Instances of Soil and Crop Heavy Metal Contamination in China

Both general and specific investigations of soil and crop heavy metal contamination were carried out across China. The former was focused mainly on Cd, Hg, As, Pb, and Cr in soils and vegetables in suburbs of four large cities; the latter investigated Cd levels in both soils and rice or wheat in contaminated areas throughout 15 provinces of the country. The results indicated that levels of Cd, Hg, and Pb in soils and some in crops were greater than the Governmental Standards (Chinese government limits for soil and crop heavy metal contents). Soil Cd ranged from 0.46 to 1.04?mg kg^?1, on average, in the four cities and was as high as 145?mg kg^?1 in soil and 7?mg kg^?1 in rice in the wide area of the country. Among different species, tuberous vegetables seemed to accumulate a larger portion of heavy metals than leafy and fruit vegetables, except celery. For both rice and wheat, two staple food crops, the latter seemed to have much higher concentrations of Cd and Pb than the former grown in the same area. Furthermore, the endosperm of both wheat and rice crops had the highest portion of Cd and Cr. Rice endosperm and wheat chaff accumulated the highest Pb, although the concentrations of all three metals were variable in different parts of the grains. For example, 8.3, 6.9, 1.4, and 0.6?mg kg^?1 of Pb were found in chaff, cortex, embryo, and endosperm of wheat compared with 0.11, 0.65, 0.71, and 0.19?mg kg^?1 in the same parts of rice, respectively. Untreated sewage water irrigation was the major cause of increasing soil and crop metals. Short periods of the sewage water irrigation increased individual metals in soils by 2 to 80% and increased metals in crops by 14 to 209%. Atmospheric deposition, industrial or municipal wastes, sewage sludge improperly used as fertilizers, and metal-containing phosphate fertilizers played an important role as well in some specific areas.     

Heavy metal contamination in vegetables grown around peri-urban and urban-industrial clusters in Ghaziabad,India

Heavy metal contamination of agricultural soils resulting from rapid industrialization and urbanization is of great concern because of potential health risk due to dietary intake of contaminated vegetables. The present study aims to evaluate the status of heavy metals contamination of agricultural soils and food crops around an urban-industrial region in India. Transfer factor values of Cu, Cr, Pb, Cd, Zn, and Ni from soil to vegetable was estimated. The mean heavy metal concentrations (mg/kg) in agricultural soils (Cu: 17.8, Cr: 27.3, Pb: 29.8, Cd: 0.43, Zn: 87, Mn: 306.6, Fe: 16984, and Ni: 53.8) were within allowable concentrations for Indian agricultural soil. The concentrations of Pb, Cd, Zn, and Ni in crops/vegetables exceeded the World Health Organization/Food and Agriculture Organization safe limits. Relative orders of transfer of metals from soil to edible parts of the crops/vegetables were Cd > Pb > Ni > Zn > Cu > Cr. The enrichment factors of heavy metals in soil indicated minor to moderately severe enrichment for Pb, Cd, and Ni; minor to moderate enrichment for Zn; no enrichment to minor enrichment for Mn; and no enrichment to moderate enrichment for Cu at different sites. Ecological risk index of soil showed considerable contamination in one of the wastewater irrigated sites.     

不同类型土壤小麦-水稻轮作体系施用含重金属污泥的环境效应

采用贵州黄壤、石灰土和浙江水稻土,通过盆栽试验探讨了在3种土壤上施用含不同浓度重金属的污泥对小麦、水稻生长及锌(Zn)镉(Cd)吸收性的影响.结果表明： 不同土壤施用同种污泥所产生的重金属污染风险不同,在黄壤和水稻土上施用高浓度重金属污泥对作物的污染风险较高.一次施用Zn、Cd浓度分别为1789、8.47 mg·kg-1的污泥1.6%,使黄壤小麦籽粒中Zn、Cd浓度分别达109、0.08 mg·kg-1;第二次施用后种植水稻,糙米中Zn、Cd浓度达52.0、0.54 mg·kg-1.而施用污泥后石灰性土壤的两种作物其可食部分均无重金属污染风险.土壤醋酸铵提取态Zn是影响麦粒和糙米中Zn浓度的主要因素,而土壤醋酸铵提取态Cd对麦粒和糙米中Cd浓度无明显影响.施用高浓度重金属污泥使3种土壤Zn、Cd全量显著提高,且两次施用后土壤全量Zn均超过国家土壤环境质量二级标准.     

