Effects of Arsenic‐Contaminated Irrigation Water on Growth,Yield, and Nutrient Concentration in Rice

Abstract

A study was undertaken to determine the effects of different concentrations of arsenic (As) in irrigation water on Boro (dry‐season) rice (Oryza sativa) and their residual effects on the following Aman (wet‐season) rice. There were six treatments, with 0, 0.1, 0.25, 0.5, 1, and 2 mg As L^?1 applied as disodium hydrogen arsenate. All the growth and yield parameters of Boro rice responded positively at lower concentrations of up to 0.25 mg As L^?1 in irrigation water but decreased sharply at concentrations more than 0.5 mg As L^?1. Arsenic concentrations in grain and straw of Boro rice increased significantly with increasing concentration of As in irrigation water. The grain As concentration was in the range of 0.25 to 0.97 µg g^?1 and its concentration in rice straw varied from 2.4 to 9.6 µg g^?1 over the treatments. Residual As from previous Boro rice showed a very similar pattern in the following Aman rice, although As concentration in Aman rice grain and straw over the treatments was almost half of the As levels in Boro rice grain. Arsenic concentrations in both grain and straw of Boro and Aman rice were found to correlate with iron and be antagonistic with phosphorus.     

Availability of Lead and Cadmium in Farmland Soil and Its Distribution in Individual Plants of Dry‐Seeded Rice

Abstract

Availability of lead (Pb) and cadmium (Cd) in farmland soils and its distribution in individual plants of dry‐seeded rice were investigated utilizing graphite furnace atomic absorption spectrometry (GFAAS) with a matrix modification technique. Five extractants were compared, and the operating conditions for GFAAS were optimized. The detection limits were 4.2 ng for Pb with the precision of 1.54% and 0.1 ng for Cd with the precision of 2.38%. The contents of the extractable Pb and Cd in soils were determined with the five extractants, and availability of Pb and Cd in farmland soil was discussed. The contents of Pb and Cd in different parts of dry‐seeded rice were lower than those in dry‐seeded rice soil. The contents of Pb and Cd in rice were lower than in other parts. The end top leaves accumulated the highest amounts of Pb and Cd.     

Soil‐solution speciation by MINEQL+4.6 model and plant uptake of Cd and Zn by barley (Hordeum vulgare L.) after application of different phosphate fertilizers

A greenhouse experiment was conducted to investigate the immediate effect of application of mono‐ammonium phosphate (MAP), single superphosphate (SSP), and triple superphosphate (TSP) fertilizers containing varying concentrations of Cd on (1) chemical speciation of Cd and Zn in soil solution by chemical‐equilibrium calculations (MINEQL+4.6 model), (2) growth of barley plants, (3) concentrations of Cd, P, and Zn in soil solution and plant tissue, as well as total plant accumulation of Cd, P, and Zn, and (4) monitoring pH and element changes during incubation periods following phosphate application. Results show that, in general, the pH of soil solution increased during the first 40 d of incubation, then declined. Also, at the end of incubation period, pH of soil solution was affected by fertilization source and fertilization rate. The concentration of Cd in soil solution changed with time. Phosphate fertilization (p < 0.05) or fertilizer source (p < 0.05) showed consistent effects. Also, the application of phosphate fertilizers with three rates significantly increased Zn concentrations in soil solution during the first half (0–30 d) of incubation period and then decreased but still more than in the control. In general, application of different sources of phosphate at 100 g kg^–1 did not change the dominant forms of Cd in soil solution during all incubation time intervals. Speciation of Zn in the control after 30 d of incubation had changed, in comparison to 10 d of incubation, and the dominant forms were Zn²⁺, ZnOH⁺, ZnHCO₃, ZnCO₃(aq), and Zn(OH)₂(aq). Adding phosphate fertilizer significantly increased both shoot and root dry weight compared to control, indicating P was a growth‐limiting factor in the control plants. The Zn concentrations in shoot and root were lower in the TSP‐ and SSP‐fertilizers treatment than those in the MAP and fertilizer treatments at all rates of fertilization. Adding phosphate increased the Cd : Zn and P : Zn ratios in the shoot and root tissue, with the effect being greater with increasing fertilization rate. Phosphate fertilization greatly increased the total accumulation of Cd of barley compared with the control plants (p < 0.001), with the effect being greater with increasing fertilization rate. Source and rate of fertilizers, and their interactions had significant effect (p < 0.05) on Cd accumulation in the whole plant.     

