Effects of Combined Pollution of Pb and Cd on Growth and Yield of Rice

[Objective] The aim was to study the damage and the mechanism of combined pollution of Pb and Cd on rice growth,yield and quality of rice. [Method]Effects of combined pollution of Pb and Cd on the growth and yield of rice were studied by pot experiment with cultivating rice. [Result] Pb and Cd could promote rice growth at low concentration while inhibit plant height at high concentration; Pb and Cd stress reduced the number of rice tillers significantly,with the increasing of stress concentration,the decrease amplitude of the number of tillers was greater; the panicle per pot,seed setting rate,1 000-grain weight and yield of rice were reduced significantly by Pb and Cd stress,the grain number per panicle decreased significantly under low concentration of Pb and Cd but increased significantly under high concentration; the brown rice rate and milled rice rate increased significantly under low concentration of Pb and Cd while at high concentration of Pb and Cd,the both two reduced significantly,the head milled rice rate reduced significantly with the decreasing of concentration; The Pb and Cd content of grains were significantly positively related to the concentrations of Pb and Cd content in soil,it had excessively exceeded hygienic standard when the concentrations of Pb and Cd in soil were medium-high and the unqualified rate reached 333% and 122%. [Conclusion]The study had provided basis for the establishment of rice cultivation system in pollution areas.

Combined Pollution and Pollution Index of Heavy Metals in Red Soil

A field experiment was conducted to study the effects of Pb, Cd, Cu, Zn and As coexisting in red soilon growth of rice (Oryza sativa L.), mung bean (Vigna rabiata (Linn.) Wilczek), alfalfa (Medicago sativaL.), slash pine (Pinus elliottii Engelm.) and aspen (Populus L.). Results showed that rice, mung bean andalfalfa were significantly innuenced by combined pollution of the heavy metals. The contents of Pb, cd andAs in rice grains greatly exceeded the National Standards for Food Hygiene of China. Heavy metals at ahigh concentration seriously retarded growth of mung bean and alfalfa, but not so obviously with slash pineand aspen. The composite index is suggested for evaluating the relativity of combined pollution witll heavymetals in soil.

Food-Security Indexes Related to Combined Pollution of Chromium and Phenol in Soil-Rice Systems

The pot-culture method combined with chemical and statistical analyses was used to get basic data for determination of the food-security indexes related to combined pollution of Cr and phenol in soil-rice systems.Regression analyses according to the experimental result indicated that the critical concentrations of Cr andphenol in brown rice were 0.37 and 0.33 mg kg-1, respectively, under the condition of Cr-phenol combined pollution.

Correlation between Cr^(6+) and Mn^(2+) Adsorption in Rock-soil Medium with Combined Pollution

[Objective] The aim was to study the correlation between Cr6+ and Mn2+ adsorption in rock-soil medium with combined pollution. [Method] Combining single Cr6+ and Mn2+ adsorption test with combined pollution test, the adsorption laws of Cr6+ and Mn2+ were studied, and the correlation between Cr6+ and Mn2+ adsorption was analysed by using correlation analysis and regression analysis. [Result] According to the comparative analysis on adsorption tests, the adsorption time, adsorption amount and adsorption speed of Cr6+ and Mn2+ were obviously distinct in single adsorption test and combined adsorption test. Correlation analysis revealed that there was a significantly positive correlation between Cr6+ and Mn2+, and there existed addition effects between Cr6+ and Mn2+ in regression analysis, that is, the adsorption of Cr6+ by the soil tested would be enhanced by Mn2+. [Conclusion] The research could provide scientific references for environmental control and environmental management.

Ecological Risk Assessment of Combined Pollution of Heavy Metals and Pesticides in Urban Soils

Urban soil is the main component of urban ecological systems and the key risk receptor from urbanization. Heavy metal and green pesticide pollutions in urban soils have been widely reported with the expanding of urbanization. Since urban soil pollution comes from various resources, application of integrated thinking and methods is needed in ecological risk assessment of urban soil pollution. This paper synthetically reviewed the combined pollution of heavy metals and pesticide, and ecological risk assessment, and then proposed some research trends and areas in the future that are required to carry out intensively according to the present situation of environmental pollution and international research fronts.

Combined pollution of Cd and Zn in soil-rice systems and its indexes

Due to the mining,smelting,sewage irriga-tion,agricultural runoff,and development ofrural enterprises,combined pollution of Cd andZn in soil-rice systems has frequently oc-curred.This problem was studied by using thepot-culture imitative method combined withhemical analysis and mathematical models.