Field accumulation risks of heavy metals in soil and vegetable crop irrigated with sewage water in western region of Saudi Arabia

Wastewater irrigated fields can cause potential contamination with heavy metals to soil and groundwater, thus pose a threat to human beings . The current study was designed to investigate the potential human health risks associated with the consumption of okra vegetable crop contaminated with toxic heavy metals. The crop was grown on a soil irrigated with treated wastewater in the western region of Saudi Arabia during 2010 and 2011. The monitored heavy metals included Cd, Cr, Cu, Pb and Zn for their bioaccumulation factors to provide baseline data regarding environmental safety and the suitability of sewage irrigation in the future. The pollution load index (PLI), enrichment factor (EF) and contamination factor (CF) of these metals were calculated. The pollution load index of the studied soils indicated their level of metal contamination. The concentrations of Ni, Pb, Cd and Cr in the edible portions were above the safe limit in 90%, 28%, 83% and 63% of the samples, respectively. The heavy metals in the edible portions were as follows: Cr > Zn > Ni > Cd > Mn > Pb > Cu > Fe. The Health Risk Index (HRI) was >1 indicating a potential health risk. The EF values designated an enhanced bio-contamination compared to other reports from Saudi Arabia and other countries around the world. The results indicated a potential pathway of human exposure to slow poisoning by heavy metals due to the indirect utilization of vegetables grown on heavy metal-contaminated soil that was irrigated by contaminated water sources. The okra tested was not safe for human use, especially for direct consumption by human beings. The irrigation source was identified as the source of the soil pollution in this study.     

改性措施对复合污染土壤重金属行为影响的研究

采用田间实验的方法,研究了在复合污染土壤上石灰＋Ｃａ、Ｍｇ、Ｐ肥处理对重金属迁移、积累的影响及重金属的作物效应．结果表明,在污染土壤上采用石灰＋Ｃａ、Ｍｇ、Ｐ肥处理可减少重金属向作物籽实的迁移和积累,特别是Ｃｄ、Ｐｈ、Ａｓ３元素;改性以后,水稻、小麦Ｃｄ吸收量比改性前降低了３１．５—５５％．４种作物对Ｐｈ的吸收量降低了２３．４－５７．８％,Ｃｕ、Ｚｎ吸收量略有降低．水稻Ａｓ吸收量增加了５６．８％,小麦、大豆Ａｓ吸收量减少６１．８－８１．１％．重金属在土壤中存在的形态发生了变化,Ｃｄ、Ｐｈ、Ｚｎ交换态百分含量不同程度地有所减少,而碳酸盐结合态有所增加,可被植物吸收利用的有效含量降低．     

Soil mercury accumulation and transference to different crop grains

Mercury contamination in agro-ecosystems is one of the most important environmental issues. Farmland soil mercury accumulation and transference to crops in Changshu City, eastern China, were investigated to identify mercury migration capacity from soil to crops. The mean content of mercury for soil samples slightly increased year after year. The mercury accumulation capacity of rice grown (bioaccumulation factor (BAF) 0.028) in submerged soils under reductive conditions was stronger than that of wheat (BAF 0.0073) in dried soils under oxidative conditions. There were clear relationships between soil mercury with organic matter (OM), cation exchange capacity (CEC), and CaCO₃ of soil samples, while apparent negative relationships between Hg in rice grain with OM, CEC, and CaCO₃ of soil existed. No clear association for Hg between crops and soil was found, indicating that mercury in crop grains is mostly affected by other factors besides soil mercury. Also, soil properties and farming patterns affected mercury transference from soil to crop grains and mercury enrichment capacity in crop grains. The results suggested that appropriate selection of crop species and water management are two major possible ways to reduce total mercury accumulation in crop grains grown in mercury-contaminated regions.     

