A Methodology Framework for Regional Land-use Change Studies based on Landsat TM images: A Case Study in Northeast China

Abstract

Land-use change is an important aspect of global environment change. It is, in a sense, the direct result of human activities influencing our physical environment. This paper analyzed the land- use change in Northeast China during 1985–2000 based on Landsat TM images. It divides Northeast China into five land-use zones based on the dynamic degree model of land-use: woodland/grassland-arable land conversion zone, dry land-paddy field conversion zone; urban expansion zone, interlocked zone of farming and pasturing and reclamation and abandon zone. The findings include the obvious increase of cropland area, paddy field and dry land increased by 75 and 276 thousand hm² respectively; urban areas expanded rapidly, areas of town and rural residence increased by 76.8 thousand hm²; areas of forests and grassland decreased sharply with the amounts of 1399 and 1521 thousand hm² respectively; areas of water body and unused land increased by 148 and 514 thousand hm² respectively. This paper also discusses the driving forces in each land-use dynamic zone and finds that some key biophysical factors affect conspicuously the conversion of different land-use types. The relation between land-use conversion and DEM, accumulated temperature (≤10°C) and precipitation was analyzed and represented. The land-use changes In Northeast China resulted from the changing macro social and economic factors and local physical elements. Rapid population growth and management changes can explain the shaping of woodland/grassland-cropland conversion zone. The conversion from dry land to paddy field in the dry land-paddy field conversion zone, apart from the change of physical elements promoting the expansion of paddy field, results from two reasons: one is that the implementation of market economy in China has given farmers the right to decide what and how they plant their crops, the other factor is originated partially from the change of the dietary habit along with the social and economic development. The conversion from paddy field to dry land is caused primarily by the shortfall of irrigation water, which in turn is caused by poor water allocation managed by local governments. The shaping of the reclamation and abandon zone is partially due to the lack of environment protection consciousness among pioneer settlers. The reason for the conversion from grassland to cropland is the relatively higher profits of farming than that of pasturing in the interlocked zone of farming and pasturing. In Northeast China, the rapid expansion of built-up areas results from two factors: the existence of a small number of towns and the huge potential for expansion of the existing towns and cities. The urban land expanded mainly in areas with a gentle topographic relief and low population density.     

聚己内酯与聚羟基丁酸戊酸酯的脱氮性能对比

以可生物降解聚合物聚己内酯(PCL)和聚羟基丁酸戊酸酯(PHBV)作为反硝化缓释碳源和微生物载体,利用清水释碳和批式反硝化试验选出适用于再生水反硝化深度脱氮生物滤池的可生物降解碳源滤料,通过比较与分析碳源滤料的表面形态及物质特性和附着微生物的群落特征揭示其性能优越的原因.结果表明,PHBV反硝化启动时间短,反硝化速率高,剩余有机物浓度低,相比PCL具有更稳定持续的反硝化效果.原因是其表面粗糙,且含有大量C—O和CO等亲水性基团,易于微生物附着和降解利用;其表面附着的微生物种类多样,其中发硫菌属(Thiothrix)、假单胞属(Pseudomonas)、菌胶团属(Zoogloea)、黄杆菌属(Flavobacterium)和脱氯菌属(Dechloromonas)等优势菌属均具有异养反硝化功能.因此,PHBV更适合作为再生水反硝化深度脱氮生物滤池的碳源滤料.     

套管保护液对钻井废水处理效果的影响＊

通过研究高含硫气田钻井完井后套管保护液对钻井废水处理效果的影响,可知:采用混凝/二次絮凝/吸附工艺处理不含套管保护液的钻井废水时,出水COD<150 mg/L;当套管保护液加量>0.5 mL/L时,出水中COD随套管保护液用量增加而急剧升高,远大于150 mg/L;采用混凝/吸附/微电解组合工艺处理含套管保护液的完井钻井废水,出水COD<150 mg/L,满足GB 8978-1996《污水综合排放标准》二级标准的要求。     

Thermal defluorination behaviors of PFOS,PFOA and PFBS during regeneration of activated carbon by molten salt

• New method of mineralizing PFCs was proposed. • Activated carbon was regenerated while mineralizing PFCs. • Molten NaOH has good mineralization effect on PFOS and PFBS. Current study proposes a green regeneration method of activated carbon (AC) laden with Perfluorochemicals (PFCs) from the perspective of environmental safety and resource regeneration. The defluorination efficiencies of AC adsorbed perfluorooctanesulfonate (PFOS), perfluorooctanoic acid (PFOA) and perfluorobutanesulfonate (PFBS) using three molten sodium salts and one molten alkali were compared. Results showed that defluorination efficiencies of molten NaOH for the three PFCs were higher than the other three molten sodium salts at lower temperature. At 700°C, the defluorination efficiencies of PFOS and PFBS using molten NaOH reached to 84.2% and 79.2%, respectively, while the defluorination efficiency of PFOA was 35.3%. In addition, the temperature of molten salt, the holding time and the ratio of salt to carbon were directly proportional to the defluorination efficiency. The low defluorination efficiency of PFOA was due to the low thermal stability of PFOA, which made it difficult to be captured by molten salt.The weight loss range of PFOA was 75°C–125°C, which was much lower than PFOS and PFBS (400°C–500°C). From the perspective of gas production, fluorine-containing gases produced from molten NaOH-treated AC were significantly reduced, which means that environmental risks were significantly reduced. After molten NaOH treatment, the regenerated AC had higher adsorption capacity than that of pre-treated AC.     