Synergy effect between tetracycline and Cr(Ⅵ)on combined pollution systems driving biochar-templated Fe_(3)O_(4)@SiO_(2)/TiO_(2)/g-C_(3)N_(4) composites for enhanced removal of pollutants

Biochar-coupled Fe_(3)O_(4)@SiO_(2)/TiO_(2)/g-C_(3)N_(4) composites were successfully constructed through simple sol-gel and calcination methods.The composites efficiently removed high-concentration toxic tetracycline(TC)by means of·OH and·O_(2)^(−),whose removal rate exhibited 91.88%during 3 h,and the degradation rate constant reached up to 0.0068 min^(−1).The excellent performance can be attributed to the high specific surface area,enhanced visible light response,the introduction of magnetic nanoparticles and biochars expediting charge transfer,Z-scheme heterojunction enhancing the spatial separation of photo-generate carriers and,importantly extraordinary adsorption capacity of 147.96 mg g^(−1).Moreover,the composites showed the most excellent efficiency under the calcination temperature of 450℃,and exhibited good stability with tolerance to a wide range of pH and anions.Interestingly,a synergistic photocatalytic effect was discovered in the TC/Cr(Ⅵ)combined pollution systems,resulting in significantly improved removal of Cr(Ⅵ).Besides,the photocatalytic mechanism and degradation path of tetracycline were also elucidated.All these findings suggested the as-synthesized catalyst was an excellent photocatalyst for removal of TC/Cr(Ⅵ)-contaminated water.

Quantitative analyses of relationships between ecotoxicological effects and combined pollution

The responses of wheat Triticum aestivum, rice Oryza sativa, earthworms Eisenia foetida, and prawns Penaeus japonicus to combined acetochlor-Cu, Cd-Zn were studied in hy-droponic and soil-culturing systems using the methods of ecotoxicology. In particular, system-atically quantitative analyses were documented by field experiments. Results showed that ecotoxicological effects under the combined pollution were not only related to chemical proper-ties of pollutants but also dependent on the concentration level of pollutants, in particular on the combination of concentrations of pollutants in ecosystems. Additionally, species of organisms, especially the type of ecosystem, determined the influences. To some extent, biological tissue targets attacked by pollutants were an important factor.

Evaluation of genotoxicity of combined soil pollution by cadmium and phenanthrene on earthworm

The DNA-damaging effects of the combined pollution of heavy metal and organic contamination on earthworms were evaluated by single cell gel electrophoresis （SCGE） assay. Earthworms Eisenia andrei were exposed to single or combined test compounds in different doses of cadmium （Cd） 5, 10, 50 mg/kg and phenanthrene （Phe） 0.5, 2.5, 12.5 mg/kg with a treatment of 14 d. In SCGE assay, isolated coelomcytes and electrophoresis were employed to determine DNA damage degree after a 14-d treatment by test compounds. The results showed that there was a significant statistical difference between earthworms treated with Cd combined Phe with them treated alone with Cd or Phe. The Olive tail moment （OTM） of SCGE assay using earthworm coelomcytes appears to be a sensitive biomarker for evaluating exposure to genotoxic compounds. These tests also revealed that the interaction between Cd and Phe to DNA damaging effects was negative, and was strongly dependent on the concentration of pollution. This study corresponds to exploratory phase in order to reveal interaction effects of heavy metal and organic contamination on earthworms and then to set up more in-depth analysis to increase progressively the understanding of the genotoxicity mechanisms involved.

Soil Heavy Metal Pollution Around the Dabaoshan Mine,Guangdong Province,China

Soil contamination in the vicinity of the Dabaoshan Mine, Guangdong Province, China, was studied through determi- nation of total concentrations and chemical speciation of the toxic metals, Cu, Zn, Cd, and Pb, using inductively coupled plasma mass spectrometry. The results showed that over the past decades, the environmental pollution was caused by a combination of Cu, Zn, Cd, and Pb, with tailings and acid mine drainage being the main pollution sources affecting soils. Significantly higher levels （P ≤ 0.05） of Cu, Zn, Cd, and Pb were found in the tailings as compared with paddy, garden, and control soils, with averages of 1486, 2516, 6.42, and 429 mg kg^-1, respectively. These metals were continuously dispersed downstream from the tallings and waste waters, and therefore their concentrations in the paddy soils were as high as 567, 1 140, 2.48, and 191 mg kg^-1, respectively, being significantly higher （P ≤ 0.05） as compared with those in the garden soils. The results of sequential extraction of the above metals from all the soil types showed that the residual fraction was the dominant form. However, the amounts of metals that were bound to Fe-Mn oxides and organic matter were relatively higher than those bound to carbonates or those that existed in exchangeable forms. As metals could be transformed from an inert state to an active state, the potential environmental risk due to these metals would increase with time.

