Effect of some herbicides on activities of microorganisms and enzymes in soil

Abstract

Laboratory tests were conducted with eight herbicides, atrazine, butylate, ethalfluralin, imazethapyr, linuron, metolachlor, metribuzin and trifluralin, applied to a loamy sand at rate of 10 μg/g to determine if these materials caused any serious effects on microbial and enzymatic activities related to soil fertility. Some herbicides showed an effect on bacteria and fungi for the first week of incubation, but, subsequently, the populations returned to levels similar to those obtained in the controls. After several herbicide treatments there appeared to cause a slight depression of nitrification. Sulfur oxidation was better than that obtained with untreated soil in all treatments. Oxygen consumption was increased significantly after 96 hr incubation with atrazine. The soil dehydrogenase and amylase activities were inhibited by ethalfluralin treatment respectively for 1 wk and 1 day, and p‐nitrophenol liberation was inhibited for 2 hrs by all herbicide treatments. Results indicated that the herbicidal treatments at the level tested were not drastic enough to be considered deleterious to soil microbial and enzymatic activities which are important to soil fertility.     

宝钢厂区植被碳储量及其固碳效益评价

以著名钢铁企业上海宝钢为例,基于厂区植被调查、航片数字化解释、优势种生物量测定及模型建立,对宝钢厂区植被碳储量和固碳能力进行估算,并通过碳税法对其固碳效益进行评价,以期为城市工业区绿地群落配置和绿化树种选择、企业绿化建设的费用效益分析提供更为科学的依据。结果表明:宝钢厂区植被总碳储量为3992.99～4736.17 t,固碳效益为13507.33～16185.85万元;平均碳密度为45.82～53.27 t/hm2,固碳能力为5.91～6.87t/(hm2.a),高于上海城市森林平均值,但小于中国森林平均值,一定程度上受平均胸径、郁闭度及群落密度等因素影响。厂区在进行绿化建设时,应考虑选择防污且固碳能力强的植物,构建防污固碳兼有型群落,发挥植被的多元功能。     

改进的灰色关联分析在滑坡危险性评价中的应用——以广东省滑坡危险性评价为例

利用改进的灰色关联分析方法,采用“中心化”无量纲的处理方法,对广东滑坡灾害危险性的影响因素进行灰色关联度分析。通过地形地貌条件、地层岩性特征、地质构造特征、岩土体结构特性、水文地质条件、植被覆盖率、降雨分布、地震、人类经济工程活动等9个评价因素与滑坡危险性的关联度计算,得出各影响因素与滑坡危险性评价的关系,具有一定的客观性、科学性和合理性。     

雅鲁河呼伦贝尔段大型底栖动物群落结构特征及水质生物学评价

在呼伦贝尔市境内雅鲁河流域设置12个点位采集大型底栖动物进行调查研究并对水质状况进行生物学评价。共采集到底栖动物24种,隶属于8目22科,其中水生昆虫19种,占总数79.2%,各点位种类不丰富。各点位优势种不同,但基本都以对水质敏感类群和中等耐污类群为主。各点位密度和生物量差异较大,底栖动物平均密度为89~493ind/m2,平均生物量为0.42~11.69g/m2。调查区域大型底栖动物以集食者和捕食者种类较多,分别为6种;各功能摄食类群分布受空间资源位的限制。Shannon-Wiener多样性指数评价结果为上游点位水质为轻-中污染型,下游点位水质为中-重污染型,BI指数评价结果显示除南大河水质为中度污染外,其余点位水质均为清洁。     

