortality were intimately linked: this in turn suggests it was a pathological phenomenon. The study highlights a problem in the adaptive bleaching hypothesis, whereby significant levels of mortality can occur in a bleaching event before any chance for subsequent recombination of the host-symbiont unit. It is argued that in order to further evaluate the significance of bleaching as a potentially adaptive mechanism, bleaching-induced and bleaching-related mortality have to be fully considered. It is necessary to incorporate the cost (in terms of mortality) of a bleaching event, the recurring cost of reverting to the original, mortal, stress–prone combination after the event, and the higher cost associated with forming a maladaptive combination.     

Elevated Levels of Cadmium and Zinc in Paddy Soils and Elevated Levels of Cadmium in Rice Grain Downstream of a Zinc Mineralized Area in Thailand: Implications for Public Health

Prolonged consumption of rice containing elevated cadmium (Cd) levels is a significant health issue particularly in subsistence communities that are dependent on rice produced on-farm. This situation is further exacerbated in areas of known non-ferrous mineralization adjacent to rice-based agricultural systems where the opportunity for contamination of rice and its eventual entry into the food chain is high. In the current study, an assessment of the degree of soil Cd and Zn contamination and associated rice grain Cd contamination downstream of an actively mined zone of Zn mineralization in western Thailand was undertaken. Total soil Cd and Zn concentrations in the rice-based agricultural system investigated ranged from 0.5 to 284 mg kg⁻¹ and 100 to 8036 mg kg⁻¹, respectively. Further, the results indicate that the contamination is associated with suspended sediment transported to fields via the irrigation supply. Consequently, the spatial distribution of Cd and Zn is directly related to a field’s proximity to primary outlets from in-field irrigation channels and inter-field irrigation flows with 60–100% of the Cd and Zn loading associated with the first three fields in irrigation sequence. Rice grain Cd concentrations in the 524 fields sampled, ranged from 0.05 to 7.7 mg kg⁻¹. Over 90% of the rice grain samples collected contained Cd at concentrations exceeding the Codex Committee on Food Additives and Contaminants (CCFAC) draft Maximum Permissible Level for rice grain of 0.2 mg Cd kg⁻¹. In addition, as a function of demographic group, estimated Weekly Intake (WI) values ranged from 20 to 82 μg Cd per kg Body. This poses a significant public health risk to local communities. The results of this study suggest that an irrigation sequence-based field classification technique in combination with strategic soil and rice grain sampling and the estimation of WI values via rice intake alone may be a useful decision support tool to rapidly evaluate potential public health risks in irrigated rice-based agricultural systems receiving Cd contaminated irrigation water. In addition, the proposed technique will facilitate the cost effective strategic targeting of detailed epidemiological studies thus focusing resources to specific ‘high risk’ areas.     

Lead,copper and zinc in atmospheric and fluvial particulates from the Caracas Valley,Venezuela

The atmospheric particulates from the Caracus Valley in Venezuela and the fluvial particulates transported by the Tuy River into the Caribbean sea have been evaluated for Pb, Cu and Zn with the purpose of determining the contamination levels in the study area. The atmospheric particulate samples were collected in the city of Caracas using a low volume sampler whereas the fluvial particulate were collected at the mouth of the Tuy River. The particulate samples were analysed by flame or graphite furnace atomic absorption spectrometry depending upon the concentration levels of the heavy metal under study. The results obtained for the fluvial particulates enabled estimates to be made of the total anthropogenic flux of Cu (383 ton year^–1), Pb (528 ton year^–1) and Zn (865 ton year^–1). These results yield annual per capita inputs for Cu (96 g),Pb (132 g) and Zn (216 g) which greatly exceed those from global anthropogenic emissions. The weighted average concentration of Pb (1.13 %) found in the atmospheric particulates was much higher than those for Cu (140 mg kg^–1) and Zn (200 mg kg^–1) and reflects the high motor car traffic in the Caracas Valley. The anthropogenic/natural ratios estimated in this study were as follows: 2.6 for Pb; 1.5 for Cu and 1.5 for Zn. This indicates that anthropogenic inputs for Cu, Pb, and Zn in the study area exceed those from natural sources, cars being the major source for Pb and industrial activities the major sources for Cu and Zn.     