Rapid ecotoxicological assessment of heavy metal combined polluted soil using canonical analysis

Quick, simple to perform, and cheap biomarkers were combined in a rapid assessment approach to measure the effects of metal pollutants, Cu, Cd, Pb and Zn in meadow burozem on wheat. Analysis of orthogonal design showed that the significant zinc factor indicated both the inhibition rate of shoot mass and that of root elongation were affected by zinc(P<0.05 and P<0.01, respectively). The first toxicity canonical variable (TOXI), formed from the toxicity data set, explained 49% of the total variance in the toxicity data set; the first biological canonical variable(BIOL) explained 42% of the total variation in the biological data set. The correlation between the first canonical variables TOXI and BIOL (canonical correlation) was 0.94 (P<0.0001). Therefore, it is reliable and feasible to use the achievement to assess toxicity of heavy metal combined polluted soil using canonical analysis. Toxicity of soil combined polluted by heavy metals to plant community was estimated by comparing the IC 50 values describing the concentration needed to cause 50% decrease with grow rate compared to no metal addition. Environmental quality standard for soils prescribe that all these tested concentration of heavy metals in soil should not cause hazard and pollution ultimately, whereas it indicated that the soils in second grade cause more or less than 50% inhibition rates of wheat growth. So environmental quality standard for soils can be modified to include other features.

Single and Combined Effects of As (Ⅲ) and Acetochlor on Phosphatase Activity in Soil

The actions and interactions of acetochlor and As on the soil phosphatase activity were investigated after 1, 3, 6, 10, 15, 30 and 60 d of exposure under control conditions. The soils were exposed to various concentrations of acetochlor and As individually and simultaneously. The results showed that acetochlor, As only, and combined pollution all clearly inhibited soil phosphatase activity. The maximum inhibition ratios of soil phosphatase activity by acetochlor, As only and combined pollution were 36.44, 74.12 and 61.29%, respectively. Two kinetic models, ν=c/（1＋bi） （model 1） and ν=c（1＋ai）/（l＋bi） （model 2）, were used to describe the relationship between the concentrations of As and acetochlor and the activity of soil phosphatase. The semi-effect dose （ED 50 ） values induced by As and acetochlor stress based on the inhibition of soil phosphatase were 18.1 and 33.11 mg kg-1, respectively, according to calculation by model 1. The interactive effect of acetochlor with As on soil phosphatase primarily consisted of significant antagonism effects at the higher concentrations tested. The step regression results show that the toxicity order was As （III）〉acetochlor〉As （III）×acetochlor throughout the incubation period.

Effect of Zn^(2+)-Cu^(2+)combined heavy metal on mechanical properties and microstructure of clayey soil

The strength deterioration mechanism of soil polluted by heavy metals plays a crucial role in the research of mine site pollution.In this study,an unconfined compressive strength(UCS)test,a pH test,a scanning electron microscopy(SEM)test,a low filed nuclear magnetic resonance(NMR)test,and an X-ray diffraction(XRD)test were conducted on Zn^(2+),Cu^(2+) and the combination of Zn^(2+) and Cu^(2+) polluted soil to investigate the strength deterioration mechanism.The results show that both the UCS and pH value of soil decrease with increasing heavy metal concentration.The UCS of Zn^(2+)-Cu^(2+) combined polluted soil is between Zn^(2+) and Cu^(2+) polluted soil at the same total concentration.However,the deterioration rate of combined heavy metal polluted soil is less than the sum of deterioration rate of the two single polluted soils at the same total concentration.In addition,heavy metal cations in polluted soil cause flocculent gels of cosmids to shrink,the micropores to become smaller and the macropores to become larger.The porosity increases slightly with the increase of heavy metal concentration due to decreased pH value.The results from SEM,low field NMR,and pH could explain the dynamic evolution process of soil structure with different heavy metals and concentrations,which provides an experimental basis for mine-site polluted heavy metal treatment technology and the prediction of clayey soil strength deterioration.