Risk Evaluation of Heavy Metals and Metalloids Toxicity through Polluted Vegetables from Waste Water Irrigated Area of Punjab,Pakistan: Implications for Public Health

Rapid urbanization has no doubt provided prosperity to inhabitants but on the other hand, it has caused severe environmental problems, particularly soil and water pollution. This research was done to determine the magnitude of metal and metalloid contamination at two sites in soil and a potential vegetable crop, sponge gourd (Luffa cylindrica L.) irrigated with wastewater in the region of Sargodha, Pakistan. The results demonstrated that the metal and metalloid levels in the soil samples were relatively below the respective maximum permissible limits of various metals analyzed. Transfer factor for metal contents was greater at site-II than that observed at site-I. Health risk was also worked out due to the inhabitants' intake of L. cylindrica irrigated with municipal wastewater. At both sites, the health risk index was greater than 1 due to Mn, Mo, Pb, Cd, Cu and As, and Ni at site-1 and Zn at site-II, whereas less than 1 due to Fe, Se, and Co. It was concluded that the dietary intake of L. cylindrica was not free of risk for inhabitants around the sampling sites. To reduce the health risk effects, it is suggested to treat the industrial wastes properly and phyto-extract the overload of heavy metals and metalloids from polluted sites. But with increase in vegetable consumption by the community the situation could worsen in the future.     

Risk Assessment of the Abandoned Jukjeon Metal Mine in South Korea Following the Korean Guidelines

Toxic metal contamination in the vicinity of Korean abandoned metal mines has been reported. A risk assessment for these metals was performed for the inhabitants in the area of the abandoned Jukjeon metal mine. Soil, groundwater, and crop samples were collected around the mine. After pretreatment of these samples, metal concentrations were measured and then a risk assessment was performed using the Korean soil-contamination risk assessment guidelines. Phytoaccumulation of metals in crops was observed in soybeans (As and Zn), red peppers (Zn), sweet potatoes (As and Zn), and cabbage (Cu), which had higher metal concentrations than soils in the area. The metal intake rate was highest for inhalation of soil. Cancer risk was highest from ingestion of As-contaminated crops. The sum of carcinogenic risks was 6.29 × 10^–3. The non-carcinogenic risk was highest for ingestion of As-contaminated crops (8.17). Most of the risks were attributable to As, Pb, and Hg contamination, therefore these three metals must be considered as the principal metals toxic to human health in the sampled area. In particular, the inhalation of metal-contaminated soil should be considered for risk assessment along with ingestion of water and crops in abandoned mine areas.     

Assessment of Hazardous and Essential Elements in a Food Crop Irrigated with Municipal Sewage Water: Risk Appraisal for Public Health

To assess the impact of sewage water on metal accretion in selected diverse varieties of wheat (i.e., Lasani-2008, ARRI-10, Faisalabad-83, Punjab-85, Aas-2010, and Sehar-2006), their seeds were sown in pots containing soil. The results showed that the concentration of heavy metals in grains from the wheat plants supplied with sewage water was considerably higher than the plants supplied with canal irrigation water (control). In canal water irrigated wheat grains the metal concentrations (mg/kg) ranged from 2.20–3.5 for Cu, 12.50–32.4 for Zn, 22.45–35.22 for Mn, 0.05–0.15 for Pb, 0.012–0.029 for Cd, 2.5–5.3 for Ni, 18.16–29.63 for Fe, and 0.90–3.64 for Cr in different wheat varieties, whereas the wheat grains raised from sewage water, had metal concentrations (mg/kg): 3.8–5.30 for Cu, 29.60–40.50 for Zn, 32.9–50.40 for Mn, 1.14–7.50 for Pb, 0.26–0.42 for Cd, 3.90–7.55 for Ni, 32.21–40.35 for Fe, and 2.88–7.84 for Cr. Since these metals bioaccumulate in wheat grains with unremitting use of metal-enriched wastewater, care has to be taken for irrigating wheat plants with household wastewater for a longer time, particularly in those soils where this crop is grown regularly.     

Soil pollution through industrial effluent and its management

During the survey of sewer water/industrial effluent composition, we identified a site at Sonepat that had turned barren due to excessive irrigation with cycle industry effluent. To study the ameliorative effect of farmyard manure, the bulk surface soil sample was brought from the site. Soil was amended with five levels of farmyard manure (0, 0.25, 0.5, 1.0, and 2.0% on a soil weight basis), and carrot, fenugreek, spinach, and wheat crops were grown as test crops in a screen house. The deleterious effect of excessive heavy metals, particularly Ni, on the yield of all the crops was reduced with the application of 2% farmyard manure. The Ni content was highest in carrot, followed by spinach, fenugreek, and wheat. With the application of 2% farmyard manure, Ni content was reduced from 434 to 267 mg/kg in carrot, 167 to 100 mg/kg in fenugreek, 300 to 166 mg/kg in spinach, and 65 to 42 mg/kg in wheat grain.     