Metal levels in computer monitor components discarded in the vicinities of electronic workshops

Levels of Pb, Ni, Cr, Cu, Zn, and Cd in the glass screens (GS) and printed wiring boards (PWBs) of obsolete computer monitors (OCMs) were determined by flame atomic absorption spectrophotometry (FAAS) following standard digestion. Metal concentrations (mg kg^?1) in GS were in the following ranges (medians in brackets): Pb ND – 3100 (46), Cd 0.5–2.6 (0.8), Cr ND – 18.7 (3.1), and Zn 8.1–600 (37) and in PWBs (mg kg^?1): Pb 34,600 ± 17,000, Cd 11 ± 9, Cr 59 ± 45, Zn 15,900 ± 7800, Cu79,000 ± 22,600, and Ni 3200 ± 2500. In GS, the levels of the six metals were lower than their total threshold limit concentrations (TTLC), except for Pb with a TTLC of 1000 mg kg^?1 in 10% of the samples. In the PWBs, the TTLC of Pb and Cu (2500 mg kg^?1) was exceeded many fold. For Zn (5000 mg kg^?1) and Ni (2000 mg kg^?1); they were exceeded by 90% and 65%, respectively. For OCMs manufactured in 2001 and later, Pb and Zn levels in GS and Cr, Zn, and Ni in PWBs were significantly reduced.     

Chemical Changes in Agricultural Soils of Korea: Data Review and Suggested Countermeasures

The monitoring of chemical properties, including heavy metals, in soils is necessary if better management and remediation practices are to be established for polluted soils. The National Institute of Agricultural Science and Technology initiated a monitoring study that investigated fertility and heavy metal contents of the benchmarked soils. The study covered paddy soils, upland soils, and horticultural soils in the plastic film houses, and orchard soils throughout the Korea from 1990 to 1998. Likewise,4047 samples of paddy and 2534 samples of plastic house in 1999 and 2000 were analyzed through the Soil Environment Conservation Act. Soil chemical properties such as pH, organic matter, availablephosphate and extractable calcium, magnesium and potassium contents, and heavy metal contentssuch as cadmium, copper, lead, zinc, arsenic, mercury, and cobalt contents were analyzed. The studyshowed that the average contents of organic matter, available phosphate, and extractable potassiumrapidly increased in plastic house soils than in upland or paddy soils. Two kinds of fertilizer recommendation systems were established for the study: the standard levels by national soil average data for 77 crops and the recommendation by soil test for 70 crops. Standard nitrogen fertilizer application levels for cereal crops changed from 94 kg/ha in 1960s, 99 kg/ha in 1970s, 110 kg/ha in 1980s to 90 kg/ha in 1990s. The K₂O-fertilizer also changed from 67 kg/ha in 1960s, 76 kg/ha in 1970s, 92 kg/ha in 1980s, andonly 44 kg/ha in 1990s. In rice paddy fields, the average contents of Cd, Cu, Pb, and Zn in surface soils(0–15 cm depth) were 0.11 mg kg^–1(ranged from 0 to 1.01), 4.70 mg kg^–1(0–41.59), 4.84 mg kg^–1(0–66.44), and 4.47 mg kg^–1(0–96.70), respectively. In the uplands, the average contents of Cd, Cu, Pb, Zn,and As in surface soils (0–15 cm depth) were 0.135 mg kg^–1(ranged from 0 to 0.660), 2.77 mg kg^–1(0.07–78.24), 3.47 mg kg^–1(0–43.00), 10.70 mg kg^–1(0.30–65.10), and 0.57 mg kg^–1(0.21–2.90), respectively. In plastic film houses, the average contents of Cd, Cu, Pb, Zn, and As in surface soil were 0.12 mg kg^–1(ranging from 0 to 1.28), 4.82 mg kg^–1(0–46.50), 2.68 mg kg^–1(0–46.50), 31.19 mg kg^–1(0.19–252.0), and 0.36 mg kg^–1(0–4.98), respectively. In orchard fields, the averagecontents of Cd, Cu, Pb, Zn, As, and Hg in surface soils (0–20 cm depth) were 0.11 mg kg^–1(ranged from 0–0.49), 3.62 mg kg^–1(0.03–45.30), 2.30 mg kg^–1(0–27.80), 16.60 mg kg^–1(0.33–105.50),0.44 mg kg^–1(0–4.14), and 0.05 mg kg^–1(0.01–0.54), respectively. For polluted soils with over thewarning content levels of heavy metals, fine red earth application, land reconsolidation and soilamelioration such as lime, phosphate, organic manure, and submerging were recommended. For the countermeasure areas, cultivation of non-edible crops such as garden trees, flowers, and fiber crops; landreformation; and heavy application of finered earth (up to 30 cm) were strongly recommended. Landuse techniques should be changed to beharmonious with the environment to increase yield andincome. Soil function characteristics should betaken into account.     

