Single and joint effects of acetochlor and urea on earthworm Esisenia foelide populations in phaiozem

Much attention is paid to soil health and environmental safety. Earthworms are an important indicator of soil ecosystem health and safety. Ecological toxicity of acetochlor and excessive urea, in both their single and joint effects, on earthworm Esisenia foelide was thus studied using the soil-culture method. Acetochlor had an enhanced toxicity from low concentration to high concentration. The mortality of earthworms after a 6-day exposure was changed from 0 to 86.7%, and the weight change rate ranged from 7.86 to -30.43%, when the concentration of acetochlor was increased from 164 to 730 mg kg(-1). Urea expressed its positive and beneficial effects on earthworms when its concentration was lower than 500 mg kg(-1). Strongly toxic effects took place when the concentration of urea was higher than 1000 mg kg(-1). The mortality of earthworms exposed to urea reached 100% when its concentration was more than 1500 mg kg(-1). When the concentration of urea was lower than 500 mg kg(-1), there were antagonistic effects between the two agrochemicals on earthworms; when the concentration of urea was higher than 500 mg kg(-1), joint toxic effects of acetochlor and excessive urea on earthworms were synergic. In any case, excessive urea application is very harmful to the health of soil ecosystems.     

Sequential extraction of copper from soils and relationships with copper in maize

We studied copper uptake by maize grown on soils that have been contaminated with CuSO₄. In soil the total copper level ranged from 24 to 135 mg kg^–1. The copper distribution in soil fractions was assessed by sequential extraction, showing that anthropogenic copper is mainly concentrated in oxides fractions. The copper concentration of maize at the maturity stage reached values from 36.3 to 65.9 mg kg^–1 compared to copper levels usually found in non-contaminated crops (5–30 mg kg^–1). Here we demonstrate that copper can be accumulated by maize and that copper concentration in maize can be predicted by equations including copper concentration of soil fractions.     

Degradation of Benzo[a]Pyrene in Soil with Arbuscular Mycorrhizal Alfalfa

Mycorrhizal and non-mycorrhizal alfalfa (Medicago sativa) was grown in pots containing soil artificially contaminated with various levels of benzo[a]pyrene (B[a]P)(0, 1, 10 and 100 mg kg^–1). Soil and plants were sampled after 30, 40, 50, 60 and 90 days and compared with unlanted pots. The percentage of mycorrhizal root length colonized by Glomus caledoniun was not significantly affected by the addition of B[a]P up to 10 mg kg^–1 but was significantly lower at 100 mg kg^–1B[a]P compared with low concentrations (p < 0.05). There was no difference in soil polyphenol oxidase and dehydrogenase activity among the controls and applications of 1 and 10 mg kg^–1 of B[a]P. However, enzyme activities were significantly higher at 100 mg kg^–1B[a]P compared with the other three treatments, and there was no mycorrhizal effect. Over a period of 90 days the concentration of B[a]P in soil in which alfalfa was grown was significantly lower than in unplanted soil (p < 0.05). Degradation rates of B[a]P added at 1, 10 and 100 mg kg^–1 without G. caledonium were 76, 78 and 53%, and with mycorrhizal inoculation were 86, 87 and 57%. The degradation rate in unplanted soil was significantly lower than in planted soil, and was significantly higher in medium- and low-B[a]P treatments than in the high B[a]P concentration tested. There is a possibility of enhancement phytoremediation of PAHs in rhizosphere soil with arbuscular mycorrhizal fungi.     

Influence of fertilizer and sewage sludge compost on yield and heavy metal accumulation by lettuce grown in urban soils

