不同镉污染农田土壤上秸秆和炭化秸秆分解动态及其对土壤镉的吸附特征

通过温室土壤培养实验，研究不同镉污染农田土壤上不同的作物秸秆和炭化作物秸秆还田后的分解动态和还田秸秆材料对污染土壤中镉的吸附特征，探讨秸秆和炭化秸秆还田做为重金属镉污染农田土壤修复剂的可行性。实验结果表明，还田的油菜秸秆和玉米秸秆在2种镉污染水稻土壤上6个月分解了43％-65％，秸秆炭化后还田则很稳定，2种镉污染土壤上还田6个月时累计分解量小于5％。2种镉污染土壤上还田的秸秆和炭化秸秆随还田时间延长镉含量逐渐增加。模拟镉污染土壤上，相同时期油菜秸秆中镉含量显著高于玉米秸秆，油菜秸秆炭中镉含量显著高于玉米秸秆炭。在镉污染土壤上，还田的玉米秸秆、油菜秸秆、玉米秸秆炭和油菜秸秆炭对土壤镉的净吸附量相近，均小于1．1μg／g。在模拟镉污染土壤上还田的油菜秸秆和油莱秸秆炭对土壤镉净吸附量最高分别达到2．74μg／g和7．03μg／g，分别是玉米秸秆和玉米秸秆炭的2倍，且显著高于其在镉污染土壤上的净吸附量，具有高的吸附能力。     

冻融循环及有机肥配施对黑土中镉形态的影响

以黑龙江黑土为对象,研究了冻融循环及有机肥配施量对黑土中镉形态分布的影响。对配施不同有机肥的土壤样品进行5次冻融循环,采用电感耦合等离子质谱仪(ICP-MS)分析土壤样品中镉的赋存形态。结果表明,冻融循环数及有机肥的配施有助于降低黑土中的总镉量;冻融循环会促使黑土中的镉由交换态、碳酸盐结合态、有机结合态向铁锰氧化物结合态和残渣态转化,而增加有机肥配施量会使黑土中的镉由交换态向其他形态转化。因此,冻融循环及有机肥配施有助于降低土壤中镉的生物有效性,进而降低其环境风险。     

改良剂对重金属复合污染土壤的修复效果

为揭示不同改良剂及其联合施用对重金属复合污染土壤的修复效果,采用室内土壤培养实验和室外盆栽实验相结合,研究不同施用量(10和20 g·kg~(-1))的蛭石(A)、泥炭(B)和骨粉(C)以及两两组合施用下,改良剂对土壤重金属DT-PA有效态、植物(以空心菜为例)生物量、株高以及植物可食部重金属含量的影响。结果表明:不同处理条件下的土壤p H值的提升与空白对照相比变化不显著;单施2%泥炭对土壤重金属Cu、Zn的钝化效果优于其他处理组,相对空白对照组,在第42天2种金属有效态含量分别降低了57.65%和65.55%,而1%蛭石和1%骨粉的混合添加能有效降低土壤中有效态Cd含量,相对空白对照组在第42天有效态Cd含量降低了40.52%;3种改良剂单施和混施对空心菜均具有增产增收的显著效果,且混施改良剂对空心菜增产效果较好;各处理组中空心菜体内Cu、Zn和Cd含量均有显著的降低,其中2%泥炭、1%蛭石+1%泥炭和1%蛭石+1%骨粉处理组分别对空心菜体内Cu、Zn和Cd含量降低效果最好,相对空白对照组分别降低了75.39%、70.75%和75.42%。因此,在该污染类型土壤泥炭、蛭石+泥炭和蛭石+骨粉分别对空心菜吸收土壤中的Cu、Zn和Cd具有较好的阻控效果。     

华北地区旱田土壤氧化亚氮的排放

在１９９１－１９９３年间用封闭罩测定了对照田、施肥田Ｎ２Ｏ的排放量。结果表明，Ｎ２Ｏ通量显示出时、空变化规律。对照田，施尿素田和施混合肥田（尿素加有机肥）Ｎ２Ｏ排放量分别是１．０３±０．４ｋｇＮ／ｈｍ２ａ；１．９１±０．６ｋｇＮ／ｈｍ２ａ和２．１１±１．０ｋｇＮ／ｈｍ２ａ．尿素和混合肥释放Ｎ２Ｏ系数分别为０．２９％和０．３５％。由土壤含水量，土壤温度和速效氮浓度等土壤变量建立了Ｎ２Ｏ排放的统计模式。     