Agricultural non-point sources and their effects on chlorophyll-a in a eutrophic lake over three decades (1985–2020)

Environmental Science and Pollution Research - Erhai Lake is the second largest freshwater lake in Yunnan Province but suffers from the deterioration of water quality and agricultural non-point...     

五氯酚胁迫对转基因杨树光合光响应特性的影响

以从美国引入的转基因杨树(Populus deltoides×nigra,DN34)为材料,设置0、50、100 mg·kg~(-1)三个五氯酚胁迫质量分数开展温室盆栽试验,利用Li-6400便携式光合作用测量系统研究五氯酚污染胁迫下转基因杨树对光强的生理响应.结果表明:与对照相比,相同光强下50和100 mg·kg~(-1)质量分数的五氯酚胁迫均降低了转基因杨树叶片的净光合速率(P_n)、蒸腾速率(T_r)、胞间CO_2摩尔分数(C_i)和气孔导度(G_s).因此高质量分数五氯酚比低质量分数五氯酚对转基因杨树光合作用产生更大的抑制响应.     

对一起管道疏通机造成触电事故的分析

１９９９年７月１２日,在我市发生一起触电事故,死亡青工正名。当日上午７：４０某家庭服务队接到某饭店电话,说饭店２楼后厨下水道堵塞,请派人去疏通。于是贾××和另一名工人带上管道疏通机前去作业。８时许,２人来到现场,从墙上配电盘下方接好电源,然后试机准备...     

肺炎嗜衣原体主要外膜蛋白基因片段在大肠杆菌中的表达与鉴定

表达肺炎嗜衣原体（Chlamydia pneumoniae,Cpn）主要外膜蛋白（MOMP）的可变区VD2-VD3区．纯化产物并进行免疫活性分析,为探索重组蛋白在肺炎嗜衣原体血清学诊断中的应用提供资料．应用聚合酶联反应（PCR）技术,从肺炎嗜衣原体标准株AR-39的MOMP上扩增出抗原优势表住VD2-VD3区,将目的片段定向插入pET-30a载体,转化大肠杆菌B121,IPTG诱导表达并以Ni-NTA亲和层析柱纯化表达产物并行western-blot鉴定．成功构建了pET-30a-MOMPVD2-VD3的原核表达系统,表达并纯化出相对分子质量（Mr）为24×10^3Da的重组蛋白．Western-blot证实重组蛋白能与Cpn MOMP多克隆抗体发生特异性反应．肺炎嗜衣原体的MOMPVD2-VD3基因可以在大肠杆菌中得到表达,其表达产物能与相应的抗体结合,为肺炎嗜衣原体诊断候选抗原的研究奠定了基础．图4,参9．     

濒危植物疏花水柏枝种子萌发的生态学特性

疏花水柏枝Myricaria laxiflora分布于我国三峡从宜昌至重庆段长江干流的消落带,分布区十分狭小.三峡工程兴建后,疏花水柏枝将失去绝大部分的生境而成为濒危物种.通过设置一系列控制实验测试了土壤水质量分数,温度和土壤类型对疏花水柏枝种子萌发的生态学的影响.实验结果表明,土壤水质量分数、温度和土壤类型对种子萌发率都有显著影响.其中种子萌发率随土壤水质量分数增加而增大,土壤水质量分数达到饱和程度时萌发率达到最大值;高温条件下的种子萌发率高于低温,种子萌发率在21～27℃达到最大值;种子在河沙基质上萌发好于在沙土基质上.结合分布区萌发季节的环境条件分析,土壤水质量分数是限制该物种分布于消落带的关键作用因子.据此就该物种的种群保护与重建提出了一些建议.     

水解酸化-缺氧生物法处理油田废水的机理

采用水解酸化-缺氧生物法对经物化预处理的油田废水进行试验研究.当进水COD为190～230mg/L,水解酸化段和缺氧段停留时间分别为10,48h时,出水COD为75～83mg/L.运用GC/MS分析油田废水有机污染物在工艺流程中相对组分变化的规律,表明水解酸化和缺氧法处理油田废水时有协同作用,可有效降解废水中酚类化合物、酮类化合物、芳烃和BTEX.运用PCR-DGGE技术,考察不同生物反应器内微生物种群及其分布特征,初步确定水解酸化和缺氧反应器内的优势菌种.