Previous research has demonstrated that many urban soils are enriched in Pb, Cd and Zn. Culture of vegetable crops in these soils could allow transfer of potentially toxic metals to foods. Tanya lettuce (Lactuca sativa L.) was grown in pots of five urban garden soils and one control agricultural soil to assess the effect of urban-soil metal enrichment, and the effect of soil amendments, on heavy metal uptake by garden vegetables. The amendments included NPK fertilizer, limestone, Ca(H₂PO₄)₂, and two rates of limed sewage sludge compost. Soil Cd ranged from 0.08 to 9.6 mg kg^–1; soil Zn from 38 to 3490 mg kg^–1; and soil Pb from 12 to 5210 mg kg^–1. Lettuce yield on the urban garden soils was as great as or greater than that on the control soil. Lettuce Cd, Zn and Pb concentrations increased from 0.65, 23, and 2.2 mg kg^–1 dry matter in the control soil to as high as 3.53, 422 and 37.0 mg kg^–1 on the metal-rich urban garden soils. Adding limestone or limed sewage sludge compost raised soil pH and significantly reduced lettuce Cd and Zn, while phosphate fertilizer lowered soil pH and had little effect on Zn but increased Cd concentration in lettuce. Urban garden soils caused a significant increase in lettuce leaf Pb concentration, especially on the highest Pb soil. Adding NPK fertilizer, phosphate, or sludge compost to two high Pb soils lowered lettuce Pb concentration, but adding limestone generally did not. On normally fertilized soils, Pb uptake by lettuce was not exceptionally high until soil Pb substantially exceeded 500 mg kg^–1. Comparing garden vegetables and soil as potential sources of Pb risk to children, it is clear that the risk is greater through ingestion of soil or dust than through ingestion of garden vegetables grown on the soil. Urban dwellers should obtain soil metal analyses before selecting garden locations to reduce Pb risk to their children.     

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.     

四溴双酚A对赤子爱胜蚓的生长和基因表达的影响

试验采用人工土壤法,通过14 d急性毒性试验,研究了不同剂量TBBPA对赤子爱胜蚓(Eisenia fetida)生长、基因表达的影响。在14 d急性毒性试验中,随着暴露时间和浓度的增加,蚯蚓生长受到了显著抑制,未出现死亡现象。超氧化物歧化酶(SOD)的基因表达量在低浓度(50 mg·kg-1)时受到诱导上调;谷胱甘肽转移酶(GST)的基因表达量在400 mg·kg-1染毒组受到明显诱导,是对照组的8.73倍;热休克蛋白(Hsp70)的基因表达量在50、100和200 mg·kg-1染毒组被诱导上调。基因表达量的变化显示,在50、100、200 mg·kg-1浓度条件下,蚯蚓可以利用自身的抗氧化能力维持体内的动态平衡稳定,使得机体免受损伤。但是在超过400 mg·kg-1浓度后,TBBPA的毒性效应超过了机体的应对能力,使机体遭受损伤,外在特征主要表现为蚯蚓身体蜷缩、变细变硬。从生物标志物角度,基因表达量的变化对TBBPA毒性效应的指示作用较生长抑制率更为敏感。     

氟虫双酰胺对蚯蚓的生化毒性与细胞毒性研究

双酰胺类杀虫剂已成为全世界第4大类最常用的杀虫剂,具有非常广阔的应用前景。然而,目前关于双酰胺类杀虫剂生态毒性评估方面的研究还比较少。为探究双酰胺类杀虫剂对非靶标生物的毒性作用,选取赤子爱胜蚓(Eisenia fetida)为受试生物,研究了典型双酰胺类杀虫剂氟虫双酰胺对非靶标动物蚯蚓的生化毒性和细胞毒性以及其在人工土和蚯蚓体内的浓度变化情况。结果表明,氟虫双酰胺在人工土壤中十分稳定,在整个暴露期间氟虫双酰胺的浓度变化不超过20%。氟虫双酰胺在蚯蚓体内的含量随染毒浓度的升高和暴露时间的推移而增加,呈明显的时间和剂量-效应关系;在染毒浓度为0.1和1.0 mg·kg-1的处理组中,氟虫双酰胺未对蚯蚓产生明显的氧化胁迫效应。在染毒浓度为5.0和10.0 mg·kg-1的处理组中,蚯蚓体内活性氧(ROS)含量显著高于其他处理组,过量的ROS诱导蚯蚓体内各种抗氧化酶活性发生异常变化,并在蚯蚓体内造成了脂质过氧化、蛋白质羰基化和DNA损伤。研究表明,当土壤中氟虫双酰胺的浓度为5.0和10.0 mg·kg-1时可能会对蚯蚓产生很高的风险。此外,彗星实验对氟虫双酰胺诱导的氧化胁迫较为敏感,可以作为敏感生物标志物对氟虫双酰胺造成的土壤污染进行预警。     