镉污染土壤的植物修复研究进展

镉会影响植物正常生长,经食物链富集,则会对动物和人体造成危害。植物修复是一种生态友好的修复手段,能有效修复镉污染土壤。因此,开展镉污染土壤植物修复的系统研究非常必要。通过研究发现,目前针对镉污染土壤的植物修复的研究主要集中于两方面:一方面是镉超积累植物和镉富集性植物的筛选,另一方面是植物-微生物联合修复技术的强化。目前已筛选出镉超积累植物11种,镉富集性植物31种,已研究出针对镉污染土壤的植物-微生物匹配组合11个,镉耐性菌16种。     

白银市区土壤作物系统重金属污染分析与防治对策研究

通过对白银市区土壤作物系统重金属含量与分布变化特征的调查分析，结果表明，只有东大沟污灌区土壤作物污染严重，Cd,Pb超标明显；西大沟清污混灌区土壤环境为轻度污染，但作物质量符合标准要求；其余灌区土壤物质符合标准要求。最后，根据土壤作物重金属含量分布变化特征，提出了相应的防治对策。     

污灌对土壤的氮效应及与地下水氮污染的关系

一、高碑店污灌区不同污灌,不同作物条件下,土壤中各形态氮的分布及动态 1.材料及方法 采集了污灌区不同污灌条件和不同作物的土壤样品,包括污灌菜地母壤、污灌并施污泥菜地母壤、污灌稻田、清灌菜地等土壤样品.为此,还采集了圆明园自然植被土壤样品,各采样地块(见表1)均按蛇形采样法布孔至少5个,分层取样后分别混合作为该地块的代表样品.其中A—E、G、H各点     

应用籽粒苋修复镉污染农田土壤的潜力

针对农田土壤镉污染问题,采用超富集植物籽粒苋并配施不同组合的外源活化剂进行盆栽实验和田间实验,并测定籽粒苋及根系土壤中镉含量并计算富集系数。结果表明,在盆栽实验的不同处理组中,施加磷酸二氢钾(0.74 mmol·kg~(-1))、EDTA(2 mmol·kg~(-1))和柠檬酸(4 mmol·kg~(-1))最有助于提高籽粒苋对Cd的提取修复效率。田间实验中添加活化剂(EDTA和柠檬酸)后籽粒苋的根、茎和叶组织对Cd的富集能力分别是不添加活化剂处理组的2.10、1.84和2.76倍;与对照组相比,籽粒苋的根、茎和叶部分的Cd含量都显著提高(P0.05),这说明外源活化剂促进了籽粒苋对土壤中Cd的吸收,提高了修复效率。每年种植两茬籽粒苋并添加活化剂,Cd的去除率可达4%～10%。种植超富集植物并配施活化剂既可以提高修复效率,又可以节约修复成本。     

海泡石及其复配原位修复镉污染稻田

以天然黏土海泡石作为钝化材料,并分别与磷肥、生物炭和硅肥复配,在湖南某镉污染的酸性水稻田进行原位修复示范实验,考察海泡石及其复配对稻谷产量、糙米镉含量及土壤中镉的有效态含量及形态分布变化用以表征修复效果;研究了海泡石及其复配对土壤pH、土壤碱解氮、有效磷含量以表征其对土壤环境质量的影响,并对各项理化指标之间的相关性进行分析。结果表明,田间示范条件下海泡石及其复配均降低了土壤中镉的生物有效性,明显降低了糙米中镉含量。其中海泡石磷肥复配和海泡石硅肥复配处理后,糙米镉含量最大降幅约为72.7%,分别降低至0.33和0.34 mg/kg。海泡石及其复配处理均能不同程度增加土壤中碱解氮及有效磷含量,对于作物生长有益。综合总体表现,海泡石磷肥复配、海泡石硅肥复配可被推荐作为镉污染酸性稻田的原位钝化修复材料,具有推广应用的潜力。     

紫茉莉修复镉污染土壤的研究

研究了紫茉莉在镉污染土壤中的生长特征、对镉的富集能力和体内分布规律。紫茉莉对镉的耐性较强，富集浓度最高可达92．82mg／kg，镉在紫茉莉的分布为根〉茎〉叶。紫茉莉在中、低浓度镉污染土壤中可取得较好的修复效果。     

The metabolic fate of N-isopropyl-N-phenyloxamic acid in the rat and the milk goat.

Rats excreted the 14C from a single oral dose of N-isopropyl-N-[14C]phenyloxamic acid [I, a soil metabolite from 2-chloro-N-isopropylacetanilide (propachlor)] in approximately equal quantities in the urine (49.2%) and feces (48.2%). A milking goat given daily oral doses of [14C]-I (1 mg of I three times daily) excreted more 14C in the feces (56.6%) than it excreted in the urine. From both species, I accounted for 97 to 100% of the urinary 14C, and all of the 14C that was extractable from the feces (73 to 75% of the 14C in feces was extractable with methanol). Goat milk samples collected 16 hr after the last dose contained no detectable 14C. Tissue residues of 14C were determined.     