Wastewater as a Non-conventional Resource: Impact of Trace Metals and Bacteria on Soil,Plants, and Human Health

Abstract

In many arid and semi-arid regions, farmers are often obligated to informally use raw wastewater for irrigating their crops. The impacts of wastewater irrigation on soil, crops, and human health were investigated, regarding trace metals and bacteria. Cr, Cu, Fe, Ni, and Zn were detected in wastewater. Cr, Cu, and Zn accumulated in soil and crops in the order rocket?>?clover?>?cabbage. The Health Risk Index reported risk from Cr and Zn in rocket. Fecal coliforms in wastewater and crops were detected along with Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. The frequency (%) was 86.7% (cabbage), 66.7% (rocket), and 43.3% (clover). The multiple antibiotic resistance index (0.503) rendered crops high risk source for contamination. The comprehensive pollution index classified wastewater severely polluted (≥2.01). Conclusions deduced crops alternative reservoirs for trace metals and human pathogens. Recommendations included implementation of low cost treatment methods, holding irrigation 5–15?days before harvest, assuming citric and acetic acids reducing solutions for trace metals, and suggested ofloxacin, amoxycillin/clavulanate, and amikacin antibiotics against reported bacteria.     

北京东郊作物土壤系统中重金属的迁移、分布、积累

 本文研究了北京东郊污灌区重金属在作物—土壤中的迁移、分布、积累规律,证实本区蔬菜中汞含量比粮食作物约大3—15倍,比水果约大6—200倍。麦粒、糙米中的Cu、Hg、Cd、Pb、Ni的含量与土壤含量相关性不显著。架豆中重金属含量与土壤中重金属含量的相关性,只有Zn,Pb达显著水平。白菜土有机质含量与重金属含量相关性达显著水平,而白菜的重金属含量与土壤的重金属含量相关性却不显著。说明除了土壤中重金属的总量外,有效态含量的多少,是影响本区作物吸收积累重金属的主要因素。 本区施污泥的土壤和生长的作物Cd／Zn大部小于1%、盆栽试验证明：施用本区污泥污水对水稻生长发育的影响比施污泥灌清水的影响大些,因此,施用含重金属污泥时,最好不要超过5000斤／亩。大田和室内模拟试验证明：重金属从土壤中迁移到植物,由植物带走输出的量极少,其中以带走输出的Hg、Cd,As相对较多,带走输出的Pb、Cr相对的少些。     

江苏省典型区农田土壤及小麦中重金属含量与评价

为了研究江苏省典型区地震带农田土壤和小麦中重金属的污染,在具有代表性的农田采集收获期小麦及耕层土壤,分析和评价了土壤和小麦中重金属Cu、Pb、Cd、Ni、Cr、Hg、As和Zn的含量及污染程度。结果表明,土壤样品中Cd、Zn、Pb的含量均超过江苏省土壤背景值,Cr、Cu、Ni和As分别有25.64%、97.44%、92.31%和92.31%的土壤样品中超过江苏省土壤背景值,Hg的含量均在背景值以下;与国家土壤环境质量标准(GB15618—1995)中Ⅱ级标准相比,Cd的含量均超出标准限值,其它7种重金属元素含量均在标准限值以下。土壤中重金属相关分析表明,Cd、Cu、Cr、Ni、Pb、Zn、As具有相同的来源的可能性较大,而Hg与Cd、Cu、Cr、Ni、Pb、Zn、As的来源均不相同。以NY 861—2004为评价标准,小麦籽粒Pb、Cr、Hg、Ni、As样品超标率分别为100%、58.97%、33.33%、10.26%、2.56%,Cu、Zn和Cd没有样品超标,由此可见小麦籽粒中Pb的污染最为严重。采用单因子污染指数法、综合污染指数法和Hakanson潜在生态评价指数法以国家土壤环境质量标准(GB15618—1995)和江苏省土壤背景值为参比值,对农田土壤重金属污染进行评价,结果显示,从单项污染指数来看只有Cd达到重度污染水平,其它元素均在安全范围以内,从综合污染指数来看土壤重金属污染达到中度污染水平,从潜在生态评价指数法来看,研究区域表现为很强的生态危害,并以Cd为主要污染因子。     