Distribution of Organo-Chlorine Pesticides (DDT and HCH) Between Plant and Soil System

This paper reports a study of the distribution of organo-chlorine pesticides (DDT and HCH) between rice plants and the soil system by spraying before the heading stage at four different dosage levels – control, normal dosage (15 kg ha^–1 of 6% HCH and 7.5 kg ha^–1 of 25% DDT), double dosage and four times dosage. Soil and plant samples were taken respectively at the 1st h, 3rd, 10th, 20th, and 40th day after spraying and at the harvest time. The results indicate that less than 5% of HCH and 15% of DDT were absorbed by the surface of rice leaves for normal dosage. Most of both pesticides moved into the soil in solution after spraying. Compared with DDT, HCH was degraded and run off more easily. HCH residues in the surface soil layer (1–3 cm) were already below 6.4 g kg^–1 at the mature stage, lower than Chinese Environmental Quality Standard for Agricultural Soils: HCH <0.05 mg kg^–1. However DDT residues in the surface soil layer remained 172 g kg^–1, higher than the national standard: DDT <0.05 mg kg^–1. According to the test f OCP residues in rice seeds, it can be concluded that the OCP sprayed onto the surface of rice leaves can move into rice plants and accumulate in the seeds at the mature stage. HCH residues in rice seeds of the double and four times dosage treatments, and DDT residues in all treatments, exceeded the Chinese National Food Standard (HCH <0.10 mg kg^–1, DDT <0.20 mg kg^–1).     

Heavy metal pollution in Jamaica 1: Survey of cadmium,lead and zinc concentrations in the Kintyre and Hope Flat districts

Despite its being highly mineralised, the Hope Mine area has become a residential district. Composite soil samples taken from 91 allotments show values for cadmium: < 2–220 mg kg^–1, lead: 6–38,000 mg kg^–1, and zinc: 66–40,000 mg kg^–1. Water samples from adits contain 52–86 g kg^–1 of lead and < 1–2 hg kg^–1 of cadmium. The soil contents of cadmium and lead in at least two areas suggest that remedial actions should be considered. Blood lead levels for 33 children aged between ten months and seven years are in the range 5.7–57 g dl^–1; haemoglobin levels vary between 9.7 and 12.7 mg dl^–1. There is no obvious relationship between Pb and haemoglobin levels. Further geochemical work to define fully the spatial extent of the polluted region and epidemiological studies including intelligence testing to define further the effects of lead on children in this environment would be valuable.To whom correspondence should be addressed.     

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.     

Exposure Assessment of Naturally Metal Enriched Topsoils, Port Macquarie, Australia

An exposure assessment was conducted on naturally metal enriched topsoils of the city of Port Macquarie in order to establish whether the soils pose any threat to human health. Surface soils (0–10 cm depth, <2 mm) were investigated for their total, bioavailable and leachable Cr and Ni concentrations. Total metal concentrations ranged from 145 to 4540 mg Cr kg^–1 and 20 to 2030 mg Ni kg^–1, whereas soil extractions revealed low leachable contaminant concentrations (EDTA extraction: <0.1–0.2 mg Cr L^–1 and <0.1–4.7 mg Ni L^–1; acetic acid extraction: <0.1 mg L^–1 Cr and Ni). Thus the bioavailability of Cr and Ni to plants is low, the leaching of metals into ground and surface waters is insignificant and the pathways of these metal pollutants from topsoils into residents are limited to the inadvertent ingestion, inhalation and skin adsorption of soil metals. Simulated gastric experiments, using hydrochloric acid, indicated that less than 0.01% of the total Cr and 0.1–2.4% of the total Ni ingested are soluble and available, for uptake into the human body. Critical receptors, such as small children would have to ingest considerable soil quantities (> 11.8 g per day) over long periods of time to experience an appreciable risk of deleterious effects. Thus, although Cr and Ni are present in high concentrations, the effective uptake of Cr and Ni from soil by the majority of residents is insignificant. The possibility that the Ni enriched topsoil induces allergic contact dermatitis in sensitised individuals remains to be evaluated.     