Effects of soil metal(loid)s pollution on microbial activities and environmental risks in an abandoned chemical smelting site

Abandoned chemical smelting sites containing toxic substances can seriously threaten and pose a risk to the surrounding ecological environment.Soil samples were collected from different depths(0 to 13 m)and analyzed for metal(loid)s content and fractionation,as well as microbial activities.The potential ecological risk indices for the different soil depths(ordered from high to low)were:1 m(D-1)>surface(S-0)>5 m(D-5)>13 m(D-13)>9 m(D-9),ranging between 1840.65-13,089.62,and representing extremely high environmental risks,of which Cd(and probably not arsenic)contributed to the highest environmental risk.A modified combined pollution risk index(MCR)combining total content and mobile proportion of metal(loid)s,and relative toxicities,was used to evaluate the degree of contamination and potential environmental risks.For the near-surface samples(S-0 and D-1 layers),the MCR considered that As,Cd,Pb,Sb,and Zn achieved high and alarming degrees of contamination,whereas Fe,Mn,and Ti were negligible or low to moderate pollution degrees.Combined microcalorimetry and enzymatic activity measurements of contaminated soil samples were used to assess the microbial metabolic activity characteristics.Correlation analysis elucidated the relationship between metal(loid)s exchangeable fraction or content and microbial activity characteristics(p<0.05).The microbial metabolic activity in the D-1 layer was low presumably due to heavy metal stress.Enzyme activity indicators and microcalorimetric growth rate(k)measurements were considered sensitive indicators to reflect the soil microbial activities in abandoned chemical smelting sites.

Ecological toxicity of reactive X-3B red dye and cadmium acting on wheat (Triticum aestivum)

Ecological toxicity of reactive X\|3B red dye and cadmium in both their single form and their combined form on wheat was studied using the experimental method of seed and root exposure. The single factor exposure indicated that the inhibitory rate of wheat root elongation was significantly increased with the increase in the concentration of the dye in the cultural solution, although seed germination of wheat was not sensitive to the dye. The toxicity of cadmium was greatly higher than that of the dye, but low concentration cadmium (<40 mg/L) could promote the germination of wheat seed. Interactive effects of the dye and cadmium on wheat were complicated. There was no significant correlation between the inhibitory rate of seed germination and the concentrations of the dye and cadmium. Low concentration cadmium could strengthen the toxicity of the dye acting on root elongation. On the contrary, high concentration cadmium could weaken the toxicity of the dye acting on root elongation.

Toxic effects of acetochlor and methamidophos on earthworm Eisenia fetida in phaiozem, northeast China

Acetochlor and methamidophos are two important agrochemicals which are widely applied to agricultural production in northeast China. The investigation on the earthworm Eisenia fetida as an important type of soil animals exposed to single and binary-combined contamination of acetochlor and methamidophos was thus carried out. The single toxic effect test showed that the two agrochemicals had their toxicity to the earthworms living in phaiozem. Acetochlor had a stronger acute toxic effect on the earthworms than methamidophos. The mortality of the earthworms exposed to individual acetochlor and methamidophos changed with an increase in the exposure time and the exposed concentrations. The LD50 value of acetochlor and methamidophos toxic to the earthworms was 115.6-275,3 and 29.5-228.6 mg/kg, respectively. The weight of the earthworms was a more sensitive index compared to the mortality in indicating toxic effects of acetochlor and methamidophos in phaiozem. When considering both the mortality and the body-weight change, the combined pollution of acetochlor and methamidophos in phaiozem resulted in their synergic toxic effects on the earthworms.

Single and joint effects of pesticides and mercury on soil urease

The influence of two pesticides including chlorimuron-ethyl and furadan and mercury （Hg） on urease activity in 4 soils （meadow burozem and phaeozem） was investigated. The soils were exposed to various concentrations of the two pesticides and Hg individually and simultaneously. Results showed that there was a close relationship between urease activity and organic matter content in soil. Chlorimuron-ethyl and furadan could both activate urease in the 4 soils. The maximum increment of urease activity by chlorimuronethyl was up to 14%-18%. There was almost an equal increase （up to 13%-21%） in the urease activity by furadan. On the contrary, Hg markedly inhibited soil urease activity. A logarithmic equation was used to describe the relationship （P〈0.05） between the concentration of Hg and the activity of soil urease in the 4 tested soils. Semi-effect dose （ED50） values by the stress of Hg based on the inhibition of soil urease in the 4 soils were 88, 5.5, 24 and 20 mg/kg, respectively, according to the calculation of the corresponding equations. The interactive effect of chlorimuron-ethyl or furadan with metal Hg on soil urease was mainly synergic at the highest tested concentrations.

