N itrogen and P hosphorus P rotocols
N itrogen and P hosphorus P rotocols
B ack ground
T he protocols described here are designed for collecting and preserving a sam ple for analysis by a
T he tw o prim ary nutrients of concern for w ater laboratory. L evels of concern are often below the quality are nitrogen (N ) and phosphorus (P). detection lim its of field sam pling kits and are
E xcess am m onia and nitrate can be toxic to stream difficult to record accurately w ith specific ion organism s and hum ans. O f particular concern is electrodes. T herefore these sam ples are best blue baby syndrom e (infant m ethem oglobinem ia) analyzed at a com m ercial analytical laboratory. caused by excess nitrate/nitrite. T hese concerns are T he first step is to determ ine w hat form s of nitrogen usually associated w ith concentrated loads from and phosphorus should be analyzed so that the m unicipal sites such as sew age treatm ent outfalls or appropriate preservation protocols can be selected they m ay result from repeated heavy applications of
(Stednick 1991).
nitrogen fertilizer or anim al w aste. N itrogen can occur in m any form s in the
T he m ost com m on basin-w ide concern w ith environm ent. N itrogen can also cycle betw een nutrients is eutrophication of stream s and lakes. these different form s (Figure 10-1.) T he nitrogen
E utrophication is an excessive grow th of aquatic form s that are m ost com m only tested are those plants. E utrophication occurs w hen concentrations w hich are the m ost biologically available: soluble of nitrogen, phosphorus and other environm ental
conditions favorable to aquatic plant grow th nitrate/nitrite nitrogen (N O 3- , N O 2-), ammonia (tem perature, light, flow velocity) are elevated and
(N H 3), and total K jehldahl nitrogen (the sum of the available.
free am m onia and organic nitrogen). N itrate is especially im portant because it is relatively soluble
T his excessive plant grow th causes daily in w ater com pared to other nitrogen form s. T he fluctuations in dissolved oxygen and pH and can
M onitoring T eam for the O PSW recom m ends that im part undesirable tastes and odors to w ater. T hese
sam ples be analyzed for nitrate/nitrite and total w ater quality im pacts can adversely affect the uses
K jehldahl nitrogen.
of w ater for fish habitat, recreation, and drinking w ater. T he U S E nvironm ental Protection A gency is currently developing new nationw ide w ater quality
criteria 10 for nutrients. B y the year 2000, num eric criteria for nitrogen and phosphorus w ill be
developed w hich w ill reflect different types of w ater bodies and ecoregions.
10 http://www.epa.gov/cleanwater/action/overview.html
Figure 10-1. T he nitrogen cycle (from Saw yer and M cC arty 1967)
Ph osph orus also com es in m an y differen t form s
E quipm ent
(Figure 10-2). T h e tw o form s for w h ich an alyses are
A list of equipm en t n eeded to sam ple for n itrogen th e m ost com m on are orth oph osph ate an d total an d ph osph orous is sh ow n in T able 10-1. Sam ple
ph osph orus. O rth oph osph ates in clude H 2PO 4-, and bottles n eed to be clean an d m ade of a m aterial th at
H PO 42-, and PO 43-. T hese are dissolved form s of does n ot leach or react w ith th e sam ple. C lean in g of ph osph orus w h ich are available for aquatic plan t use.
reusable sam ple bottles sh ould be don e accordin g to T otal ph osph orus in cludes dissolved an d particulate,
in struction s from th e laboratory receivin g th e sam ple organ ic, an d in organ ic form s.
because som e detergen ts can con tam in ate sam ples.
Nitrogen and Phosphoras Protocol
10 - 2
Water Quality Monitoring Guidebook
T able 10-1. M aterials needed to collect sam ples for nitrate/nitrite, kjehldahl nitrogen, orthophosphate, and total phosphorous.
500 m l clean, reusable polyethylene bottle 250 m l clean, reusable polyethylene bottle
0.45 µ m filter discs and syringe C ooler and ice or blue ice C oncentrated H 2SO 4
M arking pen and labels
Figure 10-2. Form s of phosphorus in w ater (from M cC utcheon, M artin, and B arnw ell 1993).
F ield M etho d
3. A dd 12 drops of concentrated H 2SO 4 (sulfuric
acid).
4. L abel and place in the cooler w ith ice to keep k je h ld a h l n itro g e n , a n d to ta l p h o sp h o ro u s . The
T his sam ple w ill be analyzed for nitrate/nitrite,
the sam ple preserved.
sa m p le m u st b e d e liv e re d to th e la b fo r a n a ly sis w ith in 2 8 d a y s.
T his sam ple w ill be analyzed for orthophosphates.
1. R inse the 500 m l bottle in the w ater body to be T h e sa m p le m u st b e d elivered to th e la b fo r sam pled, discarding initial w ater collected.
a n a ly sis w ith in 4 8 h o u rs.
2. Fill the 500 m l bottle, leaving about an inch at the top of the bottle.
Nitrogen and Phosphoras Protocol
10 - 3
Water Quality Monitoring Guidebook