Degradation of pyrene by immobilized microorganisms in saline-alkaline soil

Biodegradation of polycyclic aromatic hydrocarbons (PAHs) is very difficult in saline-alkaline soil due to the inhibition of microbial growth under saline-alkaline stress. The microorganisms that can most effectively degrade PAHs were screened by introducing microorganisms immobilized on farm byproducts and assessing the validity of the immobilizing technique for PAHs degradation in pyrene-contaminated saline-alkaline soil. Among the microorganisms examined, it was found that Mycobacterium sp. B2 is the best, and can degrade 82.2% and 83.2% of pyrene for free and immobilized cells after 30 days of incubation. The immobilization technique could increase the degradation of pyrene significantly, especially for fungi. The degradation of pyrene by the immobilized microorganisms Mucor sp. F2, fungal consortium MF and co-cultures of MB+MF was increased by 161.7% (P < 0.05), 60.1% (P < 0.05) and 59.6% (P < 0.05) after 30 days, respectively, when compared with free F2, MF and MB+MF. Scanning electron micrographs of the immobilized microstructure proved the positive effects of the immobilized microbial technique on pyrene remediation in saline-alkaline soil, as the interspace of the carrier material structure was relatively large, providing enough space for cell growth. Co-cultures of different bacterial and fungal species showed different abilities to degrade PAHs. The present study suggests that Mycobacterium sp. B2 can be employed for in situ bioremediation of PAHs in saline-alkaline soil, and immobilization of fungi on farm byproducts and nutrients as carriers will enhance fungus PAH-degradation ability in saline-alkaline soil.     

Effects of selected pesticides on Rhizobiummeliloti, and on seed germination and Verticillium wilt pathogens of alfalfa

Studies on the effects of 21 fungicides and five pyrethroid insecticides on growth of $\text{Rhizobium}$$\text{meliloti}$, emergence and survival of alfalfa seed and the efficacy of the chemicals in control of Verticillium wilt pathogens were conducted.     

湖沼钉螺孳生环境分布的遥感调查研究

以试验区不同环境类型洲滩钉螺螺情与环境因子进行了调查分析，利用遥感图像编制地貌类型图，土壤类型图和土地利用类型图，在地理相关分析与主导因素分析基础上采取多图件逐步套合方法，以土地利用类型图为主，结合地面钉螺抽样调查和钉螺被动扩散等非遥感信息进行多信息复合，编制了试验区钉螺孳生环境分布图。     

外生菌根真菌接种和施磷对油松苗抗盐性的影响

采用3种不同的外生菌根真菌Boletus edulis、Xerocomus chrysenteron和Gomphidius viscidus，在山东东营盐渍土环境胁迫下，研究外生菌根真菌接种和施磷对油松(Pinus tabulaeformis)生长的影响及其可能机理。结果表明，接种和施磷都增加了油松植株的干质量，但施磷不如接种对植物生长的促进作用明显；接种外生菌根后，油松体内的K元素含量显著增加，而Na元素的含量没有明显变化，使得w(K)／w(Na)增加，从而改变了植株体内的离子平衡，减轻离子的毒害作用。而不是通过直接减少植物对Na的吸收来增加植物的抗盐性；同时，接种后外生菌根增加了油松对P的吸收，改善了盐渍土壤导致的植物营养亏缺，促进了植物在盐渍环境下的生长。     

Speciation and fractionation of heavy metals in soil experimentally contaminated with Pb,Cd, Cu and Zn together and effects on soil negative surface charge

Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water-soluble and exchangeable(SE), weakly specific adsorbed( WSA),Fe and Mn oxides-bound(OX) and organic-bound( ORG). The results showed that fractions of heavy metals in the soil subsamples depended on their speciation. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil subsamples as SE, WSA and OX fractions simultaneously, although SE was still the major fraction. Organic-bound heavy metals were not clearly apparent in all the soil subsamples. The concentration of some heavy metal fractions in soil subsamples showed the good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with 0.20 mol/L NH4CI, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil subsamples depended greatly on pH, the composition and original heavy metal content of the soil subsamples. However, most of the heavy metals in the soil subsamples were still be retained after multiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did not show difference significantly from that of the parent one by statistical analysis. Heavy metals existed in the soil subsamples mainly as exchangeable and precipitated simultaneously.