Characteristics,and carbon and nitrogen dynamics in soil irrigated with wastewater for different lengths of time

Irrigation of agricultural land with wastewater will increase crop production, but also heavy metal concentrations and the rate of infection of farmers with pathogens. The risks associated with the use of wastewater are reduced by treating the wastewater, but treatment also reduces organic material, phosphorus and inorganic N for crops. We investigated characteristics, e.g. heavy metal concentrations, of soils of the valley of the Mezquital (Mexico) irrigated with waste from Mexico City water since 1912, 1925, 1965, 1976, 1996 or 1997, or not irrigated at all, and dynamics of C and N when soil was amended with wastewater or drainage water. Concentrations of total Mg, Hg, Mo, Ca, Cu and Cr, available concentrations of Pb, Cd and Cu increased significantly with length of irrigation (P < 0.05), but were not at hazardous concentrations. Although organic C, total N, microbial biomass C and N, and microbial activity, as witnessed by CO2 production, increased with length of irrigation, N mineralization did not. Oxidation of NO2- was inhibited and could be due to increases in salinity, toxic compounds or heavy metals. We found that N mineralization was low or absent so it will not compensate for the loss of N when the wastewater is treated and application of N fertilizer will be required to maintain the same level of crop production. The characteristics of the soils appear not to have deteriorated after years of application of wastewater, but further irrigation even with treated wastewater might increase sodicity and salinity and pose a threat to future crop production.     

Metal Toxicity Affects Fungal and Bacterial Activities in Soil Differently

Although the toxic effect of heavy metals on soil microorganism activity is well known, little is known about the effects on different organism groups. The influence of heavy metal addition on total, bacterial, and fungal activities was therefore studied for up to 60 days in a laboratory experiment using forest soil contaminated with different concentrations of Zn or Cu. The effects of the metals differed between the different activity measurements. During the first week after metal addition, the total activity (respiration rate) decreased by 30% at the highest level of contamination and then remained stable during the 60 days of incubation. The bacterial activity (thymidine incorporation rate) decreased during the first days with the level of metal contamination, resulting in a 90% decrease at the highest level of contamination. Bacterial activity then slowly recovered to values similar to those of the control soil. The recovery was faster when soil pH, which had decreased due to metal addition, was restored to control values by liming. Fungal activity (acetate-in-ergosterol incorporation rate) initially increased with the level of metal contamination, being up to 3 and 7 times higher than that in the control samples during the first week at the highest levels of Zn and Cu addition, respectively. The positive effect of metal addition on fungal activity then decreased, but fungal activity was still higher in contaminated than in control soil after 35 days. This is the first direct evidence that fungal and bacterial activities in soil are differently affected by heavy metals. The different responses of bacteria and fungi to heavy metals were reflected in an increase in the relative fungal/bacterial ratio (estimated using phospholipid fatty acid analysis) with increased metal load.     

Assessment of Heavy Metals Contamination in Agricultural Soil of Southwestern Nile Delta,Egypt

The spatial and vertical distributions of heavy metals were quantitatively determined for organic-rich agricultural soils in the Southwestern Nile Delta. This study aims to undertake an assessment of heavy metals contamination in the soils of Quessna district using the inductively coupled plasma-optical emission spectroscopy, remote sensing, and geographic information system techniques. In this study, 24 soil samples were collected at 12 sites representing the main suburbs in the Quessna district. The concentrations of the studied metals decreased in the order of Zn > Cr > Pb > Cu > Ni > Co. The contamination degree and ecological risk assessment for metals in soil samples were evaluated using the enrichment factor, geoaccumulation index, improved Nemerow's pollution index, Pollution load index, and potential ecological risk index. The spatial and vertical distribution of heavy metals concentrations were affected by soil properties such as clay and organic matter content and scavenger metals (Fe and Mn). The intensive urbanization, industrial activity, and agricultural practices are thought to be the main anthropogenic sources of heavy metals contamination. Further studies especially human health risk assessment are recommended to investigate possible risks for humans from heavy metals in this area.     