The potential ecological risk of soil trace metals following over five decades of agronomical practices in a semi-arid environment

The concentration and potential ecological risk of Mn, Zn, Cu, and Cd in the surface soils (0–30?cm) belonging to 12 soil profiles and 4 soil types (Vertisols, Chernozems, Calcisols, and Cambisols) from the cultivated soils and the corresponding uncultivated soils were investigated. Long-term cultivation caused a considerable build-up diethylene-triamine pentaacetic acid (DTPA)-extractable Mn (7–55%), and Cd (12–31%) as well as the total form of Zn (3–14%), Cu (8–25%), and Cd (33–78%) in all soil types. Following long-time cropping, total Zn (mean?=?73?mg?kg^?1), Cu (mean?=?33?mg?kg^?1), and Cd (mean?=?3.14?mg?kg^?1) and DTPA Zn (mean?=?1.2?mg?kg^?1) and Cu (mean?=?2.44?mg?kg^?1) were below their maximum allowable limits. However, the average amount of DTPA Cd in the tilled soils (min?=?0.4, max?=?0.75, mean?=?0.55?mg?kg^?1) was above its maximum permissible limit mainly due to the over application of phosphate fertilisers and the pesticides. Considering the potential ecological risk (RI) assessment of the cultivated soils (min?=?44, max?=?70, mean?=?54), the soil types were categorised as low (RI?≤?50) to moderate (50?相似文献   

Genotypic variation in element concentrations in brown rice from Yunnan landraces in China

The mineral elements present in brown rice play an important physiological role in global human health. We investigated genotypic variation of eight of these elements (P, K, Ca, Mg, Fe, Zn, Cu, and Mn) in 11 different grades of brown rice on the basis of the number and distance coefficients of 282 alleles for 20 simple sequence repeat (SSR) markers. Six-hundred and twenty-eight landraces from the same field in Yunnan Province, one of the largest centers of genetic diversity of rice (Oryza sativa L.) in the world, formed our core collection. The mean concentrations (mg kg⁻¹) of the eight elements in brown rice for these landraces were P (3,480) > K (2,540) > Mg (1,480) > Ca (157) > Zn (32.8) > Fe (32.0) > Cu (13.6) > Mn (13.2). Mean P concentrations in brown rice were 6.56 times total soil P, so the grains are important in tissue storage of P, but total soil K is 7.82 times mean K concentrations in brown rice. The concentrations of the eight elements in some grades of brown rice, on the basis of the number and distance coefficients of alleles for 20 SSR markers for the landraces, were significantly different (P < 0.05), and further understanding of the relationship between mineral elements and gene diversity is needed. There was large variation in element concentrations in brown rice, ranging from 2,160 to 5,500 mg P kg⁻¹, from 1,130 to 3,830 mg K kg⁻¹, from 61.8 to 488 mg Ca kg⁻¹, from 864 to 2,020 mg Mg kg⁻¹, from 0.40 to 147 mg Fe kg⁻¹, from 15.1 to 124 mg Zn kg⁻¹, from 0.10 to 59.1 mg Cu kg⁻¹, and from 6.7 to 26.6 mg Mn kg⁻¹. Therefore, germplasm evaluations for Ca, Fe, and Zn concentrations in rice grains have detected up to sevenfold genotypic differences, suggesting that selection for high levels of Ca, Fe, and Zn in breeding for mass production is a feasible approach. Increasing the concentrations of Ca, Fe, and Zn in rice grains will help alleviate chronic Ca, Zn, and Fe deficiencies in many areas of the world.     