Effects of the Interactions Between Selenium and Phosphorus on the Growth and Selenium Accumulation in Rice (Oryza Sativa)

The solution culture, paddy soil culture and the simulation experiments in the laboratory were conducted to clarify the interactions between selenium and phosphorus, and its effects on the growth and selenium accumulation in rice. Results revealed that a suitable supply of selenium could promote rice growth and excessive selenium could injure rice plant, causing lower biomass, especially in the roots. The supply of selenite could enhance the selenium contents of rice shoots and roots in solution culture and in soil culture. The selenium concentrations in roots were much higher than those in shoots supplied with the same rates of selenium and phosphorus. The interaction between selenium and phosphorus was evident. When the phosphorus supply increased to meet the needs of plant growth, phosphorus could promote absorption and accumulation of selenium in the shoots. If the phosphorus supply was excessive, phosphorus could inhibit the accumulation of selenium in the shoots at the lower selenite level (2 mol l^–1), but could not at the higher selenite level (10 mol l^–1). With the supply of phosphate increased, the selenium concentrations in the roots decreased significantly at both selenite levels. The presence of phosphate could decrease Se sorption on the soil surface and increase the selenium concentration in the soil solution. The concentrations of selenium in shoots and roots supplied with 0.08 g kg^–1 phosphorus were lower than those with no phosphorus supplied. With the increase of phosphorus added to 0.4 g kg^–1, the selenium concentration in shoots and roots increased. The effect of phosphorus on the concentration was statistically significant at all three selenium levels.     

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.     

Accumulation of selenium in sugarcane (Sachharum officinarum Linn.) in seleniferous areas of Punjab,India

A survey was conducted during 1986–88 to assess the level and pattern of accumulation of selenium in sugarcane plants in seleniferous areas of Punjab (India). Total and water-extractable (available) selenium ranged from 0.55 to 2.58 (mean 1.43 ± 0.67) mg kg^–1 and from 0.02 to 0.05 (mean 0.033 ± 0.007) mg kg^–1, respectively, in seleniferous areas. Corresponding values from non-seleniferous areas were 0.23–0.55 (mean 0.36 ± 0.08) mg kg^–1 and 0.015–0.025 (mean 0.020 ± 0.003) mg kg^–1, respectively. Sugarcane tops from seleniferous areas accumulated high levels of selenium ranging from 7.9 to 67.5 mg kg^–1. These selenium levels were 6–14 times higher than those from non-seleniferous areas. During the early stages of growth (June), the selenium content was highest but decreased during the months of July and August and then did not change up to maturity. In the seleniferous areas sugarcane tops and canes at maturity contained 5.7–9.5 and 1.8–2.1 mg Se kg^–1, respectively. However, the tops and canes of plants growing near the permanent boundary (bundh) contained 9.5–18.8 and 2.1–2.4 mg Se kg^–1, respectively.In a field experiment on sugarcane, application of gypsum up to 1 ton ha^–1 resulted in a significant reduction of selenium content in sugarcane tops as well as in the cane. Selenium content in sugarcane tops at maturity was reduced from 15.16 to 5.08 mg kg^–1 by applying gypsum of 1 ton ha^–1.     

Impact of Gold mining on the Environment and Human Health: A Case Study in the Migori Gold Belt, Kenya