不同土地利用类型下土壤-作物砷的积累特征及健康风险

以菜地、稻田、果园、旱地等4种典型土地利用为研究对象,通过413个土壤和对应作物样品的测试分析,探讨了研究区不同土地利用方式下土壤及其种植作物的As积累特征和对人体的健康风险。结果表明,稻田土壤As含量在5.69～148.5 mg kg-1,积累程度最高;果园土壤As含量在3.29～24.7 mg kg-1积累程度最低。研究区各土地利用类型下土壤As变异系数均在0.5以上,为中等变异性,各样点之间土壤As含量变化较大。研究区不同土地利用方式下,作物As含量差异较大,油料作物As平均含量最高达2.15 mg kg-1,旱地谷物和水果As含量均值最低,均为0.032 mg kg-1。根据研究区作物As的富集系数进行聚类分析,将研究区作物划分为4类,油料作物富集系数最高可划分为第1类,水稻划分为第2类,叶菜类蔬菜划分第3类,而富集系数较低的水果、瓜果类蔬菜、豆荚类蔬菜、根菜类蔬菜和谷物划分为第4类。依据JECFA推荐的ADI值和研究区居民膳食结构进行计算,结果表明研究区不同土地利用类型土壤As对人体健康的风险为稻田>菜地>旱地>果园,尤其是稻田土壤As对人体健康的风险较大,因水稻食用导致的居民As摄入量高达0.00...     

渭河宝鸡段表层沉积物重金属污染研究

采用现场采样及室内分析方法,在对渭河宝鸡段表层沉积物基本理化性质分析的基础上,研究了沉积物中重金属的含量、赋存形态及迁移特征,并进行了污染评价。结果表明,沉积物中Zn、Co、Cd和Hg的平均含量均高于世界、中国和陕西土壤元素背景值,其中Cd（中国和陕西土壤元素背景值的4倍）和Hg（中国和世界土壤元素背景值的7~8倍、陕西土壤元素背景值的16倍）尤为突出。Cr、Ni、Zn、Cu和Co在沉积物中主要以残余态形式存在（50%以上）,Pb主要以可还原态形式存在（近55%）,Mn和Cd主要以乙酸可提取态形式存在（近50%）。重金属迁移顺序为Mn（56.70%）≈Pb（56.65%）〉Cd（53.66%）〉Co（48.82%）〉Cu（43.99%）〉Zn（21.93%）〉N（i15.49%）〉C（r11.43%）,其中Mn、Pb、Cd、Co和Cu的危害较大,有近45%~60%可以发生迁移转化。污染评价结果表明,沉积物主要受到Cd和Hg污染,具有高的潜在生态危害。     

Amount and speciation of N leached from a sandy soil fertilized with urea,liquid digestate,struvite and NH4-enriched chabazite zeolite-tuff

The large use and the bad management of fertilizers that are applied to soil for improving crop production have dramatically impaired soil, water, and air quality. To meet the requirements to reduce nitrogen (N) losses and all the related negative impacts on the environment and food production, it is mandatory to substitute or at least partially substitute the use of inefficient and unsustainable fertilizers with more efficient alternatives. The aim of this paper was to address the amount and speciation of the N released by a sandy soil fertilized with “slow-release fertilizers” and traditional fertilizers (urea and liquid digestate) by means of a series of column leaching experiments. The slow-release alternatives were represented by NH₄-enriched zeolitic tuff and struvite, both obtained by recovering the N from liquid digestate. The treatments consisted of sandy soil fertilized with (i) urea (U) (ii) liquid digestate (LD), (iii) NH₄-enriched zeolitic tuff (N-CHA) and (iv) struvite (STRV). Eight different flushing events were performed over 38 days, leachates were collected and analysed for total Kjeldahl N, organic-N, NH₄⁺-N, NO₃⁻-N, NO₂⁻-N and pH. U and LD lost the majority of N within the first 2 flushing events as organic N and NH₄⁺-N, respectively. On the other hand, STRV and N-CHA lost less N over the whole course of the experiment and with more balanced speciation. The mass balance outlined that after the experiment, native soil N was mined in U and LD treatments while in N-CHA and STRV a fraction of N from the fertilizers was still present. The results showed a slow release of N which can be used more efficiently in agricultural applications, minimizing the N losses.     