Inactivation of cadmium in contaminated soils using synthetic zeolites

The addition of synthetic zeolite pellets to soils contaminated with cadmium significantly reduced the concentrations of cadmium in the roots and shoots of a range of crop plants. Use of synthetic foyazite group zeolites types 4A and 13X, at application rates of 1% by soil weight, caused reductions in cadmium concentrations of up to 86% in leaves of lettuce grown in pots, compared to controls with no added zeolites. The potential of these substances to reduce cadmium entry into the food chain, and as a clean up method, is noted.     

Avoidance test with Enchytraeus albidus (Enchytraeidae): effects of different exposure time and soil properties

Enchytraeids are ecologically relevant soil species and are commonly used in standardized toxicity tests. Their rapid reaction to a chemical exposure can be used as a toxicological measurement endpoint that assesses the avoidance behavior. The objectives of this investigation were to determine the effects of soil properties on the avoidance behavior of Enchytraeus albidus and to optimize the duration of avoidance test. The avoidance tests included (1) exposures in OECD artificial soil with standard or modified properties (pH, clay or peat content), and (2) exposures to copper chloride, cadmium chloride, and to the organic pesticides dimethoate and phenmedipham for different time periods. Results showed that alteration of OECD soil constituents significantly affected the avoidance behavior of enchytraeids, and that the 48-h exposure was the optimal duration of the test. Consideration of soil properties is important for selecting appropriate experimental design and interpreting the results of the enchytraeid avoidance test.     

Long-term effects of soil heterogeneity on cadmium behaviour in soil

A deterministic model for long-term behaviour of contaminants in the rootzone is developed that includes sorption, leaching, and plant uptake. The model is applied to cadmium accumulation in a sandy soil and uptake of cadmium by barley. Sensitivity analysis showed that the sensitivity of the leaching rate to changes in soil chemical and soil physical parameters decreases as a function of time, and becomes zero when steady state is reached. In contrast, accumulation of cadmium in soil and the plant uptake rate of barley are increasingly sensitive to soil chemical and soil physical parameters as time preceeds. To analyse cadmium behaviour in a field that is heterogeneous with respect to soil physical properties, the interstitial flow velocity was assumed to be a random, lognormally distributed variate. Using Monte Carlo simulation, the average plant uptake rate appeared to be much higher in the stochastic analysis than in the deterministic approach. Steady state is reached after a very long period of time. For a lognormally distributed proton activity, causing heterogeneity with respect to the sorption capacity of the soil, the model predicted similar deviations from the deterministic approach. It is concluded that reference values for groundwater and crop quality are exceeded earlier in a heterogeneous field than in a homogenous soil profile. Moreover, when average values suggest an acceptable situation, variability of the leaching rate and the plant uptake rate can still cause exceedance of reference values in part of the field. Therefore, it is reasoned that environmental quality standards should take soil heterogeneity into account.     

Methane oxidation by Dutch grassland and peat soil microflora

The ability of Dutch grassland soil and Dutch peat soil for methane oxidation was investigated. The kinetics of methane oxidation by soil from different depths were determined in batch cultures incubated with 1; 10; 100; and 10,000 ppmv methane, respectively. All 4 applied concentrations of methane were degraded by both types of soil. Thereby, the highest oxidative activities were observed between 5 and 10 cm soil depth. Most importantly, these experiments demonstrated that this soil acts as a sink for methane even at concentrations well below 1 ppmv. Especially at higher methane concentrations (100 - 10,000 ppmv) much higher degradation rates were found in the peat soil. This also correlates with the higher methane production rates which had been observed in peat soil.     

硫化钠对土壤中铅镉的固定效果简

研究了硫化钠用于固定土壤中铅镉的可行性，考察了硫化钠用量及土壤pH、有机质对固定过程中土壤铅、镉赋存形态及固定效果的影响。结果表明，添加硫化钠可改变土壤中铅镉的形态分布，明显降低可交换态铅镉的含量。条件适当时，铅镉可交换态下降值分别为63%和73%。硫化钠在固定铅的过程中，固定效率对土壤pH、有机质含量的变化较为敏感，在有机质含量较低或酸性土壤中，硫化钠对铅固定效率较高；相对于铅，有机质含量和pH变化对镉的固定效率影响不是很大。     

Effect of soil pH on availability to crops of metals in sewage sludge-treated soils. II. Cadmium uptake by crops and implications for human dietary intake