The study of gold sites in the Migori Gold Belt, Kenya, revealed that the concentrations of heavy metals, mainly Hg, Pb and As are above acceptable levels. Tailings at the panning sites recorded values of 6.5–510 mg kg^–1 Pb, 0.06–76.0 mg kg^–1 As and 0.46–1920 mg kg^–1 Hg. Stream sediments had values of 3.0–11075 mg kg^–1 Pb, 0.014–1.87 mg kg^–1 As and 0.28–348 mg kg^–1 Hg. The highest metal contamination was recorded in sediments from the Macalder stream (11075 mg kg^–1 Pb), Nairobi mine tailings (76.0 mg kg^–1 As) and Mickey tailings (1920 mg kg^–1 Hg). Mercury has a long residence time in the environment and this makes its emissions from artisan mining a threat to health. Inhaling large amounts of siliceous dust, careless handling of mercury during gold panning and Au/Hg amalgam processing, existence of water logged pits and trenches; and large number of miners sharing poor quality air in the mines are the major causes of health hazards among miners. The amount of mercury used by miners for gold amalgamation during peak mining periods varies from 150 to 200 kg per month. Out of this, about 40% are lost during panning and 60% lost during heating Au/Hg amalgam. The use of pressure burners to weaken the reef is a deadly mining procedure as hot particles of Pb, As and other sulphide minerals burn the body. Burns become septic. This, apparently, leads to death within 2–3 years. On-site training of miners on safe mining practices met with enthusiasm and acceptance. The use of dust masks, air filters and heavy chemical gloves during mining and mineral processing were readily accepted. Miners were thus advised to purchase such protective gear, and to continue using them for the sake of their health. The miners' workshop, which was held at the end of the project is likely to bear fruit. The Migori District Commissioner and other Government officials, including medical officers attended this workshop. As a result of this, the Government is seriously considering setting up a clinic at Masara, which is one of the mining centres in the district. This would improve the health of the mining community.     

Current uses of the EPA lead model to assess health risk and action levels for soil

The EPA lead model predicts mean blood lead levels and risk of elevated blood lead levels in children based on lead uptake from multiple sources. In the latest model versions, environmental data from individual homes within a community can be used to predict the overall blood lead distribution and percent risk of exceeding a specific blood lead level (i.e. 10 g dl^–1). Recent criteria used by the EPA to evaluate this information include no more than 5% of houses with a greater than 5% lead risk, and a community weighted-average risk below 5%. Environmental (primarily soil) and blood lead data from a residential community near a smelter were used to illustrate recent uses of the model. Scheduled remediation in the community will remove soil for approximately 60% of the houses (i.e. those with lead levels > 1000 mg kg^–1). After remediation, the model results indicate a relatively low community risk (0.5–1.9%), although the percentage of houses with lead risks above 5% ranged from 3 to as high as 13%, depending on the variation in blood lead and assuming the model's 7 g dl^–1 increase in blood lead with each 1000 mg kg^–1 increase in soil lead level. A comparison of the limited blood lead data with soil lead levels below 1000 mg kg^–1, however, indicated no apparent relationship. Given these uncertainties, less invasive actions than additional soil removal (e.g. exposure intervention, monitoring conditions, and follow-up as necessary) may be appropriate under the new EPA guidance for lead in soil.     

Predicting the risk of cobalt deprivation in grazing livestock from soil composition data

The objective was to derive predictive equations for acetic acid-extractable cobalt (A-ECo) in soils so that extensive national databases for total (T) Co in soils and stream sediments could be converted to plant available concentrations for the purpose of predicting risk of Co deficiency in grazing livestock. Data on the chemical and physical properties of 103 soils from 15 different parent materials and 54 soil series in England and Wales were used. Ranges for the mean values for parent materials were: TCo, 5.0–20.4 and A-ECo, 0.20–1.30 mg kg^–1; percentage (P) A-ECo, 3.4–13.5; soil manganese (Mn) 268–1174 mg kgDM^–1; pH, 3.7–8.0. There were significant effects of parent material on all parameters with Chalks, Old and New Red Sandstones particularly low in A-ECo. Multiple linear regression yielded the following equation for predicting A-ECo, which accounted for 56% of the variance with 12 outliers, including the lowest pH values, omitted:A-ECo(mg kg^-1) = 1.4 - 0.0619TCo (mg kg^-1) - 0.432TMn(g kg^-1) - 0.171pHPrediction of PA-ECo was less precise:PA-ECo(%) = 21.1 - 4.5TMn(g kg^-1) - 1.77pH(r ² = 44.8%; 88 d.f.REML was used on the complete, unbalanced, log-transformed data set to fit a Generalised Mixed Model with parent material as random effect and soil Mn and pH as fixed effects; the effect of parent material was no longer significant. It was concluded that A-ECo can be satisfactorily predicted for most soils in England and Wales from TCo, TMn and soil pH.     