Short‐term response of the Ca cycle of a montane forest in Ecuador to low experimental CaCl2 additions

The tropical montane forests of the E Andean cordillera in Ecuador receive episodic Sahara‐dust inputs particularly increasing Ca deposition. We added CaCl₂ to isolate the effect of Ca deposition by Sahara dust to tropical montane forest from the simultaneously occurring pH effect. We examined components of the Ca cycle at four control plots and four plots with added Ca (2 × 5 kg ha^–1 Ca annually as CaCl₂) in a random arrangement. Between August 2007 and December 2009 (four applications of Ca), we determined Ca concentrations and fluxes in litter leachate, mineral soil solution (0.15 and 0.30 m depths), throughfall, and fine litterfall and Al concentrations and speciation in soil solutions. After 1 y of Ca addition, we assessed fine‐root biomass, leaf area, and tree growth. Only < 3% of the applied Ca leached below the acid organic layer (pH 3.5–4.8). The added CaCl₂ did not change electrical conductivity in the root zone after 2 y. In the second year of fertilization, Ca retention in the canopy of the Ca treatment tended to decrease relative to the control. After 2 y, 21% of the applied Ca was recycled to soil with throughfall and litterfall. One year after the first Ca addition, fine‐root biomass had decreased significantly. Decreasing fine‐root biomass might be attributed to a direct or an indirect beneficial effect of Ca on the soil decomposer community. Because of almost complete association of Al with dissolved organic matter and high free Ca²⁺ : Al³⁺ activity ratios in solution of all plots, Al toxicity was unlikely. We conclude that the added Ca was retained in the system and had beneficial effects on some plants.     

鼠李糖脂淋洗修复重金属污染土壤的工艺条件优化研究

以湖南某冶炼厂周边重金属-砷复合污染土壤为对象,应用表面活性剂鼠李糖脂为主要淋洗剂,研究了不同pH值、温度和淋洗次数等工艺条件对重金属及砷淋洗效果的影响。结果表明:Zn、Cd、As在淋洗剂pH为2时提取能力最高,分别可达397、30、21 mg·kg^-1,但Cu的洗脱能力随着pH值的升高而增加;淋洗剂对Cd、Zn、Cu、As的洗脱能力在40 ℃时达到最大值,在30 ℃时淋洗液中Pb浓度最高,为54 mg·kg^-1;多次淋洗有助于土壤中重金属及砷的洗脱,Pb、Cd、Zn、Cu、As的3次淋洗效率分别可达23.1%、53.8%、44.7%、63.2%和34.4%;淋洗后土壤中重金属的酸可提取态、氧化物结合态及有机物结合态浓度大幅降低,砷的残渣态和氧化物结合态浓度明显下降。试验研究确定的最优淋洗条件为污染土壤淋洗修复工程应用提供了可借鉴的工艺参数。     

微波消解-原子荧光法测定仙草产品中砷、汞元素含量

[目的]建立微波消解-原子荧光法测定仙草及其产品中砷、汞微量元素的含量。[方法]样品经微波消解,氢化物发生原子荧光法测定砷、汞元素的含量。[结果]所测元素标准曲线相关系数均≥0.999 9,加标回收率分别为砷88.3%~96.2%、汞85.4%~90.5%,RSD均在5%以内。[结论]该研究建立的方法简便、准确、成本低廉,可用于仙草及其产品中砷、汞元素含量的检测。     

沈阳城市土壤Pb的污染状况及其化学形态研究

研究了沈阳市城市土壤Pb的含量及其化学形态分布,结果表明:沈阳市土壤全Pb平均含量为106.41 mg/kg,变幅为5.65~279.81 mg/kg,各个土地利用类型Pb含量都超过了沈阳市土壤背景值,土壤Pb污染严重。土壤Pb各形态比例为残渣态>有机结合态>铁锰氧化物结合态>碳酸盐结合态>可交换态。各土地利用类型Pb的活性不大。