沉积物溶解性有机氮藻类的可利用性

采用DAX-8树脂和732氢型阳离子交换树脂将山口湖沉积物中溶解性有机氮（DON）分成亲水组分和疏水组分，在室内培养条件下，研究了其对羊角月牙藻的可利用性。结果表明：通过DAX-8树脂后，N4和N14沉积物DON回收率分别为98.96%和104.34%。原水和亲水DON组分通过阳离子交换树脂后会吸附类蛋白物质，降低藻类生物量。培养过程中，N4原水和亲水组分DON消耗量分别为0.34 mg·L-1和0.36 mg·L-1，低于N14原水和亲水组分DON消耗量0.94 mg·L-1和0.82 mg·L-1，表明N14亲水组分藻类可利用较N4亲水组分多。由于阳离子交换树脂对N4原水和亲水组中DON去除率较高，其藻类的生物量低于N14原水组和亲水组。N4疏水性组分DON的利用量和藻细胞生物量分别为0.80 mg·L-1和15×104个·mL-1，高于N14组，这是因为N4接收了长水河农场生活污水和周围农田径流中易降解DON。利用PARAFAC模型对培养过程中三维荧光光谱数据解析出1种类蛋白物质和2种类腐殖质物质。培养初期，类蛋白物质先被藻类所利用导致其含量降低，而随着藻类生长进入对数期，释放到水体中类蛋白物质导致其相对荧光强度的增加。在整个培养过程中，类腐殖质物质相对荧光强度的增加主要来源于死亡藻类的释放。

Algal uptake of dissolved organic nitrogen in lake sediment to Selenastrum capricornutum

A DAX-8 resin coupled with 732 H-type cation exchange treatment was employed to separate dissolved organic nitrogen (DON) in Lake Shankou sediment into hydrophilic and hydrophobic fractions. The DON bioavailability to Selenastrum capricornutum was studied under the room cultivation. The results show that the recovery rates of DON in the sediments from stations N4 and N14 by DAX-8 resin treatment were 98.96% and 104.34%, respectively. Protein-like substances in the untreated samples and hydrophilic fractions were adsorbed after passage through the cation exchange resin, resulting in low algal biomass. During incubation, DON in the N14 untreated sample and hydrophilic fraction decreased by 0.94 mg·L-1 and 0.82 mg·L-1, respectively. DON contents in the N4 untreated sample and hydrophilic fraction decreased by 0.34 mg·L-1 and 0.36 mg·L-1, respectively. These results suggest that DON in the N14 untreated sample and hydrophilic fraction was more bioavailable than it was in the corresponding N4 samples. Meanwhile, higher algal biomass in the N14 untreated and hydrophilic fractions was observed because more DON in the N4 untreated and hydrophilic fractions was absorbed by the cation exchange resin. The DON reduction amount and algal density in the N4 hydrophobic fraction were 0.80 mg·L-1 and 15×104 cells·mL-1, respectively, which were higher than they were in the N14 hydrophobic fraction. The N4 station, located in the Changshuihe Lake branch, received more biodegradable DON from Changshuihe farm sewage and runoff from surrounding farmland. During incubation, one protein-like substance and two humic-like substances were distinguished for the three-dimensional excitation-emission matrix (EEM) spectra by the PARAFAC model. The protein-like substance was utilized early in the incubation due to algal uptake, then its fluorescent intensity increased due to its release from the algal cells in logarithmic phase. The relative fluorescent intensity of the humic-like substances increased due their release from dead algal cells during the incubation.