Appropriate pH-related permissible soil-limit concentrations for cadmium in sewage sludge-treated agricultural soils were estimated from the proportional changes in concentrations of cadmium in potatoes, oats and ryegrass grown on two sludge-amended soils and at different pH values. Implications for potential human dietary intake of cadmium were also assessed. Yields of crops increased with increasing soil pH, probably in response to decreasing uptake of zinc as soil pH value was raised. In general, cadmium concentrations in peeled potato tubers, potato peelings, oat straw and ryegrass decreased as simple linear functions of increasing soil pH over the range of pH values measured (pH 3.9-7.6). Cadmium concentrations in potato peel were particularly sensitive to changing pH conditions, whereas cadmium levels in oat grain were independent of soil pH. On the basis that a highly precautionary approach is adopted in setting soil standards for heavy metals, appropriate permissible concentrations of cadmium in sludge-treated agricultural soil which protect the human food chain were determined as 2.0 and 2.5 mg Cd Kg(-1) for banded pH ranges of 5.0-5.5 and 5.5-6.0, respectively.     

Contrasting effects of silicates on cadmium uptake by three dicotyledonous crops grown in contaminated soil

The effects of several silicates (talcum powder (TP), calcium silicate (CS), sodium silicate (SS), and potassium silicate (PS)), in comparison with other amendments (quicklime (QL) and potassium dihydrogen phosphate (PDP)) on cadmium (Cd) uptake by three dicotyledonous crops (Amaranthus hypochondriacus L. Cv. ‘K112’, Amaranthus tricolor L., and Brassica oleracea var. albiflora Kuntze) were investigated in Cd–contaminated soil. The effects of both application methods of amendments (singly and combined) and timing of application were also evaluated. Sodium silicate was the most effective in reducing crop Cd uptake and translocation, which was diminished by 51 % in roots, 53 % in stems, and 72 % in leaves on average. Application of CS amendment showed greater efficiency than PDP amendment in decreasing Cd uptake by crops and resulted in increased biomass. Potassium silicate only slightly decreased shoot Cd concentration. Combination of PDP and SS was able to overcome the inhibitory effect of SS on crop yield while decreasing Cd concentrations in roots, stems and leaves of the tested crops by average rates of 52, 65, and 68 % respectively. Applications of SS and PS significantly reduced the root-to-shoot Cd transfer factor. We found that Si accumulation in crops was not associated with lower Cd concentration, indicating that Si in crops may play a major role in alleviating metal stress rather than inhibiting crop Cd accumulation. We suggested that the inhibitive effect of silicates on crops Cd uptake was majorly attributed to the properties of the silicates, those were their specific effects on soil pH and cations, which increased Cd adsorption by soil and suppressed Cd uptake from soil solution by increasing the relative dissolved concentrations of competing cations.     

Mobility of isoproturon from an alginate-bentonite controlled release formulation in layered soil

The mobility of isoproturon [3-(4-isopropylphenyl)-1,1-dimethylurea] from an alginate-based controlled release (CR) formulation was investigated by using soil columns. A layered bed system simulating the typical arrangement under a plastic greenhouse, which is composed of sand, peat, amended soil and native soil was used. The CR formulation was based on sodium alginate (1.87%), isoproturon (1.19%), natural bentonite (3.28%), and water (93.66%), and was compared to technical grade isoproturon. The use of the alginate-bentonite CR formulation produced less vertical mobility of the active ingredient as compared to the technical product. There was no presence of herbicide in the leachate when the alginate-bentonite CR formulation was used. However, 0.90% of isoproturon appeared when the treatment was carried out with technical grade material. Isoproturon mobility was modelled using the programme CMLS, which showed the peat layer to retard pesticide leaching. Analysis of the soil columns showed the highest isoproturon concentration in the peat layer.     

Distribution and speciation of mercury in the peat bog of Xiaoxing'an Mountain,northeastern China

Most reports on mercury (Hg) in boreal ecosystems are from the Nordic countries and North America. Comparatively little information is available on Hg in wetlands in China. We present here a study on Hg in the Tangwang River forested catchment of the Xiaoxing'an Mountain in the northeast of China. The average total Hg (THg) in peat profile ranged from 65.8 to 186.6 ng g(-1) dry wt with the highest at the depth of 5-10 cm. THg in the peat surface was higher than the background in Heilongjiang province, the Florida Everglades, and Birkeness in Sweden. MethylHg (MeHg) concentration ranged from 0.16 to 1.86 ng g(-1) dry wt, with the highest amount at 10-15 cm depth. MeHg content was 0.2-1.2% of THg. THg and MeHg all decreased with the depth. THg in upland layer of soil (0-20 cm) was comparable to the peat surface, but in deeper layers THg concentration in peat was much higher than that in the forested mineral soil. THg in the peat bog increased, but MeHg decreased after it was drained. THg content in plant was different; THg contents in moss (119 ng g(-1) dry wt, n=12) were much higher than in the herbage, the arbor, and the shrubs. The peat bog has mainly been contaminated by Hg deposition from the atmosphere.