Selenium Distribution in Topsoils and Plants of a Semi-arid Mediterranean Environment

Selenium was determined from 25 topsoils and 25 plants in the semi-arid Central Spain where large extents of soils are developed on evaporitic materials. Some species of vegetation associated with them are of the genera Astragalus, Salsola, Mercurialis, Phlomis, Thymus and Atriplex. Total selenium in soils was determined and its bioavailability assessed by chemical sequential fractionation. Se content in soils was adequate (in the range 0.17–0.39 mg kg⁻¹) or large (in the range 0.50–4.38 mg kg⁻¹) and appeared in highly and/or potentially available forms. Several plant species showed high Se levels (in the range 5–14.3 mg kg⁻¹), which can be a potential risk of toxicity to animals. Data obtained from the study area can be used as a guide to the range of values in soils and plants of the European Mediterranean area that are relatively unpolluted from industrial sources, allowing comparison with more polluted areas.     

Trace element concentration in wheat grain: results from the Swedish long-term soil fertility experiments and national monitoring program

Concentrations of trace elements in wheat grain sampled between 1967 and 2003 from the Swedish long-term soil fertility experiments were analyzed using ICP-MS. The long-term effect of inorganic and organic fertilization on trace metal concentrations was investigated including the impact of atmospheric deposition and myccorhiza, whereas other factors such as soil conditions, crop cultivar, etc. are not discussed in this paper. Mean values derived from 10 experimental sites were reported. Significantly declining Pb and Cd concentrations in wheat grain could be explained by lower atmospheric deposition. Mean Se contents in all samples were 0.031 mg kg⁻¹ grain dry weight. No samples had sufficiently high Se concentrations for human (0.05 mg Se kg⁻¹) or animal demand (0.1 mg Se kg⁻¹). Concentrations of Co in wheat grain were extremely low, 0.002–0.005 mg Co kg⁻¹ grain dry weight, and far below the minimum levels required by animals, which applied to all fertilizer treatments. A doubling of Mo concentrations in grain since 1975 resulted in Cu/Mo ratios often below one, which may cause molybdenosis in ruminants. The increase in Mo concentrations in crops correlated with the decline in sulfur deposition. Concentrations of Cu and Fe declined in NPK-fertilized wheat as compared to unfertilized or manure-treated wheat. Very low concentrations of Se and Co and low concentrations of Fe and Cu require attention to counteract risks for deficiencies. The main characteristic of the study is that there are few significant changes over time between different fertilizer treatments, but throughout there are low concentrations of most trace elements in all treatments. In general, good agreement between concentrations in wheat from the long-term fertility experiments and the national monitoring program indicate that values are representative.     

Seasonal AVS–SEM relationship in sediments and potential bioavailability of metals in industrialized estuary, southeastern Brazil

In anoxic sediments, as those found in estuaries, the mobility of metals can be controlled by the formation of stable sulfide complexes. The potential bioavailability of a metal can then be predicted on the basis of the acid volatile sulfide (AVS) and simultaneously extracted metals (SEM) criterion. Distributions of AVS and SEM (Hg, Cu, Pb, Cd, Zn, and Ni) along the sediment profiles were determined seasonally for three rivers that constitute the Santos-Cubat?o estuarine system (SE Brazil), which is located in one of the most industrialized areas of Latin America. AVS and SEM concentrations varied significantly, from 0.04 to 31.9 μmol g⁻¹ and 0.086–6.659 μmol g⁻¹, respectively. The highest AVS levels in sediments were detected in the winter, whereas high SEM values predominated in the summer. Considering SEM–AVS molar differences as a parameter to evaluate potential bioavailability, sediments nearest to the industrial area represent higher risk to biota, especially during the summer. It is due to relatively low AVS values and not necessarily high concentrations of metals.