Effect of Heavy Metals on Wheat Seedlings: Activation of Antioxidant Enzymes

Accumulation of heavy metals in wheat grain exposed to multicomponent pollutants (industrial wastewater) was studied. The absolute content of metals (Zn, Cd, Cu, Cr, Ni, Co, Pb, and Mn) was found to be determined by the extent of purification of wastewater. An increase in the degree of grain contamination with heavy metals was accompanied by activation of antioxidant enzymes (superoxide dismutase, EC 1.15.1.1; catalase, EC 1.11.1.6; and peroxidase, EC 1.11.1.7) in leaves and activation of superoxide dismutase and peroxidase in roots. The ratio of activity of membrane enzymes to activity of cytosol enzymes was demonstrated to be high. It was concluded that the membranotropic effect of multicomponent contaminants was due to accumulation of heavy metals capable of inducing the antioxidant protection in the next generation of wheat seedlings.     

某污灌区重金属与两种持久性有机污染物(POPs)污染趋势评价

对某污灌区的土壤剖面进行采样分析,利用不同的评价方法进行评价,结果表明,土壤中金属元素Cr、As、HG、Cd、Cu、Pb、Ni、Zn和持久性有机污染物BHC、DDT含量有上升趋势,80%以上的表层土壤样品污染物含量超过土壤底层,85%以上的土壤样品污染物含量明显超过当地土壤的自然背景值.通过污染物在土壤中的残留模型预测,两种有机污染物和元素Cr、As、Hg、Cd、Cu会在土壤中累积,持续的污水灌溉可能使在土壤中累积的这些污染物进入地下水或食物链,对环境健康造成危害.     

Vegetable crop irrigation with tertiary filtered municipal wastewater

Abstract

The use of tertiary membrane-filtered municipal wastewater for irrigation as an alternative to natural freshwater sources was evaluated. Membrane filtration was considered as a viable technology to reclaim wastewater for irrigation, and the microbial and heavy metal impact on crops and soil was studied. The results of 2 years of research (2003 – 2004), carried out in Cerignola in the South of Italy, are reported. Tertiary treatment was carried out using a membrane filtration pilot plant with a hollow fibre submerged system. The water produced was used for drip irrigation of three vegetable crops in succession – processing tomato, fennel and lettuce – and compared with conventional water. Microbiological analyses were performed on the water used for irrigation, on soil samples and on marketable crops. Results show that the microbial content of soil and crops did not show relevant differences in relation to the two types of water. The measured values of heavy metals concentration in crops never exceeded toxic values. The filtered wastewater never caused an increase of bacterial concentration in the soil nor on the edible part of crops. Therefore, tertiary filtered municipal wastewater can be considered a valid alternative source of water for vegetable crop irrigation.     

Human health risks from consuming cabbage (Brassica oleracea L. var. capitata) grown on wastewater irrigated soil

The present study investigated the impact of cumulative irrigation with wastewater on the soil properties and, its health hazards on the consumers of cabbage plants at south Cairo Province, Egypt. Irrigation water, soil and cabbage plants were sample d from two polluted and other two unpolluted farms. The physicochemical properties of water and soil were analyzed and the growth parameters, as well as nutrients and heavy metals concentration in cabbage were investigated. In addition, the daily intake of metals (DIM) and health risk index (HRI) were estimated. Wastewater posed a decrease in the availability of N, P and K, but increases heavy metals in the soil solution. Cabbage stem and root lengths as well as the number of leaves and biomass were greatly reduced in the polluted farms. In addition, the photosynthetic pigments, carbohydrates and proteins were decreased under pollution stress. The concentration of most investigated metals in the leaves and roots were increased with translocation factor greater than one for Pb, Cd, As, Cr, Ni, Fe, and Co. The study revealed that the HRI exceeded one for Pb and Cd in polluted and unpolluted plants; and Fe in polluted ones. Irrigation with wastewater is not suitable for cabbage as it has health risks on humans due to accumulation of heavy metals. It worth noting that, the high ability of cabbage plants to accumulate Pb and Cd from both polluted and unpolluted soils should be taken into consideration when consuming this plant.