Distribution patterns of lead in urban soil and dust in Shenyang city, Northeast China

We investigated the spatial distribution of Pb in soil and dust samples collected from 54 sites in Shenyang city, Liaoning province, Northeast China. Soil background Pb concentration was 22 mg kg⁻¹ and control values from non-industrial areas were 33 mg kg⁻¹ for soil and 38 mg kg⁻¹ for dust. Soil Pb concentrations varied widely, ranging from 26 to 2911 mg kg⁻¹, with a mean concentration of 200 mg kg⁻¹, 9 times the background value and 6 times the control value. There was great variation in soil Pb, with a coefficient of variation (CV) of 1.06 and a standard deviation (SD) of 212 mg kg⁻¹. Dust Pb concentrations fluctuated from 20 to 2810 mg kg⁻¹, with a mean value of 220 mg kg⁻¹, almost 6 times the control value. No significant differences in distribution were observed between soil Pb and dust Pb. The highest Pb concentration was observed in Tiexi district in an industrial area. Soil Pb concentration decreased with depth and with distance from the pollution source. Lead concentrations initially changed little but then decreased with distance from the roadside, and were generally higher on the east side of roads than on the west. Lead contents in different categories of urban area differed substantially with dust and soil Pb concentrations decreasing in the sequence: industrial >business >mixed (residential, culture and education)> reference areas.     

Optimum Nitrogen Use and Reduced Nitrogen Loss for Production of Rice and Wheat in the Yangtse Delta Region

A long-term field and lysimeter experiment under different amount of fertilizer-N application was conducted to explore the optimal N application rates for a high productive rice–wheat system and less N leaching loss in the Yangtse Delta region. In this region excessive applications of N fertilizer for the rice–wheat production has resulted in reduced N recovery rates and environment pollution. Initial results of the field experiments showed that the optimal N application rate increased with the yield. On the two major paddy soils (Hydromorphic paddy soil and Gleyed paddy soil) of the region, the optimal N application rate was 225–270 kg N hm^–2 for rice and 180–225 kg N hm^–2 for wheat, separately. This has resulted in the highest number of effective ears and Spikelets per unit area, and hence high yield. Nitrogen leaching in the form of NO ₃ ^– -N occurs mainly in the wheat-growing season and in the ponding and seedling periods of the paddy field. Its concentration in the leachate increased with the N application rate in the lysimeter experiment. When the application rate reached 225 kg N hm^–2, the concentration rose to 5.4–21.3 mgN l^–1 in the leachate during the wheat-growing season. About 60% of the leachate samples determined contained NO ₃ ^– -N beyond the criterion (NO ₃ ^– -N 10 mg l^–1) for N pollution. In the field experiment, when the N application rate was in the range of 270–315 kg hm^–2, the NO ₃ ^– -N concentration in the leachate during the wheat-growing season ranged from 1.9 to 11.0 mg l^–1. About 20% of the leachate samples reached close to, and 10% exceeded, the criterion for N pollution. Long-term accumulation of NO ₃ ^– -N from leaching will no doubt constitute a potential risk of N contamination of the groundwater in the Yangtse Delta Region.     

Cadmium contents of cultivated soils exposed to contamination in Poland

Cadmium was measured in soils limed with industrial solid wastes, in cultivated lands located near waste yards and in soils of allotment gardens exposed to contamination. The median level and range of cadmium in soils of varying exposure to contamination was respectively: 0.3 mg kg^–1 and 0.01–107 mg kg^–1, 0.2 mg kg^–1 and 0.02–2,198 mg kg^–1, 0.4 mg kg^–1 and 0.05–161 mg kg ^–1. Cadmium levels exceeded the value of 3 mg kg^–1 considered permissible for arable soils in the samples of soils limed with wastes from the chemical industry (2.4%), the mining industry and metallurgy sites (2.1 %), in 12.4% samples of soils located in the neighbourhood of industrial waste storage yards and in 17.2% samples of soils from allotment gardens located on lands formerly used for waste storage.