Single and joint effects of petroleum hydrocarbons and cadmium on the polychaete Perinereis aibuhitensis Grube

Using the concentration gradient and combined pollutant exposure method, the single and joint effects of petroleum hydrocarbons （PHCs） and cadmium （Cd） on polychaete Perinereis aibuhitensis Grube, an ecologically keystone species in estuarine and coastal environment, have been investigated. The results indicate that the toxicity of PHCs to P. aibuhitensis is stronger than that of Cd to the organism. There are positive correlations between the mortality of worms and the exposed concentration of single Cd or PHCs in solution. Similarly, the accumulation of Cd or PHCs in worms increased with increasing Cd- or PHC-exposed concentrations. All the correlation relationships can be described using unitary quadratic equations （Y or Z = aX^2 ＋ bX ＋ c）. It is calculated, on the basis of these expressions, that the median lethal dose （LC50） ofP aibuhitensis exposed to a single Cd or PHCs is 793.4-13567.3 and 28.0-119.9 μg/L, respectively. The exposed time has some stimulative effect on the two pollutants and on the mortality of the worms. Thus, even a low concentration of a single Cd or PHCs may have strong toxic effects on the worms when the exposed time becomes longer. The accumulation of Cd or PHCs in worms differs with an increase in exposure time at the given exposed concentration of a single Cd or PHCs. Noticeably, the accumulation of PHCs in worms decreases with an increase in exposure time at the given high concentration of PHCs in solution. The joint effect of PHCs and Cd on P. aibuhitensis is very complicated and changes with the exposed concentrations of the two pollutants. At the given concentration of PHCs, the joint toxicity of the two pollutants on the worms changes from synergism to antagonism with an increase in Cd concentration. The accumulation of Cd in the worms significantly decreases with the addition of PHCs to exposure solution.

A New Competitive Adsorption Isothermal Model of Heavy Metals in Soils

A new competitive adsorption isothermal model(CAIM)was developed for the coexistent and competitive binding of heavy metals to the soil surface.This model extended the earlier adsorption isothermal models by considering more than one kind of ion adsorption on the soil surface.It was compared with the Langmuir model using different conditions, and it was found that CAIM,which was suitable for competitive ion adsorption at the soil solid-liquid surface,had more advantages than the Langmuir model.The new competitive adsorption isothermal model was used to fit the data of heavy metal(Zn and Cd)competitive adsorption by a yellow soil at two temperatures.The results showed that CAIM was appropriate for the competitive adsorption of heavy metals on the soil surface at different temperatures.The fitted parameters of CAIM had explicit physical meaning.The model allowed for the calculation of the standard molar Gibbs free energy change,the standard molar enthalpy change,and the standard molar entropy change of the competitive adsorption of the heavy metals,Zn and Cd,by the yellow soil at two temperatures using the thermodynamic equilibrium constants.

Influences of petroleum on accumulation of copper and cadmium in the polychaete Nereis diversicolor

Using the exposure simulation experiment, the action of petroleum affecting the accumulation of the trace metals including copper （Cu） and cadmium （Cd） in littoral polychaete Nereis diversicolor collected from the Shuangtaizi Estuary in Liaoning Province, China was examined. The results showed that there was a markedly non-linear relationship between the accumulation of Cu in worms and the experimental concentration of Cu in exposure solutions when the concentration of petroleum remained at 0, 100, and 220 μl/L, respectively. However, significantly non-linear relationship for worms exposed to Cd was observed only when the concentration of added petroleum was 0 and 220 μl/L. The accumulation of Cu in worms did not differ significantly among the three different levels of petroleum concentrations combined with various concentrations of Cu. So was the accumulation of Cd in worms （p〉0.05）. However, the addition of petroleum in exposure solutions brought about an increase in the accumulation of Cu in Nereis diversicolor, in comparison with single Cu pollution. On the other hand, when the concentration of added petroleum remained at 100 μl/L, the accumulation of Cd in worms was lower than that in worms exposed to various concentrations of only cadmium. However, the worms exposed to Cd and petroleum 220 μl/L did not show obvious and identical increase in the accumulation of Cd, compared with single Cd exposure. The accumulation of both Cu and Cd in worms did not increase significantly with the increases in concentrations of Cu or Cd in exposure solutions combined with petroleum （0, 100, and 220μl/L） under the experimental conditions. Although Nereis diversicolor is exposed to very high Cu and Cd in exposure solutions, accumulation and detoxification mechanisms are sufficient to cope with the extra metal influx in order to survive.